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Full text of "Notes on the oil and gas fields of Webb and Zapata counties. The underground position of the Austin formation in the San Antonio oil fields"

EXCHANGE 




University of Texas Bulletin 

No. 2230: August 8, 1922 






Notes on the Oil and Gas Fields of 
Webb and Zapata Counties 

The Underground Position of the Austin 

Formation in the San Antonio 

Oil Fields 



BY 
E. H. SELLARDS 



Bureau of Economic Geology and Technology 

Division of Economic Geology 
J. A. Udden, Director of the Bureau and Heatf of the Division 




PUBLISHED BY 
THE UNIVERSITY OF TEXAS 

AUSTIN 



Publications of the University of Texas 

Publications Committee : 

FREDERIC DUNCALF J. L. HENDERSON 
G. C. BUTTE E. J. MATHEWS 

KILLIS CAMPBELL H. J. MULDER 
F. W. GRAFF A. E. TROMBLY 

HAL C. WEAVER 

The University publishes bulletins four times a month, so 
numbered that the first two digits of the number show the year 
of issue, the last two the position in the yearly series. (For 
example, No. 2201 is the first bulletin of the year 1922.) These 
comprise the official publications of the University, publications 
on humanistic and scientific subjects, bulletins prepared by the 
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Technology, and other bulletins of general educational interest. 
With the exception of special numbers, any bulletin will be 
sent to a citizen of Texas free on request. All communications 
about University publications should be addressed to University 
Publications, University of Texas, Austin. 



E44-8C2-2m 



University of Texas Bulletin 



Xo. 22,'JO: Ai.feiisfc 8, 11 



Notes on the Oil and Gas Fields of 
Webb and Zapata Counties 

The Underground Position of the Austin 

Formation in the San Antonio 

Oil Fields 



BY 
E. H. SELLARDS 



Bureau of Economic Geology and Technology 

Division of Economic Geology 
J. A. Udden, Director of the Bureau, and Head 1 of the Division 




PLRL1SHED BY THE UNIVERSITY FOUR TIMES A MONTH, AND ENTERED AS. 

SECOND-CLASS MATTER AT THE POSTOFFICE AT AUSTIN, 

TEXAS, UNDER THE ACT OF AUGUST 24, 1912 



: .j ** ,." ? . ,, *; 
.''??: i.'-: :..:;".../ 



The benefits of education and of 
useful knowledge, generally diffused 
through a community, are essential 
to the preservation of a free govern- 
ment. 

Sam Houston. 



Cultivated mind is the guardian 
genius of democracy. . . It is the 
only dictator that freemen acknowl- 
edge and the only security that 
freemen desire. 

Mirabeau B. Lamar. 



EXCHANGE 



CONTENTS 

Notes on the Oil and Gas Fields of Webb and 
Z a pat a Counties 

PAGE 

SUratigraphic Geology 5 

Regional Dip 6 

Topographic Features 6 

Location of the Oil and Gas Fields with Respect to Topo- 
graphic Features.. . 8 

Charco-Redoiido Wells 8 

Jennings Gas Field 

The Mirando Pool. 9 

The Riser Gas Field 10 

The Schott Pool 10 

The Carolina-Texas Oil Company Gas Wells. 11 

Well Records 12 

Well Logs in Webb County 13 

Well Logs in Zapata County 24 

The Underground Position of the Austin Formation 
in the San Antonio Oil Fields 

PAGE 

Introduction 30 

General Structural Conditions in the San Antonio District. . 32 

Contour Map on the Austin Formation 33 

Structural Conditions as Indicated by Contouring on the 

Austin Formation 34 

Relation of Producing Wells to Structure 37 

Producing Formations 38 

Well Records 38 

LIST OF ILLUSTRATIONS 

PAGE 

Map of Webb and Zapata County Oil Fields 7 

Map Showing Underground Position of Austin Formation . . 35 



977634 



NOTES ON THE OIL AND GAS FIELDS OF WEBB AND 
ZAPATA COUNTIES: 



BY E. H. SELLARDS 



At the present time oil or gas is being obtained from several 
localities in Webb and Zapata counties. The localities include 
the Charco Redondo oil wells, Jennings gas pool, and Mirando 
oil pool in Zapata County, and the Reiser gas wells and Schott 
oil pool and the gas wells of the Carolina-Texas Oil Com-, 
pany in Webb County. Of these several localities, the Reiser 
field is the oldest as a commercial field, having been discovered 
in 1909, although previous to that time oil had been noted in 
shallow wells drilled for water at the Charco Redondo. Ranch. 
The following notes 011 the producing fields of these two counties 
are based- on a reconnaisance of about ten days made in April 
and May, 1922. 

Stratigraphic Geology 

At the March meeting of the American Association of Petro- 
leum Geologists, Dr. A. C. Trowbridge read a paper on the 
Coastal Plains formations in Texas, adjacent to the Rio Grande, 
which it is understood, will be published. Not wishing to antici- 
pate in any way the results given in this paper by Trow- 
bridge, the geology and stratigraphy of this area will be referred 
to at this time only in a very general way. 

Immediately at Laredo and for a few miles to the east, the 
rocks exposed in the stream beds and rock cuts are chiefly sand- 
stones, often glauconitic, probably representing the Cook Moun- 
tain formation. Next to the east and extending almost, if not 
quite, to Reiser, is a broad belt in which clays predominate, 
although some oyster shell beds are included. These clays rep- 
resent the Yegua formaton. About twenty-two miles east of 
Laredo (three miles west of Reiser) is found a belt of very 
sandy land which may possibly represent a remnant of the 

Manuscript submitted for publication August, 1922. Issued Sep- 
tember, 1922. 



6 I'nh'ersity of Texas Bulletin 

Fayette, or a sandy horizon in the Yegua. At Reiser and in 
a clay pit nearby, are seen clays and oyster shall beds not 
unlike those of the Yegua. 

Next east of Reiser, near Aguilares, and extending thence 
north and south is a belt of country in which the land is in 
places sandy and in which there ar$ occasional outcrops of a 
light-colored rock with a limited amount of sand. This rock, 
which in places is chietiy volcanic ash containing plant impres- 
sions,- probably represents the Fayette formation. Next to the 
east is found a belt of clay land which widens in the northern 
part of Webb County and possibly represents the Frio formation. 

About thirty-five miles east of Laredo is a prominent escarp- 
ment beyond which the land is level and slopes gradually to 
the east. The formation capping this escarpment is the 
Reynosa,. which consists of caliche filled gravel and in places of 
caliche rock. The age of this formation is either Pleistocene or 
Pliocene. In the face of the escarpment, underneath the 
Reynosa capping, there is found in places a coarse sandstone 
which may be of Miocene age. 

It is thus seen that the formations found at the surface are 
chiefly those of the Eocene series, together with possibly limited 
Miocene exposures, and in the eastern part of these two counties, 
the Reynosa limestone and gravels. Adjacent to the stream beds, 
of course, are Pleistocene and recent terrace deposits, 

Regional Dip 

The regional dip in this area is to the east. To the north and 
northeast of this area, the strike of both Eocene and Cretaceous 
formations is northeast-southwest, the dip being southeast. In 
the central and southern parts of Webb and in Zapata counties, 
the strike of the Eocene formations is approximately north- 
south, the dip being, as stated, to the east. The average rate 
of dip has not been determined. 

Topographic Features 

In traveling east from Laredo, it is to be noted that for several 
miles, after crossing Chacon Creek, the country is characterized 



Notes on Oil and Gas Fields of Webb and Zapata Counties 1 



TORCCILLAS ! 

----. cole Petroleum **1 

^ 



MAP OF 

WEBB AND ZAPATA COUNTY 
OIL FIELDS- 
SCALE 




/ 5TARR CO. 



8 University of Texas Bulletin 

by successive minor ridges which trend, in general, north-south. 
These ridges have a rather abrupt west face and represent west 
facing escarpments, marking the outcropping edges of east 
dipping strata. In some instances the escarpments are held up 
by a hard stratum consisting chiefly of oyster shell rock. About 
eleven miles east of Laredo the land becomes more nearly level. 
Just east of Mirando City is the pronounced Keynosa escarp- 
ment to which reference has already been made. 

Location of the Oil md Gas Fields with Respect to the 
Topographic Features 

The Charco-Redondo and Jennings fields are located in or 
near the belt of country referred to above as probably repre- 
senting the Fayette formation. Each of these localities is 
some distance from the Reynosa escarpment, the Charco-Redondo 
locality being possibly seven miles, and- the Jennings field prob- 
ably not quite so far. The Reiser gas field is likewise seven 
or eight miles west of the Reynosa escarpment. On the other 
hand, the Mirando and Schott pools and the gas wells of the 
Carolina-Texas Company are located immediately at the foot 
of this escarpment. 1 

Charco-Redondo Wells 

The Charco-Redondo oil wells are located in the southeastern 
part of Zapata County. The wells, now producing, are shal- 
low, varying from 135 to 160 feet in depth. The oil is from 
sands and sandy shales, slightly greenish in color, found asso- 
ciated with, and usually underlying an oyster shell stratum, 
which serves as cap-rock. About twenty-one wells have been 
drilled, of which sixteen are now being pumped, the produc- 
tion being from one to three barrels per day per well. 

The oil sand at this locality dips to the east. Thus the west- 
ernmost of the wells obtain production at a depth of from 135 
to 140 feet, while wells farther to the east on land of equal 
or lower elevation find the oil sand at from 150 to 160 feet. 
About one mile west of the oil wells there is a west facing 



gas wells more recently obtained by the Carolina-Texas 
Company one is reported to be located on the escarpment. 



Notes on Oil and Gets Fields of Webb and Zapata Counties 9 

scarp held up by an oyster shell stratum. This oyster shell 
bed is probably the same as that associated with the oil sand, 
indicating the eastward dip in the formations. 

The producing sands at this locality are probably in the Fay- 
ette formation. The oil has a gravity of about 18.5 B, and is 
said to yield a good quality of lubricating oil. 

The Jennings Gas Field 

The Jennings Gas Field is located in the northeastern part of 
Zapata County, about seven miles from the east and nine miles 
from the north county line. This field was discovered in 1914 
when a test well for water obtained gas. Ten or more wells 
have been drilled. Two of these, failing to obtain gas, were 
drilled to a greater depth and obtained fresh water at about 
1900 feet. The yield in the gas wells is said to be, for each 
successful well, between ten and twelve million cubic feet initial. 

Surface exposures of the light colored slightly sandy rock with 
strata of volcanic ash provisionally referred to the Fayette 
formation were observed four or five miles northwest of the 
Jennings Field. No exposures were seen immediately within 
the gas fields, but it is probable that the surface formation at 
this locality is Fayette. The gas horizon at this locality lies 
between 1200 and 1300 feet below the surface. It seems prob- 
able that the gas horizon is within the Yegua formation, although 
formation thicknesses at this locality are not fully determined. 

The Mirando Pool 

The Mirando Pool is located in the northeastern part of Zapata 
County, about two miles from the east and three from the 
north county line. The discovery well in this field was com- 
pleted' in the spring of 1921. Since that time drilling has 
been actively continued in this field. These wells are located 
at the foot of the Reynosa escarpment, and at a place where, 
as indicated on the sketch map, the escarpment bends abruptly 
to the east. 

The producing sands in this field lie at a depth approximating 
1450 feet from the surface. The wells are about seven miles 



10 University of Texas Bulletin 

north and five miles east of the Jennings gas pool. Since the 
regional dip is to the east, if the gas at Jennings is from the 
Yegua, it seems probable that the oil at Mirando Pool is like- 
wise from this formation. On this point, however, the evidence 
is at present inconclusive. The logs of the deep wells in and 
near this pool indicate that sandstones are entered at about 
1700 feet. 

The wells at the west edge of the Mirando Pool produce gas, 
while in the central part of the pool the wells yield oil with 
but little gas. The oil is from 21.5 B gravity, and is said to 
contain very little gasoline. 

The Reiser Gas Field 

The Reiser Gas Field, in Webb County, is located on and 
near the Texas-Mexican Railway, twenty-five miles east of 
Laredo. About twelve gas wells have been obtained at this; 
locality, the best of which are reported to have made twenty or 
twenty-five million cubic feet of gas per day. Formerly the 
gas from this field supplied Laredo, but is used at the present 
time only for local purposes. 

The chief gas horizon at Reister is found at a depth of from 
650 to 800 feet. Probably the gas in this field is obtained from 
the Yegua formation, although, as in the case of the other fields 
in this area, the age of the producing horizon cannot be regarded 
as definitely determined. 

The Schott Pool 

The Schott Pool is located about thirty-five miles east of 
Laredo, and one and one-half miles south of Mirando City. 
The discovery well in this field was completed December, 1921. 
This pool is located near the foot of the Reynosa escarpment. 
The country is somewhat rolling, and there are occasional hills 
remaining as outliers or remnants of the Reynosa formation. 

The producing horizon of the Schott Pool is found at a depth 
of from 1525 to 1550 feet. About three miles southwest of 
this pool are exposures which appear to represent the Fayette 
formation from which it seems probable that the wells of the- 



Notes on Oil and Gas Fields of Webb and Zapata Counties 11 

Schott Pool, like those of the Mirando Pool, start near the top 
of the Eocene. Production in the Schott Pool is being obtained 
from seventy-five to one hundred feet deeper than in the 
Mirando Pool, the surface elevation being essentially the same. 
Whether or not production in the Schott Pool is from the 
same horizon as in the Mirando Pool is undetermined at this 
time. At Mirando City, some oil has been obtained at a depth 
of about 1630 feet. 

A well located about three-fourths of a mile northwest of the 
Schott Pool apparently passed- the oil producing horizon at 
about 1635 feet. This well continuing to a greater depth en- 
countered a thick body of slightly sandy, blue and pink some- 
what calcareous shale which was penetrated to a depth of 2500 
feet, where sandstones were encountered. 

In the Schott Pool as in the Mirando Pool, gas is found in 
wells west of those producing oil, apparently marking the west 
margin of the pool. The producing sands as indicated by the 
wells dips to the east with possibly a structural nose. The oil 
of the Schott Pool appears to be very similar in character to 
that of the Mirando Pool. The well of the Kanoka Oil Com- 
pany in the Schott Pool, after being cleaned, produced not 
less than 800 barrels per day. 

The Carolina-Texas Oil Company Gas Wells 

The Carolina-Texas Oil Company has a well from which gas 
has been obtained, located about seven miles east of north of 
Torrecillas. This well is at the foot of the Reynosa escarpment, 
and at a place where a small stream enters from the highland, 
forming a reentrant in the margin of the scarp. 

Some gas was obtained in this well at 1295 feet, but the prin- 
cipal gas horizon is reported at a depth of 2015 feet, The for- 
mation from which the gas is obtained is undetermined. This 
well is about ten miles north and four miles east of the Schott 
Pool. A second well drilled at this locality obtained some gas 
at 1296 feet. 1 



3 Two additional wells drilled since this manuscript was submitted 
and located east of the first two wells are reported to have obtained 
gas. 



12 



University of Texas Bulletin 
Well Records 



A summary of representative wells in these two counties is 
given in the table which follows. In addition a number of logs 
are included indicating the drilling conditions in the several 
fields. 

Summary of Representative Wells in "Webb and Zapata Counties 



Name of Well. 


Location. Depth. 


Remarks . 


Oarolina-Texas Oil Co._ 


Surv. 268, 7 miles N. 
N. E. of Torrecillas 


2015 


Gas show at 1270-1279. Gas 
at 2015. 


Zapata Oil and Gas Oo. 


Charco Redondo 


1735 


Oil sand at 163-168. Gas 
show in sand at 932-965. 




Texas Company. 
Jennings No 4 


Jennings Gas Field. 

1% mi. N. W. of Ranch 
House 


3015 
1367? 

1234? 


Fresh water at 196tf. 

12 M gas at 1265-1357. Rock 
pressure 455 Ibs. 

9 M gas at 1229-1234. Rock 
pressure 4<?0 ibs. 


Jennings No 3 


2V 3 mi. N. E. of Ranch 
House - 


Cuellor No. 1 . - 


U mi. E. N. E. of 
Ranch House 






Tveeton Synd. No. 2 

Mirando Oil Co. No. 2_ 
Mirando Oil Co. No. 3. 
.Mirando Oil Co. No. 4a 
Mirando Oil Co. No. 7- 

Witherspoon Oil Co. 
No 4 


Mirando Pool. 

N. W. pt. of pool. Blk. 
23 


1467 
1502 
1426 
1453 

1490 

2000 
1460 

1476 
1730 


Gas at 1445-1467. 
Show of oil at 1447-1452. 
Producer. Discovery Well. 
Oil sand at 1433-1442. 

Oil sand 1470-1476. 100 bbls. 
Sandrock 1735-2000. 
Reported producing. 80 bbls. 

Gas well, sand 1443-145-".. 
Reported dry. 


S. pt. of pool. Blk. 5__ 
S. pt. of pool. Blk. 5__ 
S. pt. of pool. Blk. 5- 
Central pt. of pool. Blk. 
17 


N. pt. of pool. Blk. 18. 
Central part of pool 


Witherspoon Oil Oo. 
No 1 


Tenn-Zapata Oil Co. 
No 1 


S. W. pt. of pool. Blk. 
16 


Zapata Red. & Ref. 
Oo 


Surv. 113. S. of pool 






Producers Oil Com- 
pany. 
B. & M. No. 5 (Com- 
pleted by Brethwith 
& Allison) 


Reiser Gas Field. 
Near Reiser 


2598 

j 2240 
85 


Water at about 1800 ft. 
Sands 200 ft. from surf. 
Gas reported at 2500 ft. 
Mineral water at 1500. 
Gas in use for local supply. 


Reiser No. 1 ._ 


1 mi E. of Reiser 


RiCiser No 4 


Af P/iiocir 





Notes on Oil and Gas Fields of Webb and Zapata Counties 13 

Summary of Representative Wells in Webb and Zapata Counties Continued 



Name of Well. 


Location. 


Depth. 


Remarks. 


Kanoka Oil Co. No. 1. 


Schott Pool. 

N. Central pt. of pool. 
Blk. 6 


1559 


Oil sand at 1545-1559. Re- 


Laurel Oil Oo. No. 1 _ 
Leaseholders Oil Co. 
No 1 


W. pt. of pool. Blk. 9. 
W. pt. of pool. Blk. 10 


1539 
1599 


portted making 1 800 bbls. 
per day. 
Gas well. 

Gas well. 


Schott Oil Co. No. 2.. 


Central pt. of pool. Blk. 

11 


1532 


Gas and oil at 1530-1532 


Sehott Oil Co. No. 3 
Schott Oil Co. No. 1 

South Plains Oil & Gas 
Co. 


E. part of pool. Blk. 12 
West of pool. Sur. 462_- 

N. W. of pool. Sur. 460 


1588 
1750 

2500 


Oil at 1571-1588. 
Ends in red and blue shale 
and gumbo. 

Below 1600 chiefly red and 


Laredo Oil Co. No. 2 


In Mirando City - 


1635 


blue shales. 
Oil at about 1635. 











Well Logs in Webb County 

The following logs of wells in Webb County are arranged 
alphabetically according to owners of the land on which the 
wells are located, and the company owning the well. 

tog- of Albercas No. 1, Albercas Oil Co., Survey 836, About Three Miles 
North Slig-htly West of the Mirando Pool 



Depth in Feet. 





From. 


To. 


ness. 


Red sandy clay _ 





42 


42 


Blue clay and boulders 


42 


79 


37 


Shale 


79 


132 


53 


Gumbo - - - 


132 


142 


10 


Shale and boulders _ _. 


142 


163 


21 


Green ''hale and boulders 


163 


246 


83 


Lime rock 


246 


250 


4 


Hard sandy shale 


250 


281 


31 


Blue and green gumbo and shale 


281 


410 


129 


Hard gummy shale - - 


410 


506 


93 


Shale and boulders - 


506 


613 


107 


Water sand 


613 


671 


58 


Gumbo 


671 


710 


3f) 


Gummy shale and boulders _ 


710 


778 


68 


Shale and sand, oil showing. 


778 


789 


11 


Hard shale .. - - 


789 


S40 


51 


Packed sand 


840 


871 


31 




871 


961 


90 




961 


092 


31 




992 


1,055 


63: 




1,055 


1,142 


87 




1,142 


1,172 


30 


Shale and! boulders - 


1,172 


1,280 


108 


Hard sandy shale... 


1,280 


1,309 


23 



University of Texas Bulletin 



Log- of Albercas No. i, Albercas Oil Co., Survey 836, About Three Miles 
North Slig-htly West of the Mirando Pool ^Continued 





Depth in Feet. 


Thick- 
ness. 


j 
From. 1 To. 


Gumbo 


1,309 
1,318 
1,445 
1,480 
1,491 
1,505 
1,507 
1,548 
1,550 
1,559 
1,585 
1,61 
1,684 
1,709 
1,720 

1,727 
1,734 
1,739 


1,318 
1,445 
1,489 
1,491 
1,505 
1,507 
1,548 
1,550 
1,559 
1,535 
1,601 
1,684 
1,709 
1,720 
1,727 

1,734 
1,739 
1,797 


9 
127 
44 
2 
14 

9 

4 i 

9 
26 
76 
23 
25 
11 
7 

7 
5 
58 


Hard and soft shale, blue and brown _ 


Shale and boulders 


^Packed sand 


Hard shale 


Lime rock 


Hard shale, pyrites and boulders __ 


Ifime rock _. 


'Gumbo - _ 


Xhale and boulders -- 


Hard gumbo - -- 


Hard shale 




Hard shale and boulders - 




Hard sand rock, showing gas. 


Soft "ind - 


Hard shale total depth 





Began December 7, 1921; completed February 11, 1922; set 8", casing at 743'; set 6* cas- 
ing at 1735'; 1 ft. in reck. 8" casing leftt in hole and derrick left standing with inten- 
tion of drilling deeper. 

Log- of Barusly No. 1. Carolina Texas Oil Co. Survey 268, About Pour 
Miles Northeast of Mirando City 





Depthi 


n Feet. 


Thick- 




From. 


To. 


ness. 


Clay 




a 


22 


Rock - 


22 


48 


26 


Sand 




56 


8 


Rock 


56 


59 


3 


Shale 


59 


72 


13 


Sand 


72 


77 


5 




77 


103 


26 


Rock 


103 


108 


5 




108 


141 


' 1 


Rock -- 


141 


142 


1 


Sand _ 


142 


160 


18 


Rock 


160 


162 


) 




162 


195 


33 


Rock 


195 


197 


2 




197 


217 


20 




217 


220 


3 


Sand 




228 


8 


Rock 


228 


229 


1 


Sandy shale _____ 


229 


254 


25 




254 


260 


6 


Sand _ 


260 


270 


10 


Sand and boulders - 


270 


310 


40 


Rock - 


310 


312 


2 


Sand boulders 


312 


375 


63 


Rock 


375 


380 


5 




380 


402 


22 


Gumbo - 


402 


407 


5 




407 


428 


21 


Pay . 


428 


435 






435 


440 


5 


Snnrl and boulders 


440 


460 


20 



Notes on Oil and Gas Fields of Webb and Zapata Counties 15 

Log- of Barusly No. 1. Carolina Texas Oil Co. ssurvey 268, About FOur 
Miles Northeast of Mirando City Continued 





Depth in Feet. 


Thick- 
ness. 


From. 


To. 


Bock _ _. 


460 

464 
610 
616 
630 
760 
764 
780 
796 
827 
835 
910 
916 
930 
970 
1,000 
1,002 
1,060 
1,065 
1,070 
1,085 
1,088 
1,130 
1,135 
1,137 
1,155 
1,168 
1,195 
1,222 
1,226 
1,270 
1,295 

1,401 
1,466 
1,535 
1,550 
1,568 
1,573 
1,600 
1,608 
1,654 
1,685 
1,700 
1,725 
1,732 
1,800 
1,815 
1,827 


464 
610 
616 
630 
760 
764 
780 
796 
827 
835 
910 
916 
930 
970 
1,000 
1,002 
1,060 
1,065 
1,070 
1,085 
1,088 
1,130 
1,135 
1,137 
1,155 
1,168 
1,195 
1,222 
1,226 
1,270 
1,295 
1,322 

1,466 
1,535 
1,550 
1,568 
1,573 
1,600 
1,608 
1,654 
1,685 
1,700 
1,725 
1,732 
1,800 
1,815 
1,827 
1,995 


4 
146 
6 
14 
130 
4 
16 
16 
31 
8 
75 
6 
14 
40 
30 
2 
58 
5 
5 
15 
3 
42 
5 
2 
18 
13 
27 
27 
4 
44 
25 
27 

65 
69 
15 
18 
5 
27 
8 
46 
31 
15 
25 
7 
68 
15 
12 
168 


Sandv shale and boulders 


Gumbo 


Water sand _ _ 




Pink gumbo - 


Sand and boulders _> - - - 


Gas sand -- > 


Sand and boulders - 


Pay sand - - -- - - 


Sand and boulders - - - 














Bock _ 




Sand _ 








Rock - 










Gumbo - 




Pfl V 


Clay (?) - - 


No log 1,322 to 1,401. This well deepened by Trussle, Brown 
& Hodges. 
Sandy shale - 




Shale and boulders - -- - 


Sand 




Shale and boulders - -- 






Shale 






Hard shale -- -~ - - 


Shale - 






Shale 





Total depth, 2,015. Shale grades into sandy shale and apparently into a coarse 
grained sandstone, which is producing aboutl 8 M cu. ft. gas. 



16 



University of Texas Bulletin 



Log- of Breckenridse No. 1, South Plains Oil & Gas Co., Survey No. 460, 

Southeast Corner of Block 15, About One Mile 

Southwest of Mirando City 





Depth in Feet. 


Thick- 
ness. 


From. 


To. 


Surface clay 





20 
72 
120 
122 
240 
261 
272 
349 
400 
422 
428 
451 
471 
474 
487 
620 
628 
670 
680 

% 

772 
815 
830 
882 
892 
905 
940 
951 
958 
998 
997 
1,040 
1,060 
1,135 
1,155 
1,160 
1,212 
1,219 
1,282 
1,286 
1,327 
1,331 
1,348 
1,393 
1,426 
1,441 
1,444 
1,460 
1,470 
1,488 
1,498 
1,502 
1,506 
1,509 
1,547 
1,556 
1,579 
1,595 
1,603 
1,604 


20 
72 
120 
122 
240 
261 
272 
349 
400 
422 
428 
451 
471 
474 
487 
620 
623 
670 
680 
710 
771 
772 
815 
830 
882 
892 
905 
940 
951 
958 
993 
997 
1,040 
1,060 
1,135 
1,155 
1,160 
1,212 
1,219 
1,282 
1,286 
1,327 
1,331 
1,348 
1,393 
1,426 
1,441 
1,444 
1,460 
1,470 
1,488 
1,498 
1,502 
1,506 
1,509 
1,547 
1,556 
1,579 
1,595 
1,603 
1,604 
1,685 


20 
52 
48 
2 
118 
21 
11 
77 
51 
22 
6 
23 
20 
3 
1? 
133 
3 
47 
10 
30 
61 
1 
43 
15 
52 
10 
13 
35 
11 
7 
35 
4 
43 
20 
75 
20 
5 
52 
T 
63 
4 
41 
4 
17 
45 
33 
15 
3 
16 
10 
18 
10 
4 
4 
3 
38 
9 
23 
16 
8 
1 
31 


Yellow clay and boulders-- 




Bed clay and shale 




Lime rock 




Hard shale and boulders.. 




Gumbo - 




Lime rock 




Hard green shale and bou 
Shale 


Iders 




Chalk rock .. 




Gumbo 




Shale 




Packed sand 




Hardi lime rock _. 




Gumbo 




Soft gummy shale 




Soap stone 




Soft shale 




Gumbo - 








Hard shale _. 




Lime rock- 




Shale and boulders 




Gumbo 




Hard shale 




Sand rock 




Soft lime rock 




Shale and boulders 




Hard ilme rock 




Gumbo 




Soft shale 




Sand rock 




Hard sandy shale 




Water sand - - 




Hard shale 




Sandy shale 




Gumbo 




Soft shale 




Gumbo 




Hard sandy shale and bou 
Lime rock 


Iders 




Hard shale and streaks- of 
Sand rock 


gumbo 




Sandy shale 




Gumbo 




Hard shale and boulders - 




Sandy shale 








Soft shale 




Hard gummy shale 
Shale and boulders 


























Hard sandy shale 












Soft sandy shale; set 8" p 
Shell rock _. 


ipe 




Sand _ 





Notes on Oil and Gas Fields of Webb and Zapata Counties 17 



log- of Breckenridg-e No. 1, South Plains Oil & Gas Co., Survey NO. 46O, 

Southeast Corner of Block 15, About One Mile 

Southwest of Mirando City Continued 





Depth in Feet. 

mK}-i, 


From. 


ness. 
To. 


Sandy shale; set liner and bs 
Shale 


iled 


1,635 
1,641 
1,660 
1,665 
1,725 
1,731 
1,741 
1,747 
1,751 
1,784 
1,785 
1,831 
1,860 
1,866 
1,947 
1,957 
1,872 
1,998 
2,004 
2,015 
2,021 
2,036 


1,641 6 
1,660 19 
1,665 5 
1,725 60 
1,731 6 
1,741 10 
1,747 6 
1,751 4 
1,784 33 
1,785 1 
1,831 46 
1,860 29 
1,866 6 
1,947 81 
1,957 10 
1,972 15 
1,998 26 
2,004 6 
2,015 11 
2,021 6 
2,036; 15 
2,055; 19 
2,060! 5 
2,061 1 
2,067, 6 
2,100 33 
2,106! 6 
2,128 22 
2,176 43 
2,180 4 
2,186 6 
2,195 9 
2,202: 7 
2,240! 38 
2,300 60 
2,360| 63 
2,405 45 
2,475! 70 
2,476 1 
2,480 4 
2,500 20 
2,527: 27 
2,540 13 
2,542[ 2 
2,550, 8 
2,562 12 
2,578! 16 
2,588 10 
2,591 3 
2,603 12 
2,623 20 
2,630 7 
2,665 35 
2,689| 24 
2,6X>! 1 
2,709 19 
2,726 17 
2,746 20 
2,775 29 
2,8021 27 
2,807; 5 
1 fflfi Q 




Gumbo - 




Green shale 




Gumbo 




Packed sand 




Shale 




Gumbo 




Hard blue shale 




Pink shale 




Green shale, soft and hard j 
Pink shale and lime streaks 


streaks 




Blue gumbo 




Pink shale with streaks of gi 
Gyp gumbo 


imbo 




Hard pink shale 




Blue shale. 




Gumbo _ . 




Pink shale __. 




Gumbo - 




Hard blue shale 








Blue gumbo - 




2,055 
2,060 
2,061 
2,067 
2,100 
2,106 
2,128 
2,176 
2,180 
2,186 
2,195 


Lime rock 




Gyp gumbo __. 




Blue shale 








Blue shale 




Hard pink shale 




Gyp gumbo 1 




Sand - 




Sand and shale streaks 




Hard gummy shale-. _. 




Green shale and boulders 




2,202 
2,240 
2,300 


Blue shale soft and gummy- 




Green shale_- -- 




Blue and pink shale 




2,30 
2,405 

2,475 


Pink shale 




Soft lime rock 




Gumbo 




2,476 
2,480 
2,500 
2,527 
2,540 
2,542 


Hard shale and lime streaks 
Not recorded 






Sand shale 




Sand and shale streaks 




Dry sand, gas show- 




Hard sand and boulders gas 
Hard shale and shells 


show 


2,550 
2,562 
2,578 
2,588 
2,591 
2,603 
2,623 
2,630 
2,665 
2,689 
2,690 
2,709 
2,726 
2,746 
2,775 
2,802 
9 R07 




Gumbo 




Sand 




Pink shale and boulders 




Hard shale and sand streaks 
Gumbo 






Hard pink gummy shale 




Pink and blue shale 




Rock and pyrites _ ~ 




Blue slate shale 




Soft shale and sand streaks 
Sulphur water sand 






Hard sand 




Soft shale and sand streaks 
Hard sand 






Blue shale 




Shale and boulders. . 


2,816 2,8591 43 



18 



University of Texas Bulletin 



Log- of Breckenridg-e No. 1, South Plains Oil & Gas Co., Survey No. 460, 

Southeast Corner of Block 15, About One Mile 

Southwest of Mirando CityContinued 






Depth i 


n Feet. 


Thick- 




From. 


To. 


ness. 


Hard sand gas showing ... _ ' 


2 859 


2 879 


20 


Hard sand 


2 879 


2 885 


g 


Hard sand gas showing- 


2 885 


2 900 


15 


Hard sand 


2 900 


2 928 


28 


Sulphud water sand 


2 928 


o 940 


1 


Shale and boulders 


2,940 


2 980 


40 


Shale and gumbo 


2 960 


3 009 


29 











Log- of l-olts No. 1, Santa Maria de los Angeles Surrey, About One-half 
Miles East of Bruni, In Eastern Fart of Webb County 





From. 


To. 


ness. 


Soil _. __ 





5 


5 


Sand and clay 


5 


10 


5 




10 


50 


40 


Hard sand 


50 


75 


25 


Lime rock 


75 


105 


30 


Gravel and water sand 


105 


115 


10 


Sandy shale 


115 


175 


60 


Water sand 


175 


225 


50 


Hard shale 


225 


325 


100 


Gumbo 


325 


400 


75 


Blue shale 


400 


525 


125 


Water sand _ 


525 


625 


100 


Blue shale 


625 


800 


175 


Gummy red shale 


800 


1 000 


20ft 


Blue shale 


1 000 


1 100 


100 


Gummy red shale 


100 


1 200 


100 


Black shale 


,200 


1,300 


100 


Hard blue shale 


,300 


1,400 


100 


Gumbo 


400 


1 475 


75 


Hard sandy shale____________ ___________ 
Soft blue shale 

Gas sand- _ __ _____ ___ ___ 


,475 
,500 
600 


1,500 
1,600 
1 625 


25 
100 

25 


Hard black shale _ 


'_H-r 


1,700 


75 


Sea shell 


1 700 


1 705 


5 


Sandy shale 
Sea shell _ '. ' I 


1,705 
1 790 


1,790 
1,800 


85 
10 


Soft sandy shale __ _ 


1,800 


1,810 


10 











Depth in Feet. 



Casing set at 1,875 in cement; 4%" lines set at 1,650. 

Hole was bailed dry, making quite a bit of gas; pulled lines and finished hole at 
1,810', with no oil showing. 



Notes on OH and Gas Fields of Well) and Zapata Counties 19 



Of Xanola. No. l, Survey 54, About One and One-half Miles South of 
Uirautto City. After Cleaning- Well Produced 80O totals, or 
More. Discovery Well of the Schott Pool 



Depth in Feet. 



From. To. 



Thick- 
ness. 



Surface soil 

Yellow clay 

Soft Time clay 

Loose gray shale 

Red and blue shale 

Water sand 

Fine blue sand 

Red mixed shale 150 

Hard red clay 210 

Red mixed shale - 

Soft lime clay 

Red mixed shale -- 274 296 

Blue shale ^ 296 320 

Gummy shale 320 

Red and blue shale 373 

Hard gummy shale 373 

Gumbo 399 411 

Soft lime rock 411 420 

Red and blue shale 420 448 

Hard lime rock - 448 453 

Red and blue shale. 453 512 

Hard lime rock 512 

Hard blue shale and lime 522 

Hard gummy shale 601 622 

Lime rock 622 635 

Red and blue shale 35 

Lime rock 660 672 

Hard blue shale 072 

Lime rock 700 776 

Red and blue shale 776 844 

Lime rock 

Red and blue shale__, 860 940 

Lime rock 940 978 

Red and blue shale 978 1,000 

Lime rock 1,000 1,023 

Red and blue shale 1,023 1,073 

Gumbo 1,073 1, 

Lime rock 1,084 1,102 

Gumbo 1,102 1,114 

Hard gummy shale 1,114 1,129 

Red and blue shale __ 1,129 1,140 

Lime rock 1,140 1,162 

Hard gummy shale __, 1,162 1,184 

Gumbo, 1,184 l. 

Red and blue shale _ 1,196 1,216 

Gumbo 1,216 1,227 

Lime rock ^ 1,227 1,248 

Gummy shale 1,248 1,271 

Lime rock_ _.. . 1,271 1,282 

Gumbo - 1,282 1,293 

Red and blue shale ___ 1,293 1,304 

Gumbo - 1,304 1,313 

Lime rock and shale 1,313 1,328 

Red and blue shale 1,328 1,350 

Lime rock 1,350 1, 

Hard blue shale 1,362 1,374 

Red and blue shale 1,374 1, 

Lime rock 1,396 1,406 

Hard blue shale. - 1,406 1,440 

Lime rock 1,440 1,462 

Hard blue shale 1,462 1,499 

Lime rock (gas big) 1,499 1,508 

Hard blue shale 1,508 1,513 

Hard lime rock (gray sand) set casing 1515' 1,513 1,515 



20 



University of Texas Bulletin 



tog- of Xanoka No. 1, Survey 54, About One and One-half Miles South of 

MiraJido City. After Cleaning 1 Well Produced 800 btols. or 

More. Discovery Well of the Schott Pool Continued 






Depth in Feet. 


Thick- 
ness. 


From. 


To. 


Xiime rock- 




1,515 
1,517 
1,522 
1,523 
1,533 
1,537 
1,543 
1,545 


1,517 
1,522 
1,523 
1,533 
1,537 
1,543 
1,545 
1,569 


2 
5 
1 
10 
4 
6 
2 
14 


Shells and 
Sand rock. 


shale__ _ 




Shale and 
Gumbo - 


sand - 




Shells and 
Hard lime 
Hard sand 


shale 


rock 


(heavy oil sand) 





Stopped in gumbo. 
Set casing" in cement. 
Set 6&, 7". 

Log- of Laredo Oil Co., Well No. 1, Survey 458, in Mirando City 




Depth in Feet. 


Thick- 
ness. 


From. 


To. 


Surface _ . 



10 
18 
20 
35 
45 
61 
62 
76 
86 
96 
101 
115 
133 
148 
179 
184 
194 
205 
213 
231 
246 
256 
284 
294 
304 
330 
344 
360 
375 
385 
393 
413 
414 
434 
454 
460 
480 
510 
525 
533 
555 


10 
18 
20 
35 
45 
61 
62 
76 
86 
96 
101 
115 
133 
148 
179 
184 
194 
205 
213 
231 
246 
256 
284 
294 
304 
330 
344 
360 
375 
\ 385 
! 393 
413 
i 414 
434 
454 
460 
480 
510 
525 
533 
555 
587 


10 
8 
2 
15 
10 
16 
1 
14 
10 
10 

! 

18 
15 
31 
5 
10 
11 
8 
18 
15 
10 
28 
10 
10 
26 
14 
16 
15 
10 
8 
20 
1 
20 
20 
6 
20 
30 
15 
8 
22 
32 


White lime and sand ... ... 


Gravel _ 


Sand 


Clay' _. 


Sand, clay and shell 


Pink shale __ 


".Red clay _i __ 


-Gray shale . 


Blue and gray shale _ 


White lime rock 


Gray shale 


Pink gumbo 


Blue snale 


(Gray gumbo 


]Brown shale 


Blue shale _ _ 


Gray shale 




Hard shale 




Shale 


Sandy shale 


Blue gumbo - 






Brown gumbo 


Blue gumbo - 










ROCk 








Gray shale 










Grnv erumbo 



Notes on Oil and Gas Fields of Webb and Zapata Counties 21 



Log- of Laredo Oil Co., Well No. l, Survey 458, in Mirando City Continued 





Depth in Feet. 


Thick- 
ness. 




From. 


To. 


Slate with coal 


587 
615 
654 
656 
664 
715 
759 
760 
778 
800 
816 
824 
825 
875 
883 
905 
920 
952 
960 
972 
978 
1,014 
1,029 
1,039 
1,049 
1,059 
1,076 
1,084 
1,089 
1,092 
1,114 
1,146 
1,165 
1,185 
1,215 
1,230 
1,260 
1,275 
1,285 
1,291 
1,321 
1,341 
1,411 
1,431 
1,446 
1,466 
1,496 
1,521 
1,531 
1,56] 
1,581 
1,621 
1,6& 
1,6C 
1,654 
1,665 


615 

654 
656 
664 
715 
759 
760 
778 
800 
816 
824 
825 
875 
883 
905 
920 
952 
960 
972 


28 
39 
2 
8 
51 
44 
1 
18 
22 
16 
8 
1 
50 
8 
22 
15 
32 
8 
12 
6 
86 
15 
10 
10 
10 
17 
8 
5 

22 
32 
19 
20 
30 
15 
30 
15 
10 
6 
30 
20 
70 
20 
15 
20 
30 
25 
10 
30 
20 
40 
15 
14 
4 
8 




Rock _ 










White lime rock - --- 






day shale - -- 


Rock _ 


Gray shale - - - - 


Brown shale -- - - 














978 
1,014 
1,029 
1,039 
1,049 
1,059 
1,076 
1,084 
1,089 
1,092 
1,114 
1,146 
1,165 
1,185 
1,215 
1,230 
1,260 
1,275 
1,285 
1,291 
1,321 
1,341 
1,411 
1,431 
1,44 
1,4 
1,49* 
1,521 
1,531 
1,561 
1,58] 
1,62] 
1,63( 

i,ea 

1,65^ 
1,661 








Blue shale - - 


Blue gumbo - 




Blue gumbo - 


Shale - 


Lime rock - 








Shale and gumbo -- -- 




Shale 








Soft lime rock 


Gumbo 


Blue shale - - 




Shale 






Gumbo 






Shale - -- 




<hale - 




Shale 






Rock -- - - 





This well gave a flow of oil when first drilled. Subsequently abandoned on account 
of water trouble. 



22 



University of Texas Bulletin 



log- of Well On Reiser Hanch, Producers Oil Co., B. & M. Lease Well No. 5 r 

Survey 1617, About One-fourth Mile South of Reiser's 

Station. Total Depth 2,598 



s 


Depth j 


n Feet. 


Thick 




From. 


To. 


ness. 


Surface sand 





3 


3 


Sandy red clay 


3 


g 


3 


Brown sand __ __ 


6 


12 


6 


Gravel with some salty water 


12 


14 


o 


Brown shale __ 


14 


45 


31 


Sandy yellow clay 


45 


58 


13 


Brown shale 


58 


110 


59 


Sand 


110 


118 


8 


Shale 


118 


126 


g 


Shale 


126 


164 


35 


Gumbo 


164 


170 


6 


Shale 


170 


208 


38 


Lime shells with some sand 


208 


220 


12 


Red clay __ 


220 


286 


63 


Sand salt water 


286 


992 


6 


Shale black 


292 


334 


4-> 


Sand 


334 


339 


5 


Sandy shale 


339 


404 


65* 


Gumbo 


404 


413 


9 


Shale black 


413 


476 


(>3 


Sand 


476 


482 


G 


Shale 


482 


564 


82 


Gumbo 


564 


570 


6 


Brown shale 


570 


642 


79 


Sand, gas show 


642 


649 


y 


Black shale 


fi49 


674 


25 


Gumbo 


674 


686 


12 


Red clay 


686 


793 


107" 


Sand 


79S 


798 


5 


Shale with sand shell . ._ 


798 


885 


87 


Sandy shale - _ _ ____ 


885 


914 


29 


Gray salt sand 


914 


926 


12 


Brown shale 


926 


938 


12 


Sand 


938 


945 




Shale with sand 


945 


987 


49 


Sandy shale -- 


987 


1,032 


45 


Blue shale sand shells, iron 


1,032 


1,116 


84 


Gumbo - - 


1,116 


1,123 


7 


Sand 


1,123 


1,138 


15 


Sandy blue shale J_ 


1,138 


1,184 


46 


Sand - -- - -- 


1,184 


1,192 


8 


Black shale _ _. _ 


1,192 


1,203 


16 


Sand 


1,208 


1,227 


19 




1,227 


1,243 


21 




1,248 


1,285 


37 




1,285 


1,312 


27 


Shale 


1,312 


1,324 


12 


Sand 


1,324 


1,332 


8 


Sand set 8" 


1,332 


1,369 


37" 











This well is said to have been subsequently drilled to a depth of 2,598 feet. Water- 
was obtained at about 1,800 feet, and gasi is reported at about 2,500 feet. 



Notes on Oil and Gas Fields of Webb and Zapata Counties 23 



Log- of Garcia No. 2, Schott Oil Co., Survey 54, About One and One-half 

Miles South of Mirando City. Gas and Oil Well, Initial 

Production Oil Reported at 74 tobls. 





Depth in Feet. 


Thick- 
ness. 


From. 


To. 


Yellow sand 



2 
10 
30 
57 
107 
135 
168 
165 
220 
260 
290 
330 
342 
475 
490 
587 
563 
600 
637 
670 
673 
&5 
687 
700 
745 
750 
800 
805 
861 
873 
897 
900 
918 
937 
960 
968 
1,000 
1,020 
1,067 
1,083 
1,100 
1,115 
1,160 
1,187 
1,193 
1,213 
1,237 
1,275 
1,297 
1,317 
1,350 
1,357 
1,384 
1,400 
1,410 
1,427 
1,449 
1,467 
1,482 
1,500 
1,510 
1,515 
1..523 
1,527 
1,530 


2 

10 
30 
57 
107 
135 
163 
165 
220 
260 
290 
330 
342 
475 
490 
537 
563 
600 
637 
670 
673 
685 
687 
700 
745 
750 
800 
805 
861 
873 
897 
900 
918 
937 
960 
983 
1,000 
1,020 
1,067 
1,083 
1,100 
1,115 
1,160 
1,187 
1,193 
1,213 
1,237 
1,275 
1,297 
1,317 
1,350 
1,357 
1,384 
1,400 
1,410 
1,427 
1,449 
1,467 
1,482 
1,500 
1,510 
1,515 
1,523 
1,527 
1,530 
1,532 


2 
8 
20 
27 
50 
28 
28 
2 
55 
40 
30 
40 
12 
138 
15 
47 
26 
37 
37 
33 
3 
12 
2 
13 
45 
5 
50 
5 
56 
12 
24 
3 
18 
19 
28 
23 
17 
20 
47 
16 
17 
15 
45 
27 
6 
20 
24 
38 
22 
20 
33 
7 
27 
16 
10 
17 
22 
18 
15 
18 
10 
5 
8 
4 
3 
2 


Soft limA clay -- -- - 


Yellow clay 


Blue shale 


Rd clay 


Soft lime rock 


Hard blue shale 


Lime rock 


Hard blue shale 


Blue shale and sand 


Gumbo 


Blue shale __ _ ._ 


Red and blue shale 


Blue shale and sand 


Soft lime rock 


Hard blue shale and sand 


Lime rock-- _ -- 


Tough gumbo 


Lime rock 


Gumbo 


Lime rock _ _- __ __ 


Gumbo 


Lime rock 


Gumbo - - 


Hard blue shale __ 


Lime rock 


Red and blue shale 


Soft lime rock -_ _ 


Rd and blue shale 


Lime rock__ 


Gumbo 


Blue shale 


Lime rock 


Gumbo -_ 


Blue shale and sand 


Tough gumbo 


Soft rock _ __ 


Hard blue shale 


Gumbo 


Lime rock 


Red and blue shale __ 


Gumbo 


Lime rock 


Hard blue shale - 


Lime rock__ . 


Hard blue shale 


Gumbo 


Lime rock _ _ __ 


Gumbo _. _ 


Hard blue shale 


Lime rock 


Gumbo - 


Hard blue shale 


Lime rock 


Blue shale 


Soft blue mud 


Soft lime rock 


Red and blue shale 


Soft lime rock 


Hard lime rock 


Tough gumbo 


Hard lime rock- 


Soft lime rock 


Hard lime rock 


Hard blue reck, sandstone __ 


Porous gray sand rock 





University of Texas Bulletin 



Log- of Urban No. 1, Bio Grande Oil & Gas Co., Survey 7; Ten or Twelve 

Miles North of Laredo 





Depth i 


n Feet. 


Th ick- 




Prom. 


To. 


ness. 


Yellow clay 





18 


118 


White shale 


18 


30 


12 


Blue shale 


30 




30 


Pink shale _ - __ 


60 


80 


20 


Sand 


80 


Of) 


10 


Blue shale 


90 


260 


170 


Cave __ 


260 


265 


5 


Blue shale 


265 


290 


25 


Cave _ 


290 


295 


5 


Blue shale 


295 


360 


65 


Cave 


360 


365 


5 


Blue shale _ _ 


365 


545 


180 


Sand, showing of oil 


545 


553 


8 


Blue shale . 


553 


633 


80 


Slate 


633 


800 


167 


Water sand 


800 


881 


81 


Shale 


881 


860 


70 


Sand 


960 


1 000 


40 


Slate _. 


1 000 


1 006 


(j 


Sand 


1,006 


1,058 


52 


Slate 


1 058 


1 075 


17 


Sand _ - 


1 075 


1,093 


18 


Water sand 


1 033 


1 103 


10 


Slate 


1 103 


1 122 


19 


Sand 


1,122 


1,140 


19 


Slate - 


1,140 


1,145 




Sand 


1 145 


1 ?10 


65 


Slate 


1, 9 10 


1,220 


10 


Sand 


1,220 


1 255 


35 


Slate 


1 255 


1 263 


g 


Sand - 


1 263 


1,320 


57 


Sand _- _ _- 


1,320 


1,340 


2o 


Water* sand 


1,340 


1,366 


25 


Brown shale 


1,365 


1,369 


4 


Sand 


1,369 


1,400 


31 


Slate 


1,400 


1,404 


4 


Sand began underreaming' 1,130' 


1 404 


1,450 


46 


Red rock 


1,450 


1 455 




Sand -- 


1,455 


1 470 


15 


Red rock i __ 


1,470 


1,472 


2 


Sand 


1 472 


1,515 


43 


Broken formation, sand, slate, red rock _ 


1,515 


1,580 


65 


Sand 


1 580 


1 600 


9Q 











Casing record: Set 12y 2 ", casing at 553'; 10" at 1,058'. 

Log Wells in Zapaita County 

Log- of Hinnant No. 6, Mirando Oil Co., Survey 114, Block 5, Lot 1, 
Initial Production 150 btols., Mirando Pool 





Depth i 


n Feet. 


Thick- 




Prom. 


To. 


ness. 


Clay and gravel 





98 


93 


Pack sand 


98 


100 


2 


Blue shale - 


100 


140 


40 


Hard shale 


140 


150 


10 


Shale and sand 


150 


170 


20 


Shale 


170 


360 


190 


Boulders _. 


360 


371 


n 



Notes on Oil and Gas Fields of Webb and Zapata Counties 25 



of Hinnant No. 6, Mirando Oil Co., Survey 114, Block 5, Lot 1, 
initial Production 15CKJ bbls., Mirando Pool Continued 





Depth in Feet. 


Thick- 
ness. 


From. 


To. 


Shale 


371 
590 
600 
638 
641 
658 
665 
720 
725 
815 
826 
857 
860 
863 
1,040 
1,059 
1,099 
1,108 
1,123 
1,167 
1,231 
1,257 
1,320 
1,384 
1,401 
1,412 
1,425 
1,431 
1,448 
1,462 


590 
600 
638 
641 
658 
665 
720 
725 
815 
826 
857 
860 
863 
1,040 
1,059 
1,099 
1,108 
1,123 
1,167 
1,231 
1,257 
1,320 
1,384 
1,401 
1,412 
1,425 
1,431 
1,448 
1,462 
1,467 


219 
10 
38 
3 
17 
7 
53 
5 
90 
11 
31 
3 
3 
177 
19 
40 
9 
15 
44 
64 
26 
63 
64 
17 

3 

6 
17 
14 

5 


Gumbo 


Shale 


Sandy shale 


Shale 


Boulders a 


Shale 


Boulders 


Hard sandy shale _ . 


Hard red gumbo 


Hard shale 


Rock 


Shale _ __ _ -. _ 


Hard shale and boulders 


Green gumbo_ 


Hard shale 


Green gumbo- -_ _ 


Hard shale and boulders 


Blue shale 


Hard shale boulders _ _ 


Stiff blue gumbo 


Hard shale 


Shale and boulders 


Hard shale 


Green gumbo 


Pay shale and sand 


Gumbo 


Hard shale 


Pay sand and shale _ 


Boulders - -- 





Log- of Hinnant No. 7, Mirando Oil Co., Survey 307, Block 17, Lot 4, 
Completed November 26, 1921, Mirando Pool 





Depth i 


n Feet. 


Th i>lr 




From. 


To. 


ness. 


Clay and gravel 


o 


12 


12 


Mixed shale 


12 


48 


33 


Hard sandy shale 


48 


65 


17 


Mixed shale _ t 


65 


182 


117 


Hard shale 


182 


220 


33 


Hard shale and boulder r *_ 


220 


273 


53 


Hard sand 


273 


275 


2 


Sandy shale _ __ 


275 


348 


73 


Hard sand and! boulder 


348 


362 


14 


Rock 


362 


365 


3 


Hard shale 


365 


385 


20 


Hard sand _ _ _ ____ 


385 


387 


2 


Sandy shale 


387 


501 


114 


Hard shale ^- __ .... 


501 


545 


44 




545 


567 


22 


Hard shale 


567 


587 


20 


Hard shal8 and boulder 


587 


704 


117 


Gumbo 


704 


710 


c 


Hard shale and boulder - - - _-__- - - 


710 


760 


50 




760 


778 


18 


Hard shale and! boulder 


778 


840 


62 


Gumbo and boulder - ____ _ __ 


840 


865 


25 




865 


906 


41 


Hard shale 


906 


956 


50 


Gumbo 


950 


991 


35 



26 



University of Texas Bulletin 



of Hinnant No. 7, Mirando Oil Co., Survey 307, Block 17, lot 4, 
Completed November 26, 1921, Mirando Fool Continued 





Depth in Feet. 


Thick- 
ness. 


From. 


To. 


Hard shale and boulder __ 


991 
,030 
,034 
,040 
,071 
,081 
,166 
,180 
,252 
1,290 
1,S62 
1,392 
1,403 
1,446 
1,470 
1.476 


1,030 
1,034 
1,040 
,071 
,081 
,165 
,180 
,252 
1,290 
1,362 
1,392 
1,403 
1,446 
1,470 
1,476 
1.490 


39 
4 
6 
31 
10 
84 
15 
72 
38 
72 
30 
11 
43 
24 
6 
14 


Hard shale and boulder-- 


Gumbo __ 


Hard shale and boulder.. 


Boulder 


Hard shale 


Gumbo __ -_ 


Hard shale and boulder 


Gumbo and boulder 


Hard shale and! boulder 


Hard shale 


Gumbo 


Shale 


Gumbo _ 


Hard sand 


Shale _. 



Casing record: 



>'; initial production reported at 100 bbls. 



Log- of Hinnant No. 3, Witherspoon Oil Co., Surtfey 115, Block 3, 
Mirando Pool 





Depth i 


n Feet. 


Thick- 




From. 


To. 


ness. 


Red clay and gravel 





60 


60 


Soft shale 


60 


186 


126 


Shale and boulders 


186 


336 


150 


Loose shale 


336 


520 


184 


Shale and boulders __ 


520 


620 


100 


Gumbo 


620 




25 


Hard gumbo 


645 


655 


10 


Shale and boulders _ _ ._ 


655 


710 


55 


Gumbo . -- - 


710 


720 


10 


Hard gumbo ! 


720 


760 


40 


Gumbo and gravel 


760 


810 


50 


Hard gumbo 


810 


840 


30 


Pink shale 


840 


900 


60 


Gumbo - 


900 


920 


20 


Shale 


920 


940 


20 


Hard gumbo 


940 


980 


40 


Gumbo - 


980 


995 


15 


Pink shale *-_ 


995 




55 


Hard sand and boulders 


1,050 


1*070 


20 


Shale anl boulders - -- - 


1,070 


1*100 


30 


Gumbo and shale - 


1,100 


I,'l50 


50 


Hard gumbo - - 


1,150 




50 


Shale 


1,200 


1,220 


20 




1,220 


1 260 


40 




1,260 


1,320 


60 


Hard sand and boulders 


1,320 




30 




1,350 


1,360 


10 


Sand and shale - 


1,360 


1,364 


4 




1,364 




4 


Shale - 


1,368 


1,375 


7 




1,375 


1,390 


15 


Soft' shale -- - 


1,390 


1,435 


45 


Hard sand oil showing -- - -- 


1,435 


1,440 


5 


Shale and sand- 


1,440 


1,490 


50 



Reported producing 90 bbls. per day in April, 1922. 



Notes on Oil and Gas Fields of Webb and Zapata Counties 27 



Log- of 



[innant No. 4, Witherspoon Oil Co., Survey 307, Block 18, 
Mirando Fool; Well Abandoned 





Depth i 


n Feet. 


Th iflr 




From. 


To. 


ness. 


Red clay and gravel 





60 


60 


Shale .__ 


60 


180 


120 


Shale and boulders _ _ 


180 


400 


220 


Gumbo 


400 


460 


60 


Gumbo and particles of iron 


400 


520 


60 


Boulders and shale 


520 


600 


30 


Gumbo 


600 


680 


80 


Shale and, boulders 


680 


760 


80 


Sand rock _ 


760 


770 


10 


Hard' gumbo _ 


770 


820 


50 


Hard sandy shale 


820 


860 


40 


Sand and boulders 


860 


900 


40 


Hard gumbo. 


900 


940 


40 


Shale and boulders 


940 


1 110 


170 


Hard shale 


1 110 


1 140 


30 


Boulders and gumbo 


1 140 


1 220 


80 


Shale and boulders-. 


1 220 


1 250 


30 


Gumbo __ 


1 250 


1 260 


10 


Shale and sand upper pay 


1 260 


1 380 


120 


Hard gumbo and sand 


1,380 


1,435 


55 


Soft shale andi sand 


1,435 


1,445 


10 


Hard brown gumbo 


1 445 


1 450 


5 


Hard gumbo 


1 450 


1 490 


40 


Sand _. 


1,490 


1,500 


10 


Gumbo 


1 500 


1 563 


63 


Rock 


1 563 


1 565 


2 


Hard gumbo _ _. _ 


1 565 


1,600 


35 


Sand __ 


1,600 


1 610 


10 


Gumbo 


1 610 


1 690 


89 


Rock 


1 690 


1 692 


2 


Sandy shale 


1 692 


1,700 


3 


Not reeoTded 


1 700 


1 735 


35 


Hard sand rock 


1 735 


2*000 


265 











Log- of Slator No. 1, Producers Oil Co., Jose Boreffo Vosquez Grant, Within 
About a Mile of North County Line; Elevation 595 





Depth ] 


n Feet. 


ThiW 




From. 


To. 


ness. 


Soil 





45 


45 


Shale 


45 


65 


20 


Sandy shale 


65 


84 


19 


Black shale _ 


84 


208 


124 


Gumbo _- 


208 


221 


13 


Sand 


221 


230 


g 


Shale 


230 


345 


115 


'Gumbo -- 


345 


395 


50 


Shale _ 


395 


507 


112 


Sand 


507 


512 


5 


: Shale 


512 


691 


179 




691 


720 


29 


"Shale with iron 


720 


814 


94 


Rock white 


814 


820 


Q 


:Shale, black 


820 


104 


284 


:Sand . 


1,104 


,106 


2 


Black shale 


1 106 


116 


10 


:Sand 


1 116 


119 


3 


'Shale 


1 119 


291 


172 




1,291 


400 


109 


Bluo shale 


1,400 


1,419 


19 


Sand -. 


1.419 


1.424 


5 



28 



University of Texas Bulletin 



Log 1 of Slator No. 1, Producers Oil Co., Jose Boreso Vosquez Grant, Withiir 
About a Mile of Nrth County Line: Elevation 596 Continued 



1 


Depth in Feet. 


Thick- 
ness. 


From. 


To. 


Shale . ! 


1,424 
1,443 
1,400 
1,493 
1,503 
1,508 
1,527 
1,557 
1,563 
1,580 
1,588 
1,612 
1,649 
1,747 
1,750 
1,791 
1,895 
1,902 
1,920 
1,925 
1,964 
1,984 
2,020 
2,107 
2,194 
2,195 


j 

1,443 19- 
1,460 17 

1,493 33 

1,503 10 
1,508' 5 
1,527 19 
1,551 30 
1,563 6 
1,580 17 
1,588 8- 
1,612 24, 
1,649 37 
1,747 98, 
1,759 12 
1,791 38 
1,805 104 
1,902 7 
1,920 18 
1,925' 5 
l,964i 39 
1,984 20 
2,020 36 
2,107i 87 
2,194j 87 
2,195! 1 
j 2,210 ! 15 


Shale and sand _ 


Sand and iron.. 


Shale _ 


Bock and sand 


Shale _ . 


Bock sand and iron (show gas 1,582-1,540) 


Sulphur water, sand 


Sand and iron . - 


Shale 


Flinty rock and! sand 


Shelly shale 


Sand and iron - - -- - - - 


Shale _ 


Shells and pyrite 


Sha.le 


Lime rock - - -- 


Shelly shale 


Lime shell 


Shelly shale 


Slate 


Shelly shale 


Shale and slate 


Shale sandy 


Sand 


Shale, sandy - - - 




Log- of Zapata Oil & Gas Co., in ciiarco Redondo Field, Southeast Fart of 
Zapata County, Yellow Clay and Sand 





Depth i 


n Feet. 


Thick- 




From. 


To. 


ness. 


Yellow clay and sand 





18 


18- 


Light green clay 


18 


70 


52 


Blue and green shale __ _ 


70 


78 


8 


Boulders and slate 


78 


83 


5 


Blue clay and slate 


83 


163 


80 


Oil sand 


163 


168 


5 


Shells, fossil oysters 


168 


169 


1 


Clay and shale 


169 


194 


25 


Light blue clay 


194 


240 


46 


Shale and fossil shells - -_ 


240 


258 


18 




958 


< T1 


13 


Shells and shale 


271 


283 


12 


Bed clay 


283 


307 


24' 


Clay thin sand strata - - 


307 


323 


16- 


White clay 


323 


362 


39 


Bed clay 


362 


381 


19 


Green shale 


381 


390 


9" 


H^ird green shale - 


390 


438 


4b 


Shell and shale __ 


438 


443 


5- 


Shells and shales 


443 


610 


167 


Sand and shale - - 


610 


619 


^ 


Green andl blue shale - - - - 


619 


648 


29 




648 


662 


14 


Bed and green shales - - - 


662 


714 


52 


Shells and shale - ____________ 


714 


760 


46 


Tough gumbo 


760 


769 


9 




769 


783 


14 


Hard slaty shale _ 


783 


789 


6 


Gumbo - - ... 


789 


803 


14 



Xotcs on Oil and Gas Fields of Webb and Zapata Counties 29 

3- of Zapata Oil & Gas Co., in Charco Redondo Field, Southeast Part of 
Papata County, Yellow Clay and Sand Continued 





' 
Depth in Feet. 


Thick- 
ness. 


From. To. 


Hard shale and boulders 
Shale and soft slate 




803 807 
807| 826 
826 841 
841 848 
848 860 
860 932 
932 965 
965! 992 
992| 998 
998J 1,037 
1,037 1,043 
1,043 1,069 
1,069! 1,078 
1,078! 1,118 
l,118i 1,130 
1,130; 1,150 
1,150 1,172 
1,172 1,175 
1,175 1,226 
1,226 1,238 
l,238j 1,247 
1,247 1,263 
1,263 1,270 
1,270! 1,286 
1,286 1,298 
1,298 1,302 
1,302| 1,308 
- 1,3081 1,329 
1,329 1,341 
1,341 1,347 
1,347 1,5:63 
1,862: 1,268 


4 
19 
15 
, 7 
12 
72 
33 
27 

6 
26 
9 
40 
12 
20 
22 

A 

12 

9 
16 
7 
16 
12 
4 
6 
21 
12 
6 
15 
6 
17 
12 
29 
22 
14 
! 17 
18 

5 

2 
11 

8 
7 
29 
23 
26 
10 
i 21 
6 
1 12 

1 15 
14 
15 
5 

I 

!j 11 




Dull brown gumb o* 




Hard sand and shells 




Shale, shells and concret 
Shale 


ons _ _ - - 




Sand and boulders, gas 
Blue shale 


bubbles 




Sand and shale pyrite 




Shale 




Light green clay 




Dark shale _ 




Gumbo - 




Blue shale 




Sand and green shale 




Hard sandstone 




Sand and shale 




Harrl ga.nd, < ?t rm A 




Shale and gumbo 




Sha.le and sandstone 




Gumbo _ _ 




Shale and shells 




Black shale and pyrite 




Clay 




Hard dark, shale 




Sand and shale 




Hard sandstone 




Shale 




Shale and gumbo 




Hard rock . 




Shale and slate__ 




Shells 




Soft white clay 




1,368 1,385 
1,385 1,397 
1,397 1,426 
1,426 1,448 
1,448 1,462 
1,4621 1,479 
1,479 1,497 
l,497j 1,501 
1,501 1,506 
1,506 1,508 
1,508 1,519 
1,519 1,524 
1,524 1,531 
1,531 1,560 
1,560 1,583 
1,583 1,609 
1,609 1,618 
1,619 1,640 
1,640 1,646 
1,646 1,655 
1,658 1,673 
1,673 1,687 
1,687 1,702 
1,702 1,707 
1,707 1,712 
1,712 1,717 
1,717 1,725 
1,728 I,7ffl5 


Shale and slate. _ . 




Black shale and shells 




Clay with shells 




Shell rock gypsum 




Shale and shells 




Sand and shale 




Soft white clay __ _ 




Hard rock concretions 




Shale 




Rock 


* 


Soft white clay 




Rocks 




Shale-- and clay 




Shale and shells - 




Clay and boulders 




White clay 




Shales and clay 




Rock slaty. 




Rocks, concretions and 
Sandstone 


gypsum 




White clay boulders 




Shells and concretions 




Sandstone slate 




Rock pyrite 




Gumbo 




Sandstone 




Shale and sand 









30 University of Texas Bulletin 



THE UNDERGROUND POSITION OF THE AUSTIN 
FORMATION IN THE SAN ANTONIO OIL FIELDS 

BY E. H. SELLARDS 

The Austin formation, or Austin chalk, underlies all of the 
oil fields of the San Antonio district, and is itself productive 
of oil in the Alta Vista and Mission fields and perhaps to a 
lesser extent elsewhere. It is a thick formation, varying from 
possibly three hundred and fifty to four hundred and fifty 
feet or more, consisting 1 of a chalky, usually light colored or 
blue rock, and with the possible exception of the Eagleford, 
which lies next below it. is the most readily indentifiable for- 
mation of the Upper Cretaceous series. For this reason it is 
perhaps the most serviceable of the Upper Cretaceous forma- 
tions in deciphering structural conditions from well records. 
It is true that the transition from the overlying Taylor to the 
Austin is gradual, and that there is probably a lack of uniform- 
ity on the part of drillers in recognizing the top surface of 
the chalk. However, such inconsistencies as arise from this 
cause, although of importance in detailed mapping, probably 
do not materially affect the accuracy or records when used 
in mapping general or regional structures. 

The well records here used are those of the Bureau of Eco- 
nomic Geology of the University of Texas, and include many 
records contributed or made available by several oil companies 
and individuals. 

In Bexar County, the Austin is found at the surface in a 
belt of country extending through the county in a northeast- 
southwest direction and passing near, but mostly north of San 
Antonio. At its northwest margin this belt of Austin exposures 
is marked by a more or less well defined west-facing escarp- 
ment. Beyond this escarpment to the northwest, the Austin 
is wanting, and the formations at the surface, with the excep- 
tion of the Eagleford, are of Lower Cretaceous age. On the' 
other hand, to the southeast the Austin passes underneath 
later formations and is found, as stated, underlying the oil fields. 



Underground Position of Austin Formation in Oil Fields 31 

While the Austin passes below the surface to the southeast, 
the rate per mile at which it drops to a lower level is by no 
means uniform. On the contrary it is found from well records 
that while, in places, the formation drops very abruptly to a 
lower level, elsewhere it again rises towards the surface, result- 
ing in alternately structurally high and low areas. 

To the southeast of the Alta Vista and Somerset fields, the 
Austin evidently drops to a lower level very rapidly, although 
there may of course be as yet undetected interruptions or 
reversals in the dip. That the average rate of descent of thp 
Austin is rapid, however, is demonstrated by the fact that the 
formation, unless greatly altered in character, was not reached 
in the Richter well near Pleasanton, about twenty miles south 
of the Alta Vista field although drilling Avas continued to a depth 
of 4015 feet, or to a level of about 3665 feet below sea level. 

In the northwestern part of Atascosa County the Austin for- 
mation lies at a depth of 1700 or 1800 feet. The drop to the 
Richter well, allowing for difference in elevation, amounts to 
not less than 2500 or 2600 feet in fifteen miles. The average 
rate of descent in the formation crossing Atascosa County in 
a southeasterly direction is therefore not less than an average 
of 165 or 175 feet per mile. 

In referring to the underground position of the Austin chalk 
it is of course understood that this formation is but one of a 
series of formations lying in natural order, the one upon the 
other, and that where the records are such as to indicate that 
one of the formations lies at a relatively high elevation it may 
be with confidence concluded that the other formations of the 
same series, when not separated by an unconformity, likewise 
lie at a relatively high level at that locality. In this way a 
certain formation recognizable in well logs may be used in 
determining structural conditions, regardless of whether the 
formation itself is productive or not, and from structural con- 
ditions in turn may be inferred to some extent the probability 
of oil production in that particular locality. Accordingly the 
Austin, for the reasons given, is here used in depicting the 
structural conditions in this region so far as these conditions 



32 University of Texas Bulletin 

can be shown on a small map and from wells that are in 
some parts of the area much fewer in number than could have 
been desired. 

General Structural Conditions in the San Antonio District 

No more than brief reference will be made at this time to 
the general structural conditions in the San Antonio district, 
these conditions having been somewhat fully described else- 
where. The Balcones zone of folding and faulting, as is well 
known, passes through this district. The inner margin of this 
fault zone (inner in the sense of farthest inland from the Gulf) 
is marked in this part of the State by a pronounced south- 
east facing escarpment, the trend of the fault zone being north- 
east-southwest. Beyond the escarpment to the northwest the 
formations, which are those of the Lower Cretaceous, are but 
little disturbed by faulting and have a very moderate and 
scarcely perceptible dip towards the Gulf. To the southeast 
of this escarpment, on the other hand, is a region of profound 
disturbance, th$ formations being both faulted and folded. 
This disturbed zone is known to be more than twenty miles in 
width and it may be much wider. The faults observed are 
normal or tension faults, the downthrow being in the direc- 
tion of the dip of the fault plane. In most of the faults the 
downthrow is to the southeast. This, however, is not invariable 
as faults are seen at the surface and recognized in well drill- 
ing in which the downthrow is in the opposite direction or to 
the northwest. In that case the dip of the fault plane, where 
observed, is likewise to the northwest. The faults with down- 
throw to the southeast exceed in number, as already stated, 
those with downthrow to the northwest; they likewise in gen- 
eral exceed in intensity or in amount of throw. Moreover the 
regional dip is to the southeast and while there are reversals 
of dip, these are seldom continued for any great distance. The 
ultimate result of faulting and folding in this zone is to carry 
the formations very rapidly to a lower level. When averaged 
across the county from the Balcones Escarpment to the eastern 
part of Bexar County the rate of drop in the formations will 



Underground Position of Austin Formation in Oil Fields 33 

be found to fall between 100 and 150 feet per mile, probably 
a close approximation to 125 feet per mile. But that such an 
average rate of descent can be applied only in the most gen- 
eral way, becomes apparent from an inspection of the map and 
records which follow. 

Contour Map on the Austin Formation 

On the accompanying map there is assembled the information 
now available on the underground position of the Austin for- 
mation in the San Antonio oil fields. The belt of surface 
outcropping of the Austin is indicated on this map by the 
shaded area. To the east of its outcropping area the position 
of the Austin is indicated so far as practicable from records 
now at hand, by contouring, the contours being in depth below 
sea level as indicated. Likewise the location of the wells used 
in contouring is indicated and the depth with respect to sea 
level, at which the Austin was found in that particular well,, 
is entered on the map. 

In this connection it should be stated 1 that the surface eleva- 
tion of the various wells has been taken largely from the topo- 
graphic map, although for a number of the wells not on the topo- 
graphic maps the elevation has been determined approximately 
by barometer reading's. There is necessarily a small possible 
error in elevation of wells, and this should be taken into con- 
sideration in using the map. The possible error from this 
source, however, is probably less than the average error inci- 
dent to recording and interpreting well logs, and is probably 
negligible or nearly so in regional mapping. 

In 1920 a bulletin on the geology of Bexar County was issued 
by the Bureau of Economic Geology, in which structural con* 
ditions were indicated by contouring on the Del Rio, a Lower 
Cretaceous formation. 1 A comparison of the map issued at 
that time, with the present map, shows that the major struc- 
tural features recognized from the Del .Rio formation, are like- 

*The Geology and Mineral Resources of Bexar County, by E. H, 
Sellards, University of Texas, Bureau of Economic Geology and Tech- 
nology, Bulletin 1932, March, 1920. 



34 University of Texas Bulletin 

wise shown by contouring on the Austin formation. However, 
by the aid of wells drilled during the past two years, the map- 
ping has now been extended into Atascosa and Medina coun- 
ties. Accordingly the map now issued includes the greater 
part, but not all, of Bexar County, and a small part of 
Atascosa and Medina counties. In the southeastern part of 
Bexar County but little drilling has been done, and in this part 
of the county no progress in contouring the underground struc- 
ture has been made. For this reason this part of the county 
is not included in the present map. 

In the map previously issued based on the Del Rio forma- 
tion, faulting, so far as recognized from underground records, 
was indicated. The present map has been simplified to the 
extent of not attempting to indicate such apparent lines of 
faulting. It may be stated, however, that such new records 
as have been added since the first map was published in so 
far as they relate to faulting support the interpretation pre- 
viously given. 

Structural Conditions as Indicated by Contouring on the 
Austin Formation 

The outcropping belt of the Austin in Bexar and eastern 
Medina counties shows notable irregularities of outline not 
accounted for by erosion. Thus in the western part of Bexar 
County north of the Portranca public road there is a broad belt 
of the Austin which extends in a southwesterly direction into 
Medina County. This belt of Austin forms a ridge of much 
greater elevation than the plains at either side. The level and 
much lower land at the north and at the south is, for the 
most part, covered by terrace gravels, but such exposures as 
are seen indicate the Taylor formation. When followed to 
the southwest, the Austin formation is found to pass under 
later formations. Again immediately north of San Antonio 
there is found a similar, although much narrower belt of the 
Austin formation, extending into the northwestern part of the 
city, and forming the surface exposures seen in Brackenridge 
and San Pedro parks. Surface exposures of the Austin, in 



Underground Position of Austin Formation in Oil Fields 35 



UNDERGROUND 
OF A i/JTV/v FORMATION 
AND PARTS OF MED i HA 
ATASC 03 A COUNTIES 




Fig. 1. Map showing approximately the underground position of the Austin 
formation in Bexar and in the adjacent parts of Medina and Atascosa Counties. 
Shading indicates area where the Austin is at or near the surface, Contours 
on the Austin chalk. Contour interval 500 feet. Sea level datum. 



36 University of Texas Bulletin 

this locality, are found at an elevation of 800 feet or more above 
sea, while both to the north and to the south the top of the 
Austin is encountered at a much lower level. It is thus ap- 
parent that these two belts of Austin exposures are due to 
structural conditions. In the case of the Austin exposures in 
San Antonio, faults are observed which limit the exposures 
at the south, these faults giving rise to the San Pedro, San 
Antonio and Salado Springs. At the north side, the Austin 
is limited by faults with downthrow to the north or by abrupt 
northwest dips in the strata. In the case of the broad 1 belt in 
the western part of the county, the structural conditions are 
produced either by step-faulting or by folding. In each in- 
stance the structural feature is a southwest plunging anticline 
or fault block. 

While these structural features are observable at the surface 
in the central part of the county, they are more or less ob- 
scured south of the Austin belt by the non-resistant character 
of the formations together with the mantling surface materials. 
From examination of the well records, however, it becomes 
apparent that this type of structure, southwest plunging anti- 
clines or fault blocks, is characteristic of the area as far south 
at least as the south line of Bexar County. Thus the fault 
block seen from surface exposures in the city of San Antonio 
may be followed by well records to the oil and gas wells west 
of Leon Creek, and possibly also as far as the Medina River. 
The Gas Ridge field, which has produced chiefly gas, and in addi- 
tion a small amount of oil, is obviously accounted for by this 
structural feature. 

Another very pronounced structurally high area is that found 
at the Alta Vista oil field. At this locality the Austin forma- 
tion lies about 300 feet below sea or within about 900 or 965 feet 
of the present surface (900 log; 965 samples). Immediately 
north of the Alta Vista field the Austin lies at a much lower 
level, the difference being so great as to suggest the probability 
of faulting with downthrow to the north. The wells of the 
Alta Vista and Mission oil fields are located within this struc- 
turally high area. 



Underground Position of Austin Formation in Oil Fields 37 
Relation of Producing Wells to Structure. 

The principal groups of producing wells in this region are 
indicated on the map. These include the Somerset field, South 
Medina and Yturri wells, Alta Vista and Mission pools, and 
the Gas Ridge wells. It will be seen that these producing wells 
are associated with the structural features of this area. It 
is probable that production is controlled in some fields by fault- 
ing and in others by folding. In either case production is 
likely to come chiefly from the southeast slope of the structurally 
high feature. That is, the favorable location for a well is 
either on or somewhat east of the axis of the "structure." This 
is probably due to the fact that the structural features of this 
area are unsymmetrical, the northwest slope being short and 1 
hence affording but little collecting area for oil. The south- 
east slope, on the other hand, in which the strata are returning 
to their normal southeast dip, is likely to be long and thus to 
afford a considerable collecting ground for oil. With regard 
to the kind of faults that favor accumulation, it is to be re- 
membered that there 'are many faults of varying intensity mak- 
ing up what is known as the Balcones fault zone. Most of 
these faults have the downthrow to the southeast, that is in 
the direction of the regional dip. Such faults, with downthrow 
to the southeast, do not provide favorable conditions for the 
accumulation of oil, for the reason that they merely intensify 
the rate of dip or descent of the formations to the southeast. 
Some of the faults of this zone, however, have the downthrow 
to the northwest. In all of these faults, the fault plane dips 
towards the downthrow side. In the case of a fault with the 
downthrow to the northwest, it follows therefore, that the 
"d'rag" which is incidental to faulting amounts to or brings 
about a short abrupt dip of the formations in the direction 
of the downthrow, or in this instance to the northwest. These 
conditions, without doubt, explain the fact that it is the faults 
with downthrow to the northwest that bring about conditions 
favorable for production, the drag to the fault plane serving as 
reverse dip, aided possibly by deposition in the fault plane. 



38 



I'ni versify of Te.ras Build in 



Producing Formations N 

With regard to producing formations, more or less produc- 
tion, or oil showings, have been obtained from all of the Upper 
Cretaceous formations in this area and possibly to some extent 
from the Midway, which overlies the Cretaceous. In the Somer- 
set field the principal production is from about 500 feet above 
the top of the Austin chalk and probably near the contact of 
the Taylor and Navarro formations. The Lower Cretaceous now 
known to produce oil in Limestone and Caldwell counties, is 
present, underlying the Upper Cretaceous. 

Well Records 

The wells used in recording the underground position of the 
Austin formation are listed in the following table. The "map 
entry," given in the table, appears also on the map and is in- 
tended to assist in locating the well. It records also the eleva- 
tion of the top surface of the Austin with respect to sea level 
as nearly as has been determined for that particular locality. 
Thus the entry 412 records the top of the Austin as 412 feet 
above sea level. Entries preceded by the minus sign, as 1700, 
record depth of the Austin below sea level. In addition to 
the logs used in mapping a few have been added in Bexar, 
Medina, and Atascosa counties, which are beyond the area cov- 
ered by the map. 

BEXAR COUNTY 



Name of Well. 


Location. 


Eleva- 
tion. 


Total 
Depth. 


Top of 
Austin. 


Map 

entry. 


\llen , D J 


Kelly Field 9 


(80 


1 054 


600 


80 


Applewhite -- 
Arrowhead Oil Co... 


1(5 mi. S 

2% mi. W., 1 mi. X. 
Somerset 


500 
650+ 


1 ,052 
1,700 


1,896 
i,!TO 


1,396 
920 


Basse, E. E 


5 mi. N. San Antonio 


7<K)T 


590 


25+ 


735 


Benke, Mrs K 


92 mi N W 


1 030T 


1 000 


?00 


730 


Blue Win? Club 
Brendle, H 


12 mi. S 

527 Bandera St , S A. 


490T 
720 


2,444 


1,746 
180 


1 ,256 
540 


Breckenridge Well 


Near Salado Creek 


630 


1,018 


70+ 


.360 


Brown, Marathon Oil 
Co 


2 mi due E Somerset 


625+ 




1 319 


894 


Cassin 


9 mi. S. S. A 


550 


1,468- 


973? 


493 


Clamp, C. C 

Collins Gardens 


6 mi. west 
S. W Pt S A 


700 
650 


1,452 


C62 
5' 7 5 


38 
125 


Carney, Glen 


7% mi. E. of San Antonio 


650 


1 226 


o30+ 


l-'O 


Elder and Wolf 


8% mi. S. S. A. (Alt a 
Vista) 


600 


1.' 7 86 


9'iO+ 


300- 



Underground Position of Austin Formation in Oil Fields 39 

BEXAB COUNTY Continued 



Nairn' of Woll. 


Location. 


Eleva- 
tion. 


Total 
! Depth. 


Top of 

Austin. 


Map 

entry. 


Kn'derick Well - -- 


7 1 /. mi. S. W. San Antonic 


V 6. 


1,200 


740 


So 




90 1 ' Morales St S \ 






250-f 


:425 


(iovonmient Well, 
\v ;> ition Post 


6 mi \ E 


7.351 


, 374 


55H- 


680 


(Government Well --- 


Hackberry St., near Ave 
C 


('SO 


729 


258 


431 


Herf IT 


4 5 mi W 


C'8 9 


i ->e<> 


621 


62 


If ; ll and Robv 


7.5 mi S 


625 


1 890 


1 200 


575 


Hofheintz R H 


N. of Kelly Field 


680 


1,453 


600 


80 


Iloltz 


9 mi. S. W. 


610 


1 665 


1,900-H 


575 


Hot Well* 


4 5 mi S 


575 


1 878 


990 


115 


Kearney Oil and Pipe 
Line Co 


12 mi S of S A 


610 


2 355 


957 


347 


Kreutch O 


5.5 mi F S A 


678 


1 000 


420+ 


255 


Kurz 


1 mi S E of Somerset 


638 


1 650 


1 450~ 


SI 2 


Legler, W. F. 


5 mi. W. 


6fl0 


1,555 


670 


9 5 


Linn 9 


12 mi. S 


550 


1 443 


1 ! 4 


544 


Lone Star Brewing 
Co 


120 Jones Ave. 


660 


805 


248 


4l 9 


La nun 1, Ulf-Varnes 
Exploration Co 


16 mi. S. 


! 500 


2 693 


9^900-1- 


1 700 


Masterson 1, Meech- 
am Oil Co 


18 mi. W. 


750 


2 245 


255 


495 


.Mclntosh, Mrs 


7 mi. E. of S. A. 


700 


668 


30+ 


670 


Mathey 1, Bexar Pe- 
troleum Co 


1 mi. W. Losoya 


515 


2 332 


1 892 


1 377 


Medina Oil Co 


12 mi. S. 


530 


1 833 


1 01? 


48 


M. K T Ry 


Landa 


784 


643 


60+ 


724 


IVrrinot Well, 
Schlather Ind. 
Porch Well 


2 mi. S. W. Martinex 
Iiy 2 mi. S. 


680T 
530T 


1,375 
1,505 


1,239 
Not 


559 


Ridder \ J 


13 mi S W 


68 


2 911 


reached 

900+ 


975+ 
272 


S. A. & A. P. Ry._- 
San Antonio City 
Water 


Pro-baa and Simpson Sts. 
Market St. 


630 

650 


1,103 

880 


500 

2?0 


130 
430 


"San Antonio City 
Water 


Conception Mission _- 


605 


1,440 


780 


175 


San 'Antonio Port 


5 mi N . 


740 


C67 


60 


680 


Schmidt, Marathon 
Oil Co 


1% mi. due E. Somerset 


635+ 




1 579 


944 


Shatuck Well 


19th St. W T . 


678 


6(i7 


335 


343 


Smith, Sarach 
Southern Ice Co 


2 mi. E. S. E. of Somerset 
Frio and Durango Sts 


650 
655 


1,668 
822 


Not 
reached 
280 


1,018+ 
395 


Southwest Land Cor- 
poration 


4 mi. W. 


708 


1,000 


390 


318 


Somerset Well ... 


Somerset, cored by Kerr at 










'St Louis College 


1600. Austin 1,560-1,930. 
W. 5.1 


650 

760 


2,320 

7Q9 


1,560 
215 


910 
545 


"Steves Mrs J 


Steves Garden 


645 


1 185 


604 


41 


'Steves Mrs J 


509 King Williams St 


645 


758 


250 


395 


Steves Ed 


8.5 mi. S. of S. A. 


660 


1 840 


j 300-+- 


(340+ 


'Sullivan, D. 


3y 2 mi. S. E-. of S. A 


620 


1,100 


505+ 


115 


Taft, L S 


7 mi. E. of S. A. 


666 


1 240 


880 


215 


Terrell Hot WelL- 
Terrell, J. H 


5.2 mi. S. of S. A 
S. W. city limits, S. A. 


630 
675 


1,956 
1,140 


1,000 
550 


370 
12'> 


Texas Steam Laun- 
dry. 


205 Losoya St 


65 


748 


290 


375 


Tommins, R. 


South city limits, S. A.- 


630 


1,500 


900 i 


270 


Union Meat Co 


Laredo and Ralph Sts., 
S. A. 


640 


1 400 


340 


qnn 


Voght, Win. 
Walsh, Meechum Oil 
Co 

Waring Well 
Vturri 1, W. H. 
Reynolds et al 


14, mi. S. W. of S. A.__. 

12 mi. S. of S. A.. 
7.5 mi. N. W. of S. A._. 

Wz mi. S. San Antonio 


605 

550 

920 

510 


1,850 

1,736 
2,853 

3,460 


985 

1,403 
13 

1,476? 


380 

353 
907 

966? 



40 



University of Texas Bulletin 

MEDINA COUNTY 



Name of Well. 


Location. 


Eleva- Total ' 
tion. Depth, j 


Top of i 
Austin, i 

i 


Map 

entry. 


Blackaller 1, Mid- 
Ffio Oil Co 


5 mi. E. and 3 mi. N. of 
the S. W. corner of 
county 


SOOT 3 115 


1 %0 


-1 160? 


W. Garnand, Somer- 
set, Western Oil Co. 


Thomas Surv. 516 


745 1 648 


1 550 


805 


Gray Well 


Abt 1 mi S E I ytle 










8 mi., 113% Tli. Thomas 








Haas, Geo. 


414 mi S W T of Dun!ay 


1 000 1 000 


97 5> j 


125 


Kimble, Osman Oil 
Co 


Near Devine, 2 mi. S. W. 








McClure, T. S., 1 


S. Reiden, John No. 28 
3 mi. S. W. Dunlay Sta. 
on S. P. Ry. See T. S. 
McClure, 142 Goliad St. 


670 2,540 
1,233 


2,287 
740 


1.617 














ATASCOSA C01 


JNTY 






Name of Well. 


Location. 


Eleva- Total 
tion. Depth. 


Top of 

Austin. 


Map 

entry. 


Caruthers 11, Gray- 
burg Oil Co 


About 2 mi. S. W. Somer- 










set 


> 375 


1 775 




Childress No. 1, Lem- 
ing Oil & Gas Co. 
Now owned by Hol- 
lingsworth, Pleas- 
an on 


1 mi. S. of Leming 


450A . 2,600 


Not 




Foster, Grayburg Oil 
Co. 


Somerset Oil Field && mi. 




reached 


2,150+ 




W. S. W. Somerset Sur- 
vey 523 


745 \ 




1 US; 


Fowler, Gulf Produc- 
tion Co. Powler 
Lease No. 2 


Somerset Oil Field 2. mi. 










S. W. Somerset 


1,8*9 


1,825 


1,175, 


Hartung Loase 1. W. 
1. Grayburg Oil Co. 


Survey 140, 3 mi. S. W. 
Somerset 


1 979 


1 968 


1 13~ 


Hartune: 17, Gray- 
burg Oil Co. 


4% mi. S. W. Somerset 










Surv. 385, J. J. Knott.. 


2,729 


2,290 


1,640- 


McCain Lease 1. W. 
2. Grayburg Oil 
Co 


' Survey 1,970, S. W. of 








Muennick Well 2. 
Grayburg Oil Co 


Somerset 

Atascosa County 


1,975 
1 903 


1,973 
1 Q03 


' 1,323 
1 953 


Richter 1, Galvan Oil 
Co 


'l 1 /^ mi. N. E., Pleasanton 










E. H.,, Timmons Surv., 
N. W. part 


350 \ 4 015 


\}Qt 










' reached 


3,665+ 



AN INITIAL FINE OF 25 CENTS 



OVERDUE. 



LD 21-100m-7,'3! 



Binder 
Gaylord Bros- ! 

St,ckton, Calif. 
T.M. Rea-U. S.Pat- Off 





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