INTRODUCTION

The Upper Gulf Coast of Texas includes the 29 counties and 3 offshore areas which comprise Texas Railroad Commission District 3 (Fig. 1). It covers an area of approximately 25,000 sq mi in the southeastern part of the state.

The objective zones range from the Cretaceous in the northwest to the Miocene in the southeast. The subsurface strata in the area dip gently southeast toward the Gulf of Mexico, and the producing trends generally parallel the coastline. The effect of shallow and deep-seated salt features is pronounced, and most of the major hydrocarbon accumulations are in traps associated with salt domes and salt-related anticlinal highs. Fault-related closures and stratigraphic traps account for the rest of the production in the area.

Cumulative oil production in District 3 has gone over the 5 billion bbl mark, and gas production is in excess of 15 Tcf.

DEVELOPMENT ACTIVITY

Development drilling in District 3 once again declined, as the 1970 total of 492 wells drilled was only 83% of the 1969 total. Successful completions also decreased slightly from 76% in 1969 to 73% in 1970. A sharp decrease in the development drilling program at Esperson dome accounted for much of the overall decline. Salt domes once again constituted the majority of the most active fields, but several non-salt dome fields appeared on the most active list for the first time (Table 1).

EXPLORATION ACTIVITY

Drilling:
The number of exploratory wells drilled in the Upper Gulf Coast of Texas dropped from 441 in 1969 to 400 in 1970 (Table 2). The increase in drilling in the Oligocene and Cretaceous trends was not enough to make up for the sharp declines in the Miocene and Eocene trends. The 11 most significant discoveries are listed in Table 3. The producing formations of discoveries and objectives of wildcat failures are listed in Tables 4 and 5, respectively.

Geophysics:
Seismic activity in 1970 dropped to 80% of the 1969 total, continuing

Table 1. Ten Most Actively Drilled Fields

Table 2. Drilling Summary, Texas Upper Gulf Coast, 1970

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Fig. 1. TEXAS UPPER GULF COAST

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the decreasing trend which was initiated in 1967. The greatest declines were in the Wilcox-Yegua and Frio-Miocene (onshore) trends. The Miocene (offshore) showed a pronounced increase, but the most significant increase by far was shown in the Jurassic-Cretaceous trend, where crew-week activity in 1970 more than doubled the 1969 total (Table 6).

Offshore leasing:
Three sales of state offshore tracts were held in 1970 (Table 7). This was the first time since 1966 that more than 2 state sales were held in one calendar year. A total of 112,674 acres was leased at an average cost of $40.21/acre. Once again the bidding at these sales was not highly competitive, with only 22 of the 103 offshore tracts purchased receiving more than 1 bid, and only 2 of these receiving as many as 3 bids. The major buyers were Mitchell and Mitchell with 23 tracts and Pan American with 16 tracts.

The last federal sale of offshore Texas acreage was held on May 21, 1968. It is rumored that the next federal sale will be conducted in late 1971 or early 1972.

MIOCENE

There was a decrease in the number of exploratory wells drilled in the Miocene from 146

Table 3. Important Discoveries, Texas Upper Gulf Coast, 1970

Table 4. Producing Formations of Discoveries, Texas Upper Gulf Coast, 1970

Table 5. Objectives of Wildcat Failures, Texas Upper Gulf Coast, 1970

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in 1969 to 112 in 1970. Most of the decrease was accounted for in the offshore Texas area, as drilling on both federal and state offshore tracts showed a fairly sharp drop.

Block 30-L field, High Island area:
The discovery for this field was the Cherryville No. 1 State Tract 30-L well, which was completed as a gas-condensate producer in a Siphonina (lower Miocene) sandstone. Two subsequent wells were completed in the same producing zone on this faulted anticlinal structure, which is 6 mi southwest of, and along trend with, the prolific Block 24-L field. Four dry holes were also drilled in the area before the year ended.

Block 14-L field, High Island area:
This field was discovered by the Superior No. 1 State Tract 14-L well, which was completed as a gas producer in the Miocene. Very little additional information was available on this well, which is approximately 12 mi south of Sabine Pass. Structure is probably a faulted anticlinal high. A dry hole, a little less than 1 mi southwest of the discovery, was also drilled in 1970.

North New Taiton field, Wharton County:
A significant shallow Miocene strike was made by Mustang Exploration Co., with the completion of their No. 1 Schoelman as a dual dry gas producer in lower Miocene sandstones. The field was developed quickly, with Mustang completing 2 additional dual producers, and Pan American also completing 2 dual producing wells. Because of the erratic nature of the pay sandstones, several dry holes were drilled as the field was being developed.

OLIGOCENE

The number of Oligocene exploratory wells drilled increased from 130 in 1969 to 142 in 1970. This was the second straight year for such an increase, and it was enough to make the Oligocene the most actively explored trend in 1970, a title the Eocene had held the previous 2 years. It also appears that the Oligocene accounted for most of the important discoveries in 1970.

Northwest Midfields field, Matagorda County:
The Pan American No. 1 Ladner, the discovery well for the field, was dually completed in 2 zones for a combined flow of 413 BOPD from the lower Frio. The structure at both levels of production has been interpreted as downthrown anticlinal closure which appears to shift southeastward with depth. Pan American has drilled a total of 7 producers and 2 dry holes in the field, with 4 lower Frio oil pay zones being developed on the structure. This new field is considered to be the most significant Frio strike along the coastal tier this year.

Buffalo Camp field, Brazoria County:
This field was discovered with the completion of the Mobil No. 1 Smith which produced a calculated open flow of 142,000 MCFGD from the middle Frio. Mobil subsequently completed an additional gas-condensate well and 1 oil well on this interpreted downthrown anticlinal closure, and was drilling a step-out well on the east at year end.

South Duncan Slough field, Matagorda County:
An apparent significant stratigraphic discovery was made by the completion of the Royal Resources No. 1 Steele in a lower Frio pay zone. This well had an absolute open flow of 15,500 MCFGD. Production appears to be trapped in off-structure sandstones in north-dipping beds with lateral closure upthrown to a major down-to-the-coast fault. By year end, 2 additional gas-condensate wells and 1 dry hole had been drilled.

Golden Triangle field, Jefferson County:
The Prudential No. 1 Pan American Fee, the

Table 6. Seismograph Activity, Texas Upper Gulf Coast, 1970

Table 7. 1970 Texas Lease Sales, State Tracts Offshore

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discovery well for the field, was drilled approximately 2 mi northeast of the prolific Port Acres field in Jefferson County. Production is from a Hackberry pay zone in the lower Frio section. Prudential subsequently drilled a dry hole 0.5 mi north of the discovery well.

EOCENE

Exploratory drilling in the Eocene registered a fairly sharp decline in 1970. There were only 128 exploratory wells drilled compared with 156 in 1969. The most important discoveries made in the Eocene in 1970 were outpost wells and deeper tests in existing fields. Production in this trend is usually from anticlinal closures downthrown to regional down-to-the-coast faults.

Bunker Hill field, Jasper County:
Completion of the White Shield No. 1 U. S. Plywood as an oil discovery renewed interest in the Bunker Hill field area. This well was drilled 1,030 ft northeast of the depleted oil discovery for the 1-well field which had been drilled in 1960. White Shield later completed another oil well and a dry hole, was waiting on potential on a gas-condensate well, and had announced location for 3 more wells in the field area as the year ended. All pay zones are in the Yegua section.

Dorsey field, Hardin County:
Another area of renewed activity was at Dorsey field in Hardin County. White Eagle initiated this activity with the completion of their No. 1 Sternenberg as a new Yegua oil pay for the field. At year end, a total of 4 oil wells, 1 gas-condensate well, and 2 dry holes had been completed, and 2 additional locations had been announced in the field area. Three of these wells had been drilled to the Wilcox, but no Wilcox production has been established.

Glasscock field, Colorado County:
The International Nuclear No. 1 Glasscock Ranch well was significant in that it established deeper gas-condensate production in the lower Wilcox section at Glasscock field. One more gas-distillate producer had been completed and an additional well was being drilled as the year ended.

CRETACEOUS

The Cretaceous was the objective of 18 exploratory wells drilled in 1970, 9 more than in 1969. Five of these wells were successful in establishing production. Deeper drilling is required in this trend, and 8 wells were drilled below 12,000 ft, with 2 of these penetrating deeper than 18,000 ft.

The increased drilling activity was accompanied by a very active lease play in the trend, as more than 500,000 acres were leased in late 1969 and in 1970. The most active companies in the Cretaceous trend in District 3 have been Gulf, Hunt, Pan American, Mobil, Shell, and Cities Service.

Pinckney field, Tyler County:
The Gulf No. 1 Carter/Camden Timber well, approximately 10 mi southwest of the town of Woodville, is significant in that it is the most downdip well in which Woodbine sandstone production has been established. Gulf drilled a second well 3/4 mi west of the discovery well to a depth of 18,122 ft, but it failed to establish commercial production.

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