ENSERCH PRESSES E. TEXAS DRILLING

A.D. Koen Gulf Coast New Editor The exploration and production unit of Enserch Corp., Dallas, is stepping up the pace of development of six gas/condensate fields it operates in East Texas. The accelerated program is part of a sweeping plan Enserch disclosed earlier this year to help the company better serve U.S. gas markets while strengthening its balance sheet and providing a better rate of return on core assets.

April 12, 1993

6 min read

A.D. Koen
Gulf Coast New Editor

The exploration and production unit of Enserch Corp., Dallas, is stepping up the pace of development of six gas/condensate fields it operates in East Texas.

The accelerated program is part of a sweeping plan Enserch disclosed earlier this year to help the company better serve U.S. gas markets while strengthening its balance sheet and providing a better rate of return on core assets.

If all goes as planned in East Texas, Enserch by yearend 1993 will have spent about $37-38 million to drill 34 infill wells and work over another 40 wells in Opelika, Tri-Cities, Whelan, Willow Springs, Freestone, and North Lansing fields. Average Enserch interests in its portions of the fields are 50-100%.

Enserch also plans further spending to expand and reconfigure its East Texas gathering infrastructure. The company's E&P unit has budgeted $112 million for exploration and development during fiscal 1993.

THE RESOURCE

As of Jan. 1, 1993, East Texas fields marked for accelerated development held combined proved and probable reserves net to Enserch of more than 825 bcf of gas and nearly 10.5 million bbl of condensate, as estimated by DeGolyer & MacNaughton, Dallas. Enserch estimated gross cumulative production from company operated wells at more than 1.8 tcf of gas and more than 40 million bbl of oil and condensate.

Pay zones in each of the fields include more than one of the following: lower Cretaceous Travis Peak, Pettet, James, Rodessa, Bacon, and Bossier and Jurassic Cotton Valley.

Some wells on Enserch's East Texas acreage have been producing for more than 40 years, significantly altering reservoir parameters. The company continues analyzing data from many of the area's 700 wells to adapt production strategies to fit the new realities.

All wells drilled this year in Opelika, Willow Springs, and Freestone fields will test the Travis Peak. Early drilling results show Enserch can expect each new East Texas well to produce 700 Mcfd to 1.5 MMcfd.

Gary Junco, president and chief operating officer of Enserch exploration and production, said Opelika field, with more than 250 active wells, is the company's premier Travis Peak producer and accounts for 80% of Enserch's Travis Peak reserves.

With several hundred undrilled locations pinpointed on its East Texas acreage-and depending on results of work there this year-Enserch could maintain a high level of development operations through the end of the century, junco said.

STATUS OF ACTIVITY

After being slowed by rains earlier this year, Enserch's development activity in East Texas was well under way by mid-March.

The company this year is focusing on Travis Peak pay at depths of 9,00011,000 ft in Opelika field, where it owns 100% interest in all active wells. Existing Opelika wells produce from shallower Odessa and Pettet and from deeper Cotton Valley reservoirs at depths of 7,700-12,000 ft.

At the beginning of 1993, Enserch had five drilling rigs at work in Opelika field. By mid-March that number had increased to nine. The company also was drilling one well in Willow Springs and one in Freestone and had about a half dozen workovers under way.

Most of Enserch's 1993 E&P spending in East Texas will be in Opelika field, where about 24 wells are planned to average depths of about 10,000 ft. No workovers are planned in Opelika. Enserch expects to spend $3.5-5 million drilling wells outside Opelika field and another $13.5 million for workovers.

Although Enserch might slightly increase its proved reserves with accelerated infill drilling in East Texas, junco said that is not the program's intent. Rather, the company is emphasizing completing wells at low costs with refined techniques to enhance present value and rate of return.

Enserch estimates its East Texas leases have a combined reserve life of about 17-20 years.

"Present value starts dropping off quite a bit by the end of that time, so we're implementing a program to economically bring those reserves forward," Junco said.

With multiple transportation alternatives for gas out of all its East Texas fields except Opelika, accelerated development should allow Enserch adequate marketing flexibility to offer potential customers reliable long term supplies.

Gas leaving Opelika is captive to a pipeline owned by Lone Star Gas Co., Dallas, Enserch's gas utility division. With the exception of gas fueling a Sweetwater, Tex., cogeneration plant, Enserch is selling most Opelika gas through 30 day spot market contracts or longer term agreements to industrial customers.

ENSERCH EXPERIENCE

Enserch's experience in East Texas is the key to positive results with accelerated development.

Because Enserch owns 100% interests in most wells in the fields, it hasn't shared much data with other companies. That proprietary well data gives it an edge in the area, said Barry Irani, Enserch E&P's vice-president of production and engineering.

For example, the Travis Peak-and Cotton Valley are present in all of Enserch's six major East Texas fields. Irani said Travis Peak's thickness varies from 1,500 to 1,700 ft and Cotton Valley's from 1,000 to 1,600 ft. Both consist of several hundred interbedded layers of sand and shale. Thus, there are literally hundreds of isolated sand reservoirs stacked atop one another in various depositional settings, each with varying thickness, areal extent, porosity, permeability, and fluid content.

In addition, more than 40 years of development and production have depleted sands to differing degrees and altered reservoir characteristics. Although some sands in some fields have been depleted, no wells in Opelika field, the oldest, most prolific of the six fields, have been plugged.

Based on good results, in the late 1970s from massive hydraulic fracturing in five of the fields and on results of 121 workovers and 195 wells drilled during 1979-90, Enserch concluded the level of gas production from company operated East Texas fields is a function of the number of workovers, recompletions, and new wells undertaken.

Irani said, "Based on the data we have obtained, the trick is not only to effectively treat each sand, but also to allow them to produce at maximum efficient rates without hindering each other when they are comingled."

Differing vintages and producing pressures of the company's East Texas wells raise problems with infrastructure design. Tying new wells into older gathering systems changes surface facility requirements, so Enserch must add compression, lay new gathering lines, or otherwise modify existing infrastructure.

While Travis Peak and the other East Texas formations each have similar reservoir characteristics, they behave differently in different fields and must be handled differently. But by developing the reservoirs in a methodical, cautious manner, Enserch continues learning how to tailor applications that work well in one field to fit conditions found in others, Irani said.