Lopeno Field (Zapata County, Texas) and Bob West Field (Starr and Zapata Counties, Texas) are both large Upper Wilcox gas fields in South Texas. Lopeno and Bob West Fields produce from the same "Lopeno" sand sequence and may ultimately produce over 200 BCF and 1 TCF respectively.

Located six miles apart, the two fields are essentially just syncline separated, but still display significant geological differences related to post-depositional movement. Both fields produce primarily from highside closures against down-to-the-coast faults. Lopeno Field produces from 18 Lopeno sands, and Bob West from 29.

Although Lopeno Field (1952) and Bob West Field (1990) were discovered 38 years apart, the two fields are historically linked together. Lopeno Field, which has undergone five major phases of development, was the model which Tesoro Exploration and Production Company used to discover Bob West Field. In the mid-1980's. Gulf Energy Producing Company initiated a drilling program based on a new structural and stratigraphic interpretation that was highly successful. Sixteen wells were drilled, of which 15 were completed. Gas production increased from a low of less than 1,000 MCFGPD to a peak of nearly 60,000 MCFGPD. The field, which had produced about 40 BCF, has now produced over 12 1 BCF from Upper Wilcox sands.

Of more importance was the discovery of 22 new Upper Wilcox sands and an understanding of two distinct ages of Upper Wilcox faulting 45 degrees opposed to each other. Twelve new field pays have been produced since this latest drilling was initiated, and the primary production has shifted from the L-12 sand level to the deeper L-18 through L-21 sand horizons.

Tesoro Exploration and Production Company used this new information to develop Condado Prospect, which became Bob West Field. At Falcon Field, marginal production in the L 12 Sand had been discovered by Jake Hamon in 1962. Aware of the new substantial production at Lopeno Field in the L- 18 through L 2 1 sands, Tesoro and Coastal drilled Condado Prospect believing it had the potential to be a 50 to 100 BCF discovery.

At Bob West Field, 12 sands below Lopeno Field's deepest production (L-28) have been found productive, and several engineering improvements for the Upper Wilcox Trend in Railroad Commission District 4 were achieved. The first deviated wells had a substantial horizontal displacement and were drilled for geological reasons in the Upper Wilcox, resulting in multiple pays (e.g., 14 in the D-3 Guerra Well) and were operated by Tesoro. Commingling authority was granted at Bob West Field in 1991 making it and the Loma Vieja Field, the first two commingled fields in a 2500 square mile area of the Upper Wilcox. Finally, fracture stimulations were typically two to three times greater than those previously used at Lopeno Field. The result was high rate wells (often over 10,000 MCFGPD), usually producing from four or more commingled sands rather than the traditional single or dual completions.

In 1995 Mustang Oil & Gas, a subsidiary of San Antonio-based Gulf Resources Corporation, initiated an aggressive drilling program in the Lopeno Field utilizing new knowledge and technological advances learned at Bob West Field. Locations were selected using the interpretation of a new 3-D seismic survey (shot jointly with POGO Producing Company and Parker and Parsley) with great results. Four successful wells were drilled, proving over 35 BCF additional reserves. Four new field pays were discovered, and the first deviated well (12 pays) was drilled. Commingling in the field was established for the first time in new wells with virgin pressures, and the #1 and #2 Palmyra wells are the highest rate producers in the field's history. A fifth well is currently being drilled by Mustang to explore for the deeper pays known at Bob West Field. Several additional wells by both Mustang and Parker and Parsley are planned for 1996.

Whereas Lopeno Field was the geological model for the discovery of Bob West Field, the advances at Bob West Field are now being applied back to Lopeno Field, rejuvenating it one more time, 44 years after the initial discovery.

End_of_Record - Last_Page 12---------------