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Integrated Microbial and 3-D Seismic Surveys Discover Park Springs (Conglomerate) Field and Track Microseepage Reduction

By
Daniel C. Hitzman
Daniel C. Hitzman
Geo-Microbial Technologies, Inc. Ochelata, Oklahoma, U.S.A.
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Brooks A. Rountree
Brooks A. Rountree
Geo-Microbial Technologies, Inc. Ochelata, Oklahoma, U.S.A.
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James D. Tucker
James D. Tucker
Geo-Microbial Technologies, Inc. Ochelata, Oklahoma, U.S.A.
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Sam Smith
Sam Smith
Consulting Geologist Wichita Falls, Texas, U.S.A.
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Published:
January 01, 2002

Abstract

The integration of microbial hydrocarbon microseepage signatures and 3-D seismic data directed explorationists to a new play concept and resulted in discovery of the Park Springs (Conglomerate) field in Montague County, Texas. A standard 3-D geophysical

survey identified a prospective Ellenburger structure at a depth of approximately 2200 m (7200 ft) in the northern portion of the 5.6-km2 (3.5-mi2) survey area. A reconnaissance hydrocarbon microseepage survey of the area was conducted in December 1995, using the Microbial Oil Survey Technique (MOST). The Ellenburger structure was detected by a positive, but small, hydrocarbon microseepage signature. A much stronger and larger microbial anomaly was found above a structural trough, located 1 mi (1.6 km) south.

In February 1996, additional MOST samples were collected over the area of interest. The new survey confirmed the small hydrocarbon anomaly associated with the seismic prospect, as well as the large anomaly associated with the structural trough a mile south. A review of geologic play analogs for northern Texas suggested that the trough might contain Atokan conglomerates—a risky exploration target in the Fort Worth Basin—but the primary prospect remained the Ellenburger structure and its associated smaller microseepage anomaly.

The seismic prospect was drilled at the crest of the structure in March 1996. The Silver #1 well encountered 1.8 m (6 ft) of tight Salona sand in the Ellenburger section. Completion efforts recovered only marginal hydrocarbons: Approximately 340 barrels (bbl) of oil have been produced in three years. The operators intensified their investigation of a possible conglomerate reservoir. In October 1996, the J. G. Stone Sutherland Unit #1 well was drilled within the geochemical anomaly coincident with the trough; it encountered two separate conglomerate zones, each with 3 m (10 ft) of pay. Initial production in the lower zone was 500 thousand cubic feet of gas per day (mcf gas/day) and 5 bbl of oil/day (BOPD). The next well found three charged conglomerate zones, including 6.7 m (22 ft) of pay in the lower zone, and initial production near 1000 mcf gas/day. In all, 14 producing wells have been drilled in or near the conglomerate trough. In addition, four dry holes have been drilled in the trough feature, but they were located in areas outside the microbial microseepage anomalies.

In October 1997, the microbial survey was repeated in order to document changes in the microseepage signature, over time, in the new field discovery. In general, areas with background microbial values remained stable after one year’s production, while the two producing areas experienced as much as a 50% decrease in their microseepage signature. This phenomenon of apparently reduced hydrocarbon microseepage over producing fields is thought to have been caused by a decline in reservoir pressure, as well as by changes in the drive mechanism controlling microseepage.

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Contents

AAPG Studies in Geology

Surface Exploration Case Histories: Applications of Geoschemistry, Magnetics, and Remote Sensing

Dietmar Schumacher
Dietmar Schumacher
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Leonard A. LeSchack
Leonard A. LeSchack
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American Association of Petroleum Geologists
Volume
48
ISBN electronic:
9781629810591
Publication date:
January 01, 2002

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