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Soil-gas Hydrocarbon Pattern Changes During a West Texas Waterflood

By
Gary K. Rice
Gary K. Rice
GeoFrontiers Corporation, Dallas, Texas, U.S.A.
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John Q. Belt, Jr.
John Q. Belt, Jr.
GeoFrontiers Corporation, Dallas, Texas, U.S.A.
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George E. Berg
George E. Berg
Talisman Resources, Argyle, Texas, U.S.A.
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Published:
January 01, 2002

Abstract

Soil-gas light-hydrocarbon (methane through n-butane) pattern changes were measured annually for five years over part of an oil field in Brown County, Texas, U.S.A. During the monitored period, additional wells were drilled, depleted, and subjected to a waterflood. Annual soil-gas measurements detected changes in light-hydrocarbon concentrations attributable to these field operations.

Soil-gas sample reproducibility was important for comparing annual data. Background concentration, which was the reference for all measurements, reproduced within 20% during the 5-year monitoring period.

An oil well drilled on the west side of the study area depleted within two years. During that time, near-surface soil-gas hydrocarbon concentrations also decreased. After depletion, this well became the waterflood injection well. Soil-gas hydrocarbon concentrations increased near the injection well within one year after the waterflood began. While the water-flood continued, soil-gas hydrocarbon concentrations increased again the following year.

Calculated hydrocarbon vertical migration rates were 0.6–2 m/day. This result can be explained by an effusion mechanism whereby gases escaped the petroleum reservoir and migrated vertically through the water table in a gaseous phase.

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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

GeoRef

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