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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
Abstract
DOI:10.1306/10241111030
Production
-induced
fault
compartmentalization at Elk Hills field, California




Alan P. Morris,1 Kevin J. Smart,2 David A. Ferrill,3 Nathaniel E. Reish,4 Peter F. Cowell5
1Department of Earth, Material, and Planetary Sciences, Geosciences and Engineering Division, Southwest Research Institute, 6220 Culebra Road, San Antonio, Texas; amorris@swri.org
2Department of Earth, Material, and Planetary Sciences, Geosciences and Engineering Division, Southwest Research Institute, 6220 Culebra Road, San Antonio, Texas; ksmart@swri.org
3Department of Earth, Material, and Planetary Sciences, Geosciences and Engineering Division, Southwest Research Institute, 6220 Culebra Road, San Antonio, Texas; dferrill@swri.org
4Occidental of Elk Hills, Occidental Petroleum Corporation, 10800 Stockdale Highway, Bakersfield, California; nathaniel_reish@oxy.com
5Occidental of Elk Hills, Occidental Petroleum Corporation, 10800 Stockdale Highway, Bakersfield, California; peter_cowell@oxy.com
ABSTRACT
Mature and aging clastic-dominated hydrocarbon fields commonly become increasingly difficult to produce, causing lower economic return than initially forecast. A major cause of this reduced economic viability is compartmentalization, defined as limitation on the ability to produce hydrocarbons resulting from permeability barriers within a field. Three primary causes of compartmentalization are structural variations in permeability, stratigraphic variations in permeability, and permeability reduction resulting from compaction adjacent to producing wellbores. Recognition and delineation of compartmentalization permit formulation of development and depletion plans to maximize recovery and economic value. Here, we examine one of 52 reservoir-scale faults that compartmentalize the eastern shallow oil zone (ESOZ), Elk Hills field, California. Using well-log, stratigraphic, structural, and pressure data, we apply standard fault
seal
analyses to the selected
fault
. Results are compared with known pressure conditions across the
fault
and show the
fault
capable of supporting pressure differentials two to three times those expected from standard static
fault
seal
measures. Although this observation could be used as a basis for local calibration of standard
fault
seal
measures for a dynamic
seal
, such an approach assumes that these
fault
seal
mechanisms are in fact the cause of sealing behavior. Alternatively, one of the most significant changes in ESOZ reservoir conditions over the
production
lifetime of the field is the reduction of fluid pressure from approximately 1500 to approximately 200 psi (from
10.27 to
1.37 MPa). Decreasing fluid pressure would have driven stress states acting on faults in the reservoir from critical (near or at slip) to stable (nonslipping) conditions. Critically stressed faults and fractures are more transmissive than those that are noncritically stressed. We propose that decreasing fluid pressure can cause faults to become less leaky, causing
production
-induced reservoir compartmentalization.
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