--> Abstract: The Use and Abuse of Geophysics in Oil and Gas Resource Estimation, Scott L. Neal, #90098 (2009)

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THE USE AND ABUSE OF GEOPHYSICS IN OIL AND GAS RESOURCE ESTIMATION

 

Scott L. Neal, Chevron

Improvements in seismic  technology have been one of the major technical advances in the industry over the last several decades.  Progress has been rapid and multi-faceted, with significant improvements in acquisition, processing, and interpretation.  These developments have provided increasingly robust images of the subsurface that have proven valuable in enabling enhanced reservoir definition relative to historical well control methods.  In recognition of these advances and the widespread use of seismic data in reservoir description, 2009 SEC regulations permit the use of seismic as a “new technology” that is acceptable in providing support for the determination of proven reserves.  While the use of seismic data can influence many factors in a reserves evaluation, we may categorize the myriad impacts of seismic data in terms of its role in each of the following areas: (1) mapping of the geologic structure, (2) mapping of the reservoir extent, (3) determination of reservoir thickness, (4) determination of fluid contacts, and (5) evaluation of reservoir net to gross.  When viewed in the context of these five factors, the potential impact of adding seismic data to the list of SEC recognized technologies may be substantial.  However, when viewed critically, and in light of a “reasonable certainty” standard, even modern seismic datasets can suffer from common limitations that degrade the quality of the data and can introduce considerable uncertainties in reservoir interpretation.  Factors such as limited resolution (resulting from insufficient frequency content or narrow bandwidth), complex imaging problems (e.g., sub-salt, fault shadows, gas clouds, etc.), and heavy reliance on intrinsically non-unique and model-driven processing techniques (e.g., tomography, pre-stack depth migration) can each act to distort our image of the subsurface and result in substantive uncertainties in reservoir description.  Overcoming these constraints is likely to involve a mix of both technology and the use of a standardized corporate process with the objective of maintaining a consistent vision toward the application of seismic data in resource and reserve estimation.

 

AAPG Search and Discovery Article #90098©2009 AAPG Education Department, Houston, Texas 9-11 September 2009

 

 

 

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