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Stratigraphic uncertainty in field development studies

a conceptual modeling approach

Chevron Petroleum Technology Company, San Ramon, California, U.S.

Corresponding author: DKLA@chevron.com

Editor's Note: The Geologic Column, which appears monthly in TLE, is (1) produced cooperatively by the SEG Interpretation Committee and the AAPG Geophysical Integration Committee and (2) coordinated by R. Randy Ray and Lee Lawyer.

The first 20% of the full text of this article appears below.

An irony of contemporary petroleum exploration and development is that, although technological advances have been significant, risk has not been reduced in all cases. In fact, risk may actually be greater in some environments—given costs associated with deepwater platform design and subsalt reservoirs. With risk remaining significant or perhaps even growing, the definition and understanding of uncertainty is a major challenge.

	A simple classification of uncertainty

 
Geologic uncertainty about reservoirs can be divided into volumetric and recovery uncertainty.

Volumetric uncertainty, that associated with defining oil originally in place, includes uncertainty about the top and bottom of the reservoir and its width (if it is not sheet-like), effective pore volume, irreducible water saturation, and position (and tilt?) of the fluid contacts. Significant advances have been made using seismic stratigraphic and seismic attributes to more accurately interpret the original oil in place (Prasad, 1998; Hart, 1999). Volumetric risk is a key aspect in defining if a project is considered economic and also impacts recovery uncertainty.

Recovery uncertainty is more complicated, because it requires an understanding of both the reservoir's static architecture and dynamic behavior during production. Recovery depends on structural, stratigraphic, and permeability architecture, fluid and engineering properties, drive mechanism, and spacing/orientation of producing and injecting wells. Stratigraphic and permeability architecture are difficult to know precisely, and this uncertainty can lead to differences in estimates of cumulative recovery. A key static aspect of stratigraphic and permeability architecture which influences dynamic performance is the connectivity of the reservoir. Based on percolation theory, in reservoirs with greater than 20–30% oil-saturated sandstone and assuming random placement of sandstone bodies in a mudstone matrix, reservoir connectivity is greater than 95% (King, 1990; Korvin, 1992).

Because of the implications of recovery uncertainty on risk management, we studied how stratigraphic and permeability architecture impact recovery. Our focus is fields and prospects in which . . . [Full Text of this Article]

This article has been cited by other articles:

				J. M. Hovadik and D. K. Larue Static characterizations of reservoirs: refining the concepts of connectivity and continuity Petroleum Geoscience, August 1, 2007; 13(3): 195 - 211. [Abstract] [Full Text] [PDF]