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The AAPG/Datapages Combined Publications Database

Williston Basin Symposium

Abstract

MTGS-AAPG

Seventh International Williston Basin Symposium, July 23, 1995 (SP12)

Pages 41 - 46

Three-Dimensional Previous HitDepthNext Hit Imaging of Seismic Data to Help Delineate Petroleum Reservoirs in the Williston Basin

Alvin K. Benson, Department of Geology & Geophysics, Brigham Young University, Provo, Utah

ABSTRACT

Seismic reflection data can be imaged in Previous HitdepthNext Hit to form an accurate picture of the true geology of the earth in complex areas where the velocity changes abruptly, both vertically and laterally, such as some areas of the Williston Basin. A subsurface velocity model necessary to form an accurate image can be obtained from the data through self-consistent computer modeling. Where available, the modeling is controlled with nearby well data, and the imaging is done in 3-D.

A dome model is studied to illustrate (a) the complications produced by rapid lateral velocity changes, velocity pull-up, etc. and (b) the necessity of using a Previous HitdepthNext Hit Previous HitmigrationNext Hit process versus time Previous HitmigrationNext Hit plus conversion to Previous HitdepthNext Hit in complex geological areas. A case study from the Williston Basin is examined to help delineate a possible anticlinal prospect. Initially, stacking velocities were used to derive interval velocities for modeling, but this led to incorrect, contradictory geology. Subsequently, a well was drilled, and the sonic data helped produce a much improved Previous HitdepthNext Hit model for the Previous HitdepthNext Hit imaging process. A Previous Hit2-DNext Hit Previous HitdepthNext Hit imaged section leaves unexplained, crossing events due to seismic energy coming from out-of-the plane. Consequently, a two-pass, 3-D Previous HitdepthNext Hit image was produced, which provides the "best" Previous HitdepthNext Hit image, and the final interpretation is much closer to reality. Three-D Previous HitdepthTop imaging is essential for clarifying structure beneath complex overburden to help delineate and assess subsurface petroleum traps.

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