Print this pageWHITEFIELD, CHRIS1, FAISAL JAFFRI1, PAUL GRIFFITHS2, and SERENA JONES2
1Midland
Valley Services, Inc., Boerne, TX
2Midland
Valley Exploration Ltd., Glasgow, UK
Abstract: 3D Computer Modeling and Restoration of Gulf of Mexico-Type Allochthonous Salt Structures
Exploration in the Gulf of Mexico has provided an opportunity to gain better understanding of the complexities of salt structures. Technical advancements in 3D seismic acquisition and computer visualization/modeling software are key elements helping to unravel salt-related problems. This paper presents methodologies developed for restoring allochthonous salt structures, using 3D computer modeling software, enabling the explorationist to address issues of salt volume change, timing of salt withdrawal basins, and hydrocarbon migration.
The premise of this restoration technique is to reallocate salt volume to inflate salt welds and restore withdrawal basins. Salt is translated on the weld surface using fault-parallel-flow, and the supra-salt sediments are adjusted to the new salt position by simple shear. Starting with the present-day geometry, the salt volume is positioned vertically below the youngest withdrawal basin. Vertical shear is applied to restore the supra-salt sediments to the new top salt position. Continuing this procedure for older horizons will model the salt migration through time. This computer restoration technique identifies and quantifies salt volume change, when the modeled salt volume is insufficient to restore the withdrawal basin to datum. Other geologic processes, such as sediment compaction and faulting, can impact the restoration, and their effects can be incorporated into the modeling.
The topology of the supra-salt sediments can be used to analyze hydrocarbon migration pathways and culmination points. Examining key horizons at various restoration stages permits the user to identify fundamental changes in the location of hydrocarbon charge zones caused by salt withdrawal, possibly affecting the amount of captured reserves.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas