Lewis, Helen1, James A Guest1, Lisa Hammond2, Stephen A
(1) Heriot Watt University, Edinburgh, United Kingdom
(2) Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, United Kingdom
ABSTRACT: Kinematics to Geomechanics - an Exercise in Predicting Reservoir Deformation and Flow
This Exercise starts with a seismically-derived geometric interpretation of the present-day geometry of a faulted and fractured major UK Continental Shelf reservoir, derives a fault and fault block restoration sequence (kinematics) and uses this movement sequence as the displacement loading for a geomechanical model. The resultant deformation is translated into enhanced and degraded permeability and appropriate simulations are produced and assessed.
The X Field is a thick Devonian to Mississippian clastic reservoir lying unconformably on Precambrian basement and overlain unconformable by Cretaceous shales. Structural interpretations indicate a mixed fold-fault deformation style in a generally extensional environment and core and performance strongly indicate significant open fracturing. Extensive recent and heritage seismic surveys, which permit a seismic anisotropy study are available.
The geometric and restoration elements are done in the normal manner using conventional high-end software. However the restored geometries and movement history derived from the kinematic analysis are used in a less conventional manner – to provide the sequential shape, and displacement input for sequential geomechanical simulations. The material properties (here strength) for the reservoir, basement and caprock are taken from core and log information and an elastic-plastic localising material represents the reservoir interval. The resulting plastic (permanent) strain zones are interpreted, with the stress and strain magnitude and directions, to identify dilatant and compactant zones. Permeability values are increased or decreased (wrt a base value) according to simple rules and the dilatant and compactant zones are introduced into a series of fluid flow simulations.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.