Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Application of Geomechanics-Based Restoration in the Analysis of Growth Dynamics in Fold-Thrust Structures
(1) ETC-ESD, Chevron, Houston, TX.
(2) ETC-ESD, Chevron, Houston, TX.
Kinematic structural restoration has been the cornerstone of understanding the evolution of geologic structures through time. Integration of kinematic restorations with basin modeling has resulted in constraints on timing of migration and entrapment of hydrocarbons thereby increasing the confidence on pre-drill resource and risk estimates. Application of 2D geomechanics based restoration along with basin modeling can complement traditional techniques by providing knowledge of the dynamics (stress distribution) during structural growth through geologic history. Potential benefits of the technique include a spatial-temporal description of hydrocarbon trap evolution and associated reservoir or seal rock deformation.
Deepwater Niger Delta provides an excellent opportunity to study structural evolution of a variety of compressional structures. Availability of high quality seismic data helps in constraining the kinematics of structural growth. One such structural trend that evolved during middle to upper Miocene time in the western part of the deepwater basin (outer fold-thrust belt) has been investigated for this study. The structural framework is provided by depth converted 3D seismic data and comprises of folded and thrusted Paleocene through Recent clastic strata. The Miocene to Recent stratigraphic section is normally pressured (hydrostatic pore pressure).
Thrust faults present in the area sole to regional detachment within the over-pressured lower Tertiary section. Well data from the basin has been up-scaled to characterize the elastic geomechanical properties such as Young’s Modulus and Poisson’s Ratio as well as density and compaction coefficients required for the analysis. The current implementation of the restoration tool is elastic and does not include pore fluid pressure. Input pore pressure in the models has been extracted from basin modeling results at specific time intervals in order to loosely couple effective stress. Restoration and decompaction results from discrete time-steps spanning growth have been evaluated using a simple Mohr-Coulomb failure criterion along key spatial (e.g. crest, flank, near faults) and temporal points during the evolution of the structure. Results provide insight into the dynamics of structural growth. Geomechanics based restoration can aid trap integrity analysis through prediction of stability of existing faults or potential development of new faults after trap formation and hydrocarbon migration.