AAPG Annual Convention and Exhibition

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The Development and Applications of Elliptical Fault Flow: A New Kinematic Algorithm to Model and Restore Isolated Normal Faults


Kinematic algorithms for fault-related deformation (e.g. Simple Shear and Trishear), use geometric rules to predict the movement of material around fault systems. These algorithms form an integral part of geometric, palinspastic and sequential restoration workflows; techniques which are commonly applied in the oil and gas industry to assess the validity of interpretations and investigate the structural development of hydrocarbon resources. Here, a new kinematic algorithm is introduced, Elliptical Fault Flow, which allows modelling and restoration of isolated normal faults. Isolated normal faults typically accommodate relatively minor dip-slip displacements, and critically, exhibit a reduction in slip in all directions from a point of maximum offset. Within reservoir units, isolated normal faults can influence hydrocarbon migration and often form principal hydrocarbon traps. Despite the importance of these structures, most existing kinematic algorithms cannot model and restore the fault-related deformation associated with the variation in displacement along isolated normal faults. Elliptical Fault Flow models the deformation associated with isolated normal faulting by constructing a series of nested ellipses around the point of maximum displacement on the fault plane. These ellipses define the decrease in modelled displacement away from the fault, which often leads to hanging wall and footwall drag. The areal extent and orientation of the ellipses are controlled by the cross-sectional shape and length of the fault, as well as the ratio between the long and short axis of the ellipse. In the case of non-planar faults, the ellipses are distorted to mirror down-dip variations in fault shape. Additional parameters can be used to control the ratio of hanging wall to footwall displacements and the direction of movement on either side of the fault. In this presentation, the methodology and applications of Elliptical Fault Flow are detailed using a series of synthetic models. These synthetic models will explain how Elliptical Fault Flow compares to existing kinematic techniques, as well as demonstrating the benefits of using the new algorithm in restoration workflows. Elliptical Fault Flow will then be used to restore isolated normal faults interpreted from seismic reflection data in the Keathley Canyon and Walker Ridge areas in the Gulf of Mexico; these examples were selected to illustrate the real-world applications of the new algorithm.