--> Patterns of Up-Salt Faults: A Geomechanical Indication for Petroleum Exploration

AAPG ACE 2018

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Patterns of Up-Salt Faults: A Geomechanical Indication for Petroleum Exploration

Abstract

Up-salt fault structure is common and of great importance for petroleum exploration and production, because faults not only facilitate hydrocarbon migration, but also compartmentalize and seal the reservoirs. Some qualitative patterns and shapes of up-salt faults have been concluded from much observation, but the quantitative description still remains unclear, leaving great uncertainty in up-salt faults characterization and prediction.

Based on various salt morphologies, the correspondingly produced upwelling force stat in up-salt zones, and rock failure theory (Parabolic Mohr Failure Envelope Theory), three quantitative fault patterns are numerically concluded in this paper. (1) Constant upwelling force fault pattern, where the salt may be giant and its morphology is flat enough to produce constant upwelling force. All faults share the same shape and vertical distribution, being listric with the biggest dip to be 45°. They may intercut and combine with each other. (2) Linear upwelling force fault pattern, where the morphology of salt linearly heightens to one direction, so the produced upwelling force is also linearly distributed. All faults share the same shape, similar to that of constant upwelling force fault pattern, yet the vertical distribution of faults deepens as the force weakens. (3) Parabola upwelling force fault pattern, where the salt may be small or the studied area locates in the edge of big salt structure, so the amplitude of upwelling force similarly follows a certain shape of parabola. In this pattern, the shape of fault steepens from sides to the middle of that parabola, while the vertical distribution deepens from middle to sides. Combination of faults is flowerlike.

Many seismic profiles have validated these up-salt fault patterns. In this study, constant and parabola upwelling force fault patterns are applied in an up-salt case in Bohai Basin of China, for analysis of hydrocarbon migration and accumulation. High production rate of newly drilled wells validate the applied fault patterns. These up-salt fault patterns reveals the quantitative geomechanical relationship between salts and the above faults, and are of great potential to be widely used in similar up-salt cases to enhance exploration successes.