DEFORMATION OF SEDIMENTS AT SALT FLANKS AND OVERHANGS: A NUMERICAL MODELING APPROACH

The development of highly strained regions or locally upturned strata adjacent the flanks of salt diapirs and overhangs have gained focus due to their trap potential for large hydrocarbon columns. However, analog or physical models have proven to be limited due to scaling challenges in reproducing these deformed zones. Numerical simulations have been successfully used to simulate the development of such structures, yet the quantification of the state of stress/strain of these zones has not been understood in significant detail. This knowledge is vital to mitigating drilling hazards associated with such sections, the implications of fractures and fault initiation or deformation bands which could compromise sealing capability and permeability damage or enhancement of hydrocarbon reservoirs.

This study uses a two-dimensional visco-elastic finite element modeling approach to quantify the nature of salt movement relative to the state of deformation in the adjacent sediments. The analysis couples pore pressure and temperature effects as critical input parameters to predicting representative in-situ stress fields. The study also investigates the influence of heterogeneous material properties (i.e. layers of alternating competence, Poisson’s ratio, and layer thickness) in sediment packages on the resulting stress state and their effects on deformation patterns.

Stresses observed in modelling results indicate an increased likelihood for extension fractures to form at high angles in upturned sediments and a decreased likelihood of fracture occurrence away from flanks of the salt body.