LOCALIZATION OF CONCENTRIC RING FAULTS IN SEDIMENTS OVERLYING EVAPORITE SEQUENCES DURING ACTIVE SALT DIAPIR EMPLACEMENT: INSIGHTS FROM NUMERICAL MODELING

The deposition and flow of thick layered evaporite sequences (LES) with time has resulted in the localization of complex families of faults in the overlying sediments which are critical in evaluating pathways for fluid migration and traps. These include the development and distribution of concentric ring faults that could compartmentalize hydrocarbon reservoirs and either breach seals or promote the migration of fluids through reservoirs and seal units. However, understanding the dynamics forming these faults and the controls of locally induced stresses during active salt diapir emplacement remains unclear due to rare surface exposures for paleostress analysis, difficulty imaging faults obscured by gas clouds from leakages of hydrocarbon reservoirs using 3D seismic data, limitations of 2D physical modeling techniques to define 3D fault patterns and material scaling challenges.

To better understand the kinematics and dynamics of these faults around salt stocks, a forward numerical modeling approach based on 3D finite element analysis is utilized. The modeling approach uses a Lagrangian framework for accurate description of material interfaces to simulate the emplacement of a salt stock triggered by upbuilding or gravitational loading. The LES are modeled as visco-elastic and overlying sedimentary overburden as elasto-plastic rheologies respectively.

The numerical results suggest concentric ring faults develop at the crest of the diapir as a location of maximum flexure in the overburden and propagate downward with new faults created farther outward due to salt withdrawal to higher structural levels as the diapir stem constricts. Understanding the dynamics and how these faults interact in the cover sequences above salt structures could provide vertical pathways for migrating fluids which could breach seals or used as an effective exploration tool for hydrocarbon traps adjacent to these migration pathways