Numerical modeling on deformation of viscous stringers in deforming salt bodies under a compressive environment—a case study from the South Oman Salt Basin

Abstract

Salt deposits are extremely potent seals for hydrocarbon reservoirs present in the sedimentary basins worldwide. Large rock inclusions (stringers) encased within various salt bodies may adopt diverse modes of deformation and displacement. Analyzing the movement and segmentation of these elastic and viscous stringers provides a comprehensive understanding of the intricate internal deformation mechanisms in the associated salt diapirs. The difference in viscosity between the stringers and the surrounding salt deposit yields a massive impact on the internal complexity of the salt structures. An analytical finite element model was built in combination with an adaptive remeshing process in this study, to achieve a suitable downbuilding simulation. The standard model setup is regulated with observations from South Oman Salt Basin. In this paper, the evaluation of parameter sensitivity concerning the dynamics of viscous stringers in salt diapirs was carried out, especially the sensitivity study pertaining to varied salt and stringer viscosities, which contribute to the distinct pattern of the internal structure in salt diapirs. The results of the study establish that viscous stringers exhibit characteristic extension and folding. When the viscosity contrast between the salt and the stringer is 1000:1, strong folding of stringers dominates the internal structure of the salt diapirs, and when the viscosity contrast between the two is 10:1, only small-scale minor folding of the stringers takes place. This variation in the viscosity contrast causes disparate internal stress distribution of the stringers. In addition, the location of the stringers and the thickness of salt deposit between the stringers as well as between the stringers and the base also govern the deformation pattern of the internal structure of the salt domes.