Contract C211368 „ARA STRINGER PLAY STUDIES“

PROJECT A: Understanding Stringer Deformation and movement of Ara Stringers enclosed in Ara Salt

Picture_209 - Shiyuan Seimic Ara Stringer

Large rock inclusions are embedded in many salt bodies and these respond to the movements of the salt in a variety of

ways, including displacement, folding and fracturing. One mode of salt tectonics is downbuilding, whereby the top of a

developing diapir remains in the same vertical position, while the surrounding overburden sediments subside. We

investigate how the differential displacement of the top salt surface caused by downbuilding induces ductile salt flow and

the associated deformation of brittle stringers, by an iterative procedure to detect and simulate conditions for the onset of

localization of deformation in a finite element model, in combination with adaptive remeshing. The model setup is

constrained by observations from the South Oman Salt Basin, where large carbonate bodies encased in salt form

substantial hydrocarbon plays.

 

The aim of this study is to estalish numericial models and reach the results of a study aimed at contributing to our

understanding of brittle stringer dynamics during downbuilding. We use the finite element method (FEM) to model the

deformation and breaking of brittle layers embedded in ductile, deforming salt bodies.

 

 

Picture_230 - Shiyuan Ara generic model

Picture_231 - Shiyuan Ara generic model evolution model

Picture_744 - Shiyuan Ara generic model principal stress
Picture_750 - Shiyuan Ara generic model principal stress zoom1

Picture_752 - Shiyuan Ara generic model principal stress zoom3
 

Picture_746 - Shiyuan Ara generic model Smin Picture_747 - Shiyuan Ara generic model Smin zoom1

 
 

We presented first results of a study of the dynamics of brittle inclusions in salt during downbuilding. Although the model

is simplified, it offers a practical method to explore complex stringer motion and deformation, including brittle fracturing

and disruption. Under the conservative conditions modelled here, stringers are broken by tensile fractures and

boudinaged very early in downbuilding (~ 50 m top-salt minibasin subsidence) in areas where horizontal salt extension

dominates. Ongoing boudinage is caused by reorganization of the salt flow around the stringers. Rotation and bending of

the stringers is caused by vertical components of the salt flow. Flow stresses in salt calculated in the numerical model are

consistent with those from grain size data. The model can easily be adapted to model more complex geometries and

displacement histories.