Available PhD project

Sedimentologic heterogeneities and diagenesis of anhydrite seals 

This project is an integral part of the Qatar Carbonates and Carbon Storage Research Centre (QCCSRC), and is financed by Qatar Petroleum, Shell, and the Qatar Science and Technology Park.  

Anhydrite layers in the subsurface constitute ideal seals for hydrocarbons thanks to their low permeability. However, during carbonate storage operations the nature of the fluid present in the pore network will change, and the effectiveness of the seal must be investigated in order to operate in safe conditions. In particular, sub-seismic scale heterogeneities (e.g. carbonate "stringers") present in the anhydrite layers may play a major role in allowing fluid escape during CCS operations.

The aim of this PhD project is to provide a better understanding of the sedimentology and spatial heterogeneity of anhydrite cap rocks, a key information addressing some significant questions concerning seal integrity.

 

The main research questions are:

  • Are geobodies with changing sedimentologic and diagenetic trends laterally and vertically present in anhydrite seals (e.g. dolomite stringers observed in subsurface Qatar)? 
  • What are their lateral dimensions, and implications for seal integrity? 
  • What is the detailed sequence stratigraphic history of the anhydrite, how does it impact on its heterogeneities? 
  • What does it imply in terms of petrophysical property changes, and cap rock integrity for CCS? 

Fieldwork will involve mapping the lateral continuity of sedimentary and diagenetic bodies within a regional anhydrite seal, sampling relevant lithologies, and laboratory analyses. Laboratory work will involve petrography (polarization and cathodoluminescence microscope), geochemistry (S and O isotopes in evaporites, C, O and clumped isotopes in carbonate stringers, elemental analysis in all phases), and X-ray diffraction. The effect of CO2 on anhydrite will be determined by comparing samples exposed to CO2 with samples from adjacent area not exposed to CO2.

Ideal student profile: A first class degree student with strong interests in either sedimentology, diagenesis and/or isotope geochemistry

Project supervisors: Dr. C├ędric JohnDr. Veerle VandeginsteProf. Al Fraser, Imperial College London.