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Fracture permeability response to the gas adsorption/desorption process in organic rocks by coupled Hydro–Mechanical modelling


   Department of Geology

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  Dr Quan Gan, Dr K Wu  Applications accepted all year round  Self-Funded PhD Students Only

About the Project

Gas adsorption/desorption is an essential process related to gas transport in fractured organic rocks, such as coals and organic-rich shales. The induced matrix shrinkage/swelling responses due to gas adsorption/desorption in sorptive medium have significant impact in controlling fracture aperture and matrix/fracture porosity. Understanding the competition between the mechanical and chemical effects on gas adsorption/desorption can help capture the evolution of transport characteristics, including predicting gas production in organic rocks (coals and shales) and CO2 storage capacity in geological formations. Usually the permeability evolution due to sorption behavior is investigated experimentally using organic rock samples. Coupled hydro-mechanical modelling in organic rocks could provide a comprehensive approach to understand the evolution of gas flow behaviors. It has been revealed that fracture permeability can be enhanced due to failure, or reduced from normal compaction responses from variation of effective stress states (Cai et al., 2014; Gan, 2016a,b). In addition, pore fractal model has been well established to effectively evaluate the effects of heterogeneous pore-fractures (e.g. pore structure, volume, size distribution and surface area) of coals on gas permeability (Cai et al, 2016). It demonstrates that pore properties, including porosity, size distribution, and gas adsorption/desorption can substantially affect the permeability in coals.

This PhD project aims at investigating fracture permeability response to the gas adsorption / desorption process in organic rocks by coupled hydro-mechanical modelling, the detailed approaches are listed as,
1) According to the 2D and 3D reconstruction of pore-fractures in organic rocks, fractal characters of the heterogeneous pore-fracture structure will be derived and tortuous fluid flow path in pores will be established.
2) Derived fractal parameters will be applied to build the corresponding pore fracture structure in HM simulation.
3) Langmuir isothermal theory will be incorporated into current developed simulator (Tough-FLAC3D) to represent gas adsorption/desorption process at different pore pressure, and calculate induced volumetric strain from swelling/shrinkage response.

The successful candidate should have, or expect to have, an Honours Degree at 2.1 or above (or equivalent) in Geophysics, Petroleum Engineering, Civil / Geo-technical Engineering.

Essential background: Petroleum engineering, Geotechnical Engineering, Fluid Dynamics.

The student should have knowledge of theories about fluid dynamics and geomechanics (deformation and stress), thermodynamics. It will be high desirable with background in programming in finite element / finite difference / boundary element modelling and mathematics.

APPLICATION PROCEDURE:
This project is advertised in relation to the research areas of the discipline of Geology. Formal applications can be completed online: https://www.abdn.ac.uk/pgap/login.php. You should apply for Degree of Doctor of Philosophy in Geology, to ensure that your application is passed to the correct person for processing. NOTE CLEARLY THE NAME OF THE SUPERVISOR and EXACT PROJECT TITLE ON THE APPLICATION FORM.


Funding Notes

There is no funding attached to this project, it is for self-funded students only.

References

Gan, Q., Elsworth, D. Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling. Geothermics 2016a; 62:131-142, ISSN 0375-6505.
Gan, Q., Elsworth, D. A continuum model for coupled stress and fluid flow in discrete fracture networks. Geomechanics and Geophysics for Geo-Energy and Geo-Resources 2016b; 2: 43. doi:10.1007/s40948-015-0020-0.
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