Applications are invited for a self-funded, 3 year full time PhD, to commence in October 2019 or February 2020.
The PhD will be based in the School of Earth and Environmental Sciences and will be supervised by Dr. Philip Benson, Dr. Gareth Swift and Dr. Gianluca Tozzi.
The work on this project will involve:
- Applying a new method to simulate and produce hydraulic fracture in a well-controlled laboratory environment using triaxial rock deformation apparatus.
- Use the induced seismicity to understand the fracturing process, verified by post-text X-Ray computed tomography.
- Apply data to geotechnical stability models to scale up the laboratory-scale process to larger (simulated) rock masses.
The safe operation of unconventional oil reservoirs requires not only extensive knowledge of the tensile fracture mechanics of the mudrock, but also how permeable new fracture networks are to different types of fluid. In addition, elevated pore fluid pressure may have a detrimental effect on the rock mass stability via increased pore fluid pressure. To better understand these issues, this project will apply well-constrained laboratory rock physics tools to link measured permeability of freshly generated fracture networks to the fracture density and geometry across a range of fluids, and with reference to the microseismic response during initial fracture, which itself may be used as a proxy for damage and fracture zone properties.
A unique laboratory setup will mimic the field geometry. Samples of 40mm diameter and 100mm length are encapsulated in a rubber jacket fitted with an 3D array for micro-acoustic sensors and instrumented for axial and radial strain. A central axial borehole will be pressurized within an outer shell of rock to simulate a range of depths to 4km by using high pressure hydraulics. This method has been validated by the iCASE NERC project NE/L009110/1. Fracture area and size will be derived from the spatio-temporal data, validated by post-test X-ray Computed Tomography. The measured fracture data (density and aperture) will be correlated with measured fracture permeability across a range of fluid viscosities and temperatures: impossible in the typical field scenario. This suite of laboratory permeability experiments will then be repeated to test how easily the faults are reactivated (or otherwise) as a function of pore pressure magnitude and ramp rate, and, extended to field conditions via engineering geotechnical stability models using MatLab and YADE.
The novelty of the project lies in the use of a new 3D printed ‘jacket’ which will allow the fluids flowing through the newly generated fracture set to be received and measured as a function of time, allowing the permeability of the fracture to be directly measured as a function of the above variables. This project will evaluate the permeability of the induced fractures as a function of the viscosity of the fluid using water and water/glycerine mixtures, and using low viscosity “slick water” often used in the initial stages of hydraulic fracture, but is poorly understood mechanically. Such data is of direct relevance to the unconventional hydrocarbon industry in order to produce resources responsibly and efficiently.
General admissions criteria
You’ll need a good first degree in an applied science discipline from an internationally recognized university (minimum upper second class or equivalent, depending on your chosen course); an additional Master’s degree in a related area will be an advantage. In exceptional cases, we may consider equivalent professional experience and/or qualifications. English language proficiency at a minimum of IELTS band 6.5 with no component score below 6.0.
Specific candidate requirements
• Hold or expect to hold an good first degree (2:1 or higher) and/or a MSc. in Earth Sciences, Civil Engineering or a cognate discipline;
• Have a good working knowledge of numerical software such as excel and be familiar with basic numerical programming methods such as MatLab and Python;
• Have good social and team working skills.
• A working background in laboratory rock mechanics testing – or practical mechanical/electronic engineering skills – are beneficial but not strictly required as training will be provided.
How to Apply
We’d strongly encourage you to contact Dr. Philip Benson ([email protected]
) to discuss your interest before you apply, quoting the project code below.