What can hydrocarbon fingerprints tell us about fracking in organic-rich shales?

The accurate estimation of the hydrocarbon content of potential source rocks is increasingly important as unconventional sources of hydrocarbons become economically viable and we look manage of our environment responsibly as we try to meet our energy needs. This proposed PhD offers an exceptional interdisciplinary research opportunity to combine chemistry, geology and geomechanics and explore the fundamental links between the physics and chemistry of shales and the release of hydrocarbons.

Shale is an abundant sedimentary rock composed of compacted silt- and clay-sized material that often includes organic matter that may generate economically significant quantities of gas and oil hydrocarbons (Aplin & Macquaker 2011). Extracting oil or gas from shale requires pervasively fracturing the rock; termed hydraulic fracturing (“fracking”), this consists of drilling a well in the prospective shale units and injecting water under high pressure mixed with a proppant (~5%) and chemical additives (~0.2%) to fracture the rock and stimulate the release of hydrocarbons (Bickle et al, 2012). Proof-of-principle laboratory experiments (Sommariva et al, 2014) demonstrate it is possible to quantify in real-time (second by second) a wide range of non-methane hydrocarbons (NMHC) gases as they are released during a fracturing process (Figure 1). Systematic variations in total organic carbon content are known to be related to lithological differences (Könitzer et al. 2014) but this has not been linked to the types of hydrocarbons released. The release of hydrocarbons into the atmosphere from oil and gas extraction can lead to the formation of pollutants and exploitation has important implications for air quality and climate. Therefore knowledge of the abundance of methane and speciated NMHC, and how that relates to geological characteristics of the shale is important. The PhD will explore how the physical character and chemical composition (lithology, mineralogy, organic matter type, maturity and abundance, and geomechanical properties) of the rock controls hydrocarbon (methane and other volatile organic compounds) speciation.

A range of organic-rich shale (mudstone) samples will be examined to determine mineralogy, lithology and fabrics. A range of imaging techniques (e.g. optical microscopy, CT, SEM) will be undertaken on samples before and after fracture stimulation to help assess fracture efficiency. Experimental research - The fracture processes and real-time data on the mode of failure and volume of gas discharged will be undertaken through a series of analytical experiments (e.g. Blake et al, 2004, Sommariva et al. 2014). NMHC release from the crushed samples in real time will be analysed using proton-transfer-reaction time-of-flight mass spectrometry (PTR− TOF− MS). The PTR technique is not sensitive to some classes of NMHC and the whole range of hydrocarbons will be analysed using thermal desorption gas chromatography mass spectrometry (TD− GC− MS). Experiments on intact and crushed rock samples will build a detailed understanding of the fracturing processes.

This project is builds on an existing collaborative venture between the University of Leicester and the British Geological (BGS). The BGS supervisors run the Fluid Processes Research (FPR) laboratories and have extensive experience working on a range of aspects relating to the multi-phase flow of fluids through clay-rich materials and the impact fracturing has on transport properties. The BGS currently has an active research programme examining aspects of the mechanical controls on hydraulic fracturing, rock stress, and multi-phase flow in Bowland shale as part of an industry co-funded consortium.

Entry requirements
Applicants are required to hold/or expect to obtain a UK Bachelor Degree 2:1 or better in a relevant subject. The University of Leicester English language requirements apply where applicable.

How to apply
Please refer to the CENTA Studentship application information on our website for details of how to apply.

As part of the application process you will need to:
• Complete a CENTA Funding form – to be uploaded to your PhD application
• Complete and submit your PhD application online. Indicate project CENTA2-CEHM3-MON in the funding section.
• Complete an online project selection form Apply for CENTA2-CEHM3-MON