- Cutting-edge insight into science of “fracking”
- Multidisciplinary chemistry and geology
- Impacts for atmospheric composition as well as air quality and climate
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.
Geological characterisation 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.
Training and Skills
CENTA students will attend 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes.
The project is truly multidisciplinary providing training in physical/atmospheric chemistry, sedimentology and rock physics. The student will receive training in geological field sampling and in laboratory-based lithological analysis techniques using optical microscopy and the Scanning Electron Microscope (SEM) in Leicester’s Department of Geology and at the British Geological Survey. The student will receive training in designing and undertaking a range of experiments using the analytical apparatus in Leicester’s Department of Chemistry and at the British Geological Survey.
Partners and collaboration (including CASE)
Prof. Paul Monks and his group research atmospheric chemistry. In relation to this project his interests in real-time analytical instrumentation for VOC measurement will be applied. Prof Sarah Davies is a professor of sedimentology and a recognised expert on combining sedimentology and petrophysics for stratigraphic and unconventional resource analysis. 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.