Joe Emmings

University of Leicester


Controls on UK Lower Namurian Gas Shale Prospectivity: Understanding the Spatial and Temporal Distribution of Organic Matter in Siliciclastic Mudstones

PhD Summary

We (University of Leicester) seek to understand the controls on the spatial and temporal distribution of organic matter (sedimentological, biological, preservation) and how this relates to the unconventional hydrocarbon prospectivity of the Upper Bowland Shale. My objectives are to: Describe the variability of biological input to mudstones through sedimentological field logging, optical imaging of thin sections, macropalaeontological, palynological, geochemical (potentially both organic and inorganic) and isotopic methods; Interpret lithofacies variability in terms of changing processes and palaeoenvironments; Link palaeoenvironments to larger scale climate change and carbon cycle events; Investigate types of organic matter and their potential for gas generation; Develop a predictive model relating the temporal and spatial distribution to biological input to shale gas prospectivity and criteria for identifying these intervals in exploration wells. I am presently seeking to quantify the role of weathering (physical, chemical) on the alteration of organic-matter in samples collected from the Bowland Shale at outcrop in the UK. This is because organic-rich mudstones (such as the Bowland Shale) are particularly prone to alteration by chemical weathering since they contain components that are in disequilibrium with present-day surface (oxic) conditions. It is often assumed that samples collected from outcrop can be considered relatively fresh (and can hence be used for organic geochemical analyses) if these are either; ‘dug out’ from beneath the surficial weathered surface, or; are collected from sections cut by streams where it is assumed that the relatively high rate of physical erosion (hence continuous removal of material) results in minimal time afforded for organic matter alteration and removal. Yet there is no systematic approach based on lithological type for the Bowland Shale in the UK climatic regime.