Jurassic shale analogue study: from resource to reserve (JARR)

Resource to reserve calculations in unconventional shale gas or oil exploitation depends on quanitifying and characterising "sweet spots". Sweet spots typically occur where black shale deposits have high total organic carbon, stiff/brittle rheology, abundant natural fractures, sufficient thickness and maturity, and high gas-in-place. In turn, these characteristics are controlled by fundamental geological processes including organic productivity, run-off, diagenesis, and tectonic and burial histories - all of which vary from the edges to the centres of depositional basins (i.e. proximal to distal). Sweet spot characterisation requires a multi-disciplinary approach, and access to datasets that encompass the entire range of proximal to distal environments and tectonic or burial histories. Jurassic shales in NW Europe (Liassic, Kimmeridgian), include world-class hydrocarbon source rock that underlies much of the North Sea. Jurassic rocks crop out in coastal sections in the UK and northern France, crucially these strata, have been cored and logged in many North Sea wells. Taken in their entirety, these outcrop and borehole datasets should provide an unrivalled record of the proximal to distal transition within a mud-prone stratigraphic interval across a broad region characterised by varied, but well-known tectonic and burial histories. This basin-wide dataset has the potential to provide insights into sweet spot identification not available in individual shale gas concessions that comprise small, sub-areas of much larger shale basins. Further benefits would be to identify subtle, conventional stratigraphic traps, e.g. sandy intervals within an otherwise mud-prone sequence. Despite its outstanding potential, a rigorous basin-wide study of the Jurassic in NW Europe has been hampered due to the disparate and dispersed nature of the datasets. This NERC catalyst proposal will connect a multi-disciplinary team of NERC- and industrially-funded researchers at Durham and Newcastle Universities with industrial geoscientists. Our aim is to conduct a scoping study of existing Liasic and Kimmeridgian datasets to evaluate their potential for further in-depth research into sweet spot characterisation. Catalyst funding will enable us to generate an open access GIS meta-database of existing maps, outcrops, cores, cuttings and wireline logs that penetrate Jurassic rocks of the North Sea, England and northern France. To facilitate knowledge exchange and gain a deep understanding of the challenges of sweet spot characterisation, JARR will organise and host a series of industry-academia field- and core-based workshops in the UK and northern France that will focus on three key themes: (1) basin-wide variations in black shale deposition; (2) basin-wide lithostratigraphic controls on natural fractures in proximal to distal environments; (3) basin-wide variations in the mechanical properties of mud-prone sequences, held at key onshore localities. JARR will synthesize the discussions into an open access report that will critically appraise the Jurassic as a proximal to distal shale basin analogue. JARR will publish the report and GIS meta-database on its website (www.shale-research.org), available to industry and public. The project will culminate in a professionally-facilitated industry-academia "sandpit" meeting, which will develop proposals for a network of collaborative Joint Industry Projects (JIPs) based around the three key themes identified above. We anticipate the JIPs will either utilize directly the datasets identified during the scoping study, and/or develop questions raised and "lessons learned" during the workshops and sandpit discussion. The JARR proposal will help UK-based hydrocarbon companies to better understand resource to reserve conversion factors by unlocking additional value from existing datasets, and could ultimately provide them with real competitive advantage in unconventional exploration.