SHALE‐GAS POTENTIAL OF THE MID‐CARBONIFEROUS BOWLAND‐HODDER UNIT IN THE CLEVELAND BASIN (YORKSHIRE), CENTRAL BRITAIN |
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Authors: | M S?owakiewicz Maurice E Tucker C H Vane R Harding A Collins R D Pancost |
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Affiliation: | 1. Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre and Cabot Institute, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS.;2. Polish Geological Institute, Poland;3. School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ.;4. British Geological Survey, Keyworth, Nottingham, NG12 5GG.;5. Applied Petroleum Technology Ltd., 2nd Floor, 14 Wynnstay Road, Colwyn Bay, LL29 8NB. |
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Abstract: | The shale‐gas potential of mid‐Carboniferous mudrocks in the Bowland‐Hodder unit in the Cleveland Basin (Yorkshire, northern England) was investigated through the analysis of a cored section from the uppermost part of the unit in the Malton‐4 well using a multidisciplinary approach. Black shales are interbedded with bioturbated and bedded sandstones, representing basinal‐offshore to prodelta – delta‐front lithofacies. The total organic carbon (TOC) content of the shales ranges from 0.37 to 2.45 wt %. Rock‐Eval pyrolysis data indicate that the organic matter is mainly composed of Type III kerogen with an admixture of Type II kerogen. Tmax (436–454°C), 20S/(20S+20R) C29 sterane ratios, and vitrinite reflectance values indicate that organic matter is in the mid‐ to late‐ mature (oil) stage with respect to hydrocarbon generation. Sedimentological and geochemical redox proxies suggest that the black shales were deposited in periodically oxic‐dysoxic and anoxic bottom waters with episodic oxic conditions, explaining the relatively low TOC values. The Rock‐Eval parameters indicate that the analysed mudrocks have a limited shale‐gas potential. However, burial and thermal history modelling, and VRr data from other wells in the region, indicate that where they are more deeply‐buried, the Bowland‐Hodder shales will be within the gas window with VRr > 1.1 % at depths in excess of 2000 m. Therefore although no direct evidence for a high shale‐gas potential in the Cleveland Basin has been found, this cannot be precluded at greater depths especially if deeper horizons are more organic rich. |
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Keywords: | black shale shale gas biomarker characterization organic matter vitrinite reflectance thermal maturity Cleveland Basin Carboniferous Yorkshire England |
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