Abstract
The widely distributed, thick Chang 7 Shale is the richest shale oil formation in China. A calculation method for the evaporative hydrocarbon recovery coefficient based on formation volume factor is proposed considering the correction of heterogeneity-based total organic carbon differences to improve the adsorbed oil calculation method, and light hydrocarbon evaporative sampling losses, which can make mobile and total oil calculations more accurate. The adsorbed oil, S1 evaporative loss, total oil yield, and movable oil yield of 200 shale samples from the Chang 7 Member were calculated using the new methods. Results show that S1 evaporative loss accounts for 29% of S1, total oil yield is 3.5 times S1, and movable oil yield accounts for 37% of total oil yield. Based on the calculated total oil yield and movable oil yield results, the relationships among total oil yield, movable oil yield, and total organic carbon of the Chang 7 were established yielding total oil yield and movable oil yield estimates of 11.12 × 109 t and 4.01 × 109 t, respectively, revealing its tremendous shale exploration potential.
Highlights
In the past decade, as the exploration and development of conventional oil and gas has become increasingly difficult, the focus of oil and gas exploration has gradually turned to shale oil
The oil inplace (OIP) of the Mowry Shale was estimated by both PhiK and volumetric methods, and the results show that the OIPs calculated with the two methods are close at low shale maturity (Ro 0.75%)
Where TOY is total oil yield in milligram per gram rock, S1 is pyrolytic S1 yield in milligram per gram rock, S1LOSS is the evaporative loss of S1 in milligram per gram rock, DS2eq is adsorbed oil in milligram per gram rock, S2 is the pyrolytic hydrocarbon measured prior to solvent extraction in milligram per gram rock, S2EX is the pyrolytic hydrocarbon measured after solvent extraction in milligram per gram rock, keqTOC is the kex or kap, TOC is total organic carbon content before solvent extraction in %, TOCEX is total organic carbon content after solvent extraction in %, and d is carbon-hydrocarbon conversion coefficient, taken as 1200 in this paper
Summary
As the exploration and development of conventional oil and gas has become increasingly difficult, the focus of oil and gas exploration has gradually turned to shale oil. An evaluation method of the heterogeneity of the shale sample to correct the TOC difference Commonly, samples are divided into two pieces: A and B, which are, respectively, used for whole-rock pyrolysis before and after extraction. Where TOY is total oil yield in milligram per gram rock, S1 is pyrolytic S1 yield in milligram per gram rock, S1LOSS is the evaporative loss of S1 in milligram per gram rock, DS2eq is adsorbed oil in milligram per gram rock, S2 is the pyrolytic hydrocarbon measured prior to solvent extraction in milligram per gram rock, S2EX is the pyrolytic hydrocarbon measured after solvent extraction in milligram per gram rock, keqTOC is the kex or kap, TOC is total organic carbon content before solvent extraction in %, TOCEX is total organic carbon content after solvent extraction in %, and d is carbon-hydrocarbon conversion coefficient, taken as 1200 in this paper. Units: S1 1⁄4 S2 1⁄4 AEX 1⁄4 S1EX 1⁄4 S2EX 1⁄4 DS2 1⁄4 DS2eq 1⁄4 mg/g rock; TOC 1⁄4 TOCEX 1⁄4 %
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