AAPG Middle East Region, Shale Gas Evolution Symposium

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The Potential of Shale Gas Accumulation in Middle and Small Continental Faulted Basins in Eastern China from Fuxin Basin

Abstract

A great number of Mesozoic medium- and small-sized fault basins are developed in eastern China. In these fault basins, the sedimentary thickness of continental organic-rich shale is great, and the Cretaceous volcanic activities accelerate the maturity of organic matters in the shale, which provide favorable prerequisites for shale gas accumulation. In this paper, the potential of continental shale gas accumulation in the mentioned Mesozoic medium- and small-sized fault basins was analyzed with the Fuxin Basin as an example. Based on the latest drilling, core and cutting test data, six elements of shale gas accumulation in organic-rich shale in the Fuxin Basin were discussed, including thickness, distribution, total organic carbon (TOC) content, thermal evolution maturity of organic matter (Ro), reservoir capacity and compressibility. Then, depending on the characteristics of shale reservoirs, the potential of continental shale gas accumulation in the study area was investigated, and the suggestions on further exploration and development were proposed. The following results were obtained. First, continental shale in the medium- and small-sized fault basins in eastern China is characterized by great total reservoir thickness, high TOC content and moderate thermal maturity, which are advantageous for shale gas accumulation, while larger lateral thickness variation, lower reservoir capacity and weaker stimulation feasibility, which are disadvantageous for shale gas accumulation. Second, continental shale has high TOC content (averagely 5.4%), and high Ro (>1.2%) under the effect of Mesozoic volcanic activities, suggesting a gas generating window, so there is a superior material basis for shale gas accumulation. Third, it is uncertain whether the multi-stage fracturing technique of horizontal wells for the development of marine shale gas is applicable to the development of continental shale gas, so it is necessary to develop the 3D vertical multi-layer development technique of vertical wells suitable for continental shale gas. Fourth, the single-well production rate of continental shale gas is lower than that of marine shale gas, so it is necessary to strengthen the single-well economic productivity evaluation of continental shale gas in fault basins. In conclusion, the fault basins in eastern China are mostly similar to the Fuxin Basin and they have the material basis for shale gas accumulation, so these basins are the new targets for achieving breakthroughs in continental shale gas exploration. Further exploration shall focus on the identification of zones with a high reservoir capacity and of intervals with strong simulation feasibility.