Aiming at the thin interbeds of gravity flow sandstone in organic-rich shale layer of the 7th member of Triassic Yanchang Formation (Chang7 Member) in Ordos Basin, PetroChina Changqing Oilfield Company realized the cost-effective development of interbedded shale oil in continental low-pressure freshwater lacustrine basin, discovered and proved the 1 billion ton Qingcheng shale oil field, and presented proven reserves of 10.52×108 t. It took the lead in building China's first one million ton shale oil integrated development zone. With the continuous expansion of production and construction scale, the difference of geological body is obvious, and the problems of low initial production and rapid decline of single well, low recovery efficiency and high development cost become more and more prominent. Through many years of field practice, the key problems in shale oil development are put forward, and reasonable suggestions are put forward according to systematic analysis. The drilling rate of shale oil horizontal wells can be divided into longitudinal drilling rate and transverse drilling rate. Improving the longitudinal drilling rate and transverse drilling rate of high-quality reservoir is an important measure to increase the production of a single well. When deploying horizontal wells, priority can be given to the extension direction of high-quality reservoirs to improve the drilling rate of high-quality reservoirs. The contribution ratio of elastic energy of fracturing fluid to recovery is relatively low, so the reservoir reconstruction should not overemphasize large sand volume, large fluid volume, and large displacement, but should fully consider well spacing, longitudinal interlayer distribution, and fracture development, and optimize fracturing scale, construction displacement and other parameters. The change of source rock quality and the strength of diagenesis are the main reasons for the difference of oil content in sand bodies, which affect the selection of favorable areas and the distribution of high-quality reservoirs. Pre-CO2 volumetric fracturing has obvious energy increase effect, which is an effective means to reduce viscosity and improve oil recovery. It is an important measure to ensure the efficient development of shale oil in Changqing Oilfield Company by deepening the comprehensive geological research, clarifying the main controlling factors of differential shale oil accumulation, elaborating the three-dimensional sweet spot distribution, and exploring more effective development methods.
Keywords:Ordos Basin
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Shale oil development
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Chang 7 Member
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Key issues
LEI Qihong, HE You’an, GUO Qiheng, DANG Yongchao, HUANG Tianjing, LIU Changchun. Key scientific and technological issues in the development of horizontal shale oil wells in the Ordos Basin. Natural Gas Geoscience[J], 2023, 34(6): 939-949 doi:10.11764/j.issn.1672-1926.2023.01.001
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