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王士国, 金衍, 谭鹏, 夏阳. 煤系页岩储层多气共采水力裂缝扩展规律试验研究[J]. 岩土工程学报, 2022, 44(12): 2290-2296. DOI: 10.11779/CJGE202212016
引用本文: 王士国, 金衍, 谭鹏, 夏阳. 煤系页岩储层多气共采水力裂缝扩展规律试验研究[J]. 岩土工程学报, 2022, 44(12): 2290-2296. DOI: 10.11779/CJGE202212016
WANG Shi-guo, JIN Yan, TAN Peng, XIA Yang. Experimental investigation on hydraulic fracture propagation of coal shale reservoirs under multi-gas co-production[J]. Chinese Journal of Geotechnical Engineering, 2022, 44(12): 2290-2296. DOI: 10.11779/CJGE202212016
Citation: WANG Shi-guo, JIN Yan, TAN Peng, XIA Yang. Experimental investigation on hydraulic fracture propagation of coal shale reservoirs under multi-gas co-production[J]. Chinese Journal of Geotechnical Engineering, 2022, 44(12): 2290-2296. DOI: 10.11779/CJGE202212016

煤系页岩储层多气共采水力裂缝扩展规律试验研究

Experimental investigation on hydraulic fracture propagation of coal shale reservoirs under multi-gas co-production

  • 摘要: 多岩性组合煤系页岩储层在纵向上交替发育页岩、煤岩及灰岩等多类含气层,压裂后储层间的连通程度与裂缝复杂程度是决定多气共采成败的关键。通过制作模拟煤系页岩储层的多岩性组合层状岩石试样,开展真三轴压裂物理模拟试验,分析了水力裂缝纵向扩展形态及多因素影响规律。试验结果表明:岩性界面、页岩层理及煤岩割理等非连续结构面对水力裂缝垂向扩展具有显著抑制作用,水力裂缝缝高扩展往往呈非对称扩展模式;值为0.1的低垂向应力差系数更易被弱结构面捕获,高垂向应力差系数、高压裂液注入速率有利于裂缝垂向穿层扩展,水力裂缝穿透至煤岩中可激活割理系统形成复杂裂缝网络。试验结果证实了多岩性煤系页岩储层多气共采的可行性,研究结果亦可为认识煤系地层水力裂缝形态及指导现场压裂施工提供参考。

     

    Abstract: The gas-bearing formations, including shale, coal and limestone rock, are alternately and vertically developed in coal shale reservoirs. Multiple unconventional natural gases can be exploited together through the hydraulic fracture longitudinally connecting different production layers. Therefore, the degrees of formation connection and fracture complexity are the two key factors to determine the results of gas co-production. The true tri-axial hydraulic tests are carried out on the samples of artificial coal shale strata, which are comprised of different lithological combinations of layered rock. The vertical propagation geometries of hydraulic fractures are analyzed and the effects of different factors on the fracture patterns are summarized. The results show that the weak planes, such as lithological interfaces, bedding planes and coal cleats, have obviously inhibitive effects on the fracture-height growth, and the fracture height propagation always exhibits asymmetric characteristics. The trajectory of hydraulic fracture is easier to be arrested by the weak planes for the case of low vertical stress difference coefficient, as when the value is equal to 0.1. The high vertical stress difference coefficient and high fluid injection rate are beneficial for the hydraulic fracture to cross the interface vertically. In addition, as the hydraulic fracture penetrates the lithological interfaces, the cleat system can be activated, which improves complexity degree of hydraulic fractures. The results are expected to provide a guideline for understanding the hydraulic fracture morphology of coal strata and designing the field fracturing operation.

     

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