摘要
煤层顶板水平井分段压裂技术是实现碎软低渗煤层煤层气高效抽采的有效技术。文中基于流-固耦合原理,考虑分段多簇压裂时缝间应力干扰作用和射孔簇裂缝间压裂液动态分配,建立三维裂缝穿层扩展计算模型,研究了多簇射孔条件下裂缝动态延伸情况。结果表明:单簇射孔压裂形成的裂缝半长和宽度均较大,且裂缝尖端位于煤层顶板内,顶板内裂缝向前延伸后,由高应力顶板向低应力煤层中穿层扩展;三簇射孔条件下,当射孔簇间距小于15 m或压裂液排量低于8 m3/min时,中间裂缝不能获得有效的压裂液分配而发育不充分;对于煤层顶板水平井,射孔簇增多会导致压裂液分流,部分射孔簇将无法形成有效裂缝或无法穿层扩展,导致射孔簇效率降低。因此,对于多簇施工,应综合考虑压裂液排量、簇间距,以促进裂缝均匀扩展。研究成果可为煤层顶板水平井分段压裂施工优化设计提供依据。
Multi-stage fracturing horizontal well in coal seam roof has been proven to be an effective method to achieve high-efficiency extraction of coalbed methane in broken soft and low-permeability coal seams.Based on fluid-solid coupling mechanism,considering the stress interference and the dynamic fracturing fluid distribution between perforation clusters during staged multi-cluster fracturing,a 3D fracture propagation model is established to study the dynamic fracture propagation under the condition of multi-cluster perforation.The results show that the half-length and width of fracture formed under single cluster condition are larger,and the crack tip is located in the roof of the coal seam.After the fracture in roof extends forward,it penetrates downward to the low-stress coal seam from the high-stress roof.Under the condition of three-cluster perforation,when the perforation cluster spacing is smaller than 15 m or pump rate is less than 8 m3/min,the middle perforation cluster cannot obtain effective fracturing fluid,thus causing an insufficient fracture development.For the horizontal well in coal seam roof,more perforation clusters will cause fracturing fluid shunting effect,and some perforation clusters will form invalid cracks or fail to propagate through layers,thus reducing cluster efficiency.Therefore,pump rate and cluster spacing should be considered for multi-cluster fracturing to make the fracture propagate evenly.Research results can provide a basis for the optimal design of fracturing treatment for staged fracturing horizontal well in coal seam roof.
作者
李浩哲
张群
姜在炳
许耀波
LI Haozhe;ZHANG Qun;JIANG Zaibing;XU Yaobo(China Coal Research Institute,Beijing 100013,China;Xi′an Research Institute Co.,Ltd.,China Coal Technology and Engineering Group Corp.,Xi′an 710077,China)
出处
《断块油气田》
CAS
CSCD
北大核心
2022年第5期714-720,共7页
Fault-Block Oil & Gas Field
基金
国家自然科学基金项目“碎软煤层顶板水平井穿层压裂裂缝扩展机理及形态控制研究”(51874349)
中煤科工集团西安研究院有限公司科技创新基金顶层设计项目“井上下联合压裂技术体系设计及区域瓦斯高效抽采模式研究”(2020XAYDC04-01)。
关键词
煤层气
压裂液动态分配
煤层顶板水平井
分段压裂
多簇射孔
裂缝延伸
coalbed methane
dynamic fracturing fluid distribution
horizontal well in coal seam roof
multi-stage fracturing
multi-cluster perforation
fracture propagation
