穿层钻孔液态CO_(2)压裂煤层起裂压力模型探究和工程验证  

Initiation pressure model for liquid CO_(2) fracturing through upward penetrating boreholes and its engineering verification

作　　者：樊世星 文虎 金永飞 陈建[2] 童校长 程小蛟[1] 于志金 FAN Shixing;WEN Hu;JIN Yongfei;CHEN Jian;TONG Xiaozhang;CHENG Xiaojiao;YU Zhijin(College of Safety Science and Engineering,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China;Huainan Mining Group Co.,Ltd.,Huainan,Anhui 232001,China)

机构地区：[1]西安科技大学安全科学与工程学院,陕西西安710054 [2]淮南矿业(集团)有限责任公司,安徽淮南232001

出　　处：《岩石力学与工程学报》2021年第4期703-712,共10页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(51974240,51804245)。

摘　　要：针对液态CO2(L-CO_(2))压裂增透煤层技术中起裂压力的确定这一基础科学问题,依据应力叠加原理和最大拉应力准则,结合L-CO_(2)低黏强渗透性对煤岩体抗拉强度的弱化效应,将水平主应力、压裂流体压力及其渗滤效应引起的周向应力三项叠加,建立考虑增压速率的起裂压力模型,并且确定起裂压力模型的上下限。研发国内首套井下高压(30MPa)L-CO_(2)压裂增透成套装备,确定"预冷–注液–保压"三阶段压注工艺,在淮南潘三煤矿首次开展井下上向穿层钻孔L-CO_(2)压裂增透煤层现场试验。由起裂压力模型计算得到的理论值范围15.4~21.4 MPa,不仅与试验中两压裂孔四次压裂实测起裂压力值22.9,16.2和21.3,20.1 MPa在一定误差范围内实现了较好的吻合,而且与水力压裂起裂压力值的65%~70%(15.6~23.2 MPa)相接近,验证了起裂压力模型的正确性。研究成果对L-CO2压裂技术在煤层增透方面的应用具有一定的指导意义。Determining the initiation pressure of coalseam in liquid CO_(2)(L-CO_(2)) fracturing technology is a fundamental scientific issue. According to the stress superposition principle and maximum tensile failure criterion and combined with the weakening effect of low viscosity of L-CO_(2) on the tensile strength of coal,an initiation pressure model for L-CO_(2) fracturing was established by superimposing the horizontal principal stress,the fracturing fluid pressure and the circumferential stress caused by the percolation effect,and the upper and lower limits of the initiation pressure model were determined by the limit assumption of fracturing fluid viscosity. A set of high pressure(30 MPa) L-CO_(2) fracturing equipment with a three-stage L-CO_(2) injection process was firstly developed to be implemented in underground coal mine,and the first permeability enhancement field test through L-CO_(2) fracturing was carried out in Pansan coal mine in Huainan. The initiation pressure calculated by the theoretical model ranges from 15.4 to 21.4 MPa,which is not only compatible with the four measured values of two fracturing boreholes(22.9 MPa,16.2 MPa and 21.3 MPa,20.1 MPa,respectively) but also consistent with 65%–70%(15.6–23.2 MPa) of the initiation pressure using hydraulic fracturing,showing the correctness of the initiation pressure theoretical model. The research results have a certain guidance meaning for the application of L-CO_(2) fracturing.

关 键 词：岩石力学 穿层钻孔 液态CO_(2) 起裂压力 压裂增透 工程试验 

分 类 号：TU45[建筑科学—岩土工程]