摘要
为了掌握超临界CO_2(简称SC-CO_2)压裂煤岩体的起裂及裂缝扩展规律,采用TCHSFM-I型大尺寸真三轴压裂渗流模拟装置进行试验,同时采集压裂孔内压力和表面裂缝数据并结合理论分析。结果表明:超临界CO_2压裂煤岩的压力时间曲线可分为4个阶段:空腔充填阶段、孔隙增压阶段、相变增压阶段和破坏失稳阶段;其中煤和砂质泥岩起裂压力分别为12.32、19.63 MPa;煤Biot系数0.91、脆性系数16.95%、弹性模量3.48 GPa,产生平行层理的水平裂缝;砂质泥岩Biot系数0.69、脆性系数47.53%、弹性模量10.52 GPa,产生垂直层理的贯通性复杂裂缝。可见SC-CO_2压裂下煤岩裂缝起裂扩展集中于破坏失稳阶段,起裂压力较小且为水力压裂的65%～70%,煤相比于砂质泥岩,由于其层理等弱面发育、Biot系数大、弹性模量低、脆性系数小,未产生贯通性的复杂裂缝。
In order to grasp the law of the initiation and the crack propagation in fracturing coal-rock mass with supercritical CO 2(SC-CO 2),the experimental study was carried out by using TCHSFM-I large-scale true-triaxial simulation device for fracturing and seepage and by collecting pressure and surface cracks data,combined with theoretical analysis.The results showed that the pressure-time curves of fracturing coal-rock with supercritical CO 2 could be divided into four stages:cavity-filling stage,pore pressurization stage,phase-transiting pressurization stage and destabilization failure stage.The initiation pressure values of coal and sandy mudstone initiation were 12.32 MPa and 19.63 MPa respectively.The coal,with its Biot coefficient of 0.91,brittleness coefficient of 16.95%and elastic modulus of 3.48 GPa,produced horizontal cracks parallel to the bedding;while the sandy mudstone,with its Biot coefficient of 0.69,brittleness coefficient was 47.53%and elastic modulus of 10.52 GPa,produced connective and complex cracks perpendicular to the bedding.It could be seen that the initiation of fracturing with SC-CO 2 fracturing was mainly concentrated in the destabilization failure stage.The initiation pressure of was 65%~70%of that of hydraulic fracturing.Compared with sandy mudstone,coal did not produce complex-through cracks for its development of stratification and joint weakness,large Biot coefficient,low elastic modulus and small brittleness coefficient.
作者
王磊
梁卫国
WANG Lei;LIANG Weiguo(Institute of Mining Technology,Taiyuan University of Technology,Taiyuan 030024,China;Key Laboratory of In-situ Property-improving Mining of Ministry of Education,Taiyuan University of Technology,Taiyuan 030024,China)
出处
《煤炭科学技术》
CAS
CSCD
北大核心
2019年第2期65-70,共6页
Coal Science and Technology
基金
国家自然科学基金杰出青年科学基金资助项目(51225404)
关键词
超临界CO2
压裂
起裂压力
裂缝扩展
supercritical CO 2
hydraulic fracturing
initiation pressure
crack propagation
