黔北地区矿物组分对页岩储层力学特性的影响

Influence of Mineral Composition on Mechanical Properties of Shale Reservoirs in Northern Guizhou

矿物组分扮演着至关重要的角色,研究其含量对黔北地区页岩储层力学性质和压裂起裂机制具有重要意义。通过单轴压缩、巴西劈裂、声发射信号采集仪和X射线衍射全岩分析(X-ray diffraction,XRD)测定黔北地区下寒武统牛蹄塘组页岩力学性质和矿物组分,并分析矿物组分对页岩储层力学特性的影响,阐明矿物组分与页岩储层力学特性的关系。研究表明:当矿物组分占比由韧性转为脆性时,页岩在受压过程中变形破裂阶段逐渐趋于复杂;随着页岩脆性指数增大、黏土矿物含量降低,应力-时间变化曲线变得曲折且斜率大,抗压强度、抗拉强度和弹性模量升高,声发射信号多且强度高;YY-1、YY-2和YY-3系列在巴西劈裂和单轴压缩试验下的裂纹扩展模式分别为轴向贯穿型、侧面滑脱型、侧面滑脱+底部破裂型和轴向贯穿型。

Mineral composition plays a crucial role,the study of its content is important for mechanical properties and fracture initiation mechanisms of shale reservoirs in northern Guizhou.The mechanical properties and mineral composition of shales of the Lower Cambrian Niutitang Formation in northern Guizhou Province were determined by uniaxial compression,Brazilian splitting,acoustic emission signal acquisition,and X-ray diffraction(XRD),and the influence of mineral composition on the mechanical properties of shale reservoirs was analyzed in depth to elucidate the relationship between mineral composition and mechanical properties of shale reservoirs.Results that when the proportion of mineral components changes from toughness to brittleness,the deformation and fracture stage of shale gradually becomes complicated during the compression process.As the shale brittleness index increases and the clay mineral content decreases,the stress-time variation curve becomes curved and sloped,the compressive strength,tensile strength,and modulus of elasticity increase,and the acoustic emission signal becomes more numerous and intense.The fracture extension patterns of the YY-1,YY-2,and YY-3 series under Brazilian splitting and uniaxial compression tests were axial penetration type,lateral slip type,lateral slip+bottom rupture type,and axial penetration type,respectively.