潜江凹陷潜四下段页岩油储层力学性质特征研究

Study on mechanical properties of shale oil reservoir in the lower fourth member of submarine in Qianjiang depression

采用矿物成分测定,孔隙结构分析,单-三轴力学参数测定,抗拉强度、界面抗剪切强度测定,以及地应力测定等方法对潜江凹陷潜江组潜四下段典型页岩油储层进行研究。研究结果表明:①矿物成分特征主要是“低黏土矿物、低石英、高碳酸盐、局部高蒸发岩”。孔隙主要以次生孔隙为主,包括晶间孔、粒内孔;②潜四下段24韵律储层抗压强度较大,6韵律储层抗压强度较小,其余韵律抗压强度基本相当。弹性模量为4.16~18.11 GPa,泊松比为0.146~0.331,围压与峰值应力、弹性模量呈正相关关系,温度与峰值应力、弹性模量呈负相关关系,温度、围压与泊松比并无明显变化;③层理面抗拉强度小于基质抗拉强度,表明层理面更容易开启;随着法向应力增大,钙芒硝-泥岩界面抗剪切强度小于层理界面,钙芒硝-泥岩界面的黏聚力为0.57 MPa,内摩擦角为21.78°,层理界面黏聚力为0.99 MPa,内摩擦角为31.99°;④潜四下段15韵律层最大水平主应力为74.25 MPa,最小水平主应力为71.74 MPa,水平应力差为2.51 MPa,32韵律层最大水平主应力为80.61 MPa,最小水平主应力为78.01 MPa,水平应力差为2.6 MPa,均有形成压裂体积缝网的应力条件。

Through the determination of the mineral composition,pore structure analysis,single-three axis determination of mechanical parameters,tensile strength,interfacial shear strength determination and crustal stress measurement of the shale oil reservoir in the lower Eq4 in Qianjiang depression,it is concluded:①The mineral composition characteristics is"low clay minerals content,low quartz and high carbonate".The pores are mainly composed of secondary pores,including intergranular pores,intragrystalline pores,dissolution pores and fracture pores.②The 24TH rhythmical reservoir has a large compressive strength,and the 6th rhythmical reservoir has a small compressive strength.The remaining rhythmical reservoirs have a similar compressive strength. The elastic modulus ranges from 4.16~18.11 GPa, and poisson's ratio ranges from 0.146~0.331. Temperatureand confining pressure are positively correlated with peak stress and elastic modulus, while temperature, confining pressureand poisson's ratio have no obvious change. ③ The tensile strength within the bedding surface is lower than the matrix, indicatingthat the bedding surface is easier to open. With normal stress increasing, glauberite - mudstone interface shear strengthis less than the bedding interface. The glauberite - mudstone interface is 0.57 MPa, and the cohesive force of internal frictionangle is 21.78 °. The bedding interface cohesive force is 0.99 MPa, and the internal friction angle is 31.99 °. ④ The maximumhorizontal principal stress is 74.25 MPa, and the minimum horizontal principal stress is 71.74 MPa of the 15 TH rhythmicallayer. The horizontal stress difference is 2.51 MPa. The maximum horizontal principal stress is 80.61 MPa, and the minimumhorizontal principal stress is 78.01 MPa of the 32 TH rhythmical layer.The horizontal stress difference is 2.51 MPa. All have thestress conditions to form fracturing volume fracture network.