苏北盆地阜二段页岩储层力学特征评价

Mechanical characteristics evaluation of the Fu2 member shale reservoir in the Subei Basin

为认识苏北盆地阜二段页岩储层力学特征、可压性、裂缝延伸规律,以HY1井岩心为研究对象开展了矿物成分分析、三轴岩石力学实验、地应力大小和方向实验,为区块可压性评价和压裂工艺优化提供了技术支撑。研究表明,高邮凹陷阜二段以方解石(23.9%)、石英(22.7%)和黏土矿物(21.3%)为主。平均脆性指数58.6,页1~2小层平均脆性指数69.7,页3小层平均脆性指数57.9,页4~5小层平均脆性指数48.4;高邮凹陷阜二段岩心平均泊松比为0.183、平均杨氏模量为15469.6 MPa。应力应变曲线表明,阜二段岩心主要表现出弹性特征;高邮凹陷阜二段垂向应力(81.00~83.00 MPa)最大、最小水平主应力(60.00~64.00 MPa)最小、最大水平主应力(73.00~76.00 MPa)居中,最大水平主应力方向为N43.76E;阜二段矿物脆性相对较高,脆性指数较高,平均应力差异系数0.2,可形成一定分支缝,有利于形成复杂裂缝。

In order to understand the mechanical characteristics,compressibility and fracture extension law of shale reservoir in Fu2 member of Subei Basin,mineral composition analysis,triaxial mechanical experiment,and in-situ stress magnitude and direction experiment were carried out with the core of HY1 well as the research object,which provided technical support for block compressibility evaluation and fracturing process optimization.The results show that calcite(23.9%),quartz(22.7%)and clay minerals(21.3%)dominate the Fu2 member of Gaoyou Sag.The average brittleness index is 58.6,the average brittleness of page 1~2 layer is 69.7,the average brittleness index of page 3 layer is 57.9,and the average brittleness index of page 4~5 layer is 48.4.The core average Poisson's ratio and average Young's modulus of Fu2 member in Gaoyou Depression are 0.183 and 15469.6 MPa.The stress-strain curve shows that the core of the Fu2 member mainly exhibits elastic characteristics.The maximum vertical stress(81.00~83.00 MPa)and minimum horizontal principal stress(60.00~64.00 MPa)are in the middle,and the maximum horizontal principal stress(73.00~76.00 MPa)is in the direction of N43.76E.The mineral in Fu2 member is relatively brittle,the brittleness index is high,and the average stress difference coefficient is 0.2,which can form a certain branch joint,which is beneficial to the formation of complex cracks.