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深水浅部地层尚未固结成岩,上覆岩层压力较低,破裂压力也较低,发生井壁破裂与坍塌的风险较高,目前尚无完善的力学理论来预测深水浅层的破裂压力。为此,引入黏土力学超孔隙压力及其破碎性系数来对井眼周围有效应力进行修正,建立非均匀受力的圆形井眼模型、椭圆形井眼模型及其圆形井眼弹塑性力学模型,结合弹性力学理论、塑性力学理论、屈服条件及黏土力学理论,推导出深水浅层非均匀受力情况下的破裂压力计算公式,通过实际测井数据及文献数据完成模型验证,进一步对破裂压力影响因素进行分析。结果表明,深水浅部非均匀受力地层破裂压力受孔隙压力系数、岩石破碎性系数、椭圆长短轴比等因素的影响,孔隙压力系数与岩石破碎性系数越大,破裂压力越小;椭圆长短轴比越大,破裂压力越大,当长短轴比为1.0时,破裂压力最小。
Shallow shallow reservoirs have not been consolidated into diagenesis. The pressure of overlying strata is low and the fracture pressure is low, so there is a high risk of shaft wall rupture and collapse. There is no perfect mechanics theory to predict the fracture pressure in shallow water. Therefore, by introducing the super-pore pressure of clay mechanics and its crushing coefficient to correct the effective stress around the borehole, a circular wellbore model, an oval wellbore model and its round hole elasto-plasticity mechanics Model, combined with elastic mechanics theory, plasticity mechanics theory, yield condition and clay mechanics theory, deduced the formula of fracture pressure under the condition of shallow water inhomogeneity stress. Through the actual logging data and literature data to complete the model verification, Stress factors for analysis. The results show that the fracturing pressure of non-uniform shallow strata in deep water area is affected by pore pressure coefficient, rock fragmentation coefficient and elliptic long axis ratio. The larger the pore pressure coefficient and rock fragmentation coefficient, the smaller the fracture pressure. The length of ellipse The larger the axial ratio, the greater the rupture pressure. When the ratio of the major axis to the minor axis is 1.0, the rupture pressure is the smallest.