连续损伤断裂模型在水平井增产评估中的应用

Application of Continuous Damage Fracture Model in Stimulation Estimate for Horizontal Well

目的讨论一种塑性损伤模型,提出利用三维有限元解决水力学耦合问题的方法.方法运用有限元软件数值模拟的方法,建立连续损伤断裂全局模型和子模型,对油田区块岩体内部裂纹开展状况进行研究.结果在数值模拟过程中岩体材料参数和注液压力的设定,直接影响区块岩体模型的有效裂缝带的尺寸,进而影响对增产措施的有效性的判定.按照损伤变量数值不小于5%的原则来定义裂纹的有效长度,其合理性需要通过实际注液增产工程来进一步验证.结论通过连续损伤模型预测的裂缝扩展可以评价致密砂地水平井的增产措施;岩体渗透性分布情况、注液压力、有效裂缝长度和裂缝分布是主要影响因素.

This paper studied a plastic damage model and proposed a method for solving hydraulics coupling problems by 3D FEM. A global continuous damage model and a sub-model were built to study the internal crack state of rocks in the oil block. It is found that in the process of numerical simulation, material parameters and liquid injection pressures impact the effective crack size of rock block model directly and further affect the judgment for effectiveness of stimulation estimate. The rationality of the effective crack length defined by the principle that the damage variable value is not less than 5 % should be further verified through the actual injection fluid stimulation engineer- ing. Conclusion is that the stimulation of a horizontal well in a fight sand formation can be esti- mated by the predicted fracture propagation of the continuous damage model. Rock permeability distribution, liquid injection pressure, effective fracture length and fracture distribution are major in- fluence factors.