考虑基质和酸压缝应力敏感性的产能预测模型

Productivity Forecasting Model with Consideration to Stress Sensitivities of Matrix and Acid-induced Fractures

应力敏感性储层中的酸化压裂井,其基质的渗透率和主缝的导流能力均会受到地应力变化的影响,使得传统的产能预测模型出现偏差。为此,采用离散元方法进行流固耦合模拟,分析酸压主缝的导流能力在不同生产压差下的变化及其影响因素;在传统的径向流动模型的基础上,将酸压缝导流能力的变化抽象为对等效表皮系数的修正,建立同时考虑基质和酸压缝导流能力应力敏感性的产量预测模型,并考虑了压力恢复时导流能力损害的不可逆性。采用上述模型对库车西部一口酸压井的产量变化规律进行了定量分析。研究表明,基质渗透率应力敏感性和酸化压裂主缝导流能力的变化对产能的影响均不可忽略。研究对于合理制订长期生产制度具有一定的指导意义。

For stress sensitive reservoirs with wells with acid fracturing operations,both permeability of matrix and conductivity of key fractures are subject to impacts of changes in crustal stresses.Consequently,conventional productivity forecasting models are often susceptible to errors.Under such circumstances,discrete-element techniques were deployed to simulate fluid-solid coupling to analyze changes in conductivity of acid-induced fractures under different differential pressures and key influencing factors.On bases of conventional radial flow models,changes in conductivities of acid-induced fractures can be taken as correction to equivalent skin factors.In this way,productivity forecasting model with consideration to stress sensitivity of conductivity of both the matrix and acid-induced fractures can be established.During the course,irreversibility of conductivity losses during pressure restoration was also considered.Quantitative analyses were conducted for patterns of changes in productivities of a well with acid-fracturing operations in western parts of the Kuqa Block were conducted by using the innovative model.Research results show,impacts of changes in stress sensitivities of matrix permeability and conductivity of acid-induced fractures on productivities are not negligible.Relevant researches may provide necessary guidance for preparation of long-term production program more rationally.