稠油出砂冷采颗粒离散元数学模型

Discrete element method mathematical model of sand-carrying cold heavy oil production

疏松砂岩油藏渗流出砂问题的实质是砂岩地层微粒的剥蚀与运移,鉴于传统物理模拟方法的复杂性以及现有数值模拟方法在描述非连续介质方面的不足,建立了考虑流固耦合的颗粒离散元稠油出砂冷采数学模型,优选了Mohr-Coulomb屈服准则作为颗粒从母岩剥离的破坏准则,从微观角度定量描述出砂机理。数学模型模拟产砂速率、产油速率及井底压力结果与一维物理模型实验实测值均吻合较好,验证了模型的正确性和可靠性,在此基础上,定量描述了稠油出砂冷采的临界条件及蚓洞扩展规律。把所建立数学模型拓展到现场,计算结果表明,颗粒离散元数学模型能够正确描述稠油出砂冷采出砂规律,为研究稠油出砂冷采提供了一种新手段。

The sand production in unconsolidated sandstone reservoirs is essentially caused by erosion and migration of sandstone particles.Due to the complexity of the conventional physical modeling and the insufficient modeling capability of current numerical simulation for discontinuous media,this paper established a mathematical model for the Cold Heavy Oil Production（CHOP） procedure considering fluid-solid couplings by using Discrete Element Method,selected the Mohr-Coulomb yield criterion as the failure criterion of particle peeling from parent rock,and described the microscopic sand production mechanism quantitatively.The mathematical model presented very good matches with the 1D physical modeling lab results in the simulation of sand production rate,oil production rate and bottom-hole pressure,which verified the proposed mathematical model.Based on this model,the authors also investigated the critical condition of CHOP and wormhole extension rule.By applying the mathematical model into field cases,the calculation results indicate that the discrete element mathematical model can simulate the sand production mechanism in the CHOP procedure very well,which provides a new approach to study sand-carrying cold production.