油藏化学驱平衡方程解法改进

Modified solution techniques for chemical equilibrium equations in reservoir chemical flooding

针对油藏化学驱数值模拟软件的化学平衡方程解法存在的问题进行分析 ,研究出改进的方法 ,并将新方法进行编程实现、应用到化学驱数值模拟软件中。油藏化学驱过程中 ,化学反应平衡可以用一组非线性方程组来描述 ,可用经典 Newton法求解。但由于油藏地质化学反应的复杂性 ,经典方法时常失效 ,导致数值模拟的失败。针对经典 Newton法求解失效的具体情况 ,考虑几种措施 (参数 Newton法、阻尼 Newton法及最小二乘法 )改进原有的方法以求得非线性方程组的数值解 ,从而保证模拟顺利进行。该模型已应用于大庆油田化学驱采油的实际模拟中。以四注一采井组为例 ,原方法在模拟到 5 0 6.7d时作业流产 ;

Three modified solution techniques were developed to solve the nonlinear chemical equilibrium equations for reservoir chemical flooding. The chemical reactions and the equilibrium in reservoir chemical flooding were described by a set of nonlinear equations solved using the Newton method. The classical Newton method often fails to give a stable numerical solution because of the complexity of the geo chemical system. Therefore, three modified Newton approaches, the Parameter Newton method, the Damping Newton method and the Least Squares method, were used to solve the nonlinear chemical equilibrium equations for a case where the classical Newton method failed. The approaches were then applied to analyze chemical flooding of the Daqing Oil Field which could not be analyzed using the classical method. As an example, the classical method failed at a simulation time of 506.7 d, however, the modified methods can resume the simulation and complete it.