用流固耦合方法研究气藏物性参数动态变化

A RESEARCH ON THE DYNAMIC CHANGE IN PETROPHYSICAL PARAMETERS OF GAS RESERVOIR BY USE OF FLUID-SOLID COUPLING METHOD

实践表明，气藏孔隙度和渗透率等重要物性参数随气藏开发不断变化。定量描述和预测这一变化规律有十分重要的实际意义。由于目前尚无有效的解决办法，文章建立了气藏流－固耦合模型，其中考虑了以下因素：气藏岩石变形、地应力变化、气体渗流与岩石应变耦合。导出的控制方程中，因气藏渗流和岩石应变方程互含压力和位移项，非线性强，不能单独求解。用有限差分方法将两组方程离散成主对角占优的七对角矩阵，采用隐式迭代方法求解。通过模型对比和示例分析说明，文章所建模型可广泛用于研究气藏物性参数、应力应变、套管变形、射孔孔眼稳定性、以及气藏出砂和垮塌等工程问题。

It is indicated in practice that certain important parameters as porosity and permeability are unceasingly changed with gas reservoir development and it is very important to quantitatively describe and predict such a change rule. For this reason, a reservoir fluid-solid coupling model is set up in the paper, in which the following factors were considered, i. e. reservoir rock deformation, change in earth stress, gas percolation flow and rock strain coupling. In the governing equations derived, owing to the fact that the pressure and displacement terms are contained in gas percolation flow and rock strain equations, they are of strong nonlinearity and can't be solved alone. Only through discretizing the two groups of equations into seven diagonal matrixes with master diagonal domination by use of finite difference method, can they be solved by implicit iteration method. By means of comparing with the other models and analyzing certain examples, it is shown that the model may be widely used for studying gas reservoir petrophysical parameters, stress strain, casing deformation and the stability of perforations as well as certain engineering problems as gas reservoir sanding and sloughing, etc.