射孔完井高压气层出砂三维预测方法

针对射孔完井高压气层地层出砂问题,根据有效应力定律,建立了三维应力场弹塑性地层出砂模型,并运用弹塑性有限元方法进行求解。根据编制的计算程序,研究了射孔井筒附近应力、有效塑性应变的分布规律。研究发现,最大有效塑性应变位置是在射孔起始部位的上下端,因而是最容易出砂的位置;同时,地层压力越高、临界生产压力越低,就越不易出砂。临界生产压差是由岩石性质、流体性质、地应力、地层压力等条件综合确定的。尽量维持较高且稳定的地层压力和采用合理的油井生产制度,可以减少出砂量。模型适用于不同地应力条件、不同几何参数与射孔方案、不同岩石和流体参数等条件下射孔完井的气层出砂预测。

3D Prediction for Sand Production in Gas Wells of Perforation Completion

In order to solve the problem of sand production in gas-wells of perforated completion, a three-dimensional model for sand production of elastic-plastic gas formation is established based on the law of effective strain, and is then solved by the nonlinear finite element method. The trend of stress and effective plastic strain distribution in the near wellbore area is investigated according to the computation results, and it is found that the maximum effective strain occurs at the top and bottom of the starting position of perforations, where sand production is prone to happen. The critical bottom hole pressure decreases with the increasing of formation pressure, weakening the trend of sand production. The critical bottom hole pressure depends on the rock properties, fluid characteristics, values of geo-stresses and formation pressure comprehensively, and sand produced can be reduced under stable and high formation pressure and by following consistent production procedures. The model can be used under general conditions of practical geo-stresses, complex geometry and perforation proposal, and variable rock and gas properties.