气井系统出砂预测模型研究及应用

MODEL OF SYSTEMATIC SANDING PREDICTION AND ITS APPLICATION FOR GAS WELLS

系统出砂预测的基本内容包括定性出砂预测、出砂临界生产压差预测以及实际生产条件下的出砂半径预测。文章首先阐述了定性出砂预测方法;考虑气藏流体压力分布,建立弹性岩石材料的应变平衡方程,求解并结合弹性岩石的应力—应变方程得到地层岩石的弹性应力解;在孔壁上采用考虑孔隙压力的莫尔—库仑准则,便可预测出砂临界井底流压和生产压差;求解塑性变形区的应力平衡方程,并结合塑性区的应力—应变准则可得到塑性变形区的塑性应力解;根据弹、塑性边界的应力连续条件,建立弹、塑性边界上的径向应力平衡方程,求解可计算弹、塑性区边界半径即出砂半径。对涩北气田涩4-9井进行了系统出砂预测,与实际生产资料基本符合。

The basic contents of systematic sanding prediction cover the qualitative sanding prediction, the critical producing pressure drop prediction of sanding, and the sanding radius prediction under practical producing conditions. At first, the method of qualitative sanding prediction is described. According to the pressure distribution of gas reservoir fluids, the strain equilibrium equation is established for the elastic rock materials. Solving the equation and integrating the stress-strain equation of elastic rock, the elastic stress distribution of the reservoir rock can be obtained. Applying the Mohr-Coulomb criterion considering the pore pressure to the borehole surface, the critical bottom-hole flowing pressure and producing pressure drop of sanding can be predicted. Solving the stress equilibrium equation and integrating the stress-strain criterion in the plastic deforming zones, the plastic stress solution can be obtained for the plastic deforming zones. According to the stress continuous conditions of the elastic/plastic boundaries, the radical stress equilibrium equation is established at the elastic/plastic boundaries. Solving the equation, the boundary radius of e-lastic/plastic zones (i. e. sanding radius) can be calculated. With the method to conduct the systematic sanding prediction for Wells Se 4-9 of Sebei gas field, the results fit the real production data essentially.