低渗储层近井地带聚合物伤害模拟评价

Simulation and Evaluation on Polymer Damage near Wellbore Region in Low-Permeability Reservoirs

聚合物作为钻井液常用处理剂在钻井过程中得到了广泛应用,其对储层的伤害也日益被人们关注。为了建立一种快速、准确评价低渗储层钻井过程中聚合物对近井地带伤害的方法,在充分调研国内外聚合物伤害模拟评价技术的基础上,建立了低渗储层近井地带聚合物伤害模型,给出了可用于计算机编程的求解方法,并利用所建立的模型,对钻井过程中影响聚合物伤害的主要因素进行了定性分析。结果表明:聚合物伤害发生在近井地带,随着地层渗透率降低,伤害深度和程度都降低;随着压差增大,聚合物伤害程度增加;聚合物质量浓度增大,可降低工作液的滤失量,减小聚合物的伤害半径;毛管力对聚合物伤害的影响较小;启动压力梯度可降低聚合物伤害,但当其较小时,对聚合物伤害的影响不大。

Polymers are widely used in drilling as a common agent of drilling fluids and their damage to reservoirs is increasingly drawing attention.Based on investigations on the simulation evaluation techniques of polymer damage,a damage model of polymers near wellbore region of low permeability reservoirs was established for a fast and accurate evaluation method.The method of solving differential equations was also given.This method can be used for computer programming.Main factors influencing polymer damage in drilling were qualitatively analyzed by using the proposed model.The results showed that the polymer damage occurred in the vicinity of a wellbore and damage radius and the degree would decrease with the reduction of formation permeability.In addition,the degree of polymer damage would increase as the increase of pressure differential.An increase of polymer concentration could reduce the filter loss of drilling fluid and polymer damage radius.It also showed that capillary force had less effect on polymer damage and the starting pressure gradient might reduce polymer damage.But the influence on polymer damage would be much less when starting pressure gradient was quite low.