砂岩气藏基质酸化残液返排影响因素研究

Study on influencing factors of matrix acidzing residual flow back in sandstone gas pools

酸化后残液返排过程涉及气液两相渗流、气窜、液锁、气驱水等物理现象,因此影响残液返排效果的因素很多。在模拟基质酸化过程单一影响因素的基础上,进行了多因素综合研究。研究结果表明:相同条件下,渗透率越低的储层其返排效果越差;随工作液黏度增大,返排率呈下降趋势,当黏度增加到一定程度后,返排率变化不大;一定界面张力范围内,界面张力对返排率影响不大,界面张力增加,返排率只有小幅度减小。而各参数组合k/(δμ)值增大,返排率增大,且变化率由小变大。另外,酸化半径越小,越容易达到极限返排率,并且最终返排率相对较高。当酸化半径达到一定值后,最终返排率变化不大。实验结果显示不同酸化半径的最终返排率取决于储层物性。

Formation fracturing and acidizing are the important stimulation treatments for low permeability gas formation.Many physical phenomenons happen in the process of residual fluid flow back after acidzing such as gas-liquid two-phase flow,gas channeling,water locking and gas driving water,so the residual returning efficiency is affected by such many factors.The experiments stimulating the single factor and multi-factors affect on return efficiency during matrix acidzing were conducted.The research results indicated that lower permeability has lower return efficiency under the same experimental conditions.Return efficiency is decreasing with the increas-ing of viscosity and surface intension,but the change is smooth while viscosity increase to a certain degree;in a certain range of surface tension,the effect of surface tension on flow back efficiency is very tiny,which means that the increase of tension causes small decline of flowback.In addition,the effect of parameters k /（δμ） on the return efficiency is similar to the viscosity according to experimental results.The results also indicate that the smaller the acidzing radius,the easy to get to the limit of flow back efficiency and the resulting efficiency is relative higher.The value of the final efficiency changes little while the radius reaches to a certain value,and the experiment illustrates the final efficiency different form various acidzing radius which is related to formation properties.