工程钻井泥浆压力对泥浆失水过程影响实验分析

工程钻进过程中钻井泥浆在井液压力作用下通过孔壁泥皮失水是导致水敏性地层失稳的主要原因。为了深入了解井液失水规律,本文通过改变井液的压力差,对不同井液压力作用下钻井液漏水情况进行了模拟试验研究。实验结果表明:在相同时差内,失水量随井液压力的增大呈现先减小后增大规律; 在相同井液压力下,失水的速率随时间逐渐减小,并最终趋于稳定值,失水速率的稳定值与井液压力大小没有明显的相关性; 不同井液压力下,随钻井液压力的增大,前期失水量所占的比重增加; 形成泥皮的质量随着井液压力的增大而增大。标准失水量随形成泥饼质量的增加呈现先减小后增大的规律。研究成果为钻井泥浆的失水特征评价、失水量的控制提供了参考依据。

EXPERIMENTAL ANALYSIS ON EFFECT OF ENGINEERING DRILLING FLUID PRESSURE TO PROCESS OF FLUID INFILTRATION AND LEAKAGE

The infiltration of water through wall cake pore under the effect of fluid pressure is the cause of instability of water sensitive formations during drilling process. In order to better understand the laws of infiltration, infiltration test is conducted under different fluid pressures. The test results show that when infiltration time is the same, the infiltration water increases first and then decreases with increasing of fluid pressure. When fluid pressure is the same, the infiltration rate decreases with increasing of time and eventually tends to a stable value. The stable value of infiltration rate has a low correlation with fluid pressure. When fluid pressure is different, the proportion of previous infiltration volume and the cake mass(under dry conditions) increase with increasing of fluid pressure. Infiltration of water increases first and then decreases with increasing of cake mass. The results of the test can provide reference for evaluation and control of fluid infiltration.