常温下油包水乳化钻井液水侵后对裂缝性储层渗透率的伤害性能分析

Damage Analysis of Water-invasion Emulsion Drilling Fluid on Permeability of Fractured Reservoir at Room Temperature

为了分析实际钻井过程中地层水侵入油包水乳化钻井液体系对储层渗透率的影响,采用油水比分别为80∶20、70∶30、60∶40、50∶50、40∶60、30∶70钻井液体系模拟受不同程度水侵后的油包水乳化钻井液,在常温下研究了钻井液随着油水比的变化对储层的损害情况及流变性和润湿性变化。研究结果表明:随油水比的减小,一方面钻井液稳定性变差,对井壁的冲刷程度加剧,泥饼遭到破坏,滤失量增大,大量的固相颗粒进入地层造成储层伤害;另一方面裂缝表面对钻井液流体的束缚能力减小,有利于后期开采过程中近井带钻井液的反排,减小储层伤害。综合考虑,油水比40∶60数60∶40的钻井液较为合适。

In order to analyze the effect of water invasion on the reservoir permeability,the water-in-oil water emulsified drilling fluid systems after water invasion was simulated through preparing the drilling fluid with different oil-water ratio of 80：20,70：30,60：40,50：50,40：60,30：70,and the evaluation experiments of the reservoir damage on the drilling fluid,the rheological and wettability of drilling fluids with different oil-water ratios,were conducted. The results indicated that,on one hand,with the decrease of oil-water ratio,the stability of drilling fluid became worse,which would intensify the erosion degree of the borehole wall,destroy the mud cake and increase the filtration loss,making a large number of solid particles enter the formation and cause the reservoir damage. On the other hand,the binding ability of the fractured surface to the fluid was reduced,which was beneficial to the reverse flow of the drilling fluid in the near wellbore and reduce of reservoir damage. The suitable oil-water ratio of water-in-oil water emulsified drilling fluid systems was 40∶60—60∶40.