保护裂缝性储层的复合盐弱凝胶钻井完井液

钻井液侵入是裂缝性储层损害的主要因素之一，实验分析了无机盐、有机盐等不同类型水溶性加重剂对无固相钻井液性能的影响，研究了无固相钻井液快速弱凝胶特性形成条件以及高温稳定性和抑制能力的提高方法，研制出的无固相复合盐弱凝胶功能性钻井液高温稳定性达到150 ℃，具有独特的流变性（0.3 r/min黏度达到27000 mPa·s）和优良的抑制能力（150 ℃HTHP滤失量小于15 mL），成本远低于甲酸盐钻井完井液。遵循理想充填D90规则优选出了暂堵方案，应用不锈钢缝板模拟岩心与人工造缝碳酸盐岩岩心进行储层保护效果评价。实验结果表明：复合盐弱凝胶无固相钻井液加入优选暂堵组合后，HTHP滤失量进一步降低（小于10 mL），在不锈钢缝板模拟岩心（缝宽40~60 μm）端面快速形成有效封堵层，人工造缝碳酸盐岩岩心的渗透率恢复值高达97.18%，储层保护效果十分理想。

COMPOSITE SALT FREE-GEL DRILLING FLUID FOR THE FRACTURED RESERVOIRS

The invasion of drilling fluid is the main cause to the damage of fractured formation. The composite salt free gel drilling fluid is got after analyzing the influence of different kinds of such soluble adulterant as organic salt and non organic salt on the performance of the solid free drilling fluid and studying the condition to develop the free gel structure and the method to improve the fluid's high temperature stability and inhibitive property. The experiment shows that the apparent viscosity of this system is as high as 27000 mPa·s when the share rate is 0.3 r/min and the high temperature reaches at the stable level of 150 ℃ and the HTHP filtrate loss decreases to 15 ml at 150 ℃. The diversion program is selected out optimistically according to criteria of ideal packing theory D90 and the effect of reservoir protection is evaluated by the artificial fractured carbonate core and mimic micro fracture steel core. The result shows that when the bridging particles are added into the composite salt free gel drilling fluid, an effective bridging layer can be observed on the face of the steel core (the slot width is about 40-60 μm ) and the HTHP filter loss decreases to less than 10 ml, and the return permeability of the artificial fractured carbonate core increases to 97.18%. The effect of reservoir protection is ideal.