致密油储层压裂液渗吸特征及水锁损害评价

Imbibition characteristics of fracturing fluid in the tight oil reservoir and water lock damage evaluation

刘博峰 张庆九 陈鑫 杨震 张峰 曹东林

中国石油玉门油田分公司工程技术研究院，甘肃 酒泉 735000

Engineering Technology Research Institute, Yumen Oilfield Company, Petrochina, Jiuquan 735000, China

致密油储层压裂施工后仍会有大量的压裂液滞留在储层中，不仅会对致密油储层中的原油产生一定的渗吸驱油作用，还可能对储层造成一定的水锁损害；因此，为了确认压裂液在致密油储层中的渗吸特征和产生的水锁损害程度，文中研究了不同类型破胶后的压裂液对目标区块致密油储层天然岩心的渗吸驱油效果，在此基础上，开展了压裂液渗吸后对岩心的水锁损害评价。渗吸实验结果表明：破胶后，3种不同类型的压裂液中，清洁压裂液的渗吸驱油效率最高（20%以上），明显高于胍胶压裂液和滑溜水压裂液；岩心的渗透率与清洁压裂液的渗吸驱油效率不是线性关系，而是存在1个最佳的渗透率范围，在此范围内渗吸驱油效率最佳；渗吸实验温度越高，清洁压裂液的渗吸驱油效率越高。水锁损害实验结果表明：清洁压裂液渗吸后岩心的水锁损害率最小（15%左右），胍胶压裂液的水锁损害率最高（40%以上），滑溜水压裂液次之（30%以上），因此，在S区块致密油储层压裂施工时，应选择渗吸驱油效率较高、水锁损害程度较低的清洁压裂液体系。

After fracturing in tight oil reservoir, there will still be a large amount of fracturing fluid remaining, which will not only have a certain effect of imbibition and displacement on the crude oil in the tight oil reservoir, but also cause certain water lock damage to the reservoir. Therefore, in order to clarify the imbibition characteristics of fracturing fluid in the tight oil reservoir and the damage degree of water lock, the imbibition and displacement effect of fracturing fluid after different types of gel breaking on the natural cores in the study block are studied. Based on this, the water lock damage evaluation of cores after fracturing fluid imbibition is carried out. The results of imbibition experiment show that: among the three different types of fracturing fluids after gel breaking, the imbibition and displacement efficiency of clean fracturing fluid is the highest (more than 20%), which is significantly higher than that of guar gum fracturing fluid and slippery water fracturing fluid; the relationship between core permeability and imbibition and displacement efficiency of clean fracturing fluid is not linear, however there is an optimal permeability range, which makes the imbibition displacement efficiency reach the best; the higher the test temperature is, the higher the imbibition displacement efficiency of clean fracturing fluid is. The results of water lock damage experiment show that the damage rate of clean fracturing fluid is the smallest (about 15%), the damage rate of guar gum fracturing fluid is the highest (more than 40%), and the slippery water fracturing fluid is the second(more than 30%). It is suggested that the clean fracturing fluid system with high imbibition oil displacement efficiency and low water lock damage degree should be selected during the fracturing operation of tight oil reservoir in S Blocks.

10.6056/dkyqt202103006