长庆油田环西-彭阳探区长8油层自生热压裂工艺研究与应用

Research and application of self-generated heat fracturing technology for Chang 8 reservoir in Huanxi-Pengyang exploration area of Changqing Oilfield

长庆油田环西-彭阳探区长8层常规压裂改造效果差,室内研究发现关键原因是原油“冷伤害”。自生热压裂工艺是解决该问题的有效手段。对比分析目前几种自生热压裂工艺的优缺点,提出了一种改进的自生热压裂液体系,该体系的关键是稠化剂——超支化聚合物,该聚合物可以在高矿化度盐水和酸性条件下形成胶体。经实验评价,该体系可使压裂液升温幅度达55.2℃,最高携砂砂比35%,破胶性能良好,破胶液对支撑裂缝及地层基质伤害率较低,具有良好的耐温耐剪切性能,对管柱腐蚀较弱,体系反应释放出的气体可明显提高地层压力,提高返排率。2020年自生热压裂工艺在长庆油田环西-彭阳探区已实施6井次,与常规压裂工艺相比,试油产量由平均3.5 t/d上升至13.27 t/d,产液量由平均20.44 t/d上升至21.86 t/d,试油成功率由21.7%上升至50%,效果显著,为长庆油田环西-彭阳探区长8层的进一步开发提供了有力的技术支撑。

The conventional fracturing effect of the Chang 8 layer is poor in the Huanxi-Pengyang exploration area of Changqing Oilfield.Laboratory studies have found that the key cause of this problem is the“cold damage”of crude oil.The in-situ thermal fracturing technology is an effective means to solve this problem.By comparing and analyzing the advantages and disadvantages of several current in-situ thermal fracturing technologies,it is proposed an improved in-situ thermal fracturing fluid system.The key of the system is the hyperbranched polymer,which can form colloids under the conditions of high salinity brine and acid.According to the laboratory evaluation,the system can increase the temperature of the fracturing fluid to 55.2℃,with the highest sand-carrying ratio of 35%;the gel breaking performance is good,the damage rate of the gel breaking fluid to the supporting cracks and the formation matrix is low,and the system has good temperature resistance and shear resistance,which has weak corrosion to fracturing string.The gas generated by the reaction can obviously increase the formation pressure and the flow-back rate.In 2020,the in-situ thermal fracturing technology has been implemented in the Huanxi-Pengyang exploration area of Changqing Oilfield for 6 wells.Compared with the conventional fracturing technology,the average test production is increased from 3.5 t/d to 13.27 t/d,the average daily fluid production is increased from 20.44 t/d to 21.86 t/d,and the success rate of oil test is increased from 21.7%to 50%.The stimulation effect is remarkable,which provides strong technical support for the further development of the Chang 8 layer in the Huanxi-Pengyang exploration area of the Changqing Oilfield.