煤层低伤害氮气泡沫压裂液研究

A nitrogen foam fluid with low formation damage for CBM fracturing treatment

随着煤层气开发规模不断扩大,在煤层压裂增产过程中压裂液滤失量高、地层伤害严重、返排困难且压裂效果差等问题不断凸显。结合煤层气储层物性,研制低伤害氮气泡沫压裂液体系,即0.5%YSJ杀菌剂+1%FP-1复合起泡剂+2%KCl防膨剂+N2。对该氮气泡沫压裂液体系进行滤失试验和分散试验研究。结果表明:该泡沫压裂液体系起泡及稳泡性能良好,耐剪切能力强,携砂能力强;泡沫和气液两相滤饼的封堵作用可以明显降低压裂液的滤失量,并且氮气可以增强压裂液的返排能力;压裂液体系中的表面活性剂可以降低煤粉与水相的界面张力,提高压裂液对煤粉的分散能力;相对于常规压裂液体系,氮气泡沫压裂液体系对煤层气岩心的伤害较小。

Fracturing treatment is essential for the development of coalbed methane （CBM） fields. In the fracturing of coal seams, high filtration loss, serious formation damage, low flow-back and poor efficiency were the main problems when using conventional water-based fracturing fluids. A nitrogen foam fracturing fluid system with low formation damage was developed based on the geological features of CBM reservoirs. The formula of the foam fluid mainly includes a bactericidal agent, foa- ming surfactants and clay stabilizers. Filtration loss, dispersion, and microscopic foaming experiments were conducted for testing the capacities of the fluid system as a foaming and fracturing fluid. Experimental results show that the fracturing fluid has a good foaming ability and foam stability, excellent shearing bearing ability, strong sand carrying capacity. The plugging effect of foam can significantly reduce the filtration loss, and nitrogen can improve the flow back ability of the fracturing flu- id. The surfactants in the fracturing fluid can also reduce the interfacial tension between coal and water, thus improving the dispersion of coal powders in the fluid. In comparison with conventional fracturing fluids, the nitrogen foam fracturing fluid can cause much less formation damage to the CBM reservoir.