低伤害压裂液在川西侏罗系致密气藏后期开发中的应用

Application of Low Damage Fracturing Fluid in the Later Development of the Jurassic Tight Gas Reservoir in West Sichuan

针对川西侏罗系致密气藏储层物性差、孔隙结构差、喉道微小、储层敏感性强和常规压裂液残渣形成滤饼及压裂液水相滤失量大和地层压力低而储层伤害大等难点,通过降低常规压裂液稠化剂浓度和调整其他添加剂等技术处理,形成了低浓度稠化剂低伤害水基压裂液体系,并将CO2泡沫压裂液和自主研发的自生热增压型"类泡沫压裂液"应用于川西侏罗系致密气藏后期开发中的加砂压裂改造。经对比实验研究证实,低浓度稠化剂水基压裂液能显著降低残渣形成滤饼后对储层的伤害,显著提高了支撑裂缝的导流能力,压后天然气增产效果明显,泡沫压裂液和自生热增压型"类泡沫压裂液"的滤失系数及伤害性远比常规压裂液小,增压助排作用明显,压裂返排率比常规压裂液高,采用"类泡沫压裂液"施工时,返排率最高达92%,平均为77.3%,比常规液氮拌注的平均返排率高38.3%。采用3种低伤害压裂液的施工井获得的天然气增产效果远比采用常规压裂液施工的井好,现场效果明显。

West Sichuan poor pore structure, tiny fracturing fluid sludge ,a Jurassic tight gas reservoir has the fracturing difficulties of poor reservoir properties, throat,sensitive damage property of rocks and filter cakes formed by conventional large quantity of water phase loss of fracturing fluid and severe reservoir damage.Based on the processing technologies of reducing and low gas reservoir pressure the concentration of thickening agent for the conventional fracturing fluid and adjusting the concentration of other additives,a low damage water-based fracturing fluid system with low concentration of thickening agent is formed,and the CO2 foam fracturing fluid and a developed self-heat-type analogous foam fracturing fluid are applied in sand fracturein the later development of Western Sichuan Jurassic tight gas reservoir.By comparison,experimental studies have proven that the water-based fracturing fluid of low concentration thickening agent can significantly reduce the reservoir damage by the filter cake,and can improve flow conductivity of proppant fractures.Foam fracturing fluid and the self-heat-type analogous foam fracturing fluid have the far lower filtration coefficient and damage ,more obvious supercharge and cleanup and higher flowback rate than the conventional fracturing fluid.Therefore,the stimulation of gas after fracturing is obvious.After analogous foam fracturing fluid is applied in the field,the flowback rate is up to 92% at most with 77.3% of the average,which is higher 38.3% than the one by the conventional fracturing fluid.The stimulation effect of the natural gas by these three low damage fracturing fluids is better than that by the conventional fracturing fluid in the field.