页岩油前置超临界二氧化碳压裂造缝技术

Prepad supercritical carbon dioxide fracturing technology in shale oil reservoir

针对松辽盆地南部G1H井青一段泥页岩储层天然裂缝不发育的特点,为解决该井常规体积压裂缝网复杂程度有限的难题,研究了前置大排量超临界二氧化碳造缝技术。利用超临界态二氧化碳表面张力低,流动性、扩散性强的特点,提高裂缝破岩能力,增加裂缝复杂程度。温度场模拟显示,G1H井近井筒9 m以上的位置,温度都能超过31℃,同时地层压力达到25 MPa,井底满足超临界二氧化碳的形成条件。该井施工过程中,微地震裂缝监测显示裂缝形态复杂,改造体积较大,压后评估二氧化碳压裂事件产生效率约是水力压裂的4.6倍,造缝效果很好;测试过程中,稳产油36 t/d,增产效果显著。该技术对青一段泥页岩储层具有较好的适用性,为后续松辽盆地页岩油的高效开发提供了借鉴。

The characteristic of Member 1 of Qingshankou formation of well G1H in the southern Songliao Basin is that the natural fractures are not developed.In order to solve the problem of the limited complexity of fracture network by conventional fracturing technology of the well,the pre-large displacement supercritical carbon dioxide fracturing technology was studied.Supercritical carbon dioxide has the characteristics of low surface tension,strong fluidity and diffusivity,which can improve the rock breaking abilityand increase the complexity of cracks.The temperature field simulation shows that the temperature of G1H well can exceed 31℃at a position 9 meters away from the wellbore,and the formation pressure reaches 25 MPa.So the bottom hole environment can meet the formation conditions of supercritical carbon dioxide.During the construction of the well,the micro-seismic fracture monitoring shows that the fracture morphology is complex and the reconstruction volume is large.The efficiency of carbon dioxide fracturing events after fracturing is about 4.6 times that of hydraulic fracturing,and the fracture effect is good.During the test,the stable oil production was 36t/d,and the effect of increasing production was remarkable.This technology has a good applicability to the mud-shale reservoir of Qing 1st member,and provides a reference for the efficient development of shale oil in the Songliao Basin.