阳春沟区块页岩气超临界CO_(2)增能压裂研究与应用

Research and application of supercritical CO_(2)energized fracturing for shale gas in Yangchungou block

目的目前,超临界CO_(2)压裂应用前景广阔,为更好地指导现场应用,亟需明确超临界CO_(2)压裂的起裂压力和裂缝扩展规律。方法考虑压裂过程温度变化对CO_(2)物性的影响以及岩石中的热应力作用,建立热流固耦合超临界CO_(2)压裂模型。探究了水平应力差、天然裂缝逼近角以及CO_(2)注入温度对裂缝起裂的影响。结果在阳春沟Y井开展的现场试验表明:与水力压裂相比,超临界CO_(2)压裂可以明显降低裂缝起裂压力,即使在高水平应力差下,仍可以获得复杂的裂缝形态;天然裂缝逼近角增大,起裂压力随之增大,裂缝复杂程度增加;CO_(2)注入温度与地层温差越大,热应力作用越明显,裂缝形态越复杂。结论现场应用显示注入前置超临界CO_(2)可以有效降低起裂压力,有利于提高后续水力压裂的缝内净压力,增强储层改造效果。

Objective The application prospects of supercritical CO_(2)fracturing technology are broad,currently.It is necessary to ascertain crack initiation pressure and the law of fracture extension in supercrtical CO_(2)fracturing in order to guide on-site application better.Methods Based on this,considering the influence of temperature changes during the fracturing process on the physical properties of CO_(2)and the thermal stress effect in rocks,a thermal fluid solid coupling supercritical CO_(2)fracturing model is established.The effects of horizontal stress differences,natural crack approach angle and CO_(2)injection temperature on fracture initiation are explored.Results The on-site test was carried out in Well Y of Yangchungou.The results show that supercritical CO_(2)fracturing can significantly reduce the fracture initiation pressure compared with hydraulic fracturing;Even under high levels of stress difference,complex crack morphology can still be obtained.The approach angle of natural fractures increases,the initiation pressure increases,and the complexity of fractures increases accordingly.The larger the difference between the CO_(2)injection temperature and the formation temperature,the more obvious the thermal stress induction effect and the more complex the fracture morphology.Conclusions On-site applications have shown that injecting pad injection supercritical CO_(2)can effectively reduce the fracturing pressure,which is beneficial for improving the net pressure inside the fracture in subsequent hydraulic fracturing and improve the effect of reservoir transformation.