八道湾组全直径岩心不同压裂液下真三轴压裂裂缝延伸特征

选用新疆焉耆盆地博湖坳陷,宝浪苏木构造带,下侏罗统八道湾组X井全直径岩心制备300 mm的立方体试样,分别开展滑溜水压裂液、瓜胶压裂液和超临界二氧化碳压裂,研究不同压裂液下的破裂压力和裂缝延伸形态特征。结果表明：瓜胶压裂液压裂下的破裂压力最高,滑溜水压裂液次之,超临界二氧化碳的破裂压力最小,压裂时间最短,可以形成更加复杂的缝网,与滑溜水和瓜胶压裂液相比,破裂压力分别降低了26.0%和33.3%;滑溜水压裂液压裂岩样表面可以形成分支缝,全直径岩心可以形成转向裂缝;瓜胶压裂液压裂岩样表面和全直径岩心均形成较为平直的双翼裂缝;超临界二氧化碳压裂岩样表面裂缝形态复杂,裂缝易发生转向,迂曲度大,主缝为双翼非对称缝,可以诱导产生多条贯穿主裂缝,裂缝整体分布呈现“Y”形和“H”形,全直径岩心内裂缝复杂程度高,可形成缝网和转向裂缝,裂缝面具有凹凸不平特性,这对于压裂裂缝自支撑具有重要作用。室内物理模拟实验研究结果可为现场压裂施工设计提供参考。

The Extension Characteristics of True Triaxial Fracturing Fractures in Full Diameter Cores of the Badaowan Formation under Different Fracturing Fluids

300 mm cubic specimens were prepared from the full-diameter cores of well X in the Lower Jurassic Badongwan Formation in the Bohu Depression of Yanqi Basin, Baolang Sumu Structural Belt. The specimens were subjected to hydraulic fracturing using slickwater, guar gum fracturing fluid, and supercritical CO2 fracturing fluid, and the fracture pressure and fracture morphology characteristics under different fracturing fluids were investigated. The results show that the fracture pressure under the guar gum fracturing fluid is the highest, followed by the slickwater fracturing fluid, and the fracture pressure under the supercritical CO2 is the lowest, with the shortest fracturing time and the ability to form a more complex fracture network. Compared with the slickwater and guar gum fracturing fluids, the fracture pressures were reduced by 26.0% and 33.3%, respectively. The slickwater fracturing fluid can form branching fractures on the surface of the rock sample, and turning fractures can be formed in the full-diameter core. The guar gum fracturing fluid can form relatively straight wing fractures on the surface of the rock sample and the full-diameter core. The supercritical CO2 fracturing fluid can induce multiple fractures that penetrate the main fracture, and the overall distribution of the fractures shows a "Y" or "H" shape. The complexity of the fractures in the full-diameter core is high, and the fractures can form a fracture network and turning fractures, with uneven fracture surfaces, which are important for self-supporting of the fractured fractures. Through indoor physical simulation experiments, reference can be provided for on-site fracturing construction design.