为探究鄂尔多斯盆地太原组灰岩储层的水力压裂裂缝扩展规律,首先,基于三轴水力压裂物理模拟实验,对灰岩露头采样加工成300 mm ×300 mm ×300 mm正方体试样,根据水力压力曲线和压裂后裂缝扩展形态对灰岩的裂缝扩展规律进行分析;然后,根据太原组地质资料构建数学模型,从杨氏模量、泊松比、压裂液用量、压裂排量和顶底板夹层组合方面对于裂缝长度和高度进行模拟.结果表明,①灰岩样品表面存在较多的天然裂缝和层理面,又不同于页岩的层叠形式,裂缝开启后会快速和天然裂缝沟通,最大主应力垂直于天然裂缝时,对缝网形成更为有利;②压裂液黏度提高可以使主裂缝高度大幅提升,压裂过程中增大压裂排量可以开启更多天然裂缝和层理面;③数值模拟得出,杨氏模量大于20 GPa、泊松比小于0.16的灰岩更有利于形成更大面积的人工裂缝,压裂液用量、压裂排量和夹层顶底板组合等参数也对人工裂缝有控制作用.
Propagation pattern of hydraulic fractures in Taiyuan Formation limestone
To investigate the fracture propagation patterns during hydraulic fracturing in the Taiyuan Formation limestone reservoirs of the Ordos Basin,firstly,an triaxial hydraulic fracturing physical simulation experiment was conducted.Limestone outcrop were sampled and processed into 300 mm × 300 mm × 300 mm cube specimens.The fracture propagation law of limestone was analyzed according to the hy-draulic pressure curve and the fracture propagation morphology after fracturing;subsequently,a mathematical model was constructed based on geological data from the Taiyuan Formation,simulating fracture length and height influenced by factors such as Young's modulus,Pois-son's ratio,fracturing fluid volume,fracturing rate,and the combination of roof and floor interlayers.The findings indicate that the surface of the limestone samples contains numerous natural fractures and bedding planes,which is different from the layered form of shale.Once fractures are initiated,they rapidly communicate with natural fractures,and the formation of a fracture network is more favorable when the maximum principal stress is perpendicular to these natural fractures;increasing the viscosity of the fracturing fluid significantly enhances the height of the main fracture,and increasing the fracturing displacement during the fracturing process can open up more natural fractures and bedding planes;numerical simulations show that limestones with a Young's modulus greater than 20 GPa and a Poisson's ratio less than 0.16 are more conducive to the formation of larger artificial fractures.Parameters such as fracturing fluid volume,fracturing displace-ment,and the combination of roof and floor interlayers also play a controlling role in the development of artificial fractures.
万方数据
维普
