致密薄互层水力压裂裂缝垂面扩展施工因素数值模拟

Numerical Simulation on the Construction Factors of Vertical Fracture Propagation in Tight and Thin Interlayer Hydraulic Fracturing

中国具有丰富的致密油气藏储量,必将成为中国接替的油气资源。致密油藏开发主要依靠水力压裂技术,对于致密薄互层,施工因素作为可控因素,对于现场施工具有重要意义。因此,本文研究针对鄂尔多斯盆地致密储层,低孔低渗、储层厚度薄等特点,以该地区L井F12地层为例,采用Abaqus有限元软件进行了模拟计算,研究了施工过程中的排量以及压裂液黏度对裂缝垂面扩展规律的影响,并且根据实际情况对模型进行验证,确定了模型和模拟方法的准确性。研究结果表明:压裂液的排量对于裂缝的扩展具有重大影响,排量越大,裂缝的扩展速度越快,裂缝的缝高和缝宽越大;压裂液黏度对裂缝的扩展行为影响微乎其微。并进一步分析发现,针对致密薄互层,仅仅只改变压裂液排量和黏度并不能将裂缝控制在储层内,采用变排量控缝高技术辅以其他控缝高手段能够更好地将裂缝控制在储层内,为现场压裂施工提供了基础。

Our country has abundant reserves of tight oil and gas reservoirs is abundant in our country,and will become our replacement oil and gas resources.The development of tight oil reservoirs mainly relies on hydraulic fracturing technology.For tight and thin interlayer,the construction factor as a controllable factor is of great significance for on-site construction.Therefore,aiming at the characteristics of tight reservoir in Ordos Basin,such as low porosity and permeability and thin reservoir thickness,F12 formation of Well L in this area was took as an example,the Abaqus finite element software was adopted to conduct simulation calculation,the influence of displacement and fracturing fluid viscosity was studied in the construction process on vertical fracture propagation law,and the model was verified according to the actual situation.The accuracy of the model and simulation method is determined.The results show that the fracturing fluid displacement has a significant impact on fracture propagation.The larger the displacement,the faster the fracture propagation speed,and the larger the fracture height and width.The viscosity of fracturing fluid has little effect on fracture propagation behavior.Further analysis shows that,for tight and thin interbed,only changing fracturing fluid displacement and viscosity can not control the fractures in the reservoir,and adopting variable displacement fracture-control high technology and other fracture-control high means can better control the fractures in the reservoir,providing a foundation for on-site fracturing construction.