大庆油田致密砂岩储层压裂裂缝扩展形态实验研究

大庆油田在致密油砂岩储层体积压裂上取得了较好效果,但裂缝形成机理认识不清,制约技术的进一步提高。为了明确大庆松北地区致密砂岩储层裂缝形态特征,采用水力压裂模拟装置,在真三轴条件下对天然致密砂岩岩心进行了水力压裂物理模拟实验,分析了注入压力曲线特征和岩心裂缝形态变化规律。结果表明,裂缝形态主要受水平主应力差控制,层理特征对裂缝形态影响明显;脆性指数及杨氏模量对裂缝形态影响不明显。当水平主应力差小于3 MPa时,储层层理特征越明显,压裂后水力裂缝越容易沟通层理弱面并发生转向,裂缝形态越趋于复杂。

Experimental study on fracture propagation pattern of tight sandstone reservoirs in Daqing oilfield

The volume fracturing of tight oil in Daqing oilfield has achieved good effect, while the mechanism of fracture formation is not clear, which restricts the further improvement of technology. In order to clarify the fracture morphological characteristics of tight sandstone reservoirs in Songbei area of Daqing oilfield, a hydraulic fracturing simulation device was used to carry out a hydraulic fracturing physical simulation test on the natural tight sandstone cores under the true triaxial condition. The curve characteristics of the injection pressure and the fracture morphological change regularity of the cores were analyzed. The results show that the fracture morphology is mainly controlled by the horizontal principal stress difference, the influence of bedding characteristics on the fracture morphology is obvious, while the effect of brittleness index and Young's modulus on fracture morphology is not obvious. When the horizontal principal stress difference is less than 3 MPa, the reservoir stratigraphic characteristics are more obvious, it will be easier for hydraulic fractures to communicate with the weak surface of bedding and begin to turn after fracturing, and then the fracture morphology will become more complex.