大庆外围油田压裂水平井参数优选及渗流特征

Fracture Parameters Optimization and Seepage Characteristics of Fracture Horizontal Well in Daqing Peripheral Oilfield

压裂水平井已成为开采特低渗透油藏的重要手段。为深入了解压裂参数及渗流规律对水平井开发效果的影响,针对大庆外围某特低渗透油藏水平井开发的实例,应用特低渗透非线性渗流理论,建立了考虑非线性渗流的数学模型,给出已钻水平井的最优压裂参数,研究了不同渗流规律下压裂水平井的渗流特征。结果表明,在水平井水平段长度、压裂缝长一定的条件下,裂缝条数和裂缝间距对开发效果的影响显著;裂缝条数越少,裂缝间距对水平井产能影响越大;裂缝条数大于3条,裂缝间距的影响减小;对比了达西渗流规律和考虑启动压力梯度的非线性渗流规律下压裂水平井的渗流特征,非线性渗流模型计算的水平井产油量较低,见水后含水上升速度较快,剩余油饱和度较高;非线性渗流模型中注水井井筒附近和主流线附近的压力等值线密集,能量消耗大,压力梯度高,水平井井筒附近压力梯度较大,但低于直井;非线性渗流模型的地层渗透率与压力梯度呈正比关系。

Horizontal well with fracture has become one of main methods to exploit ultra-low permeability. In order to gain the in-depth knowledge of the effect of fracture parameters and seepage pattern on horizontal well productivity, a nonlinear flow mode optimizing the fracture parameters has been established based the actual case of horizontal well exploitation in Daqing Peripheral Oihqeld. The nonlinear flow theory is applied to the mode and the optimization results are provided under the constant condition of both horizon length and fracture length. The fracture number and fracture intervals have a significance impact on exploitation effect. The larger fracture number is, the more obvious the effect of fracture intervals is. However, as number of fractures exceeds three, the effect of fracture intervals is reducing. Contrast to the characteristics of nonlinear flow with that of Darcy flow, the former has the lower productivity, higher remaining oil saturation, and higher water cut as soon as water is produced. In the nonlinear flow model, pressure isopleths are concentrated, pressure gradient is higher, and energy consumption is larger around the area of wellbore and injection-production line. Horizontal well