低渗油藏CO2驱井网优化调整及开发效果影响因素

CO2驱、水平井开发技术对于低渗油藏有着较好提高采收率的作用,但是对于非均质性较强的低渗油藏,水驱开发后存在动用程度低的问题,因此有必要研究低渗油藏后期注采方式及注采井网的调整优化和开发效果的影响因素。首先依据目标油藏建立非均质概念地质模型,建立了一个上下分别为低渗和高渗储层油藏模型,采用油藏数值模拟方法对油藏进行了模拟计算。在油藏模型进行一段时间水驱后,加密调整井网采用水平井注CO2进行二次水气同驱的开发模式。对比不同加密井网模式的采出程度和地层压力,得到最优的加密井网模式进行二次优化开发。然后基于以上得到的最优井网优化调整模型,研究了井排距、储层渗透率和注CO2压力对该调整井网模式开发效果的影响。油藏数值模拟计算表明：加密水平井采油优于加密直井采油；加密水平井注气可以适当缩短排距,使CO2的驱替更充分,当井距/排距为0.4时,采出程度最大；在不同储层渗透率条件下,在其他生产条件一致的情况下,加密水平井井网时,可以将水平井沿水平渗透率较小方向安置；适当增大注气井注入压力可以有效地提高采收率恢复地层能量。本文研究成果对该类非均质低渗油藏的开发具有较好的借鉴意义。

Optimization and adjustment of well pattern and influencing factors of CO2 flooding in low permeability reservoir

CO2 flooding and horizontal well development technology have a good effect on enhancing oil recovery in low permeability reservoirs, but for low permeability reservoirs with strong heterogeneity, there is a problem of low production degree after water flooding development. Therefore, it is necessary to study the injection-production mode and the adjustment and optimization of injection-production well pattern in late stage of low permeability reservoirs and the influencing factors of development effect. Firstly, a heterogeneous conceptual geological model is established according to the target reservoir, and a reservoir model with low permeability and high permeability is established. Reservoir numerical simulation method is used to simulate the reservoir. After water flooding for a period of time in the reservoir model, the infilling and adjusting well pattern adopts CO2 injection in horizontal Wells to carry out secondary water and gas co-flooding. By comparing the recovery degree and formation pressure of different infill pattern patterns, the optimal infill pattern was obtained for secondary optimization development. Then, based on the optimal well pattern optimization and adjustment model, the effects of well spacing, reservoir permeability and CO2 injection pressure on the development effect of the adjusted well pattern were studied. Numerical simulation of reservoir shows that infill horizontal well is better than infill vertical well. Infused horizontal well gas injection can shorten the row spacing properly, so that CO2 displacement is more sufficient. When the well spacing/row spacing is 0.4, the recovery degree is the largest. Under different reservoir permeability conditions, the horizontal well can be placed along the direction of low horizontal permeability when the well pattern of horizontal Wells is encrypted under the same production conditions. Properly increasing the injection pressure of gas injection well can effectively improve the recovery of formation energy. The research results of this paper have a good reference for the development of such heterogeneous low permeability reservoirs.