体积压裂致密油藏注水吞吐产能影响因素

致密油藏储层致密,地层压力系数一般较低,开发非常困难,而注水吞吐对补充油层压力和实现稳产具有明显优势.针对体积压裂致密油藏,采用嵌入式离散裂缝模型描述复杂体积压裂缝网,建立考虑应力敏感和启动压力梯度的致密油藏油水两相渗流模型,并采用有限体积法建立相应的数值求解方法.通过数值模拟方法模拟了12个吞吐轮次下单个压裂段致密油藏的开采过程,分析了基质和裂缝性质对致密油藏注水吞吐开发产能的影响.研究结果表明:当基质渗透率、微裂缝渗透率和微裂缝密度升高时,基质中含水饱和度波及范围变大,累积采油量显著升高;水力裂缝渗透率升高对基质含水饱和度分布影响不大,但累积采油量明显上升,而当水力裂缝上升到一定程度时,累积采油量上升幅度变小.可见基质和裂缝性质对致密油藏注水吞吐开发效果均有显著的影响.

Influencing Factors of Water Huff and Puff Production in Volumetric Fracturing Tight Oil Reservoir

Tight oil formation is commonly tight with a low formation pressure coefficient, which makes the development of tight oil very difficult. As an alternative, water huff and puff has great advantages on maintaining reservoir pressure and oil production. In this paper, based on the embedded discrete fracture model, a mathematical model with threshold pressure gradient and stress sensitivity for tow phase flow in volumetric fracturing tight oil reservoir is developed, and the numerical schemes are established. Then 12 huff-puff cycles of production process in a one-stage fractured tight oil reservoir model is simulated with the established numerical simulation method, and the effects of matrix and fracture properties are investigated. The results show that with the increase of matrix permeability, micro-fracture permeability and micro-fracture density, the water-spreading area increases, and the cumulative oil production also greatly increases. The hydraulic fracture permeability has little impact on water-spreading area, while greatly increases the cumulative oil production. However, the cumulative oil production increases little when the hydraulic fracture permeability increases to a certain value. It can be seen that the properties of matrix and fractures have great effects on water huff and puff EOR in tight oil reservoirs.