低渗透储层垂直缝延伸规律研究

随着我国低渗透砂岩油藏越来越多地被发现并投入开发，人们逐步认识到裂缝性低渗透油田开发的特殊性：不仅基质岩块具有低渗透开采的特点，而且由于天然或人工裂缝的存在，大大改变了流体在地层的流场。在注水开发过程中，发现沿裂缝方向有水窜现象，直接影响了注水开发效果。为研究裂缝的延伸规律，首先做了一些假设，根据假设，建立了裂缝延伸模型，然后用标准的四阶Runge-Kutta法可迭代解出裂缝几何尺十、缝中流量分布和压力分布。以安塞油田王窑区长61储层参数为例，设计了不同的方案，对裂缝的延伸规律进行了研究，认为：侧向应力不高、储层致密是造成注水时裂缝张开并大距离延伸的主要原因；裂缝延伸长度与注入量成正比，而与渗透率和裂缝内外压差成反比。建议通过周期性注水来延缓水沿裂缝窜进到油井的时间。

Research on Vertical Fracture Extension Rules in Low Permeability Reservoirs

With the development of more and more low permeability sandstone reservoirs, we pay much attention to the particularity of fractured low permeability oilfields: the matrix has the features of low permeability reservoir development, and fluids flow field in formation also changes due to the existence of natural or artificial fractures. During water flooding water channeling along fractures directly affect the results of water flooding. In order to study the extension rules of fractures, fracture extension model is built based on assumptions. Then the fracture geometry, flow rate distribution and pressure distribution in fractures can be calculated with the application of 4th order Runge-Kutta method. For example, according to the parameters of Chang61 reservoir in Wangyao area of Ansai oilfield, different plans are designed to research the extension rules of fractures. the results prove: Fracture openness and extension are mainly caused by relative low lateral stress and consolidated reservoir; The extension length of fractures is in direct ratio to injection rate while in inverse ratio to permeability and pressure differential between inner fracture and outer fracture. Periodical water injection is recommended to decline water breakthrough time from fractures into producers.