特低渗透纵向非均质油藏周期注水研究新方法

A New Method of Cycle Water Injection of Vertical Heterogeneity Special-low Permeability Reservoir

大庆外围某特低渗油藏不仅储层薄,渗透率特低,而且纵向上非均质性较强,水驱开发过程中层间矛盾严重,明确注水方式对特低渗透纵向非均质油藏的影响对于解决层间矛盾十分必要。建立了基于该区块地质特征的纵向正韵律非均质地质模型,采用5点井网进行数值模拟计算,考虑流体在特低渗透储层中遵循的非线性渗流规律及压力敏感性特点,研究不同周期注水方式的渗流规律。结果表明,增注-减注注水方式相同含水率下采出程度高于增注-停注注水方式;增注-减注注水方式比增注-停注注水方式储层吸水剖面均匀,相对低渗储层吸水能力增强,相对高渗储层吸水能力减弱;增注-停注注水方式增注周期注水井附近压力梯度普遍高于0.2MPa/m,注水能量被消耗在建立水流通道上。该模型能直观判断周期注水方式对非均质性开发效果的影响。

The reservoir in the Daqing Peripheral Oilfield is characterized not only by thin thickness, small sand scale, and ultralow permeability, but also by strong vertical heterogeneity. Interlayer interference is a serous problem in waterflooding exploitation. It is absolutely necessary to recognize the effect of vertical heterogeneity on reservoir development before interlayer interference being solved. Based on the geological characteristics of actual data, a five-point well geological model which is vertical heterogeneity and positive rhythm for the numerical simulation is established. Considering the non-linear seepage law and pressure sensitivity features in special- low permeability reservoir, the seepage law of different cycle water injection is studied. The results show that with the same water ratio, the recovery degree of augmented-abated injection mode is higher than that of angmented-suspended mode. The injection profile of augmented-abated mode is more uniform than that of augmented-suspended mode, the water absorption ability of relatively low permeability reservoir is strengthened, and the water absorption capability of relatively high permeability reservoir is weakened. The pressure gradient of injection well near bottom is generally higher than 0.2MPa/m it, the increasing part of augmented-suspended water injection mode; water injection energy is expended in an establishing water flow path. The distributions could provide the intuitive judgment on the affect of cycle water injection on the vertical heterogeneity development.