基于非线性渗流方程数值解的段间距优化方法研究

海上低渗油气藏渗透率一般为1~10 mD, 原始储层的流动能力对段间距优化有重要影响; 此外, 裂缝扩展模拟与实际压裂效果仍存在较大差距。为此, 文章基于海上油田已有压裂直井的开发数据, 开展段间距优化新方法研究。首先, 建立非线性渗流模型, 基于PEBI网格建立数值求解方法, 利用关井压力数据反演非线性渗流参数; 然后, 通过累积产油量拟合获取应力敏感性参数, 即拟合得到主裂缝导流能力与衰减系数以及压裂改造区域的渗透率与应力敏感性; 最后, 根据最优产量确定最优段间距; 同时, 还探讨了非线性参数与开发制度对产量的影响规律。海上某低渗油藏的应用案例表明, 文章方法在充分考虑瞬态压力和累积产量的条件下, 能为油田段间距优化提供有益指导。

The permeability of offshore low-permeability oil and gas reservoirs generally ranges from 1 mD to 10 mD. The flow capacity of the original reservoir has a significant impact on the optimization of fracture spacing. Additionally, there remains a considerable gap between fracture propagation simulations and actual fracturing outcomes. Therefore, based on the development data from fractured vertical wells in offshore oilfields, a study on the optimization method for fracture spacing has been conducted. A nonlinear seepage model was established, and a numerical solution method was developed based on PEBI grids. Nonlinear seepage parameters were inverted using shut-in pressure data, while stress sensitivity parameters were obtained by matching cumulative oil production. This process yielded the main fracture conductivity and its decay coefficient, as well as the permeability and stress sensitivity of the fracturing-stimulated zone. Finally, the optimal fracture spacing was determined based on the optimal production rate. Additionally, the influence of nonlinear parameters and development systems on production was investigated. An application case from an offshore low-permeability reservoir demonstrates that the proposed method, which fully considers transient pressure and cumulative production, can provide valuable guidance for optimizing fracture spacing in oilfields.