缝洞型碳酸盐岩油藏油井产量及压力变化模型

Flow rate and pressure variation modeling for production wells in fractured-vuggy carbonates reservoirs

建立了缝洞型碳酸盐岩油藏多缝多洞串联型油藏流体流动的数学模型,得出了产量和压力的变化规律。单缝单洞油藏的压力和产量均呈指数递减,多缝多洞油藏靠近生产井的溶洞产量的递减规律为几个指数递减函数的代数和,压力的递减规律为几个指数递减函数与井底流压的代数和。以同等大小的三缝三洞油藏为例,远离生产井的溶洞压力下降速度远远慢于靠近生产井的溶洞;生产初期产量主要是靠近生产井的溶洞在作贡献,远离生产井的溶洞逐渐开始补充。这对于缝洞型碳酸盐岩油藏油井的动态分析和预测,认识缝洞连通模式和缝洞参数,以及储量计算有一定的理论意义。

A mathematical model is built for fluid flow in fractured-vuggy carbonate reservoirs with muhiple fractures and vugs connected in series to analyze the patterns of flow rate and pressure changes. In reservoirs with ideal single fracture and single vug, both the flow rate and pressure decline exponentially. However, in reservoirs with multiple fractures and multiple rugs, the flow rate and pressure decrease much differently. For vugs near production wells, the decline of flow rate is the algebraic sum of several exponential decline functions, and the decline of pressure is the algebraic sum of several exponential decline functions and bottom hole flowing pressure. Taking the ideal triple fracture-triple vug reservoirs with the same sizes as examples, the pressure decline in rugs far away from the production well is much slower than that in vugs near the production well. The vugs near the production well contribute most of the oil flow in the initial stage and the vugs far away from the well join in progressively later. The study bears certain theoretical significances for analyzing and predicting well performance in fractured-vuggy carbonates reservoirs, understanding the patterns of fracture-vug connection and parameters of fractures and rugs, and reserve calculation.