Abstract:

A mathematical model is built for fluid flow in fractured-vuggy carbonate reservoirs with multiple 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 vugs,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 vugs 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 vugs,and reserve calculation.

Key words: flow rate, pressure, mathematical model, dynamic analysis, fractured-vuggy carbonate reservoir