Three-dimensional hydrocarbon migration and accumulation modeling based on finite volume method

Aiming at the issue that the application effect of current 3-D hydrocarbon migration and accumulation modeling technique cannot meet the actual requirement because of over-simplified geologic model, a 3-D dynamic geologic model using PEBI grid in bedding and columnar shape was established, which can be used to solve the heterogeneity in reservoirs of various sedimentary facies, and to reduce the effect of mixed lithologies on modeling accuracy. A 3-D numerical modeling technique based on finite volume method was established, including the construction of variable grid flow equation, decomposition and calculation of full-tensor permeability, and calculation of conductivity etc. Some related processing techniques, such as smoothing of key parameter curves, stability processing of upstream and downstream of grid flow, etc. were used to improve the convergence of Newton's iteration. Automatic adjustment of time step and multi-core parallel computation were taken to enhance the running efficiency of the software. In a case study of Nanpu sag in the Bohai Bay Basin, the hydrocarbon migration and accumulation process, oil saturation and hydrocarbon resources abundance in various periods were simulated, the modeled oil saturation, accumulation quantity and hydrocarbon distribution locations coincide with current exploration status. The results also showed that the proved ratio of hydrocarbon resources in target layers is 84.4%, the majority of the resources are distributed in Block B and Block C, and it is predicted that undiscovered resources are mainly near Well NP2-16 in Block C and in the structure north of Well NP5-4 in Block A.