Well-controlled dynamic hydrocarbon reserves calculation of fracture–cavity karst carbonate reservoirs based on production data analysis

摘要

Fracture–cavity karst carbonate reservoirs have multiple storage space with irregular geometry and various scales, and this caused strong heterogeneity and complex flow characteristics. Accurately calculating the well-controlled dynamic reserves of this kind reservoir effectively is the basis to optimize oil field development plan and making the transformation measures of production well. In order to solve the problem that conventional well-controlled dynamic hydrocarbon reserves calculation method is not suitable for such type reservoirs, we applied a method based on production data analysis. Classification standard of oil well types is established based on the fracture–cavity reservoirs geological static and production dynamic characteristics. Conceptual characteristics of geological model and fluid flow pattern for different types of production wells are assumed. Calculation workflow for well-controlled reserves of fracture–cavity reservoir is established. In the process, some technical key points are proposed to improve accuracy of curve fitting, such as converting the bottom hole pressure from wellhead pressure, correcting the well control range and converting the PVT parameters at the pseudo-steady state. We verified correctness of this method by comparing the calculated results with numerical simulation results of actual production well. This method is well used to Tahe Oil field of Tarim Basin in China. The result shows that the well-controlled reserves quantitative calculation results through this method are in conformity with oil field actual understanding, and the remaining dynamic reserves mainly exist in the drainage area of the wells that drilled different reservoir bodies with good connectivity, especially at the top of large karst caves, and that is the target of further adjusting.