Pressure Transient Analysis (PTA) Enables a New Approach for Building Robust Reservoir Permeability Distribution for Miscible Gas Injection Development

Abstract

Abstract Accurate estimation of oil recovery and optimization of reservoir performance requires realistic estimates of permeability distribution. This paper presents an approach to build different modeling realizations for testing possible reservoir behavior during miscible gas injection (MGI) and UR range for MGI development. Multiple geological realizations were built for nine Area-H carbonated reservoirs to bracket the permeability distribution range away from well control, which is a major uncertainty impacting production behavior and history match. Two main factors that affect ultimate recovery and production forecasts are property distribution and permeability range. Therefore, different geological and dynamic model realizations were built to test the reservoir behavior during MGI, which helped to make reliable estimates of production profiles and UR. Full-field reservoir models were constructed for multiple geological realizations, and permeability distribution results showed that using permeability-thickness (KH) and high-perm model methods increased confidence by preserving high-permeability streaks and introducing higher heterogeneity. Fewer changes were required to calibrate the full-field reservoir model to actual pressure data with KH than with conventional core-based permeability. High-permeability streak models provided faster gas breakthrough, higher GOR, and lower UR than conventional and KH-matched models. High-contrast permeability models provided a higher confidence estimation of faster gas breakthrough and oil recovery. High-permeability streaks and high-contrast models can mitigate the negative influence of enhanced reservoir heterogeneity on field production performance forecast. As a result, robust ranges of production profiles and promise would help the project forecast robustness check against low case realizations and upfront planning on potential mitigation/recovery options in case of heterogeneity indies thief zone behavior leading to faster gas breakthrough. A new approach is presented that helps to estimate realistic production forecasts and UR ranges for gas injection development projects. It allows testing models for different subsurface realizations and generating robust project economics. The methodology given in this study can show a good practice for the characterization of heterogeneous reservoirs for MGI flooding development, especially for capturing the downside as an alternate geological realization.