Optimizing gas injection in high-pressure carbonate reservoirs: controlling bottomhole and tubing head pressures to avoid formation fracturing

Background: In high-pressure carbonate reservoirs, miscible gas injection is a key method for enhancing oil recovery and maintaining reservoir pressure. The main challenge lies in controlling bottomhole pressure (BHP) and tubing head pressure (THP) while maximizing injection volumes and preventing formation fracturing. Current strategies typically rely on THP regulation and injection rates as the primary means of well control.

Aim: This study aims to analyze an optimized gas injection strategy based on precise well control to prevent formation fracturing and improve injection efficiency.

Materials and methods: The study uses production and geological data analysis, empirical forecasting models, and statistical techniques to enhance the accuracy and reliability of predictions. Modern algorithms and data-processing technologies are applied to handle large datasets, allowing for more accurate and consistent forecasts of key field development indicators.

Results: The results indicate that gas injection can be optimized by lowering reservoir pressure and increasing tubing head pressure (THP). This stabilizes bottomhole pressure (BHP) because of increased frictional losses in the tubing string. Controlling THP and gas rates allows stable BHP operation. Currently, maximum BHP limits have been established for the wells, while allowable THP is restricted but can be increased based on previous test results. An increase in THP would enable higher gas injection volumes, leading to improved oil recovery. BHP remained within safe limits and was monitored directly with downhole pressure gauges.

Conclusion: This study presents an optimized approach to gas injection management, based on real-time pressure monitoring, well–reservoir nodal analysis, dynamic control of tubing head pressure (THP), and regulation of gas flow rates. The results emphasize the need to consider nonlinear pressure losses when designing safe and efficient injection strategies. Considering these effects helps prevent formation fracturing and ensures long-term reservoir integrity.