This paper focuses on simulation modeling of a gas injection pilot operated in the Eagle Ford Shale play. The main objective of this case study is to understand the flow mechanisms in the reservoir due to hydraulic fracturing of multiple wells and gas injection operations.

A dual porosity numerical reservoir simulation model coupled with geo-mechanics was built to investigate the hydraulic fracturing and flow dynamics of the pilot area using a sophisticated numerical reservoir simulator. The methodology used in this study integrates the hydraulic fracturing process, multi-phase flow and geo-mechanics within the reservoir simulation. In this approach, the change in mean stress for each grid block is implicitly solved together with pressure and the other flow variables using poro-elastic information. Geologic, geo-mechanical and reservoir properties were gathered from the static geo-model. The actual stage-by-stage hydraulic fracture treatment jobs were simulated to investigate the stimulated rock volume (SRV) characteristics of the study wells. The simulation model was calibrated to match the hydraulic fracturing, flow back, depletion and multiple huff and puff cycles. Oil, water and gas production/injection data together with pressure data were matched during calibration. Additional sensitivity runs were performed to examine the potential benefits of gas injection under different operational scenarios.

The results show that the Eagle Ford pilot area is quiet in terms of natural fractures. There is an indication of weak zones that provide preferential connectivity paths for water and gas flow. These weakness points could be related to the lithology or natural fractures. They were defined as easily breakable planar zones in the model. The most important knowledge gained from the calibration of the gas injection period is the establishment of connectivity paths and their poro-elastic behavior during gas injection. The results showed that oil swelling and vaporization of oil into gas are the two mechanisms that impact the huff-n-puff performance. Maintaining most of the injected gas around the huff-n-puff pattern also improves the performance.

You can access this article if you purchase or spend a download.