A Gas-assisted Gravity Drainage Process in Naturally Fractured Reservoirs

Abstract

Water alternating gas injection or simultaneous water and gas injection have been proposed as a good candidate to minimize gravity segregation and provide more efficient enhanced oil recovery performance in comparison to conventional continuous gas injection. However, water alternating gas-based processes can cause some difficulties with an increase in water saturation (e.g., water shielding) including diminished gas injectivity (Rao et al., 2004). As an effective alternative for water alternating gas injection, gas-assisted gravity drainage was developed for conventional reservoirs (U.S. Patent 2006/0289157) that takes advantage of the natural segregation of gas from liquid hydrocarbon during injection. The gas-assisted gravity drainage process consists of placing a horizontal well near the bottom of an oil column and injecting gas through existing vertical wells. Gravity segregation of injected gas will cause liquid hydrocarbon and water to drain down to the aforementioned horizontal well. Application of gas-assisted gravity drainage for enhanced oil recovery in a naturally fractured reservoir is evaluated in this article based on some facts and figures.

Keywords:

• fractured reservoir
• gravity drainage
• improved oil recovery
• simulation