Permian Basin: Seminole San Andres Unit Residual Oil Zone CO2 Flood
The life of Seminole San Andres Field, which was
discovered in 1936, is being extended by development of the Residual Oil Zone
(ROZ) by Hess Corporation.
The San Andres formation, the most significant pay zone in the field, was unitized for secondary recovery waterflood operations in 1969. By the late 1980's the 17,000+ acre SSAU contained some 600 wells and was well into its tertiary oil recovery phase with a successful Main Pay Zone CO2 flood. Establishing CO2 flooding as a viable recovery process at SSAU led to renewed interest in the Residual Oil Zone of the San Andres formation. The ROZ contains similar STOOIP as in the San Andres MPZ, but ROZ oil is only recoverable via a tertiary process such as CO2 flooding.
Two small scale projects were implemented to evaluate ROZ response to CO2 flooding at SSAU. The Phase 1 project was developed with four 80 acre 2:1 line drive patterns with all producers commingled between MPZ and ROZ. Phase 1 began CO2 injection in July, 1996. The Phase 2 project was developed with nine 40 acre inverted 5-spot patterns with all producers commingled between MPZ and ROZ and all injectors deepened to ROZ only. Phase 2 began CO2 injection in June, 2004.
Following the two pilot projects, the SSAU partners agreed in 2007 to the first stage of the ROZ full field expansion which included deepening producers and injectors in 29 patterns and an increase of 70 MMSCFD gas handling capacity at the Seminole Gas Processing Plant.
The Stage 1 project was developed with 80 acre inverted 5-spot patterns with all producers commingled between MPZ and ROZ and all injectors deepened to ROZ only continuous CO2 injection, The MPZ flood changes in the project area from an 80 acre inverted 9-spot to an 80 acre 2:1 line drive. The project commenced in 2007 and was completed in 2009.
This presentation will briefly review the performance of the two ROZ pilots and then discuss the Stage 1 project and show some early production performance from the Stage 1 area.
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