Gas Injection into the Tengiz oilfield began in January 2007 with sweet gas injection as Phase 1 of the SGI pilot project. Phase 2 of the project, sour gas injection, began in October 2007, but was interrupted due to initial injection start up problems. Continuous sour gas injection began in January 2008. As part of the SGI Surveillance Plan, a variety of reservoir measurements are routinely acquired to monitor the progress of the flood. The SGI project has four signposts for success: Compressor reliability, Injectivity, wellbore durability, and reservoir performance. The sour gas compressor at Tengiz was the first of its kind and has had greater than 90% availability when SGP has been operational. Injectivity has exceeded expectations and wellbore durability has also been excellent. The fourth area is reservoir performance and all indications are that the reservoir is performing as expected. The SGI project consists of seven inverted five-spot patterns. To expedite data acquisition, the SGI well patterns were designed to include one "super-spot" pattern (twin injectors 100 m apart providing dedicated injection support to different geologic layers) and three short-spaced producers (producer-injector spacing approximately 1/3 of the standard spacing). Tracers, pulse tests, multiphase meters, gas saturation logging, and production and injection are used to monitor and understand reservoir performance. A specialized simulation model (Monitoring Model) was constructed which uses local grid refinement in the SGI pattern area. On August 22, 2008, gas breakthrough occurred in Well T-318, the first of the short-spaced producers. This breakthrough was predicted with the Monitoring Model. Predictions from Monitoring Model suggest most likely breakthrough is near top of reservoir, and this was substantiated by logs. The gas injection project will continue to be closely monitored to improve our understanding and reservoir forecasts.

The Tengiz oilfield is a giant, carbonate reservoir of Devonian to Carboniferous age located in the Pricaspian Basin of the Republic of Kazakhstan. Gas Injection at the Tengiz field began in January 2007 with sweet gas injection as Phase 1 of the Sour Gas Injection (SGI) pilot project followed by sour gas injection as Phase 2. Phase 2 injection began in October 2007, but was interrupted due to initial start up problems. Continuous sour gas injection was achieved three months later in January 2008.The SGI project has four signposts for success: compressor reliability, injectivity, wellbore durability, and reservoir performance. The sour gas compressor at Tengiz was the first of its kind and has had greater than 90% availability when the Second Generation Plant (SGP) has been operational (SGI injection gas is produced through SGP). Injectivity has exceeded expectations and wellbore durability has also been excellent. Reservoir performance is a longer term signpost which is monitored though an extensive surveillance program. The Tengiz Reservoir appears to be performing as expected to the sour gas injection.The SGI project is a first-contact miscible gas injection process consisting of seven inverted five-spot patterns. To expedite data acquisition, the SGI well patterns were designed to include one "super-spot" pattern (twin injectors 100 m apart providing dedicated injection support to different geologic layers) and three short-spaced producers (producer-injector spacing approximately 1/3 of the standard spacing). Tracers, pulse tests, multiphase meters, gas saturation logs, and production and injection logs are used to monitor and understand reservoir performance. A specialized simulation model (the SGI Monitoring Model) was constructed which uses local grid refinement in the SGI pattern area. This model is used to determine how well the reservoir characterization is able to capture the dynamic reservoir response to the miscible SGI process.An earlier paper (Darmentaev et. al., 2010) discussed preliminary results from the SGI project. The proposed paper will discuss recent results from the reservoir surveillance program, how these recent results compare to the preliminary results, and the integration of all results into our current understanding of SGI performance. In addition, updates to the Monitoring Model, lessons learned and best practices developed since the commencement of sour gas injection will be discussed.

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