ABSTRACT:

Bati Kozluca Field with an OOIP of 138 MMSTB has been producing for more than 20 years. Main producing formation is the carbonate Alt Sinan. Oil gravity is 12.0 °API with a very high viscosity of 500 cp at reservoir conditions. Production mechanism is rock and fluid expansion with a very weak bottom water drive. By the year 2005, the cumulative oil and water production are 4,668,751 stb and 747,109 stb respectively and daily oil production is 570 stb/day with 20 % WC. This study was initialized by screening the applicability of in-situ combustion process. Laboratory studies carried out to determine pilot design information (self-ignition, fuel availability, air requirements). These included reaction kinetics and combustion tube tests. The combustion tube tests showed excellent burning characteristics (peak temperature profiles > 500 °C). The laboratory simulations were then used to explore various additional sensitivities. Dry and wet forward combustion runs for Bati Kozluca heavy oil were performed under different experimental conditions. A vertical combustion tube was packed with crushed limestone and saturated with crude oil and water. A total of four runs were conducted to study the in-situ combustion process variables. It was observed that peak temperatures were higher when stabilized combustion was achieved and decreased as the combustion front approached the outlet end of the tube. In all runs, excess carbon-dioxide productions were observed due to the decomposition of carbonate minerals. The numerical simulator used is the multi-phase, multi-component, thermal simulator, STARS, developed by CMG. The dimensions of the pilot field prototype reservoir are 70 m wide, 70 m long and 30 m thick. The thermal sweep efficiency of the process is very high and virtually all of the oil in the zones contacted by the combustion front is produced, except for the small fraction consumed as fuel. Several air injection scenarios with different well configuration were considered, including variation in air injection rates, and injection completion zones, and wet combustion as a follow-up to dry. This study has resulted in several observations that assist in understanding the validity of production performance computations for an in-situ combustion process using a numerical simulator and laboratory combustion tube data. The paper provides a better understanding of the impact and relative significance of process variables, which may be used in improved design of a project

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