Study of the Optimal Production Period During Cyclic Steam Stimulation : A Case Study of a Sudanese Field

Abstract

Enhanced oil Recovery methods had been used around the world for enhancing oil production and getting higher recovery factor from oil reserves. Cyclic Steam Stimulation is one of the most wide used methods which means injection of high temperature steam into the production well, then shut in the well for soaking phase, then the same well will be used as production well. Generally the most effective parameters in cyclic steam stimulation applications are injection parameters, soaking time and production period. In this thesis production period had been studied to determine the optimum production period for the nominated wells by assuming that all other variables are constant and time is only changed. Three different cases had been selected according to the different reservoir considerations for the selected field, which had thick sand sequences deposited in braided stream environment in continental fluvial channel and overbank depositional conditions. CMG Thermal simulator had been used for solving numerical equations with conditions T=43.7 ◦C, Pi= 575.8 PSI, and time step one day for more accurate results. Thesis is organized into five chapters. Chapter I (Introduction to understanding heavy oil and its properties also provides methodology used and the objective of the study. Chapter II provides description of the Enhanced oil Recovery Processes that can be applicable for heavy oil and their s mechanism, and literature review of commercial method used. Chapter III discusses important concepts generally used in cyclic steam stimulation process and up to date new technology for improving it. Simulation models used also will be explained in detail in Chapter III. Chapter IV gives a complete explanation of the results obtained from different cases runs. This chapter also provides comparisons of oil production rate and cumulative oil steam ratio among each case. Finally, main conclusions and recommendation of this research are given in Chapter V. Results showed that the optimum production period ranged between 300 days to 500 days for the selected wells in DH field, results could be used for other wells with the similar criteria.