Analysis of Cyclic Steam and Solvent Stimulation in a Northeasters Brazilian Reservoir
LASER, cyclic steam and solvent stimulation, reservoir simulation, thermal methods.
One of the main challenges facing the oil industry today is improving land field recovery. Of the hydrocarbon land reserves, a significant portion is made up of heavy and extra-heavy oils. Thermal and miscible methods help to increase hydrocarbon production by reducing viscosity, capillary forces and interfacial tension. They can be combined by steam and solvent stimulation. One of the most versatile solutions for heavy oil recovery is cyclic vapor and solvent stimulation, known as Liquid Addition to Steam for Enhancing Recovery, as it delivers sizable volumes and returns on a short time. The potential for increase in recovery factor can be greater than 5% and greenhouse gas reduction by approximately 25%. Therefore, this work aims to technically and economically evaluate the cyclic steam and solvent injection process in a heavy oil reservoir with characteristics of Brazilian northeastern. The simulations were performed in a commercial oil reservoir modeling program. For this analysis a complete 2x34 experimental design and a 35 design were performed, varying factors such as: solvent type, solvent percentage, injection temperature, fluid injection flow rate, rock compressibility, injection time, soaking time and cycle interval. A study of the behavior of the temperature along the well and the energy losses was performed. The accumulated volume of oil produced was analyzed. The results show that the analyzed variables that had the greatest influence on the accumulated oil production were formation compressibility, injection flow rate, solvent percentage, cycle interval and injection phase duration. The compressibility was the variable that influenced the most. And among the three solvents used (pentane, heptane and diesel) heptane presented superior performance and the other two presented similar performances. The temperature along the well was more influenced by the injection flow rate. The temperature recorded along the well was different, with the upper part warmer. Temperature changes occurred when analyzing the same periods of different cycles. Higher flow rates provided greater heat losses in the reservoir. Economic analysis has shown that higher amounts of steam and solvent make the project economically unviable.