Abstract
There are heavy oil reservoirs found in oil industry. However, due to the high viscosity, traditional means of technologies such as natural depletion, pumps installation, and pressure maintenance are inefficient to extract the remaining oil in place. Therefore, there is a need for an efficient method for more recovery of heavy oil. In this study, a new method is proposed where combination of toe-to-heel (TTH) and cyclic steam stimulation (CSS) methods is employed to optimize the recovery from such reservoirs. Steam is injected in one of the wells and it is allowed to soak for some time and production is taken then from the reservoir.
The main objective of this study is to optimize oil production from the heterogeneous reservoir by viscosity reduction via injection of steam in TTH manner. Cyclic steam stimulation in TTH configuration is a new method and has never been studied. It requires vertical and horizontal wells both for injection and production. A 3D reservoir model is built in commercial software. Five parameters such as steam injection rate, injection time, soaking time, oil production rate and oil production time are used for sensitivity analysis and optimization. All parameters are found influential and interrelated when sensitivity is performed. An optimization tool (i.e. CMA-ES) is also used to get the optimum values for the parameters. The optimized parameters are steam injection rate, injection time, soaking time, oil production rate and oil production time. This study involves three cases: i) a range of values for all the parameters to be optimized were provided and the optimization tool gave the most appropriate values for those parameters, ii) steam is injected from vertical well and production is taken from horizontal well. The optimized parameters are utilized to determine the recovery from this pattern and, iii) a case vice versa of second case which is applied and the recovery is determined. Results show that both cases (ii) and (iii) give low recovery of oil which is about 4% and 13% respectively. In contrast case (i) used optimization tool where recovery factor shows about 40%. This means that in order to maximize the recovery, it is necessary to optimize different rates and times in cyclic steam stimulation method and arrangement of vertical and horizontal wells in TTH manner. It is also necessary to evaluate the performance of the heavy oil reservoirs.
