Study of cyclic waterflooding for improving oil recovery in Lukeqin heavy oil reservoir

Abstract

Long term water injection in Lukeqin heavy oil field results in a rapid increase of water cut. It is an urgent need to conduct a study on the influencing factors of heavy oil waterflooding. Experiments are used to conduct the effect of heavy oil viscosity change law on the development. Numerical simulation is used to analyze the viscosity and rhythmic conditions to clarify the production mechanism of waterflooding in heavy oil reservoirs. The feasibility study of cyclic water injection in heavy oil reservoirs is analyzed because water channeling is serious in continuous water injection, while cyclic waterflooding can slow down the injection water surge. To begin with, when using the improved cyclic waterflooding method, the working mode, reasonable number of cycles and the timing of cyclic waterflooding need to be optimized to obtain the optimal combination injection scheme. Furthermore, to investigate the mechanism of oil increase by cyclic waterfiooding, different production wells were divided into the channeling well, the seepage channel well and the normal wells according to the streamline strength, and then analyzed the mechanism influencing factor such as pressure difference and capillary force to study when cyclic waterflooding for the three types of production wells. Pressure differential are the most effective in increasing oil in the normal well, followed by the seepage channel well, and channeling well. The capillary force have the best water control effect on the channeling well, followed by the seepage channel well and the normal well. The capillary force play a dominant role in the well water control in the channeling well. The effect of increasing oil in the normal well is dominated by pressure difference. Well pressure difference and the capillary force have little to no dominant effect on the seepage channel well. The results demonstrate that cyclic waterflooding can effectively improve the recovery rate of three types of wells, with the degree of improvement from good to bad, in the order of the normal well, the channeling well and the seepage channel well. The novelty of this work lies in the combination of experimental and numerical models (mechanistic and practical) and simulation studies using three different types of wells, thus analyzing the mechanistic influence of pressure differential and capillary forces in it and concluding the dominant mechanism of action - the mechanism of development of heavy oil cyclic waterflooding is the effect of pressure difference control on production increase and capillary force control on reducing water cut.