Remaining oil distribution characteristics in an oil reservoir with ultra-high water-cut

Abstract

An accurate mapping and understanding of remaining oil distribution is very important for water control and stabilize oil production of mature oilfields in ultra-high water-cut stage. Currently, the Tuo-21 Fault Block of the Shengtuo Oilfield has entered the stage of ultra-high water cut (97.2%). Poor adaptability of the well pattern, ineffective water injection cycle and low efficiency of engineering measures (such as workover, re-perforation and utilization of high-capacity pumps) are the significant problems in the ultra-high water-cut reservoir. In order to accurately describe the oil and water flow characteristics, relative permeability curves at high water injection multiple (injected pore volume) and a semi-quantitative method is applied to perform fine reservoir simulation of the Sand group 3–7 in the Block. An accurate reservoir model is built and history matching is performed. The distribution characteristics of remaining oil in lateral and vertical directions are quantitatively simulated and analyzed. The results show that the numerical simulation considering relative permeability at high injection multiple can reflect truly the remaining oil distribution characteristics after water flooding in an ultra-high water-cut stage. The distribution of remaining oil saturation can be mapped more accurately and quantitatively by using the ‘four-points and five-types’ classification method, providing a basis for potential tapping of various remaining oil types of oil reservoirs in late-stage of development with high water-cut.