Assessment method for remaining oil recoverable potential in ultra-high water-cut reservoirs based on projection pursuit model

Abstract

The factors affecting the remaining oil recoverable potential in ultra-high water-cut reservoirs are extremely complex， exhibiting substantial variations in their impact. Conventional methods often rely on singular indicators such as remaining oil saturation or remaining oil abundance to assess remaining oil recoverable potential， which fails to guide tapping remaining oil in ultra-high water-cut reservoirs effectively. By considering the factors affecting the remaining oil recoverable potential in these reservoirs and comprehensively characterizing the heterogeneity of reservoirs， the scale of remaining oil reserves， watered conditions， and oil/water flow capacity， we constructed a quantitative assessment indicator system to tap the remaining oil recoverable potential in ultra-high water-cut reservoirs. In addition， according to the control degree difference of the indicators on remaining oil recoverable potential， we determined the objective weights of each evaluation indicator by combining the accelerated genetic algorithm and the projection pursuit model. We constructed the remaining oil recoverable potential index to form a new quantitative assessment method of the remaining oil recoverable potential in ultra-high water-cut reservoirs. Taking the NmIL sand body of the main production layer in the south area of Bohai Q Oilfield as an example， we quantitatively assessed the remaining oil recoverable potential in ultra-high water-cut reservoirs. The results reveal that the new method can comprehensively characterize the effects of reservoir physical properties， remaining oil reserves， and dynamic characteristics of oil/water flow on the remaining oil recoverable potential in different locations and realize the differential quantitative assessment of the distribution of remaining oil recoverable potential in NmIL sand body of the main production layer. In addition， the dominant recoverable potential area is clearly characterized， and it is taken as the potential area for the subsequent adjustment of infill wells in the NmIL sand body to accurately guide the deployment of infill horizontal wells， thereby offering a novel perspective for tapping remaining oil resources in such reservoirs.

Keywords

• ultra-high water-cut period
• remaining oil
• recoverable potential index
• projection pursuit
• dominant recoverable potential abundance