A New Potential Fine Trapping Technology for High Water Cut Stage in Heavy Oil Reservoirs with Bottom Water Based on Physical Properties of the Reservoir Varying over Time

The current water coning variation formulae of heavy oil reservoirs with bottom water fail to take into account the changes in reservoir physical properties caused by long-term large liquid volume erosion, resulting in a relative large calculation result of the water flooding sweep volume. In order to accurately describe the change laws of water coning and water crest as well as the distribution of remaining oil in the high water cut stage, a mathematical model of water coning and water crest variations for heavy oil reservoirs with bottom water while taking into account the physical properties time-varying was established by considering the physical properties change of reservoirs caused by long-term large liquid volume erosion. Further, an equivalent seepage resistance method was used to implement the equivalent characterization of the reservoir permeability inside and outside the sweep area. The analysis showed that the reservoir physical properties that varied over time had a significant effect on water coning. Under the same water coning width, the mathematical model that took into account the factor of time-varying physical properties was 46.3% smaller than the calculated swept height that did not consider this factor. Comparing the calculation results of the former model with the results of the adjacent well logging interpretation, the relative error was only 5.3%. According to the contact relationship between the water coning and water crest of the heavy oil reservoir with bottom water considering the time-varying physical properties under the current well spacing conditions in the Bohai Q Oilfield, three types of remaining oil distribution patterns among the wells of this oilfield were summarized, and the corresponding potential trapping strategies were developed. The pilot test confirmed the reliability and effectiveness of this potential fines-trapping technology in the high water cut stage of heavy oil reservoirs with bottom water, could provide technical supports for recovering the remaining oil in those reservoirs.