Abstract:

In order to find out the complex situation of remaining oil distribution at the middle and high water-cut stage of Suizhong 36-1 Oilfield, and by the study of the flow field variation characteristics of nine-point well pattern for complex heterogeneous reservoirs by high temperature and high pressure experiments, the physical simulation experiments for the nine-point well pattern and the characteristics research for flow field of infilled row shape injection-production well pattern were designed and carried out based on the newly developed 3D large-scale core modeling technology and the stereoscopic acquisition system for oil-water saturation. For the injection and production patterns with complex rhythms, the distribution of remaining oil was also very complicated, but there were certain rules: under the condition of single positive rhythm, the subsidence of injected water was obvious even in the experiments, and the remaining oil was mainly distributed in the upper part of the positive rhythm; under the condition of inverse rhythm, the injected water could spread evenly to all permeability layers of the model, and the remaining oil was mainly accumulated in the weak hydrodynamic area; under the condition of complex compound rhythm, the distribution of remaining oil depended on the low permeability zone with weak water flooding in the complex structure, and it was not necessarily the area without streamline between corner wells. At the same time, based on the above characteristics, it was found that the water flooding degree of nine-point well pattern was high, most recoverable reserves could be produced. And when nine-point well pattern transformed into row injection-production well pattern, the recovery rate of heterogeneous reservoir could be improved by about 8 % ~ 10 %. Experimental studies suggest that no matter for the nine point injection production well pattern or the converted row shape injection-production well pattern, the maximum recovery rate of structure reservoirs with complex rhythmic was difficult to exceed 40 %.

Key words: remaining oil distribution, nine-point basic well pattern, water flooding, sedimentary rhythm, heterogeneity