Influence of geological factors on air foam flooding efficiency in a tight oil reservoir

Key words:  tight oil reservoir  air foam flooding  geological factors  sedimentary facies  channel control system  flow unit system

Abstract:

Air foam flooding is one of the most promising techniques to enhance oil recovery, which has dual roles of profile control and oil displacement with relatively low cost in comparison with other gas injections. In order to study the influence of geological factors on air foam flooding efficiency, reservoir sedimentary facies and physical property control systems were featured out in a case study of the well group 8100 in a tight oil reservoir of Chang-Six, in which well logging data were used to characterize the sedimentary and channel systems and classify the flow unit systems among the injection and production wells. The reasons for good and poor performance of different well groups were analyzed based on the dynamic production data. The results show that the sedimentary facies and the physical property control systems have a significant effect on the performance of air foam flooding. If the injection and production wells locate in a different channel control system, the production will be not effective. If the injection and production wells belong to the same channel control system and same flow unit system, good production performance can be observed. If the injection and production wells belong to the same channel control system but with poorly connected flow unit system, a mixed (good or poor) production response can be observed. Based on the analysis results, the following recommendations should be adopted in order to increase the air foam flooding efficiency. The injection well should locate in the center of the main channel. If the well group is near the channel margin, nine-spot injection pattern can be changed to five-spot pattern. The inter-well distance can be increased along the channel direction, but reduced in perpendicular directions.