Distribution of remaining oil and improved oil recovery methods in fractured-vuggy carbonate reserviors

In view of the unclear understanding of the Tahe oilfield carbonate fractured-vuggy reservoir remaining oil distribution problem, based on the geological characteristics of the seam hole reservoir, combined with the comprehensive connectivity analysis, studies of injection-production effects, and oil-water distribution characteristics using solid drilling, measures, and effects of injection-production well analysis, Sum up and propose control factors in macroscopic, microscopic and apparent three aspects of remaining oil distribution, depending on characteristics of reservoir geological, seam hole development and development factors respectively. On this basis, combining the reality of reservoir development, the distribution patterns of remaining oils in 3 major categories and 14 sub-categories of Tahe oilfield carbonate fracture-cavity reservoirs are proposed. It is clear that 5 sub-categories belong to the macroscopic residual oil determined by the reservoir geological characteristics, 6 sub-categories belong to the micro-remaining oil determined by the fracture-cavity development characteristics, and 3 others sub-categories belong to the apparent residual oil caused by the development of uncertain factors. At the same time, suitable mine development countermeasures are put forward for different types of residual oil, among them, the vertical well method uses the main fracture separation type, the branch fracture point filling type, the water cone oil bucket type, the longitudinal multiple sets of channel type, the valley corner hole type, and the large gap hole lateral separation type; Hole-relation type, finger-separated type, dark river filling type; The residual oil of the orifice channel type is adopted by using the flow regulating channel, the large pump extracting liquid or the selective water blocking method; The longitudinally separated type and the crack closed residual oil of the large slit hole are adopted by the segmental acid pressure and the large acidification method. The research on the remaining oil types and development countermeasures of different karst fracture hole reservoirs has achieved good development results in the main area of Tahe oilfield, laying the foundation for tapping the potential for the remaining oil in similar reservoirs.