Abstract:

The connected media of fault-karst reservoir are fractures, caves and pores, the decrease of pressure will lead to the decrease of permeability and conductivity, which will have an irreversible impact on oil well production. According to the stress-sensitive characteristics of fault-karst reservoir, 72 groups of physical simulation experiments on conductivity are designed and carried out to analyze the stress-sensitive characteristics of different connected media and influencing factors. Based on the results of physical simulation experiment and the theory of porous flow, a numerical inversion model of flow in fractured solution reservoir is established, and the stress sensitivity effect caused by reservoir pressure drop on oil well production is studied. The results show that the pressure drop has great influence on the conductivity, productivity and recovery ability of different connected media. The pressure inflection points of fracture type, karst cave type and pore type are 5.3 %, 20.4 % and 35.1 %, respectively, and the conductivity loss of the first two are 99.7 % and 45.0 %. The conductivity loss of pore type decreases linearly in the test range. The research on the characteristics of pressure drop inflection point provides the basis for reasonable production control and the determination of energy replenishment time, and has important guiding significance for stable production of oil wells.

Key words: pressure drop inflection point, flow conductivity, oil well production, water injection timing, fault-karst reservoir