Discrete numerical well test and water injection optimization of fracture-cave type reservoirs

 The carbonate oil reservoirs in the Tahe Oilfield belong to ancient karst fracture-cave type reservoirs. It has strongly heterogeneous characteristics and its space distribution is not continuous. The cracks which connect caves are the primary seepage channel and the fluid is mainly stored in the caves, so complex fluid flows lie in the reservoir. The traditional well test methods are hard to correctly describe fracture-cave type reservoir characteristics and fluid flow law. In view of the geologic features of fracture-cave type reservoirs, we regard reservoir as discrete media and set up a discrete numerical well test interpretation method. The results show that interpretations are more in line with the true fracture-cave reservoir geological features, and can better describe fracture-cave reservoir structure. According to the discrete numerical well test analysis combined with geological features, the paper divides carbonate oil reservoirs in the Tahe Oilfield into five typical reservoir types and explains cave sizes, distances and other key reservoir parameters. Well test interpretation results can effectively guide the injection wells optimization, injection parameter optimization and other supporting measures for production. It has an important significance for EOR of fracture-cave type reservoirs.