Experimental Study On Mechanism Of Gas-water Cooperative Displacement In Fractured-vuggy Reservoir

The fracture-vuggy carbonate reservoirs are rich in oil and gas resources,which are characterized by deep burial,high temperature and high pressure,the reservoir space is diverse and the scale is different,so it is difficult to develop.In the early exploitation of fracture-vuggy carbonate reservoir,the production decline is fast,energy replenishment is difficult and recovery is low;gas-water cooperative displacement can control the fluidity and delay gas channeling,expand sweep volume and improve displacement efficiency to maintain reservoir pressure by using Jamin effect.In order to study the mechanism of gas-water cooperative displacement in carbonate fracture-vuggy reservoir,on the basis of the karst background of fracture-vuggy carbonate reservoir and the actual geological data of Tahe oilfield,based on the similarity criterion,simplified physical models of fracture-vuggy structure with three different filling types,physical models of resistivity monitoring,and three-dimensional visualized multi-well complex fracture and cave unit models with different karst backgrounds are designed and made,a physical simulation methods of fracture-vuggy reservoir resistivity monitoring were established,and gas-water cooperative mechanism experiment was carried out to reveal the mechanism of gas-water cooperative displacement,determine the length of gaswater mixed zone,and clarify the effect of gas-water cooperative displacement to enhance oil recovery.In fracture-vuggy carbonate reservoir,gas-water synergistic effect is affected by gas-water ratio,injection-production relationship and reservoir structure.The results of different gas-water ratio show that the oil displacement effect is better when the gaswater ratio is 1:1.The low gas-water ratio can control the fluidity and delay gas channeling better,and the oil displacement effect is better than the high gas-water ratio2:1.The experimental results of different injection-production relationships show that the interwell single channel injection and production has the best displacement effect,while the interwell double channel two injection and production has the worst displacement effect,and the formation of gas-water mixed zone is beneficial to improve the recovery factor.The experimental study on the characteristics of gas-water mixing zone shows that high temperature and high pressure are favorable to gas-water miscibility,and gas-water separation is not easy.The filling material in the karst structure has shear effect on gas-water mixing,which is favorable to delay the occurrence of gas-water differentiation.The experimental study of gas and water injection in the same well or different well shows that the effect of gas and water injection in the same well is better than that in different well,and gas and water injection form gas-water mixed zone and improve oil displacement efficiency.In the reservoir with better connection between the dark river and weathering crust,it has better EOR effect.In the fault solution reservoir,the gas-water separation phenomenon is more likely to occur due to the existence of large faults,and the EOR improvement effect is poor.