Study On The Solid Plugging Agent Transporting Law With Nitrogen Foam In Fractured-vuggy Reservoir

The deep carbonate reservoirs in Tarim are typical fractured-vuggy reservoirs with high temperature,high pressure and high salinity.During the development process,the problems of water channeling and gas channeling are prominent,which indicates that channeling plugging is a necessary measure to improve the oil recovery.The solid plugging agent has the characteristics of high strength,temperature resistance and a wide range of salinity resistance.It can play an effective plugging effect in fractured-vuggy reservoirs through deposition and bridging,and the plugging position is important for the plugging effect.Foam has the characteristics of low density,high viscosity,and strong carrying capacity,and can be used as a medium for transporting solid plugging agents.Investigating the transporting capacity of solid plugging agents and particles migration laws with foam in fractured-vuggy reservoirs is of great significance for improving the plugging effect of particles and realizing effective placement in deep formations.In this paper,the Waring Blender method is used to comprehensively evaluate the foaming performance of several temperature and salt-resistant foaming agents.The effect of foaming agent concentration,salinity,and temperature resistance on foam stability is studied,and the stability of foam system in deep high temperature and high salinity formation conditions in Tarim was studied by visual PVT system,the gas-liquid interfacial tension under different temperature,pressure and foaming agent concentration conditions were tested by interfacial tensiometer.Foam microstructure was observed by Foam Scan equipment under high temperature and pressure conditions.And the stable mechanism of foam is comprehensively analyzed.Through the capillary rheometer tests,the apparent viscosity and rheological parameters of foam at different foam qualities and temperatures were determined,and the static sedimentation of the plugging agent particles in foam was expanded to verify the transporting capacity of the particles.The visualization experiment studies the evolution process of foam in rough fractures and the plugging mechanism of foam-transporting particles in the fracturedvuggy model.Finally,through the CFD numerical simulation method,the migration law of the foam-transporting particles is studied and the influence of the particle density,particle size,foam quality and injection velocity on the particle migration is analyzed in fractured-vuggy system.The results show that the optimized foaming agent system can meet the requirements of high temperature and salinity reservoir conditions in Tarim deep fractured-vuggy reservoir.Foam is a typical power-rate fluid.With the increase of shear rate,the apparent viscosity of foam decreases gradually.With the increase of foam quality,the apparent viscosity and consistency coefficient of foam first increased until foam quality reaches 83.3% and then decreased.Foams with a quality range of 65%-85% have good stability and apparent viscosity,and good suspending ability to solid particles plugging agent.Under the condition of fracturedvuggy reservoir,the change of fracture roughness can effectively promote the regeneration of foam,and foam can transport particles to the deep fracture and achieve bridging and plugging at the joint of fracture and caves effectively control the channeling flow and expand the swept volume.At the same time,gas separation can improve the effective use of top attic oil.The numerical simulation results show that the higher flow rate and foam quality,the lower particle density and particle size can ensure that the particles reach the deep formation.The carrying efficiency of foam in fracture increases with the increase of dip angle.Under the condition of fractured and caves,the settlement phenomenon is obvious when the particle plugging agent with higher density passes through the cave,and the particle plugging agent with lighter density can pass through the smaller cave smoothly.For fractures,plugging agent particles with relatively large density can be selected to achieve plugging by settling and bridging.