Study On Flow Mechanism And Acidizing Mechanism Of Atomized Acid In Gas Injection Reservoir

Acidizing can effectively remove the pollution and blockage of reservoir near wellbore,improve the connectivity between wellbore and reservoir,restore and improve oil and gas production,which is the main technical means of developing fracture-cave reservoir.The fracture-cave reservoir is highly heterogeneous,with a large number of fractures and caves.When conventional acid treatment is used,the acid solution is easy to accumulate in the fracture-cave reservoir and dissolve and expand the fracture-cave reservoir,thus inhibiting the expansion of acid wormhole and making it difficult to effectively communicate with the fracture-cave reservoir.Combined with the development of fracture-cave reservoir by gas injection,the atomization acidizing process is proposed for the first time,with gas phase as continuous phase and acid liquid as discontinuous phase.Atomized acid can sweep,etch and start the undeveloped gas drive channel,expand the reserve range of gas injection production,effectively communicate the discontinuous fracture-cave reservoir,which is conducive to the formation of high oil and gas diversion channel.Based on the self-developed simulation platform of acid atomization wellbore flow,the atomizer is designed and optimized.In order to achieve better atomization effect,when the mass ratio of gas to liquid is 21.5,0.05% content of atomizing stabilizer SDBS is added to achieve the best flow state of atomized acid.At this time,the median droplet size is 80 μm,and the atomization rate can reach 82.22%.Based on the population balance equation,the flow model of atomized acid wellbore is established.It is found that the atomized acid can still keep the fog flow into the formation after flowing through 4000 m wellbore under the oil field condition.It is found that the corrosion rate and acid rock reaction rate of atomized acid is one order of magnitude lower than that of conventional acid,and it has excellent corrosion inhibition performance.Based on the classical two scale continuous model,the homogeneous model was introduced to establish the atomization acidification model,and the numerical simulation of atomization acidification of different fracture hole combination units was carried out.Comparing atomized acid with liquid acid acidization,it is found that fracture shape and location have little influence on atomized acid,and the wormhole generated is more slender;atomized acid is easier to use and communicate with fracture-cave reservoir to expand acidization radius,when penetrating the same depth formation,atomized acid takes less time and consumes less acid,which is more conducive to realize deep acidization.