Study On Flow Field Migration And Cavity Expansion Of Double-well Water-soluble Chamber In Salt Rock

According to the report of the 19 th National Congress of the People's Republic of China,a sound energy security system will be formed in China by 2020,and the country's demand for the number of gas storages will continue to increase.Single well pad method can not meet the growing need of national energy strategic reserves because of the long period of cavity cavity and the small volume of the cavity.Therefore,this paper has carried out the theoretical research on the Double-well water-solubilizing cavity of salt rock gas storage.Accelerate the construction of underground reservoirs in China to provide a theoretical basis and decision support.This paper takes the Huai'an Salt Cave Gas Storage Project as the engineering background,and compares the single-factor and multi-factor dissolution characteristics of salt rock at home and abroad.On the basis of acquiring dissolved characteristics,a double-well cavity platform was set up.By studying the flow field migration law of different cavity stages and different well groups,the interaction mechanism between flow field and concentration field was studied based on the distribution characteristics of solution cavity concentration field.Combined with the flow field law of the water injection area in the cavity of the horizontal well,the cavity expansion law of the whole process of the Double-well cavity was analyzed through the water-solubilizing cavity experiment.This part of the study can provide technical guidance for the development of Double-well water-solubilizing chamber on site.It mainly includes the following research work:(1)Salt mineral properties and dissolution rate of salt rock: According to the single factor dissolution experiment of temperature,concentration and erosion dip angle of domestic argillaceous salt rock,type salt and foreign salt rock,the dissolution characteristics of salt rock at home and abroad were studied,found The dissolution characteristics of salt rocks are basically the same.While the dissolution characteristics of domestic high muddy salt rocks are relatively complex.A multi-factor coupled dissolution experiment was conducted.The influence of the three experimental factors on the weights was analyzed using the range analysis method and the analytic hierarchy process.It was found that the dissolution dip angle had the greatest influence on the dissolution rate of salt rock.(2)Study on flow field of water-solubilizing chambers in Double-well: Establishing an experimental platform through similarity theory,analyzing the flow law of flow field in different cavity stages and different well groups by dyeing method,and dividing the solution cavity based on the distribution characteristics of dissolved cavity concentration field.The four main areas are: border area,plume area,jet area,and bottom area.Each area influences each other.The floating plume area drives fluid flow throughout the cavity,and a differential mathematical model of the plume is established based on fluid mechanics.The boundary erosion area can be divided into normal boundary area and turbulent wall floating area.The jet region can be divided into the main jet region and the reverse jet region.Using the Lagrangian method,the continuity equation,momentum equation,and energy equation are established.According to the continuity equation,the time required for the brine to flow through the cavity can be estimated.After the concentration of the fluid in the bottom zone is stable,it is approximately linear in the depth direction,but it is saturated for a long period after stratification.When selecting the well group to control the dissolution,horizontal well inclination needs to be improved,and a corner-curved "L" tube is selected to ensure the dissolution of the middle section roof.The flow patterns of the wells in the double-wells and the distribution characteristics of the concentration of the solution cavity have important effects on the rate and shape control of the cavity.(3)Experimental study of the injection hole area in the process of the horizontal well cavity: Based on the dimension analysis method in the similarity theory,an experiment was conducted in the injection hole area of the horizontal well cavity process,and the flow pattern of the flow field,The influence of factors such as the shape of water injection hole and the flow rate of water injection on the migration of flow field.The study shows that the flow patterns of the two types of wells are different.Through the qualitative analysis of the stages,it is found that the horizontal water injection ports are superior to the vertical water injection ports in terms of migration speed and influence range.However,due to the extreme height of the vertical water injection ports,It is more advantageous to control the dissolution.(4)Research on the Expansion Law of Large-size Salt Water Soluble Chamber: A similar simulation platform for Double-well water-solubilizing cavity was developed.By extracting the cavity profile,the whole process experiment of Double-well water-soluble cavity expansion was carried out,and the expansion law of the cavity was analyzed.Combined with the distribution of flow field analysis.The research shows that the dissolution of the Double-well water-solubilizing cavity mainly occurs in the deviated well section,and the vertical well end volume is approximately one-third of the inclined well end,but the dissolution of the horizontal insoluble area is significantly accelerated after the well-dip.