Flow Filed Migration Rule Of Two-well Solution Mining With Small Interwell Distance And 3D Numerical Simulation

Energy is the material foundation to the survival of humans,it is the objective prerequisite of the development of national economy,how to ensure energy security become the strategic target of each country.General Office,on “the energy development strategic plan(2014-2020)”,noted that “perfecting energy alternatives and reserving emergency system,focusing on enhancing the energy supply capacity.And a more perfect system of energy security will be formed,basic emergency system will be built in 2020.”In order to realizing the sustainable development of energy in our country,we need to improve the reserves ability of oil and gas,accelerate the construction of gas storage,be more conducive to gas storage and emergency load capacity.The reserve types mainly conclude: the ground repository,underground storage repository,sea.Contrast to the other types,Underground storage has the characteristics of safety,economy,and being more practical.There are 60% strategic energy reserves under the ground around the world.Salt has low permeability,the stable mechanical properties and damage self-healing capability.Therefore,salt is the wordwide-recognized ideal reserve medium of storage cavern.Currently,single-well solution mining technology is a widely method to build storage cavern.It apply to great geological and less sandwich rock conditions.In our country,however,the salt rock conditions has many interlayers,and the method of single-well is difficult to meet the demand in cavity volume and making cavity cycle.These problems will lead to low efficiency.In 1997,Botho made a point of two-well solution mining with small interwell distance,which can shorten build cavity cycle and improve the efficiency of building cavity.Since then,the related theory study of this method were carried out.This paper was based on the gas storage project in Yunying salt mine,researched conventional dissolving characterister of the salt in domestic and foreign,got dissolved parameters to make indoor model test,and combined computational fluid dynamics(CFD)to explore migration characteristics of flow field of two-well solition mining with small interwell distance.Research work mainly includes the following aspects:(1)Taking the micro experiment of salt in domestic and foreign,such as EDS energy spectrum analysis,XRD and SEM test.Meanwhile,comparing their similarities and differences.And,salt dissolution mechanism was analyzed,carried out the dissolution experiments of multi-factor influence for the both,explored the influence of environment temperature,environmental concentration and dissolution angle to both salt.Research found internal and overseas salt rocks exist commonness and individuality under different factors.(2)Research of small spacing well in vast cavity flow field movement rule.According to the characteristics of the flow,adapting to the method of dyeing,rock-salt cavity could be divided into four main areas:boundary layer,floating plume area,main body and the bottom area.Their influence with each other.Floating plume drived the whole cavity flow and plume differential mathematical model could be set up through the fluid mechanics calculating.As the boundary of plume limit height,the main body of rock-salt cavity could be partitioned to explore the flow characteristics respectively.Boundary layer region could be divided into the common boundary area and turbulent buoyant jet wall area,turbulent buoyant jet area influence the diameter of cavity.The concentration of the bottom area was linear at the beginning of the brine injection.When keeping a steady state,cavity tended to saturation.As the boundary of shoe plane,cavity presented different characteristers of concentration distribution.The migration regularity of flow field and concentration distribution characteristers had a reference value for controling cavity dissolution and shaping rock-salt cavity.(3)Making the indoor experiment of small interwell distance cavity flow field characteristics in multi-factor.To analyze the small well spacing of rock-salt cavity flow field characteristics,exploring different factors change respectively from three aspects:the water injection flow,height of lift pipe,interlayers.And the study have shown that increasing water injection flow rate lead to the the buoyant plume limit height higher and make salt dissolution rate faster,but the changing rate of concentration in cavity will be smaller.The changing of tube height changed the scope of plume essentially,as a result,influence area was varied.The interlining could hinder the scope of local flow field area,but not change the layer distribution of cavity concentration.(4)Launching numerical simulation research of two-well solution mining with small interwell distance.Based on the parameters obtained in the above,using the ICEM modeling and FLUENT to verify flow field migration rule and the concentration distribution characteristics.The study found that the results of macro flow field was similar between numerical simulation and indoor model experiment,but in the local area,numerical calculation show the complex characteristers of different curl.This phenomenon explained many doubts existing in the “dyeing” physics experiment.And the result of numerical simulation of cavity presented obvious concentration distribution characteristers.What's more,through using numerical simulation,the paper analyzed that the time to be stable of cavity was longer in mass flow,but concentration rised faster in small flow.