Research On Technology Of Secondary Brine Discharge And Mud Sand Control In Gas Storage

Since the 1950 s,foreign countries have begun to build salt-cavern UGSs,while my country has only begun to work on salt-cavern UGSs at the end of the 20 th century,more than 50 years later than foreign countries.However,through the unremitting efforts of my country,more than 20 salt-cavern gas storages have been built,and due to the advantages of high safety and large working gas capacity,salt-cavern gas storages have developed rapidly in recent years.Salt cavern gas storage is to store natural gas by injecting fresh water into dissolved salt layers through ground drilling to form caves.The geological conditions of the saltcavern gas storage in my country are that there are a large number of layered salt layers,the thickness of the salt layer is thin(about 150 m),and there are a large number of insoluble muddy interlayers(15%-40%)between the salt layers,and the number of interlayers is large.And the thickness is thick(3~11 m).After the water-soluble salt layer,the insoluble muddy interlayer in the salt layer loses support and gradually collapses,releases and settles,and finally accumulates at the bottom of the gas storage cavity.The sediment is released and accumulated by the free dissolution of insoluble matter,and the arrangement is loose,and there is abundant pore space between the particles.This part of the space is occupied by a large amount of nearly saturated brine,and the clay minerals will soften and expand,so the sediment occupies the storage space.In most of the gas storage space,during the first gas injection and brine discharge process,only the clean brine above the deposit can be discharged,leaving 2~5 m of brine layer and brine in the pore space of the deposit.It is urgent to explore the second The secondary gas injection,brine removal and mud sand prevention technology can further discharge the residual brine and brine in the pores of the deposits at the bottom of the cavity to reduce the loss of storage capacity.The deposits at the bottom of the salt cavern gas storage cavity are formed by free deposition,without compaction and cementation,and the accumulation is loose,with many fine muddy particles,which are easy to migrate and block the brine discharge pipe;the residual water in the cavity is nearly saturated brine,which contains salt If the amount is high,it is prone to blockage by salt crystallization.In this paper,the mineral characteristics,particle size and distribution characteristics of the mud at the bottom of the salt cavern gas storage cavity are fully understood by XRD and sieve analysis methods.Alternative solutions for mud and sand: screen sand control experiment,gravel packing-artificial well wall sand control experiment,and chemical cementation sand consolidation experiment.Aiming at these three experimental schemes,an indoor simulation device suitable for secondary gas injection,brine removal,and silt control in high salinity salt caverns is designed and built.The diameter and height are 25 cm.The influences of gas brine discharge pressure,brine layer height and insoluble matter particle size on sand production and liquid drainage rules were investigated,and the influence rules of the characteristic parameters of the deposits at the bottom of the cavity and the parameters of brine drainage on the sand control effect of secondary brine drainage were found out.The artificial well wall and resin cementation method is used to study the strengthening sand control method,and the corresponding sand control process parameters are optimized.Well wall sand control technology system.