Design and experimental study of stratified control tool for solid fluidization and gas lift in three-gas combined mining
Three-gas combined mining is one of the effective ways to realize early commercial development of offshore natural gas hydrate.However,the existing downhole production allocators used for offshore oil and gas wells are unable to realize the stratified and precise control of the pressure and flow rate of natural gas produced from each layer in three-gas combined mining,and nor can meet the need of efficient gas lift assisted drainage of solid fluidized hydrate slurry.To solve the problem that downhole production allocators can hardly meet the need of stratified control of natural gas in different layers,this paper proposes an implementation plan of stratified control engineering for solid fluidization and gas lift of natural gas hydrate,and invents a downhole stratified control tool with two-stage throttling structure composed of cage section and fixed choke,which can realize the accurate control of natural gas pressure and flow rate by regulating the spool module of stratified control tool according to the production demand.And the following research results are obtained.First,the multi-stage throttling structure consisting of cage section and fixed choke in the spool module of downhole stratified control tool has the advantages of good depressurization performance and moderate cooling range.Second,with the increase of outlet pressure,the gas mass flow rate at the outlet fluctuates within a small range of 13.0 kg/s.When the outlet pressure reaches 13 MPa,the lowest temperature of natural gas inside the valve core is lower than the threshold hydrate formation temperature.Third,with the change of spool opening,the change of gas mass flow rate and volume flow rate inside the valve core is approximately linear,so that the control tool can achieve an accurate control of natural gas flow rate under a high pressure environment.In conclusion,the downhole stratified control tool invented in this study can meet the need of linear accurate control of natural gas flow rate,as well as the technical need of efficient gas lift assisted drainage of solid fluidized hydrate slurry in three-gas combined mining,and provide engineering and technical equipment support for the commercial development of natural gas hydrate in China.
Offshore oil and gas wellNatural gas hydrateThree-gas combined miningStratified controlControl tool
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维普
