Modeling And Optimization Methods For Planning Of The Whole Process Of Offshore Oil And Gas Production

China's dependence on crude oil consumption has reached 60.6%,which seriously threatens China's energy security and national security.The development of offshore oil and natural gas is an important means to alleviate the shortage of China's oil and gas resources,but the cost and resources of offshore oil and natural gas exploitation are extremely high.Using the plan optimization method to optimize the whole process of oil production will undoubtedly bring huge economic benefits.Based on this,this paper proposes a whole process integration optimization method from underwater oil production system to water platform for offshore oil recovery process.On the basis of comprehensive consideration of the production arrangement of the tree,injection,storage,artificial lifting and the flow safety of the submarine pipeline,the multi-cycle planning optimization model for the whole process of offshore oil and gas production was established for the first time.Aiming at the mixed integer nonlinear programming(MINLP)model,the Lagrange optimal decomposition strategy based on batch decomposition of subsea production units is studied.Under the consideration of uncertainties such as the demand for crude oil orders and changes in the underwater environment,the optimization of uncertain offshore oil and gas production plans was studied.The main research contents of the thesis are as follows:In view of the optimization of the oil and gas production operation level in the current research,the integration plan optimization of the typical offshore oil and gas production process was proposed and studied for the first time.For the operation layer,comprehensive consideration is given to the start-stop of the underwater production well,the change of the bottom hole pressure,the energy consumption of the artificial lift(electric submersible pump),the influence of the chemical flooding injection on the recovery rate and the storage of crude oil;For the purpose of flow assurance,the establishment of the underwater pipeline temperature prediction model is studied,and the prevention of hydrate formation and the prediction of the wax removal cycle are considered.Based on the process model,the discrete time representation method is finally used to describe the integration plan optimization problem as MINLP model.Aiming at the large-scale MINLP problem of the established optimization model,this paper proposes a strategy to optimize the simultaneous decomposition of multi-batch units into single-lot units.Using the Lagrange relaxation algorithm,the Lagrange multiplier is introduced to loosen the multi-batch unit coupling constraint,and the dual problem is constructed to form a loop iteration to solve the long-cycle multi-unit operating state binary variable and the operating load continuous variable simultaneously.Optimization,and there are nonlinear problems.On the surface of the simulation results,the method can greatly reduce the solution scale,quickly optimize the results,and improve the efficiency of the model.Considering the uncontrollable conditions that may exist in the production process,the modeling and solution of offshore oil and gas production plans under uncertain conditions are studied to improve the robustness of the planned optimization results.Using the robust dual optimization theory,using the uncertain set of uncertainties to describe uncertain factors,such as product demand and stochastic fluctuations of geological parameters,an uncertain model for offshore oil and gas production uncertainty planning based on discrete time representation is established.The probability description of the opportunity constrained programming is used to determine the size of the robust uncertain set.The uncertain constraints in the uncertain plan model are transformed into deterministic constraints,and then solved to obtain the optimization results.The algorithm studied in the paper simulates the actual offshore oil and gas production.The results show that the established MINLP model can adapt to the actual production process,and the optimization result can greatly reduce the production cost.The research provides a new approach to marine oil and gas production optimization.