Development of Algorithms to Control the RPM System under Full Implementation of the Swag Injection Technology at Roman Trebs' Oilfield

Abstract

Abstract To maintain reservoir pressure and to increase efficiency of oil production at Roman Trebs' oilfield it is planned an injection of water-gas mixture into reservoir. Reservoir pressure maintenance (RPM) system is a branched double-tube network – gas and water pipelines are laid in parallel in all sections. Water pipeline provides water delivery from pad pumping station (PPS), and gas pipeline delivers gas from compressor station (CS) to multywell pads of injection wells. Further water and gas are mixed on well pads in individual mixing devices, and water-gas mixture is pumped into injection wells. Control of water and gas volumes injected in each well is achieved by means of control valves mounted on gas and water supply lines of each mixer. Pipeline of RPM system with injectors represents a complex dynamic facility and managing such complex dynamic object is a problem with a nontrivial solution. This problem is complicated by the fact that it is planned injection not of a single-phase liquid but two-phase water-gas mixture. Moreover, problem of controlling injection of water-gas mixture includes maintaining a certain ratio of water and gas in each well. This article shows problems of complex object management (multidimensionality, multistability, influence of injected agent's properties) and ways of solving these problems. While developing control algorithms, RPM system was studied as a nonlinear non-steady multidimensional control object with vector input and output. Characteristics of transient modes were defined. There were studied the algorithms of structural-parametric identification of dynamics of multidimensional control object. Various options of regulator structure were investigated: PID-control, modal PID controllers, controllers with a higher degree of astatism, controllers with identifiers. Based on analysis of simulation results there were found the recommended paths of well starting and decommissioning. Similarly, recommendations were made on settings changes. In addition to lower level of water and gas control it was proposed to apply an additional upper level control of wellhead pressure, which allows operation of well, even when settings are taken not from work area. As a result, it was shown how developed control model allows continuous operation of entire RPM system with a desired injection level.