Downhole gas compression (DHGC) in gas wells is a relatively new concept in production engineering, but it represents one of the most promising technologies to revive dead wells, to boost gas production and to maximize total gas production recovery. This technology could be analogous to electrical submersible pumps (ESPs) for oil wells, as it increases well production by reducing the back pressure at the wellbore sand face; this is achieved by providing boosting pressure to cover for outflow pressure requirements (i.e. tubing losses and well head backpressure). However, downhole wet gas compression applications are considerably more challenging than those for ESPs. The purpose of this paper is to describe step by step the procedures and workflows to evaluate downhole gas compression applications, from information preparation, to multiphase flow calculations and sensitivity analyses.
The applications of this technology are more complex than conventional pumping methods for oil wells. Calculations are more involved with considerations for gas compressibility, multiple flow regimes, liquid volume fraction at compressor intake, compressor pressure ratio requirements, liquid loading conditions, discharge pressure and discharge temperature, among other effects, which are some of the main factors to be measured for this type of application.
There is no standard methodology in the oil industry for gas well modeling and sensitivity analysis for DHGC applications. Just few publications can be found in the literature with some description of the evaluation process but missing some other relevant aspects of the application. This paper presents a systematic process to evaluate applications of DHGC including well performance modeling and compressor simulations.
A new comprehensive methodology has been used for downhole compression application in this study, using nodal analysis software for well performance modeling in combination with a process system simulator to model compressor performance.