Compression Technology Selection for Downhole Application in Gas Wells

Abstract

Downhole gas compression technology is an artificial lift method that aims to boost production, maximize recovery and delay onset of liquid loading in gas wells. There are different available compression technologies that can be considered for downhole applications, such as screw, scroll, centrifugal and axial compressors. Selection of the appropriate type mainly depends on expected well performance, ambient conditions, compressor operating envelope, technology characteristics, limitations and size constraints. The objective of this study is to perform a feasibility evaluation of compression solutions applicable for a given set of candidate gas wells. Aerodynamic and hydraulic models are used to determine operating conditions, compressor performance, and to select equipment specifications such as impeller diameter, compressor envelope, shaft HP requirement and number of stages among other parameters. A Pugh analysis is performed for all compression technologies and their characteristics to down-select the most suitable solutions for the given set of wells. The results of the analysis indicated an optimal downhole compression technology that covers most of the gas flow rate requirements and meet the performance expectations. The study also provided critical specifications for the compressor, including high-speed operation needed to provide the required flow rates and compression ratio for a relatively small housing diameter. The study also finds that other technologies may be applicable but only to certain population of wells, as the flow rate spectrum is narrower than the optimal solution at the studied conditions. The analysis for the discarded compression technologies in this study showed relatively significant disadvantages for downhole application when compared to the selected compressor. This study presents a holistic analysis for compression technology selection for gas wells that, as per to the understanding of the authors, is unique in the existing literature of gas well applications.