Highly Reliable Subsurface Compressor System Enables Increased Natural Gas Production and Recoverability

Abstract The primary objective of this paper is to examine the performance of an electrically driven, high-speed downhole compressor system to increase the rate of natural gas production and extend the economic usefulness of natural gas wells relative to traditional surface wellhead compressors. By developing and integrating enabling technology building blocks to the compression system, effective drawdown near the perforations and increased delivery of reserves are feasible and demonstrated in several field trials. The Subsurface Compression System (SCS) for gas wells is comprised of a novel architecture developed for increasing gas production with superior downhole reliability to reduce the production downtime and workover costs commonly caused by failures of equipment. There are three core technology building blocks forming the novel architecture of the subsurface compressor. A hermetically sealed, high-speed permanent magnet motor block, which completely isolates all electrical components from gasses and liquids present in the external environment and can spin up to 50,000 Revolutions per Minute (RPM). A wide frequency Variable Speed Drive (VSD), located on the surface, drives the downhole motor with wide speed ranges to accommodate changing well conditions throughout the life of the subsurface compressor. A magnetic coupling block that maintains a hermetic seal of the motor while effectively transmitting torque from the motor to the compressor magnetically without rotary seals between the motor chamber and downhole environment. A multi-stage hybrid axial compressor capable of producing multiphase gas without sustaining performance inhibiting damage to the sleeve or blades of the compressor when operating with solids present due to the vertical flow path. The downhole assembly demonstrates highly efficient and reliable performance by increasing suction pressure close to the perforations without pipe friction loss and eliminating failure-prone components of conventional artificial lift technologies, such as rotating seals, lubricating oil and motor pressure compensating chambers from this architecture. In this architecture, the system has proven 200% increased natural gas production and 70% increased recoverable reserves. The enabling technologies demonstrated by the SCS are also available for use on the surface of gas wells through the Inline Compressor System (ICS). The ICS offers the significant advantages of producing gas and process liquid simultaneously from the wellhead through the compressor without the need for liquid separation. It also improves safety compared to traditional surface wellhead compressors by eliminating the need for dynamic seals, therefore lowering H2S exposure risk.