Rig less In-Tubing Gas Lift System with Dual-Flow Safety Barrier for Oil Wells Experiencing High Water-Cut
Authors: Varghese V. , Negi R. S. , Russell N. D. , Oliphant M. , Brehme M. , Menon A. 
Published: November 2024

An onshore oil well in Asia with depleting reservoir pressure and severe liquid loading was identified to be energized for continued production. The solution was needed to furnish the dual purpose of providing gas injection for liquid unloading with the additional feature of a surface controlled dual flow safety valve to isolate both the injection and production conduits.

The well was completed with 4-1/2 × 3-1/2 × 2-3/8 in. tubing design producing from 2 reservoir layers and, anticipated an early water cut. The conventional solution is to re-complete the well with GLV. Weatherford proposed a retrofit in-tubing gas lift system with minimal surface modifications and no workover. With the In-tubing gas lift system, the installation could be performed on a Coiled Tubing unit comprising of a smaller crew and reduced Carbon emission compared to a Workover rig. Furthermore, the system does not rely on annular integrity and enables gas injection below the production packer depth. Both injection and production are performed within the tubing bore itself.

A comprehensive study of Nodal analysis using simulation software was performed to assess system performance, identify coiled tubing size, and gas injection depth. It was inferred that a gas injection depth of 2800 m would change well deliverability performance and increase oil production. Sensitivity studies on water cut were performed for 10%, 15%, 20%, and 95%, and a gas injection rate of 500 to 2000 MMSCFPD. Optimum gas injection rates were found to be 500 to 1000 MMSCFPD, with 1.25 inch OD coiled tubing exhibiting maximum flow area and minimal pressure drop due to frictional losses. For a high water cut scenario of 95%, a high gas injection rate of 2000 MMSCFPD was anticipated from the simulation.

Bottom injection string was run and installed using Hanger and Dual Flow Safety Valve. This safety valve landed across the locked open and communicated existing subsurface safety valve. The top section was run and latched into the polished bore, while also landing the top hanger into a modified spool adaptor on the surface. With this system in the well, coiled tubing acted as the gas injection path and the coiled tubing/tubing annulus provided the production path. Control line pressure release closed the flapper in the dual flow safety valve, stopping fluid movement in both the injection and production flow areas.

The simulations and sensitivities performed utilizing the actual well test data enabled the operator to choose the optimum operating parameters and coiled tubing string size to be utilized in the system, and provided the option of deepening the gas injection point to a depth even below the pre-existing side pocket mandrels. The remedial completion system saved the operator from workover costs through a rigless operation with minimal personnel and a reduced carbon footprint.

This paper details the implementation of an in-tubing gas lift system in the well facing liquid loading challenges covering the various stages of the project from simulation and analysis of the candidate well to the implementation of the system and the post-installation production outcome.

The following aspects of the Inverse Gas Lift system installation will be discussed in this paper: Well Background and Data CollectionSimulation and AnalysisSystem OverviewOperations & System InstallationResults and Conclusion