Abstract
Traditional gas-lift technology blossomed between 1929 and 1945, with about 25000 patents being issued during this time (Wikipedia 2017). Minimal innovation other than improved materials has been realized since then, with gas-lift in the 1000 psig injection pressure range being the norm onshore. The case for high pressure gas-lift to eliminate the need for problematic gas-lift valves is made, as technology and conditions exist to implement it now, as has been done offshore.
The concept of High Pressure Gas-lift (herein after referred to as HPGL), as discussed in SPE 14347 (Dickens 1988), has two potential onshore applications. First, total elimination of gas-lift valves in horizontal wells with sub-7000 psi BHP's. This is feasible due to improvements in compressor technology created to support CNG fuel, and elevated casing pressure ratings necessitated by hydraulic fracturing requirements. A second application is replacing failure-prone submersible lift as the initial form of artificial lift in horizontal oil wells by reversing flow with high rate, high pressure gas-lift.
The case for eliminating failure-prone gas-lift valves is self-evident. However, the case for the second application will be proffered. Conventional gas-lift, while recognized as excellent for producing high volumes of solids- laden fluid from deviated wells, underperforms ESP's in new horizontal oil wells due to frictional losses associated with high tubing flowrates. The case will be made that SPGL combined with reverse flow mitigates the frictional losses associated with high flowrates. Similar to a coil tubing cleanout using high pressure nitrogen, high pressure natural gas can lift large volumes of fluid without the need for gas-lift valves.
Technology and products for HPGL currently exist. Multiple compressor designs will be summarized to show that only one additional stage of compression is needed to support HPGL, with three and four stage designs being capable of performing the task. The recommendation will be made that HPGL compressors be assembled from readily available components, and that multiple pilot tests be made by industry. The importance of maintaining temperatures through the compression process high enough to prevent hydrocarbon condensation will also be explained.
