Surface Controlled In Situ Gas Lift for Appraisal of Oil Reservoir in a Gas Well

Abstract

Abstract Gas lift is an artificial lift technique, using injected gas from the tubing-casing annulus to aerate the fluid column to reduce its density. The formation pressure is then able to life the fluid column and forces the fluid out of the wellbore. The same application can be provided through many different deployment strategies. The most common deployment would be through a downhole gas lift mandrel and valve, with gas supplied by a surface gas compressor. The gas lift rate is mainly controlled by the compressor discharge pressure, well pressure as well as the orifice size of the operating gas lift valve. An alternative deployment available is called Auto Gas lift (AGL). The main difference is on the gas lift source, where AGL taps into an existing gas reservoir. The gas lift rate is controlled by an Inflow Control Valve (ICV) which operated through a hydraulic line. In an existing well, AGL may still be pursued even though there is no possibility of deploying an ICV. Instead, once perforation to the gas reservoir is made, a tubing patch with a preinstalled gas lift valve can be installed. The main limitation for this application would be on the tubing patch installation, the resulting ID restriction as well as the operation required to change the injection rate or to close in the gas interval. This paper will discuss the first application of AGL with surface control to appraise an oil reservoir in an existing gas well. The application eliminated requirement of coil tubing deployed 13Cr tubing patch and gas lift valve installation. The methodology used to evaluate the application is described and its results discussed and compared to the actual well result.