Rethinking Gas Lift Intervention
Donald Mitchell, Engineering Director at Wireline Engineering
Gas lift is an artificial lift technique used either in wells in which natural reservoir pressure is insufficient to deliver fluids to the surface at the initial production stage, or has depleted to the point where it is no longer capable of bringing fluids to the surface.
Gas is delivered from surface-based compressors by way of the annulus between the casing and production tubing to a series of gas lift mandrels (conduits), which are positioned at strategic points within the production tubing string. When a predetermined gas pressure is reached, valves that are set within the mandrels open, causing gas to be ‘injected’ into the tubing, reducing the produced fluid density and enabling flow back to surface.
Various types of valves are used in gas life mandrels, depending on the need of the well. These valves are typically preinstalled and deployed with the production tubing string during well completion and may need replacement later in the life of the well. This will require an intervention.
The industry remains cautious when designing gas lift completions, tending to place gas lift mandrels in areas of the well that are considered accessible when using standard slickline techniques. Most operators, if possible, place mandrels at no more than a 60° deviation within the completion string. However, this approach can lead to a suboptimal gas lift completion, with the benefit of optimising production rates by placing mandrels at greater true vertical depth (TVD) traded for ease of intervention access.
Donald Mitchell, Engineering Director at Wireline Engineering, discusses this issue, and Wireline Engineering’s dedication to developing and improving the efficiency of gas lift intervention, in the Journal of Petroleum Technology.
Read the full article here. http://www.spe.org/jpt/article/8351-technology-update-2-12/