CO2 Tracer for Gaslift Surveillance and Optimization

Abstract

Abstract Production Surveillance is a key activity carried out by oil and gas operators in the quest to maximize production. In Malaysia, specifically the East Malaysia Region, most of the wells in production are operated with the assistance of gaslift. Gaslift is an artificial lift method which involves injecting high pressure gas from the casing to enter the tubing via gaslift valves. Gaslift often hides inefficiencies, however by monitoring the operating conditions at the surface, an engineer will be able to obtain some clues on the performance of a gaslifted well. Before the introduction of CO2 tracer technology, the only method available to operators to determine if a gaslift valve is open or closed downhole is to run a Flowing Gradient Survey (FGS) in order to determine the pressures and temperatures of the fluids in the tubing. Using a FGS in a well involves certain risk as it requires well intervention by running electronic memory gauges either on wireline or slickline to acquire data from a flowing well. There are also times where a FGS survey is inconclusive if the well is surging and have large changes in the surface pressures. Since this is the fisrt such application in the field, two gaslift wells were surveyed for pilot application. The CO2 tracer technology is very effective for quick and reliable determination of lift gas entry points in the well. The technology allows the operator to detect the operating lift depth, detect multiple points of injection and even detect tubing leaks. This technology can be used as an alternate to FGS for the following advantages: Minimum equipment hook-up and no need to shut-in or choke the well, thus minimize production deferment.No wireline tools introduced into the wellbore, thus eliminate well intervention risk.Suitable for wells where a FGS is not possible due to well slugging, significantly deviated or with downhole obstruction.Possible to run survey on dual string wells to determine the gaslift split factor of a dual completionPossible to determine exactly how much gas is injected through each injection point of a well This paper will describe the project objectives, the well candidate selection criteria, explain the execution of the survey and interpretation of the results and the value gain from implementing the recommendations from the survey results.