Patent ID: 8150637
Filing Date: 2012-04-03
Classification: E21B,G01F

Abstract:
1. A method for evaluating the performance of a gas lift well, the method comprising: injecting a tracer into an annulus formed between a well casing and a production tubing of the gas lift well, the annulus including a lift gas, the gas lift well including one or more points of communication between the annulus and the production tubing, wherein each of the one or more points of communication corresponds to a valve position; measuring, over a period of time, a concentration of the tracer present in a substance retrieved from the gas lift well; determining one or more actual travel times of the tracer based on a deviation of the concentration of the tracer measured over the period of time from a pattern present in a baseline tracer concentration, wherein each of the one or more actual travel times of the tracer corresponds to a point of entry of one or more points of entry of the lift gas into the production tubing; segmenting the gas lift well into a plurality of ranges of well depth; determining one or more lift gas loss parameters, each of the one or more lift gas parameters corresponding to a point of entry, each of the one or more lift gas loss parameters accounting for an effect of entry of a portion of the tracer into the production tubing at the corresponding point of entry on the actual travel time of the tracer that enters the production tubing at each point of entry located at a depth greater than the corresponding point of entry; calculating a velocity of the lift gas in the annulus and a velocity of the lift gas in the production tubing for each of the plurality of ranges of well depth based on the one or more lift gas loss parameters; and determining the one or more points of entry of the lift gas into the production tubing based on: wherein one or more of the steps of the method are controlled by at least one computer processor executing one or more computer program instructions stored on at least one memory device operatively coupled to the at least one processor.