Abstract

Gas lift is an artificial lift technique used to increase oil wells flow rate. In this method, high pressure gas is injected into the well oil column to reduce its average density and make it flow to the surface. The main objective in gas lift system design is to obtain the optimum gas injection rate. Obtaining the optimum gas injection rate is important because excessive gas injection will reduce production rate and also increase the operation cost. Some other parameters are also important in a successful gas lift operation that if not chosen properly, make the operation impossible or at least uneconomical; namely gas injection pressure, well head pressure, depth of operating and unloading valves, valves spacing, etc.

Field A, located in south-western Iran, has been producing oil for more than 60 years. Through that period, the early average oil production rate of 20 MSTB/D for each well has dropped severely by a factor of 8. At present, the field produces 185 MSTB/D through 73 active oil wells. However, the high reservoir pressure drop and continuous increase of water cut and gas oil ratio through the years, have influenced some of the wells to a greater extent such that the oil does not flow or flows at a lower rate than that of scheduled.

In this paper, nodal analysis is used to compare and analyze the effects of different parameters on a sample well production.Firstly, a model is constructed and matched with the real data and thereby the best fluid and well production correlations are selected. Secondly, Sensitivity analysis tests are performed and the results are compared. Finally, the optimum parameters are chosen considering economical aspects. By applying the stated optimizations of this paper, the flow rate can be increased by 80%.

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