Perpustakaan Digital ITB

The importance of gas lift valve performance in the design of gas lift structure is signifcant,and cant be overemphasised. It involves determination of gas temperature in the tubing at the specific depth of a valve when the surface injection temperature is known.Production engineer must be able to determine the volume of gas that can be injected to the tubing through a specific valve in order to obtain the proper gas to liquid ratio needed to lift the fluids to the surface. The gas injection temperature is set at the surface. In addition, gas-lifte application in an oil well is capable of failure through gas lift valves which are considered as the heart of the gas lift system for controlling the amount of the gas inside the tubing string. The gas lift valves must be designed not only to allow gas passage through it and prevent oil passage, but also for gas injection into wells to be started and stopped when needed. The result of gas injection to oil production rates equations are solved numerically by shooting technique with 4th order Runge-Kutta method and is represented as the Gas Lift Per-formance Curve (GLPC). The gas injection pressure and the temperature changes along the tubing and casing. Matlab software is used to conduct numerical simulation. The temperature profile with respect to the depth is calculated using mixture temperature and Hasan-Kabir correlation, and the GLPCs are calculated for each possible position of opening valve. The position of the opening valve is then obtained by selecting the closest GLPC to the production data. Hagedorn-Brown method is applied in determination of valve efficiency and examine presence of leakage in the valve. The result shows good consistenc. There is gas leakage seen in well 1 and well 4. It is concluded that estimation of valve opening can be made by calculating the pressure changes for each open valve as well as by reading on the gas lifting performance curve (GLPC). The greater temperature change occurs at the point of the injection.