Optimizing Gas Lift Design: Unveiling Ideal Wellhead Temperature Across Diverse Reservoirs at Mehsana Oil Fields

Abstract

Abstract The operation of gas lift valves of the gas lift systems at field scale is controlled by the nitrogen pressure charged in the dome. Nitrogen pressure in gas lift systems is influenced by the gas injection temperature and production fluid temperature. In gas lift wells completed in water drive reservoirs, emulsion flowing with high water cut causes an increase in opening pressure of the topmost gas lift valves (GLV). When these wells are shut or provided with low gas injection supply pressure, these wells get loaded with minimal gas injection taking place. In depletion drive reservoirs, lower reservoir temperature causes a decrease in the opening pressure of the bottom-most gas lift valve, causing higher gas injection and lowers the grid pressure. In mixed drive reservoirs, any abrupt wellhead and reservoir temperature gradient will cause an ineffective gas lift operation. Flowing bottom-hole surveys with convection and conduction thermal methods are the prerequisites for the compact thermal model. Through the analysis, it was established that the nitrogen gas temperature in the dome is much more influenced by radial heat transfer along the mandrel-GLV interface than the axial heat transfer along the GLV body. The mathematical correlation for the ideal wellhead temperature was established based on heat transfer coefficients of production fluid and injection gas, and it can be expressed in terms of production fluid and injection gas temperatures. Conventional Gas Lift (CGL) wells experience the phenomenon of loading due to higher temperatures brought by bottom water to the surface and Intermittent Gas Lift (IGL) wells experience the problem of grid pressure drop. Both problems can be tackled by the unveiling of the wellhead temperature during design and can improve the efficiency by reducing downtime. The paper will focus on gas lift valves operating on diverse reservoir drive mechanisms and the calculation of their wellhead temperature using a unique thermal model for conventional gas lift mandrels.