INCREASING THE GASLIFT EFFECTIVENESS BY ADJUSTING MULTIPHASE FLOW HYDRAULIC CHARACTERISTIC

Abstract

Real media that are encountered in hydrocarbon production industry are normally represented by systems, comprised of at least two phases, of which one is dispersed and distributed in another. As it is known, production, gathering, preparation and transport of oil and natural gas are based on multiphase technology, comprised of lifting the hydrocarbons from the formation to the surface, transport to the separation facilities, separation and intrafield transport of multiphase mixtures, consisting of oil, natural gas, formation water and mechanical particles. This article strives to determine the optimal work regimes of production of gaslift systems based on the relations between production rates and gas pressure in cylindrical flows. Knowing the parameters of the well borehole as well as the parameters of the produced fluid and gas injection rates it is possible to determine the optimal flow regime as a derivative of a function of pressure losses versus production rates (ΔP/Q). This function is called the flow hydraulic characteristic, and it is this function, by optimizing which an optimal flow regime of the gaslift operated well can be achieved. Estimation the hydraulic characteristic relies heavily on calculation of pressure losses of the gaslift producing well. These losses consist of two independent factors: gravitational and frictional. Frictional pressure losses have linear dependence versus the flow rate, while gravitational losses exhibit an inverse, hyperbolic, correlation to changes in flow rate. To get the full picture of the pressure loss both aspects must be accurately calculated from the given field data. In order to do so, it is important to estimate real gas content of the multiphase flow, which is a complex function of direction and velocity of the multiphase flow, gas and liquid flow rates, gas slippage, etc. Once the pressure losses have been calculated it is comparatively simple to optimise the gas flow rate to adjust the hydraulic characteristic, guiding the gaslift production process towards optimal production rates. Keywords: Gaslift, multiphase flow, pressure losses, joint transport, gas content.