Slip Loss Research Articles

Effect of the Inclination Angle on Slippage Loss in Gas-Liquid Two-Phase Flow

The lifting efficiency and stability of gas lift well are affected by the socalled slippage-loss effect in gas-liquid two-phase flow. The existing studies on this subject have generally been based on vertical and horizontal wells. Only a few of them have considered inclined pipes. In the present work a new focused study is presented along these lines. More specifically, we use the non-slip pressure drop model with Flanigan’s fluctuation correction coefficient formula (together with the parameters of slippage density, slippage pressure drop and slippage ratio) to analyze the influence of the inclination angle on slippage loss for different conditions (different gas-liquid superficial velocity and pipe diameters). Moreover, the “standard regression coefficient method” is used for multi-factor sensitivity analysis. The experimental results indicate that slippage loss is affected by multiple factors, and the influence of the inclination angle on slippage loss is less significant than other factors. The change of the slippage pressure drop with the superficial velocity of gas-liquid is similar to that of the total pressure drop. The inclination angles of 45° and 60° have the greatest influence on slippage loss. The correlation between slippage density and slippage ratio is not obvious. Using the so-called slippage ratio seems to be a more accurate option to evaluate the degree of slippage loss.

A One-Dimensional Flow Analysis for the Prediction of Centrifugal Pump Performance Characteristics

A one-dimensional flow procedure for analytical study of centrifugal pump performance is done applying the principle theories of turbomachines. Euler equation and energy equation are manipulated to find pump performance parameters at different discharge coefficients. Fluid slippage loss at impeller exit and volute loss are estimated. The fluid slippage is modeled by the slip factor approach using Wiesner empirical expression. The volute loss model counts friction loss associated with the volute throw flow velocity, diffusion friction loss due to circulation associated with volute flow, loss due to vanishing of radial flow at volute outlet, and loss inside pump volute throat. Models for impeller hydraulic friction power loss, disk friction power loss, internal flow leakage power loss, and inlet shock circulation power loss are considered by suitable models. Pump internal volumetric flow leakage and volumetric efficiency are related to pump geometry and flow properties. The procedure adopted in this paper is capable of obtaining performance characteristic curves of centrifugal pump in a dimensionless form. Pump head coefficient, manometric efficiency, power coefficient, and required NPSH are characterized. The predicted coefficients and obtained performance curves are consistent with experimental characteristics of centrifugal pump.

Simulation and Optimization of Continuous Pig Lift Systems

Abstract In a typical gas lift system, slippage between gaseous and liquid phases results in increased water cut and decreased reservoir pressure which reduces lifting efficiency and causes low oil recovery. Pig lift is a novel artificial lift technique proposed in recent years for effectively reducing liquid accumulation and increasing two-phase flow stability in certain special cases, such as high gas-liquid ratio, low reservoir pressure, horizontal and/or rather deep wells, highly viscous or waxy oil, sand production, etc. In this paper, a theoretical study is conducted to simulate the dynamic gas-liquid flow behaviour and optimize the operating parameters of a continuous pig lift system. First, two new flow theories, i.e., non-instantaneous separation and three segment flow, are proposed to simulate the transient two-phase upward flow process during which the pig is launched periodically into the injecting gas. Then, a two-phase flow model, which comprises a set of one-dimensional mass, momentum, energy balance equations, and the equation of state for real gas, is developed to accurately predict gas-liquid flow behaviour in the wellbore. An algorithm to solve this transient flow problem by coupling the gas-liquid flow model and the flow model with the pig is developed and implemented. Finally, a method for the design and optimization of continuous pig lift wells is presented by using nodal system analysis. The detailed simulation results show that, compared with conventional gas lift, pig lift decreases the pressure drop in the wellbore and reduces the slippage loss significantly. The pig launching frequency is the most important parameter in the pig lift system. Increasing the pig launching frequency decreases slippage loss; when the pig launching frequency reaches a certain value, which is the so-called optimal pig launching frequency in this paper, the pressure drop tends towards a non-slippage pressure drop. At the given bottomhole pressure and production rate, the wellhead flow pressure increases with the increase of time, and finally, is close to non-slippage wellhead flow pressure under the optimal pig launching frequency. The gas lift performance curve can be used as an optimization tool to select the optimal operating parameters for the pig lift system. Introduction In a typical gas lift system, gas is continuously or discontinuously injected in the production well to modify the mixture density of producing fluids, decrease the pressure gradient in the liquid and then provide sufficient energy to produce fluid flows. However, during production, the slippage between gaseous and liquid phases results in increased water cut and decreased reservoir pressure, which causes liquid loading, reduces lifting efficiency and causes low oil recovery, especially for some special cases, such as high gas-liquid ratio, low reservoir pressure, horizontal and/or rather deep wells, highly viscous or waxy oil and sand production, etc. Pig lift is a novel gas lift technique proposed by Lima et al.(1) in recent years for effectively reducing liquid accumulation and increasing two-phase flow stability in those cases. They developed a model for the intermittent pig lift system operation and incorporated it into software.

Study of Pressure Gradients Occuring During Continuous Two Phase Flow

About this subject various studies haue been made by many investigators. The author tried to find the energy loss of vertical flow dividing it into two parts which are "Slippage loss" and "frction loss" Many equations were made by using field datas, and the solution is by caluculating simultaneous equations. Although this paper is not excellent enough comparing with the previous one, there calculated factors show a few interesting peculiarities.