A Systematic Approach to Predicting Liquid Loading in Gas Wells

Abstract

Loading up of liquids in wellbore has been recognized as one of the severe problems in gas production for many years. Accurate prediction of the problem is vitally important for taking timely measures to solve the problem. Although previous investigators have suggested several methods to predict the problem, results from these methods often show discrepancies. Also, these methods are not easy to use because of the difficulties with prediction of bottomhole pressure in multiphase flow. An accurate and easy-touse method is highly desirable. This paper fills the gap.Starting from Turner's analysis for prediction of the minimum gas velocity for liquid removal, the minimum kinetic energy of gas that is required to lift liquid droplets was determined in this study. In order to compare gas kinetic energy with the minimum required kinetic energy, a four-phase (gas, oil, water, and solid particles) flow model was developed for mist flow. Applying the minimum kinetic energy criterion to the four-phase flow model resulted in a closed-form analytical equation for predicting the minimum gasflow rate.The kinetic energy theory indicates that the controlling conditions for liquid drop removal in gas wells are bottomhole conditions rather than tophole conditions. Our case studies show that Turner's method with 20% adjustment still underestimates the minimum gas velocity for liquid removal, and the newly developed equation is more accurate than Turner's method. The new method is easier to use than other existing methods. This paper provides production engineers with a systematic approach to predicting the minimum gas-production rate for the continuous removal of water and oil from gas wells. Engineering charts are provided for two typical tubing sizes and wellhead pressures.

Inflow Profiles Obtained With Pulsed Neutron Logs in Subcritical-Velocity Wells

“…It has been observed by Turner et al 3 11 that the flow stream velocity required to continuously move the liquid film along the conduit wall is consistently greater than that required to suspend and lift the entrained liquid droplets upward in the flow stream. As noted by Turner et al 3 , as well as from field observations of wellbore liquid unloading conditions [4][5][6][7][8][9][10][11] , that the criteria for the translation of entrained liquid droplets in the flow stream generally provides a better indication of the ability of a well to continuously transport wellbore liquids to the surface.…”

Liquid loading in gas wells: From core-scale transient measurements to coupled field-scale simulations

“…As presented in Table 1, several investigators have suggested different modified expressions derived from Turner model. Turner et al, 1969 Created the widely accepted Turner equation Coleman et al, 1991 Suggested not to use the 20% correction factor for low pressure gas wells Nosseir et al, 2000 Considered influences from different flow regimes Li et al, 2002 Involved the droplets' shape Veeken et al, 2003 Defined the concept of Turner ratio Guo et al, 2006 Took the minimum required kinetic energy of gas flow into account Belfroid et al, 2008 Concerned with the effects due to wellbore inclination Sutton et al, 2010 Used more realistic PVT properties Zhou and Yuan, 2010 Included the liquid droplet concentration in gas wells Veeken et al, 2010 Designed a specific expression for offshore gas wells Luan and He, 2012 Comprised droplets rollover in the gas rising process…”

A New Comprehensive Model for Predicting Liquid Loading in Gas Wells

“…It is possible that interfacial shear stress calculated with the Wallis (1969) correlation is too small at the transition from annular to intermittent flow. Many other interfacial-friction-factor correlations have been developed to match the experimental data, such as Fore et al (2000), Andritsos and Hanratty (1987), Whalley and Hewitt (1978), and Henstock and Hanratty (1976). Among these correlations, the correlation of Fore et al (2000) exhibited the best match with field data.…”