A Systematic Approach to Predicting Liquid Loading in Gas Wells

Abstract

A Systematic Approach to Predicting Liquid Loading in Gas Wells Boyun Guo; Boyun Guo U. of Louisiana at Lafayette Search for other works by this author on: This Site Google Scholar Ali Ghalambor; Ali Ghalambor University of Louisiana at Lafayette Search for other works by this author on: This Site Google Scholar Chengcai Xu Chengcai Xu Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Production Operations Symposium, Oklahoma City, Oklahoma, April 2005. Paper Number: SPE-94081-MS https://doi.org/10.2118/94081-MS Published: April 16 2005 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Guo, Boyun, Ghalambor, Ali, and Chengcai Xu. "A Systematic Approach to Predicting Liquid Loading in Gas Wells." Paper presented at the SPE Production Operations Symposium, Oklahoma City, Oklahoma, April 2005. doi: https://doi.org/10.2118/94081-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Oklahoma City Oil and Gas Symposium / Production and Operations Symposium Search Advanced Search AbstractLoading 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 due to the difficulties with prediction of bottom hole pressure in multiphase flow. An accurate and easy-to-use 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 4-phase (gas, oil, water, and solid particles) flow model was developed for mist flow. Applying the minimum kinetic energy criterion to the 4-phase flow model resulted in a closed form analytical equation for predicting the minimum gas flow rate.The kinetic energy theory indicates that the controlling conditions for liquid drop removal in gas wells are bottom hole conditions rather than top-hole conditions. Our case studies show that Turner's method with 20%-adjustment still under-estimates 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.IntroductionGas wells usually produce natural gas carrying liquid water and/or condensate in the form of mist. As the gas flow velocity in the well drops owing to the reservoir pressure depletion, the carrying capacity of the gas decreases. When the gas velocity drops to a critical level, liquids begin to accumulate in the well and the well flow can undergo annular flow regime followed by a slug flow regime. The accumulation of liquids (liquid loading) increases bottom hole pressure that reduces gas production rate. Low gas production rate will cause gas velocity to drop further. Eventually the well will undergo bubbly flow regime and cease producing.Several measures can be taken to solve the liquid loading problem. Foaming the liquid water can enable the gas to lift water from the well. Using smaller tubing or creating a lower wellhead pressure sometimes can keep mist flow. The well can be unloaded by gas-lifting or pumping the liquids out of the well. Heating the wellbore can prevent liquid condensation. Down-hole injection of water into an underlying disposal zone is another option. However, liquid loading is not always obvious and recognizing the liquid loading problem is not an easy task. A thorough diagnostic analysis of well data needs to be performed. The symptoms to look for include onset of liquid slugs at the surface of well, increasing difference between the tubing and casing pressures with time, sharp changes in gradient on a flowing pressure survey, and sharp drops in a production decline curve. Keywords: reservoir surveillance, minimum gas flow rate, volumetric flow rate, production rate, systematic approach, gas well deliquification, gas flow rate, specific gravity, production monitoring, minimum gas velocity Subjects: Artificial Lift Systems, Well & Reservoir Surveillance and Monitoring, Gas well deliquification, Production logging This content is only available via PDF. 2005. Society of Petroleum Engineers You can access this article if you purchase or spend a download.