A Novel Foamer for Deliquification of Condensate-Loaded Wells

Abstract

Abstract Continuous increase in worldwide brown-field activity and overall depletion of current gas fields has renewed focus on maximizing gas production from existing wells. In most gas wells, water and/or condensate is produced along with gas. In mature gas wells, decreasing formation pressures and gas velocities gradually cause the wells to become "loaded" with liquids. A method commonly used to deliquify these wells is through the application of chemical "foamers". However, these traditional foamers tend to be ineffective as the condensate-to-water ratio increases. This paper describes the performance of a novel foamer specifically designed to unload condensate from wells. This foamer helped unload a gas well that produced condensate via intermittent production at 2:1 condensate-to-water ratio. Parameters for well selection are described, as well as operational processes to maximize continous production. As a result of this treatment, the daily average gas production rate increased significantly and shifted the daily on:off production cycle from 1:1 to 11:1. This minimized well down time and increased the overall daily production averages by 60 percent. Introduction Gas producers traditionally have observed that increasing amounts of liquid hydrocarbon (condensate) significantly affect the ability of conventional foamers to deliquify liquid loaded gas wells. This situation is prevalent in several wells in South Texas. This work describes the results from a trial using a foamer specifically designed for condensates. Because of the difficulties in treating liquid-loaded wells with higher condensate cuts, the operator at this location uses a variety of methods to prevent liquid loading in marginal gas wells. These methods include: the use of intermitters; velocity strings; adding additional compressor capacity; and applying chemical foamers. The newly-developed condensate foamer was designed to provide a more cost-effective way to unload condensate-loaded gas wells. Intermitters allow for periodic gas flow interruptions that enable the formation to temporarily increase down-hole gas pressure in the reservoir during the shut-in phase. This accumulated pressure provides sufficient gas velocity to unload liquids from the well when opened. This continues until the actual gas velocities decrease below the critical velocities where loading occurs. The disadvantage of this type of production method is the loss of gas (and condensate) production during the "off" periods. Velocity strings are inserted tubing strings that are narrower than the existing tubing (typically a wide capillary string) that enable the user to physically increase the linear velocity of the gas and, in turn, prevent liquid loading. The disadvantage of this type of production method is the possible loss of production, due to the restriction the string creates. Added compression capacity reduces the overall wellhead pressure and thus increases the differential pressure with the down-hole pressure. This removes gas back-pressure restrictions that are conducive to liquid loading. The disadvantage of this option is the large capital expenditure required to add compressors. For this trial, the condensate foamer was applied to a well where an intermitter was being used to prevent liquid loading. This paper discusses the well selection criteria used to identify candidate wells, in addition to presenting the performance results of the condensate foamer applied to this well.