ABSTRACT
Liquid buildup in gas wells causes an additional back-pressure that can reduce gas productivity and, in worse cases, stop production completely. Gas well deliquication is the subject of its own annual European conference, and the reader is encouraged to browse the lists of presentations for other information not provided here.1-3 Besides mechanical techniques, a well-known chemical method to remove the liquid (usually water) is to inject a foaming surfactant.4-8 The surfactant is injected at the bottom of the well, where it mixes with the liquid and gas, lowering the surface tension and forming a foam of lower density than the bulk liquid, which can then be produced from the well.9 The surfactant can be applied as a liquid concentrate, either continuously or batchwise, or it may be applied as “foam sticks.” The latter is more common for low-volume gas-producing wells: the surfactant is compounded within a wax “candle,” which is simply lowered down the well. The use of foaming surfactants to unload liquid in gas wells is very common. About 40% of gas wells worldwide suffer from liquid buildup and are therefore producing at below optimum rate. Most deliquiers are designed for use in gas and gas condensate wells. Few products are available for foaming crude oil. General test methods for foamers have been reported using model surfactants.7,10 This usually involves measuring the dynamic surface tension as well as foaming properties in customized rigs. Laboratory testing of a wide range of crude oils and water cuts have led to the development of a new foamer that has been eld-trialed successfully.11
