Low Temperature Dehydration of Natural Gas

Abstract

Abstract A process for low-temperature dehydration of natural gas utilizingJoule-Thomson effect in expansion through a throttling orifice has been testedin a full-scale field installation. The results of these tests are presented inthe form of performance curves from which the process may be easilyevaluated. The effect of separation temperature on condensate recovery from the processis also shown. Introduction The transportation of natural gas from producing well to the consumer hasalways encountered the problem of hydrate prevention. This problem has becomeincreasingly important in the past ten years due to the rapid increase inproduced gas volumes, production pressures, transportation pressures anddistance from producing wells to consumer. Natural gas, as normally produced from gas or gas-condensate wells, issaturated with water vapor at well-head conditions of temperature and pressure.The solution of the hydrate problem requires but one basic process -dehydration of the gas to a water content which will result in a waterdew-point below the minimum temperature to be encountered from the producingwell to the point of consumption. Much of the recent development of gas and gas-condensate reserves in theGulf Coast Area has been in locations which are accessible only by water. Highwell-head pressures, pipeline construction and maintenance costs and thedesirability of final central gas-condensate separation facilities havestimulated the development of dehydration equipment which can be installed ateach well and which will permit hydrate-free transportation of both gas andcondensate in the same line to central facilities. There are four types of natural gas dehydration processes now used:Adsorptive processes.Absorptive processes.Chemical reaction processes.Refrigeration processes. The first three of these processes are indirect in that they require use ofadsorbents, absorbents or reactive chemicals. These materials requireregeneration and part of the total gas stream is consumed in the regenerativeprocess. Indirect processes have a wide range of flexibility as defined byallowable operating pressure and temperature, but most are not easily adaptedto automatic operation. The refrigeration process described in this paper was designed forinstallation at the producing well-head. It requires no regenerative cycle andwith normal well-head temperatures no external source of heat. The flexibilityof this process is limited only by the pressure drop which may be allowedbetween well-head and transportation line. T.P. 3022