A Method For Transporting Wet Natural Gas Utilizing Hot Water Tracing

To transport wet natural gas through gathering or transmission systemsrequires either the removal of the free water phase, the use of hydrateinhibitors or alternatively the maintenance of the temperature throughout thesystem above the hydrate equilibrium temperature. This paper describes an unique method of preventing hydrate formation usinghot water tracing of buried gas pipelines. The decision to utilize such asystem was made in consideration of circumstances peculiar to a particular gastransmission problem. The gathering system was to be installed in which theultimate design capacity would be one hundred million cubic feet per day of wetsour gas and yet, in the first one to two years of operation, the throughputwould be at forty percent of capacity. The use of heat rather than dehydrationappeared to be an economical method of preventing hydrate blockage, however theuse of conventional line heaters posed certain problems in a non-unitizedfield. The principal problem was that there were to be four wells connected toa thirteen mile trunk line and the competitive operation of the wells would notpermit cascaded operation. Consequently a situation existed where heat transferareas would be large and that mass transfer rates would be low. Preliminarydesign calculations indicated that as many as twenty-five conventional lineheaters would be required in a thirteen mile system in order to offset thisproblem. A hot water tracing system was installed in the Wildcat Hills gas fieldduring the last three months of 1961. The system was placed into operation andat the time of preparation of this paper, it has been operated four months.While the initial performance of the system was exceedingly satisfactory, it isnot yet possible to compare design calculations with field observations for allranges of weather and soil moisture conditions. It is generally accepted thatany system using heat for hydrate prevention faces its crucial test during the Spring break-up period.