Abstract: The last station (Lunnan station) of west to east gas transportation in Tarim Oilfield is a commercial trade station which transmits all gas from every oilgas operational facility to west to east transporation pipeline.Quality of the gas from here will exert an important influence on down stream gauge and aplication.According to the drained waste liquid frequency statistics at the last station,however,it is found out that as tempreature lowers down in winter,the amount of condensated liquid becomes more dramastically,the peorid of draining liquid gets shorter and the frequency higher.By means of the physical property data of drained liquid and the component analysis of condensated liquid from main gas source Kela 2 and the last station,as well as the gydrocarbon dew point analysis along gas supplying spots,it is recognized the reason that the amount of drained waste liquid at the last station increases is mainly the heavy hydrocarbon in the gas supplied by Kela 2 factory being not eliminated in the process of treatment,in the winter time,because of decrease of the temperature in pipeline,the amount of condensated liquid gets more.The dew point of hydrocarbon is higher than that of water,so the condensated liquid is mainly condesated oil in pipeline or facilities,containig a little glycol and glycerol.The water dew point of the gas at the last station in oil field can meet the nees.It is suggested to recover the waste liquid.

Key words: west to east gas transportation, natural gas, waste liquid, analysis