The interpretation of DST data for Donghae-1 gas field, block VI-1, Korea

Donghae-1 gas field is located in Ulleung basin at offshore Ulsan, Korea, a nd its recoverable reserve is expected to be 170 to 200 BCF (Billion cubic feet). The field was confirmed to have potential gas and condensate reserve s from an exploration well in 1998 and two appraisal wells in 1999. This fi eld consists of five zones. with an average reservoir depth of about 7,000 to 8,000 ft. In this study, we have performed an analysis of Gorae V DST (D rillstem test) #2 for testing B4 zone which has the biggest reserves and Go rae V-l DST #2 for testing B3 and B4 zones simultaneously among DST data ac hieved in a total of 11 zones at three wells. The pressure and flow rate re corded from two tested zones were used to obtain the reservoir characterist ics and the well productivity. For pressure transient test data, we carried out the analysis of reservoir permeability, skin factor, wellbore storage effect and barrier effect by using the Horner plot and type curve matching methods. Also, with the deliverability test data, we estimated the absolute open flow which is the maximum flow rate of the gas well, and extracted th e correlations representing production rate with reservoir pressure. Accord ing to the analysis, Gorae V DST #2 of B4 zone has a permeability and skin factor of 37 md (Millidarcy), 4.54, and Gorae V-l DST #2 of B3 and B4 zones has 23 md and 21.0, respectively. It was also found that the wellbore stor age effect was not significant for the two wells tested. From the deliverab ility test analysis, the AOF (Absolute open flow) of the Gorae V DST #2 is 152.8 MMSCFD (Million standard cubic feet per day), and that of the Gorae V -l DST #2 is calculated to be 68.2 MMSCFD.