ABSTRACT: Hydrocarbon exploration in the Ulleung (Tsushima) Basin, Offshore Korea and the recent gas discovery

Choi, Byeonggoo, and Heeran Jang , Korea National Oil Corporation (KNOC), Anyang, South Korea

The hydrocarbon exploration of the Ulleung Basin mainly covered by Block VI-1 was started with regional seismic data and one exploration well in 1970. It provided the first direct evidence of the thick clastic sediment of Tertiary age in the Basin. After establishment of KNOC in 1979, it took over the exploration of the Block. The first gas discovery of the Block was recorded in 1987 and the first commercial gas discovery from the "Gorae V" prospect according to the new play concept in 1998 is being developed for production in 2002.

The area of Block VI-1 is 12,918 sq.km and there are seven exploration wells and eight appraisal wells controlled by 12,868 L-km 2D seismic and 504 sq.km 3D seismic data. It is worth noting that to date at least one of every two wells in this area has discovered hydrocarbons. Various hydrocarbon plays have been recognized in the Block after the integrated interpretation of seismic and well data. "Gorae V" prospect is a structural nose trapped by an updip reservoir truncation and a shale-fill submarine canyon.

The result of exploration and three delineation drilling of "Gorae V" was successful with the flow rate of 75 - 100 MMscf/d containing about 99% hydrocarbon-rich gases and around 1560 bbl/d of condensate. There are some more prospects and leads around the gas discovery, and new 3D seismic data of 400 sq.km was acquired to evaluate them in 1999. It may provide a serial of gas field in Block VI-1 in the near future.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia