Arthit gas and condensate field is located 230km offshore of Thailand’s Songkhla province in the Gulf of Thailand. It covers an area of 4,185km² across five concession blocks – B14A, B15A, B16A, G8/50 and G9/48. The field lies at a water depth of 262ft (80m).

First production from the field was achieved in March 2008. The field was developed with an investment of $1.4bn.

PTT Exploration and Production (PTTEP), the operator of the field, holds 80% interest.

Partners include Chevron Thailand (16%) and Mitsui Oil Exploration Company (MOECO) Thailand (4%).

Average production from the field in the second quarter of 2011 ranged from 280 to 330 million standard ft³/day (mmscfd) of natural gas and 13,000 to 14,000 barrels a day of condensate.

Discovery of the Taiwanese gas field

Arthit was discovered by PTTEP in 1999. PTTEP conducted a 3D seismic study of the concession area in 1998 and launched a drilling programme which confirmed the presence of hydrocarbons at the field.

Geology and reserves at the Arthit reservoir

The Arthit field reservoir is of the Late Eocene to Late Oligocene formation and consists of Miocene retrograde gas sands.

The field is estimated to contain proven gas reserves of 1.9 trillion cubic feet (tcf).

Exploration and drilling programmes

PTTEP commenced the first phase of exploration and appraisal drilling programme for the field in 1999. Seven wells were drilled during the first phase which lasted until 2000. The Trident XV jack-up rig was contracted for the drilling activities.

The second phase of the drilling programme was started in 2001. It involved drilling of 14 wells and was completed in February 2002.

The remaining 20 wells, except for one, in the drilling programme successfully proved gas and condensate reserves existed.

Field development at the gas and condensate field

Development drilling at the field commenced in 2004. The first well was spud in October 2005 by the Smedvig Rig T-3. Two Arthit Working Platforms (AWP) were installed between September and November 2005 to facilitate the development drilling.

The field development has been divided into several phases such as 1B, 1C, 1D, 1E and 2A. Production commenced from the initial phase of development. A total of 50 wellhead platforms are expected to be installed.

Phase 1B included the installation of four AWPs and four sealines, and drilling of 53 development wells. This phase was completed in 2009.

Phase 1C was completed in the fourth quarter of 2010. It included installation of four wellhead platforms and sealines and drilling of 45 development wells.

Phase 1D includes installation of four wellhead platforms and sealines, and drilling of 50 development wells. The wellhead platforms were installed by the second quarter of 2011. Development drilling is expected to commence in 2011.

Three appraisal wells were drilled as part of phase 1E in the fourth quarter of 2010. Work on phase 2A commenced in April 2011. It includes the installation of four wellhead platforms and sealines, and drilling of 70 development wells.

Arthit North development

PTTEP commenced development of the Arthit North prospect in 2006 to meet the high demand for gas.

Arthit North is located northwest of the Arthit field in concession block B14A. It contains estimated reserves of 200bcf.

Production commenced in May 2009 through three wellhead platforms tied back to the Lewek Arunothai FPSO.

The Arthit field is currently in production through more than 90 production wells tied back to six wellhead platforms. The produced gas and condensate are sent to the Arthit central processing platform for processing.

Arthit central processing platform

The Arthit Central Processing Platform is the biggest offshore platform in southeast Asia, weighing 17,000t. It was constructed in Batam Island, Indonesia, and features gas and condensate processing facilities.

Exporting gas produced from the Arthit field

The produced gas is exported to the Erawan Riser Platform through a 200km long, 42in diameter subsea pipeline. The condensate is exported to the Bongkot FSO2 through a 30km long subsea pipeline, 8in diameter.