The Wassana oil field is located in the Gulf of Thailand G10/48 licence, south of the Pattani Basin, at a water depth of approximately 60m. It is the first field to start production under KrisEnergy’s operatorship.
KrisEnergy (Gulf of Thailand) acquired a 25% non-operated working interest in G10/48 in November 2009 and became the sole operator of the block in May 2014 by acquiring Mubadala Petroleum’s 75% working interest, with an investment of approximately $102.5m. The company farmed out an effective 11% working interest to Palang Sophon in February 2015. The G10/48 covers an area of approximately 4,696km² and further accommodates the Niramai and Mayura discoveries.
The final investment decision (FID) for the project was made in June 2014 and production began on 14 August 2015. Peak oil production from the field is estimated to reach 10,000 barrels per day (bpd).
Discovery, reserves and geology
The initial Mayura discovery was made in 1994 followed by a second successful Mayura well in 2009. The Wassana and Niramai discoveries were made in 2009. A 3D seismic survey covering an area of 554km² was performed at G10/48 in 2010.
The Wassana field is estimated to hold recoverable reserves of approximately 13.6 million barrels of oil and is expected to deliver for seven years. Reserves within the G10/48 block are located within thin and stacked layers of fluvial sandstone reservoirs deposited approximately 20 million years ago.
Wassana oil field development details
The development of the offshore oilfield primarily involves the installation of a mobile offshore production unit (MOPU), floating storage and offloading vessel (FSO) and a catenary anchor leg mooring (CALM) buoy. A jack-up rig will drill up to 15 development wells, including 14 producer wells and one water disposal well. Half of the wells at the field are expected to bedrilled horizontally.
The processing facility for the project is MOPU Ingenium, which separates the oil, water and gas from the wells. The produced gas is reused as fuel for onboard generators, whereas the produced water is pumped back into the reservoir.
The MOPU is connected to the CALM buoy via a 2km-long subsea pipeline. The CALM buoy’s hull is moored to the seabed using six mooring lines guided through rotating chain stoppers, and connected to high-capacity power anchors.
A rotatable platform is located on top of the hull, which accommodates the FSO mooring hawsers and floating hoses. Fluids are transferred from the CALM buoy to the FSO using the floating hoses integrating a custom-made dual-path swivel unit, which enables the transfer of fluids even when the vessel rotates.
Prospects in the block, including the existing discoveries, are expected to increase the number of platforms at the block to four, and the gross reserves by an additional 40 million barrels of oil in the near future.
Contractors involved with the Wassana field development
KrisEnergy acquired the rights for chartering the Rubicon Vantage FSO vessel and the CALM buoy from their respective owners Rubicon Vantage International and Equatoriale Services in October 2014. The contract for the use of Shelf Drilling’s Key Gibraltar jack-up rig was earlier signed in June 2014.
The MOPU Ingenium and Rubicon Vantage FSO were refurbished and modernised at Batam, Indonesia, and at a drydock in Thailand respectively.
Details of MOPU Ingenium and Rubicon Vantage FSO
MOPU Ingenium has an oil processing capacity of up to 20,000bpd and a water injection capacity of 15,000bpd. It is a converted jack-up rig where the drilling equipment has been replaced with an oil and gas processing system. The MOPU provides accommodation facilities for 39 crew members.
The Rubicon Vantage FSO has an overall length of 228.6m, a total fluid storage capacity of 597,206 barrels, accommodation for up to 40 people and a helideck. It was earlier chartered by Salamander Energy at its Bualuang oil field in the Gulf of Thailand.