The Wassana oil field is situated in the Gulf of Thailand’s G10/48 licence area, south of the Pattani Basin at a water depth of around 60m.
KrisEnergy, an oil and gas company based in Singapore, initially operated the field.
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The final investment decision for the Wassana project was reached in June 2014, with production commencing in August 2015.
In June 2020, KrisEnergy temporarily halted production at the Wassana field due to the economic impact of Covid-19 and resultant low oil prices. Subsequently, the leased floating storage and offloading (FSO) vessel was released from its contract and left the field. Despite this, the wells and the mobile offshore production unit (MOPU) were preserved in a state of readiness and were well-maintained.
Valeura Energy, an oil and gas company based in Canada, acquired KrisEnergy’s 89% interest in the G10/48 licence in June 2022 and the remaining 11% from Palang Sophon in April 2023.
Valeura’s special purpose vehicle subsidiary company Valeura Energy Asia holds all the assets of the company in Thailand, including the Wassana oil field. Valeura resumed production at the field in April 2023, following the acquisition.
In July 2023, the project faced another interruption when the FSO vessel unexpectedly moved from its mooring, colliding with the field’s catenary anchor leg mooring (CALM) buoy leading to a precautionary suspension of operations.
Valeura successfully reinstated production at the Wassana oil field by December 2023.
Discovery 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 also made in 2009. A 3D seismic survey covering an area of 554km was performed at G10/48 in 2010.
Reserves within the G10/48 block are located within thin and stacked layers of fluvial sandstone reservoirs deposited 20 million years ago. The field produces medium-weight crude oil.
Field appraisal
Valuera successfully drilled two appraisal wells on the flanks of the Wassana oil field, targeting deeper portions of the reservoir in September 2023. Wells A28 and A28-ST1 confirmed net oil pay of 72ft and 75ft respectively, proving the presence of oil deeper than previously known.
The company began working on development options to expand production infrastructure, which could increase production and extend the field’s operational life beyond 2030.
The Wassana field development drilling programme was expanded to include five horizontal wells, with the first two boosting field output to more than 4,000 barrels per day (bpd) in February 2024. The company intends to continue drilling, aiming for a total of five wells.
Reserves
The Wassana field 2P reserves have increased from 6.1 million barrels (mbbls) to 12.9mbbls, as of December 2023.
Wassana oil field development details
The Wassana oil field includes a MOPU, FSO and a CALM buoy. Up to 15 development wells were drilled from the MOPU, including 14 producer wells and one water disposal well.
The processing facility MOPU Ingenium separates the oil, water and gas from the wells. The produced gas is reused as fuel for onboard generators and the water produced is pumped back into the reservoir.
The MOPU is connected to the CALM buoy via a 2 km-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.
MOPU Ingenium and Rubicon Vantage FSO details
MOPU Ingenium has an oil processing capacity of up to 20,000bpd [barrels per day] and a water injection capacity of 15,000bpd. It is a converted jack-up rig in which 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.
Wassana crude oil storage vessel details
A crude oil tanker, renamed MT Jaka Tarub, arrived at the Wassana oil field in 2023 to store oil produced from the field.
The MT Jaka Tarub is a Panamax-sized oil tanker, with a storage capacity of 460,000 barrels. It was modified to be compatible with the Wassana field’s infrastructure and is capable of tandem crude oil loading and offloading.
Contractors involved
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 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.
Valuera signed a charter agreement with PT Samudra Alam Transport, a subsidiary of PT Buana Lintas Lautan, for a crude oil tanker in November 2022.
