As drilling adds more hydrocarbons to the table, production restart at Thai oil field comes into view

Canada-based oil and gas company Valeura Energy has carried out the drilling of two appraisal wells at an oil field in the Gulf of Thailand, which is currently offline. The production restart is expected in the fourth quarter of 2023.

According to Valeura, two appraisal wells have been drilled on the flanks of the Wassana oil field to test for suspected additional oil accumulations in the field’s Tertiary clastic section, targeting the deeper portions of the reservoir section, which holds most of the remaining underdeveloped oil reservoirs in the field. After a recently reprocessed 3D seismic data suggested upside in a thickening of the reservoir section in the targeted locations, both wells fulfilled these objectives. The company believes these results indicate the potential for substantial further development of the field, which could yield an increase in production and a significant extension of the field’s economic life.

Furthermore, the first well, A28, was drilled in the main producing fault block of the field, downdip of existing production wells, and encountered 72 ft of net oil pay. While previous reserves estimates were based on a demonstrated oil-down-to depth of 5,517 ft true vertical depth sub-sea (TVDSS), Valeura explains that the new well confirmed the presence of oil down to at least 5,594 ft TVDSS, exceeding its expectations for the vertical extent of the oil column. In addition, the well encountered a thicker package of reservoir sands and new oil-filled sands that had not been previously developed.

On the other hand, the second well, A28-ST1, was drilled to confirm the presence of oil in an untested area south of the main producing part of the field. It encountered 75 ft of net oil pay proving the presence of oil in this undeveloped area. As a result, Valeura is currently re-mapping the field to integrate the new data and anticipates that the results will yield an increase in its volumetric estimates. These additional volumes will be assessed as part of the firm’s next external third-party reserves and resources evaluation.  

Moreover, the preliminary analysis indicates that an additional 20 production well targets are now potentially viable within the reservoir section appraised by these two wells. In light of this upside potential, the Canadian player has begun the concept selection phase of a project to expand the development of the Wassana field. This is envisaged to involve deploying additional wellhead and oil processing structures to be used as a higher-capacity production hub than is currently available through the existing mobile production facility.

Valeura is targeting an increase in rates to 4,500 bbls/d as a result of a five-well infill drilling programme, which was slated to start in the second quarter of 2023. To this end, the company chartered the PV Drilling 1 jack-up drilling rig. A few months ago, the firm disclosed that Borr Drilling’s Mist rig was on location at the Manora oil field, where it was planning to drill three wells aimed at increasing production from the field and by extension, adding to the economic life of the asset. Upon completion of operations at Manora – anticipated in early August 2023 – the rig was set to move to the Wassana field for the firm’s five-well infill drilling programme.

The Canadian player highlights that the rig has mobilised to the Jasmine oil field where it is kicking off a four-well drilling programme, comprising two production wells and two appraisal wells, to support additional production well drilling in 2024. After the work at Jasmine is done, the rig is scheduled to return to the Nong Yao oil field for a five-well infill drilling campaign.

Back in July 2023, Valeura suspended production operations at the Wassana field in order to undertake a review of the safety and operating practices of the field’s third-party-owned and operated FSO vessel. Following the review, the firm and the FSO’s third-party owner have opted to select a new sub-contractor to operate the FSO going forward and are working together to formalise the engagement. Valeura intends to implement a phased transition plan resulting in production resuming in 4Q 2023.

Sean Guest, Valeura’s President and CEO commented: “This is an excellent outcome for the Wassana field and a demonstration of our team’s ability to uncover further value-adding subsurface opportunities. As a result of a thorough review of the asset, we are now facing several opportunities to increase the scale of the Wassana field, and see the potential for further reserves development, increased production, and an extension of the field’s economic life well into the 2030s.

“Wassana is shaping up to deliver much more than its original expectations, a characteristic which is consistent with the ultimate recovery we are achieving at our other fields in the Gulf of Thailand. We are also making good strides toward resuming production operations at the field, which prior to the suspension, accounted for approximately 10 per cent of our total aggregate production.”