Canadian independent Valeura Energy is evaluating the new platforms and potentially also floating facilities that could be required to expand production at its Wassana oilfield offshore Thailand after a recent successful appraisal drilling campaign.

Valeura is remapping the field to integrate the new data from the drilling campaign and anticipates the results will yield an increase in its volumetric estimates.

Preliminary analysis indicates that an additional approximately 20 production well targets are now potentially viable within the reservoir section appraised by these two wells.

In light of this upside potential, the operator has begun the concept selection phase of a project to expand the development of the Wassana field, which could boost production and extend the field life beyond 2030.

Valeura envisages this will 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.

“This is an excellent outcome for the Wassana field and a demonstration of our team’s ability to uncover further value-adding subsurface opportunities,” Valeura chief executive Sean Guest said.

“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.”

He added that the Wassana is shaping up to deliver much more than its original expectations — a characteristic that is consistent with the ultimate recovery Valeura is achieving at its other Gulf of Thailand fields.

Floater incidents

In July, Valeura suspended production at its Wassana field to undertake a review of safety and operating practices of the field’s third-party owned and operated floating storage and offloading vessel.

Wassana is exploited via wellhead platforms tied back to the MT Jaka Taruba FSO and was producing 2400 barrels per day of oil when output was stopped in early July after the second safety incident in just three months.

In early July the FSO had hit the field’s catenary anchor leg mooring (Calm) buoy, while in April there had been a similar clash between the third-party owned floater and the buoy.

As a result of this review, Valeura and the FSO’s owner have opted to select a new subcontractor to operate the floater going forward and are working together to formalise the engagement.

Valeura said it intends to implement a phased transition plan resulting in production resuming in the fourth quarter of this year.

“We are also making good strides toward resuming production operations at the field, which prior to the suspension, accounted for approximately 10% of our total aggregate production,” Guest added.

“We look forward to restarting under conditions that fit with our high standards for health, safety, and environmental responsibility.”

Appraisal details

Valeura recently drilled two successful appraisal wells targeting deeper reservoir sections on the flanks of the Wassana oilfield.

The A28 and A28-ST1 wells respectively confirmed 72 feet and 75 feet of net oil pay and confirmed the presence of oil deeper than had been previously proven.

The two appraisal wells were designed to test for suspected additional oil accumulations in Wassana’s Tertiary clastic section.

Both wells targeted the deeper portions of the reservoir section. which holds most of the remaining underdeveloped oil reservoirs in the field.

Valeura noted that the appraisal programme was driven by an oil-water contact in this section not having yet been penetrated, implying potential for additional down-dip oil volumes. Also, recently reprocessed 3D seismic data suggested upside in a thickening of the reservoir section in the targeted locations.

“Both wells were successful in fulfilling these objectives and we believe the well 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,” the operator said.

The first well, A28, was drilled in the main producing fault block of the field, downdip of existing production wells and encountered 72 feet of net oil pay.

While previous reserves estimates were based on a demonstrated oil-down-to depth of 5517 feet true vertical depth subsea (TVDSS), the new well confirmed the presence of oil down to at least 5594 feet TVDSS, exceeding Valeura’s expectations for the vertical extent of the oil column.

Also, the well encountered a thicker package of reservoir sands and new oil-filled sands that have not been previously developed.

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 Wassana field. The well encountered 75 feet of net oil pay, proving the presence of oil in this undeveloped area.

The drilling rig has since mobilised to Valeura’s Jasmine oilfield where it is commencing a four-well programme comprising two production wells and two appraisal wells to support additional production well drilling in 2024.

After the programme at Jasmine, the rig is scheduled return to the Nong Yao oilfield, also in the Gulf of Thailand, for a five-well infill drilling campaign.

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