ADX Energy has embarked on the next critical phase at its Welchau-1 discovery in Upper Austria, commencing flow testing on the prospective Reifling formation to verify the presence of light oils and potential hydrocarbon flows. The company has finalized all preparatory work, including acid stimulation and damage repair, ensuring the wellbore is clear and ready for action under its ADX-AT-II licence.
Discovery and Initial Evaluations
The Welchau-1 well was drilled in early 2024, penetrating a substantial 450-metre interval that revealed significant hydrocarbon shows, highlighting the prospect's considerable scale. Early assessments indicated a sizable gas and condensate resource, with estimates ranging from 12 to 217 million barrels of oil equivalent, and a robust mean estimate of 85 million barrels of oil equivalent.
Shift to Light Oil Focus
However, in September 2024, ADX Energy announced that the discovery appeared to contain high-grade light oil with associated gas, representing a materially more lucrative outcome than the initially anticipated liquids-rich gas play. The company holds a 75 per cent economic interest in the licence and expresses confidence that new insights into the reservoir's hydrocarbon composition could facilitate the conversion of this large trap into future production.
Structural Connections and Testing Setup
ADX Energy notes that its analysis of pressure readings and structural ties links Welchau-1 to the nearby Molln-1 gas-condensate discovery from the 1980s, suggesting a broad and interconnected setup with ample gas-condensate volumes under highly pressured conditions. Testing on the Reifling formation, the shallowest of four reservoirs encountered in the well, is now underway, facilitated by MB Well Services and its AW-24 tubing installation rig.
Flow Testing Process and Objectives
The flow testing process begins with an injectivity check, followed by pumping acid into the zone to soak and dissolve drilling-induced blockages. Subsequently, the well will flow back for monitoring and sampling. This testing round aims to determine the hydrocarbon type and flow behaviour of the Reifling formation, while potentially validating a large section of light oil that coincides with the oil-water contact in Welchau-1.
ADX Energy reports that this up-dip oil could extend as much as 500 metres above the contact, moving up-dip and to the west. If confirmed, this would constitute a very voluminous hydrocarbon trap. To date, only one of the three testable reservoirs has undergone flow testing, leaving room for further evaluations as results emerge.
Overcoming Challenges and Geological Insights
The original Reifling flow test was halted in January last year due to challenges from environmental groups over clearances, but a September ruling from the Upper Austrian court cleared the path forward. The Welchau discovery taps into the Northern Calcareous Alps play, targeting Middle Triassic carbonates sealed by the Lunz-Partnach layers.
Post-drill refinements, incorporating well data, surface mapping, and updated 2D seismic information, have shifted the anticline's crest further west. The updated model has also identified a duplex thrust stack beneath Welchau-1, where compressional forces have sliced and stacked multiple rock layers, creating a series of repeated structural slices with potential reservoir upside.
Future Prospects and Ongoing Studies
These up-dip features align with Molln-1's gas-condensate zones, opening new interpretations and potential that earlier pre-drill views had considered too deep and expensive. ADX Energy states that ongoing refinements to the structure continue to sharpen the picture, with pressure links confirming a strong seal and recharge across the fairway.
Welchau-1 is firmly back at the forefront of ADX Energy's agenda in Austria, with a potential sidetrack off the well aimed at pursuing the up-dip oil target. Testing is now in motion, and studies are progressing as ADX Energy anticipates a series of updates that could solidify the discovery's path to value, blending oil and gas elements in a proven European basin.
