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ADX Energy to chase oil up-dip with Anshof-2 sidetrack

Updated: Mar 25

ADX Energy’s Anshof-2 well operations in Upper Austria. Credit: File.

After encountering about five-times thicker net reservoir than Anshof-3, ADX Energy’s latest well – Anshof-2 – has hit lower than expected oil saturation, resulting in a sidetrack being required for viable completion.

Oil shows at the top of the Eocene reservoir section in Anshof-2 indicate higher oil saturations can be expected slightly up-dip from the well’s cut point, meaning it likely intersected reservoir just below the field oil-water contact.

So, ADX now plans to chase the higher oil saturation by sidetracking Anshof-2 from the bottom of the 9 5/8-inch (244mm) casing to hit an up-dip bottom hole location in the Eocene sand above the field oil-water contact where it expects to find oil-charged reservoir. That sidetrack will be planned at a later date, but will likely deviate to the north-east, closer to the crest of the Anshof structure.

The company says the Eocene reservoir oil saturation seen at Anshof-2 is about 34 per cent, which is disappointing and essentially means the well’s cut point was below the field’s oil-water contact. Rather than the sandstone reservoir being charged with oil at the cut point, it was charged mainly with water.

But there are some technical positives to be gleamed from the Upper Austrian well. The company says 12m of vertical net thickness Eocene reservoir seen by Asnhof-2 has excellent porosity of about 20 per cent and is thicker than pre-drill models suggested.

The Eocene reservoir was also hit about 40m to 50m vertically higher than prognosed, meaning the Anshof trapping structure is likely flatter than previously thought, allowing a higher crestal hydrocarbon volume to be attributed to the Eocene section across the field.

It may mean the field will require less production wells due to higher productivity and reserves recovery per well. The company says Eocene oil-producing wells in the basin with similar reservoir quality have produced at rates of about 1000 barrels of oil per day (BOPD).

ADX’s rig will now finish suspension operations at Anshof-2 before moving off location, giving management time to complete well planning for the sidetrack hole and install surface production facilities. As a result, Welchau will now get some attention, with the Welchau-1 well coming up next using the same rig as was used to drill Anshof-2.

Welchau is a gas prospect and has the potential to be massive to the tune of 807 billion cubic feet (BCF) equivalent as a best technical prospective resource located about 20km south-east of Anshof in the Austrian Northern Calcareous Alpes and within the ADX-AT-II exploration license.

The company says Welchau-1 is expected to spud in the third week of January next year and drilling will take about 40 days.

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