ADX Energy’s ongoing drilling of its Anshof-2 appraisal well in Upper Austria has encountered Eocene reservoir with a vertical gross thickness of at least 22m – and there is still about 85m of drilling to go.
In an update released today, the company says the Eocene sand thickness compares favourably to the 6m-thick section intersected at the same stratigraphic level by the Anshof-3 discovery well, just 1.8km away. Electric logging of the well is expected to begin in two days.
Anshof-2 is the second well in the Austrian oil field, flowing on from the Anshof-3 discovery well drilled by ADX and kept as a producer.
A successful Anshof-2 well may allow the company to reasses the Anshof field reserves, which it says could be as high as 26 million barrels of oil equivalent (MMboe). ADX hopes the Eocene reservoir intersected at Anshof-2 will contribute about 300 barrels of oil per day to the total Anshof field production.
Management says Anshof-2 is currently being drilled at about 2235m measured depth (mMD) at an inclination of some 70 degrees and will terminate at 2320mMD.
Measured depth is the distance measured along the drill-pipe from the rig’s drill floor to the bit. The inclination of the well is measured from vertical, with zero degrees being vertical and 90 degrees being horizontal.
The 22m gross vertical thickness Eocene reservoir was the primary target of the Anshof-2 well and was identified using drill cuttings viewed at the wellsite following their circulation back to the surface, in addition to “logging while drilling” (LWD) gamma ray logs from a sensor run-on pipe behind the drillbit.
ADX says the gas shows on mud logs are comparable with those seen at a similar section within the Anshof-3 well.
Management says the top of the Eocene reservoir was hit at about 40m to 50m vertically shallower than prognosed – a positive outcome which may allow a larger hydrocarbon to be interpreted should the oil-water contact, or oil-down-to depth be intersected at pre-drill estimates.
Pre-drill depth estimates for formation tops are commonly “off” in oil and gas drilling due to the tops being picked on seismic data. The shallower intersection of the top Eocene reservoir has allowed ADX to pull the Anshof-2 well’s total depth up short of the planned total depth of 2650mMD, saving time and money as the stratigraphic target has been obtained.
Though LWD gamma ray logs are generally reliable for picking formation tops that show a good change in character from shale to sand, the data will soon be superseded by higher-confidence, multi-suite electric logs to be run in the hole on drill-pipe following the completion of drilling.
The electric logging suite will provide ADX with much more information regarding the quality of the sand, including porosity and hydrocarbon saturation, allowing critical net-to-gross calculations to be made and revealing just how much of the Eocene reservoir can be classified as pay.
The company says the electric logging tools will be run on drill-pipe to allow the tools to be dragged to the bottom of the near-horizontal hole under the weight of the pipe, rather than attempting to get the tools to the bottom on wireline, as would be done in a vertical well.
Below the Eocene reservoir, Anshof-2 intersected the Upper Cretaceous section, where the company says gas shows compare favourably with those seen in a comparable section at the Anshof-3 cut point. Again, electric logging will be required to quantify the prospectivity of the section.
ADX says the next Anshof-2 drilling update will come next Tuesday and it is expected to include logging results and a preliminary interpretation of the reservoir parameters.
Is your ASX-listed company doing something interesting? Contact: office@bullsnbears.com.au