As announced yesterday, operator Wintershall and partners DNO (30%) and Spirit Energy (30%) concluded drilling appraisal well 6406/3-10A on the Bergknapp discovery in the Norwegian Sea – about 8 kilometres west of the Maria field.
Having a pre-drill estimated range of 30-60 MMboe, the combined recoverable volume of 53-140 MMboe thought to be in place now is clearly a step in the right direction when it comes to considering Bergknapp for development.
The below schematic cross-sections show the evolution of the Bergknapp discovery from pre-drill to appraisal, using a cross-section published by Faroe Petroleum (the company that was acquired by DNO in 2019) as a starting point. Although the Wintershall version of this reconstruction may be different, it aims to paint a picture of how the prospect evolved from pre-drill through to appraisal using the NPD press releases for both 6406/3-10 and 6406/3-10A as a guide.
Pre-drill and the first well
Looking at the pre-drill section, it is clear that Faroe expected oil to be present in four individual Lower to Middle Jurassic reservoir intervals, sealed through fault sealing in a southwest direction. The discovery well did prove oil in three out of the four expected reservoirs, with the Tofte Fm sands probably missing or of very poor quality.
Just looking at the section, it may be concluded that the 120 m gross column in the Tilje Fm was the best surprise in the well given the supposedly higher contact in the pre-drill situation, but during a talk about the discovery well at the NCS Recent Discoveries Conference last year the Garn Fm was earmarked as the main reservoir. This is probably because of the reservoir quality and the more patchy nature of the Tilje Fm sands.
The discovery of oil in the Garn Fm was a positive outcome anyway, as the presence of thief sands in the seal was thought to be a main risk.
Appraisal well 6406/3-10A
Although the azimuth of the appraisal well is not known, based on the cross-section it is projected in a southwest direction to test both the updip Garn, Ile and Tilje formations as well as the Åre Fm deeper down. When subsequently using the information from the NPD press release, a few inferences can be made.
First of all, the continuation of the Garn and Ile oil legs may not be as was hoped for, given the small columns of 7 and 3 m found in these intervals respectively. This may have either be caused by reservoir quality deterioration or no effective sealing against the overlying Spekk Fm.
The second interesting aspect of this appraisal well is the discovery of a 260 m gas column in the Åre Fm. Although this is a gross column with approximately 82 m of poor reservoir quality sands, it did add between 13 and 57 MMboe to the oil already found higher up and also proved the fault sealing element of the closure.
In summary, when comparing the pre-drill to the appraisal setting, it is clear that Bergknapp has delivered in terms of potential volumes, but has probably also resulted in a more complex reservoir quality and distribution pattern than initially hoped for.
HENK KOMBRINK
