Negativ EM-anomali gir tørr brønn Prospektet Sandia som nå bores har ingen EM-anomali. Ifølge EMGS vil det derfor ikke bli gjort et lønnsomt funn. (c) EMGS

Negativ EM-anomali gir tørr brønn

Why is it that explorationists are so poor at predicting volumes and – not the least – where/why are they failing?

Seismic has always been, and will indeed always be, the cornerstone of exploration – but it is important that we acknowledge its limits. The most important of these is purely physical and relates to saturation. No matter what you do to your seismic data, it is inherently impossible to properly de-risk saturation using seismic – the information is just not there from a physics perspective.

The one geophysical dataset that can infer saturation is CSEM. The reason being is that resistivity increases exponentially with hydrocarbon saturation.

Tror spirit vil bore tørt

It is important to here that while CSEM in its infancy was widely touted as a direct hydrocarbon indicator (DHI), it is patently not. It is simply a remote sensing tool for resistivity. Just like when interpreting well logs, an increase in resistivity does not infer hydrocarbons, as cemented sands, source rocks, salt and basalt all can have high resistivities.

But crucially, and also just like in well logs, the relationship between saturation and resistivity does strongly suggest that a lack of resistivity is inherently related to low saturation levels.

Or – to put it differently – while CSEM is not a direct hydrocarbon indicator, it can clearly be a direct hydrocarbon killer – this is also heavily supported by actual well results.

Read the full story – written by Lodve Berre in EMGS – on