While nowadays quite a common form of well logging, the innovation of electrical well logging is a fundamental for supplementary tests in order to help the Depth Conversion process along. But what exactly is electrical well logging, and how does it vary from what is normally obtained using sound?
Working in exactly the same manner of acoustic waves, electrical well logging is essentially charges being applied to the ground, and recorded when they come back up. They differ from acoustic means due to the fact that When electrochemical reactions are administered to the borehole, the readings for potential and resistivity are available – something which is not in acoustic waves.
To obtain a clear reading of a bed, you need to first understand the contributing factors to any test. For instance, the amount of water directly affects the conductivity of any electric well-logging which has a large bearing of the electrodes as they are applied to the test area.
For the actual logging, an electrode on the surface and an electrode in the well are paired and also polarised. This helps to decipher the readiness of the contents of the well for logging by contrasting the two figures. Depending on the depth that is being traversed, varying frequencies are applied.
For the electrodes themselves, you can either opt for them in a single or multi form that differs in values for either. If you choose singular then you will find it is cheaper but not nearly as proficient for large-scale operations as they do not have nearly as much lateral penetration.
Despite this, the single-electrode technique still offers as reputably accurate readings as the multi-mode with some speculating that it may even be more advanced. This is down to its exceptional ability to figure out the correlation between wells.
There are one or two drawbacks to this method however as with no water base, a test becomes redundant because no readings will be correct. Therefore, the area usually has to be filled with water or converted to mud.
An unavoidable aspect of any logging is the interference of nature. The curve or gradient at which it’s being logged can invariably drift off to the left in the hole and cause unsuitable conditions. There is nor easy fix for this except for to try again elsewhere.
An excellent example of recent successes thanks to electrical well logging being part of the Depth Conversion process is in Norway. In recent times, a vast discovery has been made on a marine basis- the Arctic Ocean is replete with precious minerals.
To the north of the Norwegian company Statoil’s home, an impressive amount of oil has been unearthed in prospects that have been logged for the first time since the early 1990s.
The estimated sum has come in at a potential 20 to 50 million barrels of oil available for extraction.
A spokesman for Statoil has said: “Statoil puts a lot of effort into proving additional oil resources in the Johan Castberg area in order to make the field development project more robust. We are pleased to see that our efforts now pay off.
“Skavl was the third of the four wells in the Johan Castberg area we have on our drilling plan this year. The first two wells, Nunatak and Iskrystall, proved only gas, but we know from experience that it takes stamina and persistence to succeed in the Barents Sea.
“It is also encouraging that we have confirmed a new play model in the area with the oil discovery in the Fruholmen formation, something which will be followed up in future exploration.”
This news comes off the back of a Trindad and Tobago company finding an estimate of 50 to 115 million barrels of crude oil. As the first of its kind since 2012, there has been a lot of excitement surrounding the news, least of all from Chief Executive Officer of Trinity Exploration and Production, Monty Pemberton.
“The TGAL-1 discovery is exciting news for all of Trinity’s stakeholders, and our team has done an excellent job in delivering this successful well safely. Trinity’s industrial thesis has always been to pursue low risk opportunities in T&T, which we believe is a prolific but under-exploited hydrocarbon province,” Mr. Pemberton said.
With this grand discovery and the prior story in Norway, it seems as if oil logging is going through a purple patch of success which can only be good news for specialists all over the globe.