GEO ExPro

Finding Oil – Using Geochemistry

While well geochemistry is a routine service in exploration drilling, surface geochemistry is now growing in popularity, in particular in deep water frontier basins. That's a market Geolab Nor wants their fair share of.
This article appeared in Vol. 5, No. 5 - 2008

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Managing Director Malvin Bjorøy does not anticipate major changes following Fugro’s acquisition of GeolabNor. The main benefit may be that the oil industry will get easier access to surface geochemical surveys and more multiclient well geochemistry studies. Photo: Halfdan Carstens "The recent acquisition of Geolab Nor by Fugro may result in a considerable increase in the use of surface geochemical services," says Malvin Bjorøy, managing director and founder of Geolab Nor. "Fugro has a huge fleet, and the access to vessels all over the world is now made much easier". The ultimate result may be that more oil and gas is found, something that is a bare necessity if the "peak oil" advocates are right. That is good news for all of us.  

Fugro is a world-wide leader in geotechnical surveys and geoscience services, and Geolab Nor works closely with their subsidiary Fugro-Robertson out of Llandudno in Wales. In this way, two companies with expertise in petroleum geochemistry have merged, thereby creating one of the largest companies in the world of its kind.  

GeolabNor, founded in 1984, is a service company with global outreach. The geochemical experts have worked on hundreds of medium- and large-scale regional projects from the North Sea, Russia, FSU, SE Asia, India West Africa, North Africa and the Middle East. While the company has also done work in Australia, this is a little too far away, taking into account the cost of transporting samples all the way to the laboratory in Norway.  

Up to date, contracts have been secured in 40-50 countries. That is, to say the least, quite impressive for a small company situated far away from a large share of the market. "In the future we expect that we will divide the world between ourselves and our colleagues in Wales, the days of competition are gone," says Malvin.  

Well geochemistry

GeolabNor has invested millions of dollars in instruments, and have also themselves contributed to the development of both analytical techniques and new instruments. Photo: Halfdan Carstens Well geochemistry involves extensive analyses of cuttings, cores, drilling mud and formation fluids, including water, gas and oil. It is an exploration tool that has been used for several decades for assessing the source rock capabilities within a basin.  

"The primary purpose is to investigate if a potential source rock can generate oil or gas and if it is mature or not," Says Malvin.  

The essentials of any geochemical analysis is thus to evaluate the richness, maturity and type of kerogen in the source rock. This will enable the geologist to tell if the source rock is rich or lean and if it will give oil or gas. It is well known that few wells actually drill into the "oil window", and it is equally true that few cores are recovered from the actual source rock. Most source rock studies will therefore rely on analysis of cuttings outside the "oil window".  

To supplement the source rock evaluation, fluids within the reservoir are also analysed. This will assist in finding the true source of the hydrocarbons, and it is also necessary in order to understand how the fluids interact with the reservoir rock itself.  

Another aspect of well geochemistry is termed reservoir geochemistry. "We do geochemical analysis of hydrocarbons in the reservoir, either by analysing oil samples or core samples, and in this way we can determine the migration pathway. We can actually decide from what direction the reservoir has been filled," explains Malvin.  

"Such knowledge can be of importance when evaluating satellite structures of a given field. The operator can also get information about barriers to fluid flow, both vertical and lateral," something that is very important when the production planning is undertaken."

Surface geochemistry

Surface geochemistry is a tool that is cost-efficient in deep water frontier basins. Photo: Jan Erik Bjorøy "Surface geochemistry is now being used in the initial exploration in every deep water frontier basin. This is a very cheap method to find out if the basin contains hydrocarbons," Malvin says.  

"We can tell if hydrocarbons have been generated, and if this is oil or gas. Moreover, if it is oil, we can tell what kind of source rock that has been generating the liquids. Having access to good seismic, it may also be possible to have some ideas about where the oil comes from."  

The basic principle underlying the use of surface geochemistry as a tool in exploration assumes that few if any sedimentary rocks are totally impermeable. In most cases, salt may constitute an exception, hydrocarbon molecules can migrate upwards in the sedimentary succession via permeable carrier beds and faults. This will cause detectable accumulations in near-surface sediments, and through the use of sensitive analytical techniques it should be possible to detect and characterize hydrocarbon seeps.    

"In petroleum exploration, surface geochemistry is applied to soils or seabed sediments to detect and determine the nature of hydrocarbons that have leaked to the surface from either source rocks or reservoir rocks in traps," says Malvin.  

"In the laboratory we are using the same instruments as in well geochemistry, but there is a difference in order of magnitude in the volumes we need to measure. While we use ppm (parts per million) in well geochemistry, we need to measure in ppb (parts per billion) in surface geochemistry. This also means that everything has to be extremely clean. We have absolutely no tolerance for contamination , something that applies from the moment we get the sample and until it is analysed."  

Malvin says that approximately 50% of the business they have had during recent years relates to surface geochemistry. This year is an exception though, as they have been doing a large study for RWE-Dea in the Barents Sea. Altogether 375 cores have been taken and brought to Trondheim, Norway, for analysis and further studies by the oil company.

Surface geochemistry is an old game in petroleum exploration. The first attempts were made in the 1930's, while a rapid development in data analysis was made in the 1980's and the 1990's. The most recent development is the use of an ever increasing number of samples being taken. One example is an ONGC study including 3000 samples in 6 areas, a volume that is equal to the total market for 2 years.  

"We now also see that it is not only the major companies that are being interested in surface geochemistry. Some of the middle sized and smaller companies are also showing an interest," says Malvin, being confident that surface geochemistry is an exploration tool to be used ever more both in frontier and mature basins. However, Malvin believes that the industry will gain most from the technique in virgin areas. "Also, a combination with heatflow measurements taken simultaneously with geochemical coring in virgin areas will bring an extra value to such studies."

Looking forward

Geolab Nor has been around as a separate entity for almost 25 years, and the founder is still going strong based on his solid geoscientific achievements in general and his skills in geochemistry in particular. He has been successful in building a company that serves the entire oil industry with quality products on five continents. During the same time, petroleum geochemistry has developed from being mainly a source rock identification and correlation tool, to involve most aspects of petroleum exploration and production.  

From now on, his company's logo will also feature the Fugro logo and the company will be renamed Fugro Geolab Nor AS. The company has fifteen staff, comprising 3 senior scientific staff, 3 chemical engineers, 6 laboratory technicians, and they will all be part of the Geoscience Division under the management and guidance of Fugro Robertson Ltd. Current management will, however, stay in place, meaning that Malvin Bjorøy will still be around. That is good news, because we need people like him - a real entrepreneur who does not belong to the common flock.

 

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