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A new way to determine density deviations

Sunday, August 27, 2017

A Czech company has developed a new way to determine density deviations - by new geodetic and geophysical approach which uses set of precise Earth's parameters including accurate geoid potential constant W0.

GeoApplications, a UK company based in Brno, Czech Republic, has developed a new way to determine deviations in density of the subsurface - by studying shape of sea surface, based on set of precise Earth's parameters including accurate geoid potential constant W0.

Their method, called Density mapping technology (DMT), is a new geophysical method, which calculates completely new geophysical-physical geodetic data - Density Deviations.

The data is processed together with many different constants and ceofficients describing physical parameters of the Earth, to develop a density deviation picture which provides new information about density variations compared to gravity survey, the company says. Their approach is not reprocessing of other geophysical data, but calculation of new geophysical parameter.

The technology was invented 8 years ago by two Czech professors - Viliam Vatrt, a specialist in geodesy, and associate professor Lubomil Pospíšil, a specialist in gravity for petroleum exploration.

Since then, the inventors have been developing the technology and putting together demonstrations, based on public data, showing how it is able to identify potential hydrocarbon bearing structures.

Two years ago, Brno venture capital company Opifer Ventures took an interest in the company, invested in company and together they expanded the team of partners and advisors and incorporated experts from several fields of exploratory geology (Geophysics, Geoscience, Petrophysics, Complex geological interpretation and Basin analysis).

Now the company is making the technology more accessible for use in oil companies, for example by providing it as plugins to the popular Schlumberger Petrel and ESRI ArcGIS software.

So far the technology has been verified for offshore exploration and it is sure it could also be used onshore.

Density deviations

The technology grew out of a project Viliam Vatrt was engaged in, to develop a new way for unification of altitudes in the world, including altitudes for aeroplanes by GPS and other military use in NATO.

Mr Vatrt is a professor in the Department of Geodesy, Faculty of Civil Engineering, at Brno University of Technology, Czech Republic. Geodesy is defined as "the branch of geophysics that deals with shape and surface of the earth".

Mr Vatrt determined a 'global geodetic constant' called W0, representing the gravitational potential of the Earth, irrespective of any tides or other factors, so it can be used in many applications including DMT technology.

This constant can be used together with the sea level at each point on the earth's surface, which position can be measured by satellite.

Mr Vatrt noticed that the potential of earth varies by small amounts, based on a precise understanding of distribution of the masses in the earth's crust.


So putting all of this data together - the geodetic constant, precise understanding of the true shape of the earth and other geodetic and geophysical constants, variations in the sea level and changes to the satellite track, make it possible to determine a picture of density deviation beneath area of points on earth.

An enormous quantity of different coefficients are used in the calculation.

It can show density at chosen resolutions depending on the density of point on earth's shape.

Application to petroleum

Mr Vatrt thought that the method to determine density deviations might be useful in petroleum exploration, so he joined up with Lubomil Pospíšil, Associated Professor at the Brno University of Technology, a specialist in geophysics, and an honorary member of the Czech Association of Geophysicists (CAAG).

Lubomil Pospíšil is a gravity expert. He has worked in remote sensing for the Ministry of Geology in Moscow, and with the Winter Education Training Program of AAPG in Houston, working on reservoir characterisation (mapping surfaces, properties and volumes), subsurface mapping, developing frontier exploration opportunities, and shapes of sedimentary bodies.

Associate professor Pospíšil has been working to show ways that the technology could be used as part of an oil and gas exploration process.

The density deviations are showing if there is a change in the density of the subsurface in the measured area.

A change in density could be due to changes of geological structure.

Benefits

The company has been developing geological case studies which can show how this technology could play a part in a broader subsurface interpretation process. The DMT Technology has extensive images available, showing how its density deviation maps have much higher resolution understanding than standard gravity deviation maps.

The company has used its data together with publicly available seismic subsurface data covering the Rockall Basin (UK, off North West Scotland), around the Faroe Islands (north of UK), the Statfjord - Gullfaks area in the Viking Graben (West of Norway), the Southern North Sea offshore Netherlands, and the Beaufort Basin (Alaska).

DMT technology would have identified in these areas different hydrocarbon bearing structures, such as subsurface channel complexes, small sub-basins and basement ridges. Existence of these structures have been verified by seismic data.

Case studies show several beneficial applications of the DMT method which are usefull in exploration at two stages.

In the pre-seismic stage the main added value of the DMT method is success increase of seismic survey planning. In the second stage, after seismic acquisition, the DMT method is used together with seismic data for effective refinement of seismic interpretation.

The first application in pre-seismic stage is precise density mapping of subsurface - a geologist can use information about density deviationsto get a better understanding of the subsurface, and perhaps use it to identify areas which are worth commissioning more expensive seismic surveys.

Another application is pre-seismic structural mapping, because complex structures, such as faults, folds and their combination, often create density contrasts. Distribution of these density contrasts allows to interpret structures, potential trapping system, role of faults in hydrocarbon migration paths.

Density contrasts between basement and sedimentary infill is basis for next two beneficial applications of DMT, which are exploration af basin structure and its sedimentary infill and exploration of basement surface.

Combination of DMT method with the existing seismic data enables to gain more information from seismic interpretation. Density Deviations are useful to define structures that are poorly visible on seismic sections, for example below basalt sequences.

Another benefit is DMT Trend Surface, which is special combination of DMT and 2D seismic surface in order to identify structures lost between 2D seismic lines.



Associated Companies
» GeoApplications
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