Checking with the past
scientists in the United Kingdom have undertaken a unique project that could help to pinpoint oil and gas deposit sites. The project, which will take two years, involves studying weather information dating back 320 million years and correlating it into a global database.
The scientists go back in time to ascertain the variable effects of solar radiation on the polar ice and the resultant changes in sea levels. By charting these and identifying the geological patterns the researchers at Cardiff University in Wales claim to be able to predict potential areas with best quality reservoirs of gas and oil.
The relationship between sea level changes and reservoir quality was accidentally noticed by researchers while looking at oil fields in West Texas and New Mexico in the United States four years ago. But it was only the Cardiff team that was able to combine it with earlier research on how solar insolation (radiation on a given area) varied in the carboniferous age. The team achieved a breakthrough by weaving the two factors together into a useful exploration tool.
Team leader Paul Wright said: "The Earth's orbit is elliptical on a cycle of about 100,000 years. This affects the amount of radiation from the sun reaching the Earth's surface and it is possible to work out the 320 million-year-old pattern of the variability of solar radiation which alters the size of the ice sheets. We are interested in the resultant rapid sea fluctuations that began at this time when the cycle switched to a 400,000-year-cycle.
"During this period, sea levels have fluctuated by as much as 60 metres as ice sheets have been built up and thawed over hundreds of thousands of years. This dramatically affected the geology of the Earth. These fluctuations exposed atolls, similar to the Bahamas today, allowing the sea water to leach them and created much of the porosity we are interested in. Very much later, hydrocarbons migrating out of the nearby deep water basin passed through this porous limestone to leave behind liquid oil and gas trapped in the pre-existing holes.'
The Cardiff team is still at the stage of interpreting the data collected from Kentucky, Nevada, Texas and New Mexico in the US. He and his colleagues are busy compiling information for a global database that can be applied to exploring.
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