LEXINGTON, Ky., April 2 (UPI) -- Two new studies that scrutinize how underground sandstone is formed may help companies locate valuable energy resource deposits. The findings, presented Tuesday at the North-Central and Southeast Geological Society of America meeting in Lexington, Ky., should help take some of the guesswork out of oil, gas and coal exploration.
Jesse Korus, a geological sciences graduate student at Virginia Polytechnic Institute in Blacksburg, used electrical logs from gas and oil wells to interpret the makeup of underground rocks in the New River Gorge area of West Virginia.
The logs measured the natural radioactivity of the rocks which reflects the types of formations that are likely to exist below ground. Shale, for example, is more radioactive than sandstone.
Using this data, Korus was able to piece together a picture of how the rock formed millions of years ago. His findings suggest that very large rivers flowed through the region, eroding and depositing rock over time. The basin that formed as a result of this process was also slowly sinking. The southeast side of the basin, however was sinking faster than the northwest side which created channel-like sandstone bodies that preserved coal deposits.
This grand picture of how the New River Gorge took shape will help coal companies better understand where energy resources are likely to occur, said Korus.
"This finding has implications beyond West Virginia. It has implications for other gas and oil reservoirs in other regions around the world," said Korus.
Geological scientists have been closely studying sandstone because its porous quality makes it a likely reservoir for gas and coal.
"This study is trying to map out the trends [in the sandstone] of these channel and valley systems. It's economically significant because if these sandstones have some pore space, they are likely to be important reservoirs," said Ron Martino, chairman of the geology department at Marshall University in Huntington, W. Va.
Virginia Tech doctoral candidate Jason Reed examined a different angle of sandstone formation but his work has similar implications. He looked at the chemical and physical changes that sediment undergoes before it becomes sandstone, a process called diagenesis.
Specifically, Reed studied how initial sediment grain composition, climate history and the environment of sediment deposition influence sandstone formation.
These controls determine whether the sediment forms void spaces where oil, gas and water are likely to exist.
While it's not clear how climate and the environment of sedimentation affect the sandstone, Reed found that the kind of grain involved in formation determines whether or not it will be porous.
Sandstone composed predominantly of quartz grains had more void space than other varieties of sandstone and could therefore harbor fluids more easily.
"If that pore space is clogged up with minerals during diagenesis you're unlikely to find it (fluid) there," he said.
The findings provide another tool for zeroing in on energy resources below the surface.
"Reed's work focuses mainly on the sequence of changes that would occur in between sand grains and in the sands themselves," Martino said. "It's important because it would determine how much pore space would be left for gas."
The research was funded by the American Society of Petroleum Geologists.
(Reported by Koren Capozza in San Francisco)
