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Transcript for The Future of Energy Gases, segment 05 of 13
These conventional resources represent only a part of the natural gas that's available to us. Natural gas also occurs in places that are more difficult to develop and more expensive to produce. These occurrences known as unconventional resources include tight gas, coalbed methane, deep gas, and methane hydrates. Together these have the potential of providing large amounts of natural gas for the future.
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Tight gas occurs in rocks like the massive sandstones that form the cliffs of Mesa Verde National Park in southwestern Colorado. Farther south these same layers lie buried beneath thousands of feet of rock in the San Juan Basin. Here they house vast stores of natural gas but hold it tightly locked in isolated cells. Pores in these tight gas reservoirs are unconnected like holes in a Swiss cheese or linked only by microscopic cracks. The gas moves slowly through the rock or not at all, making it difficult to collect, but large natural fractures crack open the pore space, freeing the gas.
Zones of intensely fractured rock form concentrations of natural gas. New technologies let drillers pierce these zones horizontally, tapping several from a single well and making the difficult job of recovery more efficient.
Tight gas sandstones hold immense quantities of natural gas, but much of it may be too expensive or even impossible to recover, yet reasoned estimates suggest that tight gas might supply four hundred trillion cubic feet of natural gas, enough to meet our present needs for twenty years.