Pamela Gladwin, age 11, ofUtica, N.Y., for her question:

WHAT EXACTLY IS OIL PRODUCING SHALE?

Most of. us heard about oil producing shale during the energy crisis. It is mentioned as a sort of last resort in the urgent business of extracting petroleum from impossible places. It is true that gasoline and other petroleum products can be processed from certain stubborn shale rocks, but at present the project is not very feasible.

Our present supplies of petroleum are extracted from very porous sedimentary rocks, such as sands and silts, corals and other limestones. The oily deposits are thought to be the fossil remains of countless creatures that lived and died in shallow seas within the past 1 million to 300 million years. And as we all know these world supplies are running low.

However, we are told that far greater supplies of underground petroleum are trapped in certain deposits of tough \shales. This is only partly true. These hard shales are dense, compressed layers of heavy clays and silts. The so called oil, trapped in their tiny pores is a solid substance called kerogen.

It is true that kerogen, like petroleum, is a rich mixture of fossilized hydrocarbons. But we cannot drill down to the supply and expect the oily liquid to gush to the surface, as it does in our present oil fields. Extracting and processing petroleum from so called oil shales is enormously difficult and costly.

First the stubborn shale must be dugout and crushed. Then the mixture must be heated to about 900 deg. At this temperature its hydrocarbon molecules break apart into the usual oils and gases extracted from other petroleums. The heating process uses vast amounts of energy  and the unused. ore would be left to disfigure the landscape with huge piles of barren slag.

Some experts estimate a trillion barrels of petroleum could be recovered from the so called oil shales of North America. But at present these experts cannot explain how this promising daydream can be done at a price we can afford to pay.