Earl Robinett, Exxon's site superintendent, wiped his brow and picked up his cost sheet. "As of 6 a.m. today we've spent $3,341,908 on this well, and now we're getting ready to plug it," he said in a slow, tired voice.

The big Delta Drilling rig hired by Exxon had drilled 16,075 feet down through the folded sedimentary rocks of Patterson Creek Mountain a few miles notrhwest of Moorfield, W.Va., about 120 miles west of Washington -- and came up dry.

Last year a few miles to the north and west in Mineral County, not far from Keyser, it was another story. The same Delta rig, working then for Columbia Gas Transmission Co., which supplies gas to Washington gas light Co., drilled 8,500 feet into the Oriskany sandstone and made a "major" gas discovery. One well flowed a huge 88.1 million cubic feet of gas a day, though daily production would be only a small fraction of that rate.

And last year, too, Amoco Production Co., with UGI, a Pennsylvania-based gas distribution company as a 10 percent partner, continued to drill wells in several parts of Pennsylvania, adding to its gas discoveries.

In a program that began in 1975, Amoco now has 13 wells producing 8.6 million cubic feet of gas a day, and next month will begin production of 4.5 million cubic feet daily from a 1977 single discovery well not far from State College, Pa. The well is so large that it will supply the entire State College area (except in winter), including several glass manufacturing plants.

Oil and gas production is not just the province of Texas and Louisiana or Alaska. With the big increases in oil and gas prices, both the international oil giants like Exxon and Amoco, as well as hundreds of smaller companies, are taking a serious look at a much drilled-over area known as the Eastern Overthrust Belt. The belt runs from Alabama to New York and includes significant parts of the western edge of Virginia and maybe parts much further east.

But the Overthrust Belt -- which takes its name from the fact that the oil-and-gas-bearing rocks were squeezed, folded and faulted as they were pushed or thrust westward over older rocks -- is a jumble that can leave a geologist pulling his hair. Very small quantities of gas, often too small to be worth connecting to a pipeline, are as easy to find as larger quantities are difficult to find.

Drilling below the Oriskany sandstone is particularly risky business. "A high-risk, high-potential frontier area," said L. Bryant Williams Jr., Exxon's Southeast Division exploration manager. Amoco tried its luck last year at greater depths in Northumberland County, about 50 miles north of Harrisburg. Like exxon's attempt in West Virginia, it was a dry hole.

After Amoco made its big 1977 discovery at more than 11,000 feet in the Tuscorora sandstone, it drilled anoter close by on the same fractured structure and found nothing. Yet other Amoco wells in the same general area have turned up gas. In another attempt to find gas in the Tuscorora, Amoco is drilling not for to the north.

With such uncertainties, larger companies want to sew up a lot of acreage before they start to drill. Amoco, for instance has leased 2.5 million acres in the Eastern Overthrust Belt so far with more being acquired constantly as its search moves south into Maryland and West Virginia.

So-called land men are on the scene in several states offering to pay landowners for the right to look for and produce oil and gas on their property. Until those rights are locked up, no company will drill.

There's a brisk business these days recording leases in the courthouses in places like Romney, the county seat of Hampshire County, W. Va., on Route 50 west of Winchester. Exxon, Columbia Gas and Sun Co. are among those with leases recorded for Hampshire County this year.

Landowners usually are offered the standard industry royalty of one-eighth of any oil and gas produced on the property and a small annual "delay rental" of $1 dollar an acre to keep the lease in effect if no drilling activity is begun within the first year. Sometimes the first year's rental payment is larger, with $3 an acre reportedly the going rate in Hampshire County this year with some reports of higher figures, too.

Meanwhile, the action is creeping eastward. A few leases have been recorded recently at the Frederick County courthouses in Winchester, and there are unconfirmed reports landowners are being approached in Culpepper and Rappahannock counties east of the Blue Ridge, only 60 or 70 miles to the southwest of Washington. Courthouse officials say no leases have been recorded recently in either county, however.

The movement of leasing to the east may be due to the findings of geologists Leonard Harris and Kenneth Bayer of the U.S. Geological Survey in Reston. Last October they startled other geologists by suggesting the present area for natural gas exploration in the Eastern Overthrust Belt from Virginia to Alabama " can perhaps be doubled in size." o

Harris, presenting a paper to a group of petroleum geologists meeting in Morgantown, W. Va., said that in the past the Appalachian Mountains have generally been divided into two main parallel parts: an eastern part, including the Blue Ridge and the Piedmont, and the western valleys and ridges of the Overthrust Belt.

The Blue Ridge and Piedmont are older, crystalline rocks that would not contain either oil or gas, as opposed to the younger shales and sandstones of the Overthrust Belt to the west. The organic matter that found its way into those shales and sandstones is the original source of the oil and gas now found there.

Bus Harris said seismic surveys "have revealed that faulting has in the past moved crystalline rocks of the Blue Ridge and Piedmont westward at least 100 miles, burying a large section of sedimentary rocks of the Eastern Overthrust Belt." This buried segment ranges from 10,000 to 20,000 feet thick and extends eastward more than 60 miles hidden beneath the faulted crystalline rocks. The crystalline-rock cover ranges from about 5,000 feet thick along its western edge to more than 10,000 feet thick in the east.

In other words, a well drilled on the eastern slope of the Blue Ridge in, say, Rappahannock County, would, after it got through the extremely hard, older rocks on top, encounter the same oil and gas-bearing sedimentary rocks found on the surface farther west.

That is true frontier country. No deep wells have even been drilled to prove or disprove even the presence of the sedimentary rocks, much less whether they contain oil or gas. And drilling would be difficult and expensive since getting through those harder crystalline rocks on top would be no picnic.

Moreover, why risk drilling money there when the Overthrust Belt itself is so little explored? It includes 36,000 square miles and less than 30 deep wells have ever been drilled in it. But such reasoning may not stop some people from trying to put together blocks of leases in hopes of interesting someone in drilling.

Meanwhile, the Delta Drilling rig was moving from Patterson Creek Mountain above the valley of the South Branch of the Potomac back to Mineral County, where Columbia Gas plans another well near last year's major discovery.

Amoco has encountered problems in drilling its latest well in the area north of State College. Known as General Refractories #1 -- wells are almost always indentified by the name of the owner of the land -- the drillers "lost the hole" when a soft salt formation through which they had drilled closed up again, according to James F. Trickett, Amoco's district superintendent.

So the hole was plugged above the salt, a special curved, wedge-like device called a shoe was inserted at the top of the plug to cause the new hole to be drilled off at an angle. Once far enough away from the old, plugged hole, the drillers can turn the drilling angle back to the vertical. This time they will place a metal casing in the hole as they drill through the salt layer, Trickett says.

With normal operating expenses of $15,000 or more a day at the site, however, this kind of delay is expensive. At another drilling site a few miles away where the Reuben Griffith #1, a gas find, a is now being tested, such problems developed last year that nearly 7,000 feet of hole was abandoned, the drill rig skidded over about 25 feet and a new hole was begun.

Trickett says much of Amoco's activity simply would not be economic except for passage of the Natural Gas Policy Act in 1978, which has led to much higher prices for newly discovered gas. Even the big well that will shortly be supplying State College might not otherwise have been committed to production.

The natural buyer of gas from that well was the pipeline compnay supplying State College, since the line passed only a short distance from the well. But gas from the Tuscarora sandstone contains large amounts of nitrogen, the unburnable gas that makes up a large part of the air we breathe. Since the single well would by supplying the entire area most of the year, there was no higher quality gas in the line with which to mix that from the well.

Therefore, after spending several million dollars on the well, Amoco has had to pay another $3.8 million to construct a small, custom-built gas processing plant at the site to remove the nitrogen.