Is There Oil in Your Backyard?
While the glory days of petroleum in the northeast are probably over, this region was, for several decades in the late 1800's, the most important oil-producing region in the world. Known since the1860's as the Oil Regions, western Pennsylvania (and the adjacent area in southwestern New York) has an oil history that predates European settlement. Many of the oil reservoirs are very near the surface, and the multiple fractures in the rocks allow for oil to seep to the surface. Native Americans for centuries have used the oil as a medicine and for waterproofing of canoes as well other objects. The first discovery of oil by Europeans from North America probably came in 1627 by a Franciscan missionary travelling near Cuba, New York. In 1821, William Hart drilled for and discovered gas at Fredonia, New York, near the shores of Lake Erie, making him the first to do so. A primitive pipeline was constructed from hollowed-out logs, and soon the entire main street was illuminated by natural gas.
The global petroleum industry first got its start in the Appalachian Basin in northwestern Pennsylvania. In Titusville, Pennsylvania, the first well drilled with the intent of finding oil hit "black gold" in the summer of 1859, at a depth of only 69 1/2 feet (21.18 meters), forever changing the course of modern history. (learn more about it) All of the oil and gas found thus far in the Northeast originates in the Paleozoic rocks of the Appalachian Basin of western Pennsylvania and New York, with limited hydrocarbons coming from the Valley and Ridge province of western Maryland and south central Pennsylvania. The Appalachian Basin extends from northern New York all the way south into northern Georgia and Alabama.
Think of a basin as a broad region where sediments were deposited in the geologic past, even if no sediments are being deposited there today. For example, the Appalachian Basin is currently high above sea level, located largely in mountainous terrain, and is no longer a basin. However, 300 million years ago, thick accumulations of mud, sand, and organic material settled at the bottom of a shallow sea that was once located here. The alteration of these sediments, and the "cooking" (maturation) of organic-rich muds is what gives us oil, natural gas and coal.
Most of the reservoirs in Pennsylvania are Devonian and Mississippian aged sandstones. These rocks are part of the western extent of the Catskill Delta, a thick wedge of sandstones, siltstones and shales that were deposited into a shallow sea beginning 400 million years ago. The source of these deposits came from tall mountains, located at this time near the current Hudson River of New York State. Highly porous sandstones became interbedded with shales in western Pennsylvania and New York. In many cases, the shales act as both source rock and trap rock for the hydrocarbons. The main trap types are structural and stratigraphic. Anticlines run parallel to the axis of the Appalachian Basin itself, trapping oil and natural gas. Stratigraphic traps are formed by alternating shale and sandstone layers. Some of these sandstone layers are not continuous and are trapped on all sides by shale. These form "pods" of sand known as "lenses", and act as an effective hydrocarbon trap in the Appalachian Basin and elsewhere. Pennsylvania oil is very high quality crude, with considerably less impurities than most oil produced in the United States. Because less work in the refineries is necessary before the product hits the market, Pennsylvania oil is slightly more valuable than oil from most other places.
The most prolific oil field in the region is the Bradford oil field in northwestern Pennsylvania (McKean county) and extending into extreme southwestern New York (Cattaraugus County). Here, the oil comes from the upper Devonian Bradford sands, which are about 1000 feet (~300 meters) below ground and up to 90 feet in thickness. These reservoir sandstones and siltstones are not only thick, but are much more horizontally widespread than other reservoir rocks in the region. The trap is mostly stratigraphic (the reservoir sands are actually part of an ancient river delta that was surrounded by mud), though it does rest at the crest of an anticline. In 1881, this field produced an incredible 83% of the USA's total oil output. Since its discovery in 1871, Bradford field has produced more than 1/2 billion barrels of oil.
The Paleontological Research Institution