Digging Deep

Much of what is Texas today was under ancient seas millions of years ago. Geologists know this because many rock layers containing fossil remains of marine life have been found throughout the state. Millions of microscopic marine plants and animals lived in the seas and oceans, eventually died and then settled on the ocean floor. The dead plants and animals were often buried by sand and other sediment, much like the bread fossil. Heat from beneath the earth's crust "cooked" the plant and animal remains forming oil and natural gas deposits within the rock layers. This is why oil that is produced in the sedimentary rock is called a "fossil fuel."

Today, oil and natural gas companies drill holes in the subsurface rock looking for crude oil and natural gas deposits. A core sample is a way for geologists to gain evidence about rocks found deep in the ground. Most core samples are extracted from a special type of drill with a hollow steel tube called a core drill. In the petroleum industry, core samples are used to find areas with sedimentary rock, which are good source rocks for crude oil and natural gas. These rock formations are sometimes in depths of five miles or more. As oil and natural gas are being depleted from existing wells, geologists are constantly searching for undiscovered sources of petroleum. Many scientists believe that oil and natural gas are possibly forming under the ocean floor. However, the organic matter will not form petroleum until millions of years have passed. That is why oil and natural gas are considered to be non-renewable energy resources.

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