AboutKeith Patton Expertise I can answer questions concerning physical and historical geology, environmental geology/hydrology, environmental consulting, remote sensing/aerial photo interpretation, G&G computer applications, petroleum exploration, drilling, geochemistry, geochemical and microbiological prospecting, 3D reservoir modeling, computer mapping and drilling.I am not a geophysicist.
Experience I have 24 years experience split between the petroleum and environmental industries. I have served as an expert witness in remote sensing, developmental geologist, exploration geologist, enviromental project manager, and subject matter expert in geology and geophysical software development.
Organizations American Association of Petroleum Geologists
American Association of Photogrammetrists and Remote Sensing
Education/Credentials Bachelor and Master of Science
Registered Geologist in State of Texas
Question What funtion does crude oil fulfill before it is removed from the earth? Does it serve at all to help regulate temperature?
Answer I don't know of any purpose other than to provide a food source for hydrocarbon consuming microbes. Hydrocarbons do absorb some of the heat of the surrounding rocks at depth, but their total volume in a body of rock is miniscule in comparison to the whole volume of the crust.
Remember that hydrocarbons are diseminated in the PORES of a porous rock. It does not sit pooled in a cavern or underground lake. Pick up a brick or peice of pourous sandstone and place it in a bucket of water. Notice the bubbles forming on its surface and breaking free? That is called imibition. The water is moving into the pore spaces of the brick or sandstone and displacing the air. The rock is imbibing the water. Once the rock has become saturated with water it is in the same state as the oil filled reservoir rock. Now imagine you did the same thing with petroleum rather than water and you have the typical reservoir rock. A decent reservoir rock only has about 10% porosity. Higher porosities exist, but they are not the norm and present their own problems because when the oil is removed, the rock compacts causing the ground above to sink or subside as the hydrostatic pressure is released.
The rocks overlying the reservoir exert trememdous pressure on the underlying rock and the fluids they contain, be it brine, petroleum or natural gas. When the reservoir is pierced by a drill this pressure forces the oil or gas up in the classical "gusher" of oil under pressure blowing out of the well. We don't see those today unless an accident occurs because we now know how to prevent them and control the pressure in the well.
This pressure is how the oil is forced out of the tiny pore spaces. Some reservoirs are formed in porous rock like sandstones, others in fractured rocks like limestones. Limestone can be porous due to fractures and joints like you see in rocks in a road cut, or due to the porousity you see in reefs, but the reefs have been buried.
Remember too the reservoirs occur at depth ranging from thousands of feet to miles. Most of the shallow reservoirs (~1500 feet) were found decades ago and wells today are commonly >8000 feet or more. So the cost of wells has increased tremendously costing millions and off shore wells...forget about it. They can cost several million depending on the water depth and sea surface conditions.
Also only about 30 percent of the oil (or the fluid in the brick or sandstone in your experiment) is recoverable. the other 70% stays in the reservoir to await secondary or tertiary recovery methods if the producer can afford them. They are not cheap. They involve pumping CO2 or detergent into the reservoir to break the surface tension of the oil, to release it from the pours. To illistrate this, put your thumb and forefinger close together, put it under a drinking fountain or faucet and let the water run. Lift your finger, the small bit of water clinging between the space between your fingers is held there by surface tension or capillary action. This is the force that keeps the 70% in place.
