One thing that is certain, however, is that the air pollution resulting from the combustion of fossil fuels such as petroleum and coal is of increasing concern to the inhabitants of planet Earth. Thus, the search for a non-polluting replacement energy source is one of the most important challenges faced by humankind.
One thing that is certain, however, is that the air pollution resulting from the combustion of fossil fuels such as petroleum and coal is of increasing concern to the inhabitants of planet Earth. Thus, the search for a non-polluting replacement energy source is one of the most important challenges faced by humankind.
The different properties of hydrocarbon compounds are determined by differences in the number and arrangement of hydrogen and carbon atoms they contain. Carbon is much heavier than hydrogen and thus the weight of the hydrocarbon molecule is predominantly determined by the number of carbon atoms.
This theory suggests that oil originated as the remains of countless organisms that either lived in the sea or were deposited there with mud and silt from prehistoric rivers and streams. The remains of these ancient plants and animals were transformed into oil and gas by bacterial action with heat and pressure resulting from deep burial beneath other sediments (Figure 2.1).
There are many references to asphalt in the Bible, including that it was used by Moses' mother to waterproof his cradle of bulrushes, and by Noah to caulk the Ark.
One thing that is certain, however, is that the air pollution resulting from the combustion of fossil fuels such as petroleum and coal is of increasing concern to the inhabitants of planet Earth. Thus, the search for a non-polluting replacement energy source is one of the most important challenges faced by humankind.
A sponge is a good example of a household object that is porous or in other words possesses porosity if we take a dry sponge and dip it in water, the sponge will soak up the water. The water that is soaked up is absorbed into pore spaces within the sponge. The sponge has porosity. If we now squeeze the sponge, we will close up some of these pore spaces and water will be forced out of the sponge
In sketch A above, the pore spaces are well connected allowing fluids to flow quite easily. This rock has good permeability. In sketch B, the pore spaces are largely isolated from one another giving this rock poor permeability. Sketch A may be some-what confusing as it appears that the grains are being held in free suspension with nothing to support them. Remember, ho w-ever, that this is just a simplified two dimensional sketch. The grains make contact with other grains somewhere out of the plane of the sketch.
During transport, the sedimentary particles become sorted by size and density. This means that the larger and heavier fragments will settle faster than the lighter ones. The very smallest particles (fine sand and mud particles) can be carried hundreds of kilometers out to sea before settling to the bottom in the quiet deeper waters. The larger pieces (sand, gravel and boulders) will be deposited closer to the shore such as along beaches.
Now we know how petroleum is formed in underground sedimentary rocks and how it migrates into underground traps. How geologists and geophysicists search for geologic structures to select location to drill for oil and gas accumulations. But how can you determine the elevations of a sandstone layer that is buried under 500 meters of rock? This is something we will address in Chapter 6. For now, we will imagine that you can shovel off the 500 meters of rock and walk around on top of the sandstone layer. Suppose you (with your surveyor) found that the top of the dome was at an elevation of – 400 meters (the minus sign indicates that an “elevation” below sea level). Then, if you walked 10 meters down the dome to an elevation of – 410 meters and started painting a line on the surface of the sandstone at that elevation, you'd find you would paint a line clear around the dome and end up back where you had started painting. The line you had painted would be the – 410 meter contour on the sandstone layer. Drop down another 10 meters and paint the – 420 meters contour. You will have a longer walk and use more paint this time. Nevertheless, keep dropping down and painting a line at each ten- meter elevation until the whole structure has been contoured. You will know that you have completed contouring the structure when the line you are painting no longer "closes" or in other words no longer comes back to the point at which you started painting it.