This involves the evaluation of the earth's history, and comparison with other areas where gas and oil are known to be present. Once such an area is designated for exploration, the geologist begins to conduct more specific tests to determine the likelihood that gas and oil are indeed present in the area. He or she may study above ground rock formations to determine the precise area where the folding of layers may have caused traps to form. In areas where wells are already present, the geologist may study samples of rock that were taken from previous drillings, as well as information acquired from logs , or instruments lowered into wellbores to measure the properties of rock layers. Technology's Role in Exploration 0 ne of the most exciting and effective technological advances that has aided the geologist in finding gas deposits is seismology.
Seismology is the study of how sound or seismic waves move through the earth's crust.
It was first used to study earthquakes, and it still is today. However, it has also proved an invaluable tool for the geologist in studying the lower layers of the earth's crust without actually drilling into them. The idea behind seismology is that earthquakes, or other sources of vibrations in the crust interact with different kinds of rock differently so that by recording how a wave of vibration is reflected by a certain layer of rock, the geologist can make an educated guess regarding what kind of rock is present, and approximately how deep in the crust it can be found. A good analogy is the waves of energy from the source of the vibration react with different layers of rock much like bouncing a ball on different surfaces produces different results. If you bounce the same ball on concrete, and then on soft dirt or sand, the ball will bounce much higher after hitting the concrete than it will after hitting the dirt or sand.