Petroleum Geology plays an important role in today's society. Petroleum Geologists are the men and women who know how to read the story told by the very earth beneath our feet in order to find oil and natural gas, which are vital resources in our lives. Politics and prices often overshadow the story of what happens before the oil and gas ever reaches the headlines.
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HIGHLIGHT NEWS
China has told Vietnam to immediately stop unilateral oil exploration in parts of the South China Sea and not harass Chinese fishing boats, raising tension in protracted maritime territorial disputes with its neighbours. more >
China has told Vietnam to immediately stop unilateral oil exploration in parts of the South China Sea and not harass Chinese fishing boats, raising tension in protracted maritime territorial disputes with its neighbours. more >
AAPG . VOLUME 97 . NUMBER 1 . JANUARY 2013
This paper presents a review of carbonate deposition in lacustrine and marine rift settings. These examples can be used to improve our understanding of the spatial distribution of lacustrine and restricted marine carbonate deposits in early rift settings at a variety of scales. more > |
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Origin of Oil and Gas
The crude oil and natural gas in use today originated from the solar energy synthesized by organic life hundreds of millions of years ago.
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Burial in Sedimentary Source Rock
Organic matter living in surface waters of rivers, oceans, and lakes is the major constituent from which crude oil and natural gas form. With continued deposition of sediment on top, organic remains become buried before they decay. These buried sediments with preserved organic remains can become source rocks for crude oil or natural gas. Temperature and Pressure Convert Organic Material to Oil and Gas As sediment is overlain by more sediment, the temperature and pressure of the buried material increased. As the temperature of the buried material reaches 150 degrees F, chemical reactions begin to transform the buried organic material into forms of hydrocarbon, one of which is crude oil. At burial temperatures greater than 300 degrees F, the chemical reactions convert the organic material, including crude oil, to natural gas. |
Migration in terms of Density and Volume
Crude oil and natural gas are less dense than the solid organic material from which they originate. Also, oil and especially gas occupy more volume than the solid organic material. The space in the source rock is insufficient to hold the oil and gas in place, so the oil and gas migrate out of the source rock and into the surrounding porous and permeable rock beds until it is stopped by a subsurface barrier. If a barrier is not encountered, then the oil and gas will escape to the surface.
Crude oil and natural gas are less dense than the solid organic material from which they originate. Also, oil and especially gas occupy more volume than the solid organic material. The space in the source rock is insufficient to hold the oil and gas in place, so the oil and gas migrate out of the source rock and into the surrounding porous and permeable rock beds until it is stopped by a subsurface barrier. If a barrier is not encountered, then the oil and gas will escape to the surface.
Reservoir Traps hold Oil and Gas in place
Eventually, the migrating oil and gas encounter an impermeable barrier and form an accumulation described as an oil and gas pool or field. Reservoir traps are generally characterized as structural traps, stratigraphic traps or a combination of the two. The tectonic folding of the earth’s layers into an anticline is an example of a structural trap. When the earth’s layers are lenticulated, or pinched out, the trap is called a stratigraphic trap. Sedimentary Reservoir Rocks Most oil and gas fields are found in sedimentary rocks like sandstone and limestone because they have the interconnected pore spaces needed for oil and gas to move through and accumulate in, thereby forming a pool or field. The two factors required for this process to |
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work are the pore space, called rock porosity, and the interconnectivity of the pore space, called rock permeability. The pore space determines the capacity of the pool and the permeability determines the productivity of the pool.
SI INTERNATIONAL!
GeoMyanmar 2012
The Myanmar Geosciences Society (MGS) is organizing GeoMyanmar 2012, the first International Conference of its kind ever to be held in Myanmar. The Conference is designed to be a forum for exchange of various geological perspectives on Myanmar in a regional context and is aimed to promote investment for E & P in petroleum and mineral resources sectors. The Conference is to be held for two full days from 0900 AM to 1700 PM with sponsored lunch from 1230PM to 1330PM on March 1 and 2, 2012 at Sedona Hotel in Yangon. more > |
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Petroleum GeologyPetroleum refers to any naturally occurring hydrocarbons that are found beneath the surface of the earth, no matter whether these hydrocarbons are solid, liquid or gas.
Mankind has used the various forms petroleum for centuries. The Babylonians used asphalt to pave paths and caulk boats, and the ancient Egyptians used tar to prepare their mummies. In fact, mummy is a derivation of the Arabic word for tar. Condensate was an essential ingredient of Greek fire, the secret weapon of Byzantium, and the ancient Chinese used natural gas to light their imperial palaces. These ancient cultures found petroleum by simply looking for oil seeps or gas seeps and hoping that an adequate source was nearby, but the search for oil and gas today is much more complicated. To find a convergence in the subsurface of the geologic elements necessary to form an oil or gas pool requires a careful blend of science and art. To discover what geometries and compositions the rocks might possess deep underground, geologists examine the rocks where they are exposed in surface outcrops, or they examine aerial photographs and satellite images when surface access is limited. Geologists also work closely with geophysicists to integrate seismic lines and other types of geophysical data into their interpretations. |
The collection of seismic data involves sending shock waves into the ground and measuring how long it takes for the subsurface rocks to reflect these waves back to the surface. The shock waves that are used today are usually generated by pounding the earth with giant vibrator trucks, but in the past geophysicists preferred to explode small dynamite charges in shallow holes. However, environmental restrictions in most places today prevent using explosives to collect seismic data.
When shock waves created by the vibrator trucks travel into the earth, boundaries between the rocks reflect the waves back, and the arrival times of the waves back at the surface are detected by listening devices called geophones. Computers then process the geophone data and convert it into seismic lines, which are nothing more than two-dimensional displays that resemble cross-sections. Seismic lines in the old days were just that two-dimensional lines created by laying the geophones out in single line. But today, the data is commonly collected as an intersecting |
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grid of seismic lines referred to as 3-D seismic volume. Data collected in this fashion may even be used to help create 3-D computer models of the underground geometries of the rocks.
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Geologic and geophysical clues are enticing, but drilling is the only way to learn if an oil or gas field really exists. Once a well is drilled, well logs yield data on the types of rock present and, most important, what fluids these rocks contain. The information interpreted from the logs is used to decision whether a well should be completed and used to produce oil and gas, or filled with cement and abandoned. The logs are also used to update the geologic models originally used to locate the well.
Today, the average wildcat well has only one chance in ten of finding an economic accumulation of hydrocarbons. A rank wildcat, if drilled in a frontier area, stands only one chance in forty of success. The odds are much better for a development or extension well, but nothing is a sure bet in the oil business. Thus, even though explorationists (oil and gas prospectors) of today have better tools than their ancient predecessors, luck remains a significant factor in the search for oil and gas. The reality is that most wildcats turn out to be dry holes, in fact about 82% of those drilled. Also, not every development well becomes a producer, which demonstrates that nothing is a "sure bet" in the oil industry. San Joaquin Valley!
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Schlumberger Petroleumgeology GeologicalSociety San Joaquin Valley Oil on my shoes
Schlumberger Petroleumgeology GeologicalSociety San Joaquin Valley Oil on my shoes