Petroleum reservoirA petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence of high heat and pressure in the Earth's crust. Petroleum reservoirs are broadly classified as conventional and unconventional reservoirs.
Oil wellAn oil well is a drillhole boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas may be termed a gas well. Wells are created by drilling down into an oil or gas reserve that is then mounted with an extraction device such as a pumpjack which allows extraction from the reserve.
PetroleumPetroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name petroleum covers both naturally occurring unprocessed crude oil and petroleum products that consist of refined crude oil. A fossil fuel, petroleum is formed when large quantities of dead organisms, mostly zooplankton and algae, are buried underneath sedimentary rock and subjected to both prolonged heat and pressure.
Unconventional (oil & gas) reservoirUnconventional (oil & gas) reservoirs, or unconventional resources (resource plays) are accumulations where oil & gas phases are tightly bound to the rock fabric by strong capillary forces, requiring specialised measures for evaluation and extraction. Petroleum reservoir Oil and gas are generated naturally at depths of around 4 or 5 kms below Earth’s surface. Being lighter than the water, which saturates rocks below the water table, the oil and gas percolate up through aquifer pathways towards Earth's surface (through time) by buoyancy.
FrackingFracking (also known as hydraulic fracturing, fracing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of bedrock formations by a pressurized liquid. The process involves the high-pressure injection of "fracking fluid" (primarily water, containing sand or other proppants suspended with the aid of thickening agents) into a wellbore to create cracks in the deep-rock formations through which natural gas, petroleum, and brine will flow more freely.
Extraction of petroleumPetroleum is a fossil fuel that can be drawn from beneath the earth's surface. Reservoirs of petroleum are formed through the mixture of plants, algae, and sediments in shallow seas under high pressure. Petroleum is mostly recovered from oil drilling. Seismic surveys and other methods are used to locate oil reservoirs. Oil rigs and oil platforms are used to drill long holes into the earth to create an oil well and extract petroleum. After extraction, oil is refined to make gasoline and other products such as tires and refrigerators.
MethaneMethane (USˈmɛθeɪn , UKˈmiːθeɪn ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it poses technical challenges due to its gaseous state under normal conditions for temperature and pressure. Naturally occurring methane is found both below ground and under the seafloor and is formed by both geological and biological processes.
Oil sandsOil sands, tar sands, crude bitumen, or bituminous sands, are a type of unconventional petroleum deposit. Oil sands are either loose sands or partially consolidated sandstone containing a naturally occurring mixture of sand, clay, and water, soaked with bitumen, a dense and extremely viscous form of petroleum. Significant bitumen deposits are reported in Canada, Kazakhstan, Russia, and Venezuela. The estimated worldwide deposits of oil are more than ; Proven reserves of bitumen contain approximately 100 billion barrels, and total natural bitumen reserves are estimated at worldwide, of which , or 70.
Petroleum industryThe petroleum industry, also known as the oil industry or the oil patch, includes the global processes of exploration, extraction, refining, transportation (often by oil tankers and pipelines), and marketing of petroleum products. The largest volume products of the industry are fuel oil and gasoline (petrol). Petroleum is also the raw material for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, synthetic fragrances, and plastics.
Natural gasNatural gas (also called fossil gas, methane gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon dioxide, nitrogen, hydrogen sulfide, and helium are also usually present. Methane is colorless and odorless, and the second largest greenhouse gas contributor to global climate change after carbon dioxide.
Shale gasShale gas is an unconventional natural gas that is found trapped within shale formations. Since the 1990s a combination of horizontal drilling and hydraulic fracturing has made large volumes of shale gas more economical to produce, and some analysts expect that shale gas will greatly expand worldwide energy supply. Shale gas has become an increasingly important source of natural gas in the United States since the start of this century, and interest has spread to potential gas shales in the rest of the world.
KerogenKerogen is solid, insoluble organic matter in sedimentary rocks. It consists of a variety of organic materials, including dead plants, algae, and other microorganisms, that have been compressed and heated by geological processes. Altogether kerogen is estimated to contain 1016 tons of carbon. This makes it the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. The type of kerogen present in a particular rock formation depends the type of organic material that was originally present.
Peak oilPeak oil is the point in time when the maximum rate of global oil production is reached, after which production will begin an irreversible decline. It is related to the distinct concept of oil depletion; while global petroleum reserves are finite, the limiting factor is not whether the oil exists but whether it can be extracted economically at a given price. A secular decline in oil extraction could be caused both by depletion of accessible reserves and by reductions in demand that reduce the price relative to the cost of extraction, as might be induced to reduce carbon emissions.
Oil shaleOil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitutes inorganic substance and bitumens. Based on their deposition environment, oil shales are classified as marine, lacustrine and terrestrial oil shales. Oil shales differ from oil-bearing shales, shale deposits that contain petroleum (tight oil) that is sometimes produced from drilled wells.
Oil and gas reserves and resource quantificationOil and gas reserves denote discovered quantities of crude oil and natural gas (oil or gas fields) that can be profitably produced/recovered from an approved development. Oil and gas reserves tied to approved operational plans filed on the day of reserves reporting are also sensitive to fluctuating global market pricing. The remaining resource estimates (after the reserves have been accounted) are likely sub-commercial and may still be under appraisal with the potential to be technically recoverable once commercially established.
Enhanced oil recoveryEnhanced oil recovery (abbreviated EOR), also called tertiary recovery, is the extraction of crude oil from an oil field that cannot be extracted otherwise. Although the primary and secondary recovery techniques rely on the pressure differential between the surface and the underground well, enhanced oil recovery functions by altering the chemical composition of the oil itself in order to make it easier to extract. EOR can extract 30% to 60% or more of a reservoir's oil, compared to 20% to 40% using primary and secondary recovery.
Petroleum geologyPetroleum geology is the study of origin, occurrence, movement, accumulation, and exploration of hydrocarbon fuels. It refers to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil exploration). Petroleum geology is principally concerned with the evaluation of seven key elements in sedimentary basins: Source Reservoir Seal Trap Timing Maturation Migration In general, all these elements must be assessed via a limited 'window' into the subsurface world, provided by one (or possibly more) exploration wells.
Hydrocarbon explorationHydrocarbon exploration (or oil and gas exploration) is the search by petroleum geologists and geophysicists for deposits of hydrocarbons, particularly petroleum and natural gas, in the Earth's crust using petroleum geology. Visible surface features such as oil seeps, natural gas seeps, pockmarks (underwater craters caused by escaping gas) provide basic evidence of hydrocarbon generation (be it shallow or deep in the Earth). However, most exploration depends on highly sophisticated technology to detect and determine the extent of these deposits using exploration geophysics.
BitumenBitumen (ˈbɪtjʊmɪn, bɪˈtjuːmən,_baɪ-) is a sticky, black, highly viscous liquid or semi-solid form of petroleum. In the U.S., it is commonly referred to as asphalt. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used. The word is derived from the ancient Greek ἄσφαλτος ásphaltos. The largest natural deposit of bitumen in the world, estimated to contain 10 million tons, is the Pitch Lake in southwest Trinidad.
Fossil fuelA fossil fuel is a hydrocarbon-containing material such as coal, oil, and natural gas, formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. Fossil fuels may be burned to provide heat for use directly (such as for cooking or heating), to power engines (such as internal combustion engines in motor vehicles), or to generate electricity. Some fossil fuels are refined into derivatives such as kerosene, gasoline and propane before burning.
