Limestone is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of CaCO3. Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as the accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life.
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2Si2O5(OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. Shale is characterized by its tendency to split into thin layers (laminae) less than one centimeter in thickness. This property is called fissility. Shale is the most common sedimentary rock.
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment, and may be composed of geological detritus (minerals) or biological detritus. The geological detritus originated from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement, which are called agents of denudation. Biological detritus was formed by bodies and parts of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies. Sedimentation may also occur as dissolved minerals precipitate from water solution.
Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.
Petroleum 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.
Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation, transport, deposition and diagenesis. Sedimentologists apply their understanding of modern processes to interpret geologic history through observations of sedimentary rocks and sedimentary structures.
Kerogen is solid, insoluble organic matter in sedimentary rocks. Comprising an estimated 1016 tons of carbon, it is the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. It is insoluble in normal organic solvents and it does not have a specific chemical formula. Upon heating, kerogen converts in part to liquid and gaseous hydrocarbons. Petroleum and natural gas form from kerogen. Kerogen may be classified by its origin: lacustrine (e.g., algal), marine (e.g., planktonic), and terrestrial (e.g., pollen and spores). The name "kerogen" was introduced by the Scottish organic chemist Alexander Crum Brown in 1906, derived from the Greek for "wax birth" (Greek: κηρός "wax" and -gen, γένεση "birth").
The abiogenic petroleum origin proposes that most of earth's petroleum and natural gas deposits were formed inorganically. Mainstream theories about the formation of hydrocarbons on earth point to an origin from the decomposition of long-dead organisms, though the existence of hydrocarbons on extraterrestrial bodies like Saturn's moon Titan indicates that hydrocarbons are sometimes naturally produced by inorganic means. A historical overview of theories of the abiogenic origins of hydrocarbons has been published.
Oceanic anoxic events or anoxic events (anoxia conditions) describe periods wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O2), creating toxic, euxinic (anoxic and sulfidic) waters. Although anoxic events have not happened for millions of years, the geologic record shows that they happened many times in the past. Anoxic events coincided with several mass extinctions and may have contributed to them. These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating. On the other hand, there are widespread, various black-shale beds from the mid-Cretaceous which indicate anoxic events but are not associated with mass extinctions. Many geologists believe oceanic anoxic events are strongly linked to the slowing of ocean circulation, climatic warming, and elevated levels of greenhouse gases. Researchers have proposed enhanced volcanism (the release of CO2) as the "central external trigger for euxinia."
The sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Steps of the sulfur cycle are:
Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than 1⁄16 mm and are too small to study readily in the field. At first sight, the rock types appear quite similar; however, there are important differences in composition and nomenclature.
In petroleum geology, source rock is rock which has generated hydrocarbons or which could generate hydrocarbons. Source rocks are one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including deep water marine, lacustrine and deltaic. Oil shale can be regarded as an organic-rich but immature source rock from which little or no oil has been generated and expelled. Subsurface source rock mapping methodologies make it possible to identify likely zones of petroleum occurrence in sedimentary basins as well as shale gas plays.
Shallow water marine environment refers to the area between the shore and deeper water, such as a reef wall or a shelf break. This environment is characterized by oceanic, geological and biological conditions, as described below. The water in this environment is shallow and clear, allowing the formation of different sedimentary structures, carbonate rocks, coral reefs, and allowing certain organisms to survive and become fossils.
Pyrobitumen is a type of solid, amorphous organic matter. Pyrobitumen is mostly insoluble in carbon disulfide and other organic solvents as a result of molecular cross-linking, which renders previously soluble organic matter insoluble. Not all solid bitumens are pyrobitumens, in that some solid bitumens are soluble in common organic solvents, including CS
2, dichloromethane, and benzene-methanol mixtures.
The Persian Gulf Basin is found between the Eurasian and the Arabian Plate. The Persian Gulf is described as a shallow marginal sea of the Indian Ocean that is located between the south western side of Iran and the Arabian Peninsula and south and southeastern side of Oman and the United Arab Emirates. Other countries that border the Persian Gulf basin include; Saudi Arabia, Qatar, Kuwait, Bahrain and Iraq. The Persian Gulf extends a distance of 1,000 km (620 mi) with an area of 240,000 km2 (93,000 sq mi). The Persian Gulf basin is a wedge-shaped foreland basin which lies beneath the western Zagros thrust and was created as a result of the collision between the Arabian and Eurasian plates.
The Tarfaya Basin is a structural basin located in southern Morocco that extends westward into the Moroccan territorial waters in the Atlantic Ocean. The basin is named for the city of Tarfaya located near the border of Western Sahara, a region governed by the Kingdom of Morocco. The Canary Islands form the western edge of the basin and lie approximately 100 km to the west.
The Delta Field is located offshore from Nigeria on Oil Mining Leases (OML) 49 and 95. This is located within the Niger Delta Basin and sits in 12 feet of water. In 1965, the Delta 1 well was completed and the Delta Field opened in 1968 for production.
Bituminite is an autochthonous maceral that is a part of the liptinite group in lignite, that occurs in petroleum source rocks originating from organic matter such as algae which has undergone alteration or degradation from natural processes such as burial. It occurs as fine-grained groundmass, laminae or elongated structures that appear as veinlets within horizontal sections of lignite and bituminous coals, and also occurs in sedimentary rocks. Its occurrence in sedimentary rocks is typically found surrounding alginite, and parallel along bedding planes. Bituminite is not considered to be bitumen because its properties are different from most bitumens. It is described to have no definite shape or form when present in bedding and can be identified using different kinds of visible and fluorescent lights. There are three types of bituminite: type I, type II and type III, of which type I is the most common. The presence of bituminite in oil shales, other oil source rocks and some coals plays an important factor when determining potential petroleum-source rocks.
The Greater Green River Basin (GGRB) is a 21,000 square mile basin located in Southwestern Wyoming. The Basin was formed during the Cretaceous period sourced by underlying Permian and Cretaceous deposits. The GGRB is host to many anticlines created during the Laramide Orogeny trapping many of its hydrocarbon resources. It is bounded by the Rawlins Uplift, Uinta Mountains, Sevier overthrust belt, Sierra Madre Mountains, and the Wind River Mountain Range. The Greater Green River Basin is subdivided into four smaller basins, the Green River Basin, Great Divide Basin, Washakie Basin, and Sand Wash Basin. Each of these possesses hydrocarbons that have been economically exploited. There are 303 named fields throughout the basin, the majority of which produce natural gas; the largest of these gas fields is the Jonah Field.
The Officer Basin is an intracratonic sedimentary basin that covers roughly 320,000 km2 along the border between southern and western Australia. Exploration for hydrocarbons in this basin has been sparse, but the geology has been examined for its potential as a hydrocarbon reservoir. This basin's extensive depositional history, with sedimentary thicknesses exceeding 6 km and spanning roughly 350 Ma during the Neoproterozoic, make it an ideal candidate for hydrocarbon production.
Sandstone with fossil shells
