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Hydrocarbon 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. Areas thought to contain hydrocarbons are initially subjected to a gravity survey, magnetic survey, passive seismic or regional seismic reflection surveys to detect large-scale features of the sub-surface geology. Features of interest (known as leads) are subjected to more detailed seismic surveys which work on the principle of the time it takes for reflected sound waves to travel through matter (rock) of varying densities and using the process of depth conversion to create a profile of the substructure. Finally, when a prospect has been identified and evaluated and passes the oil company's selection criteria, an exploration well is drilled in an attempt to conclusively determine the presence or absence of oil or gas. Offshore the risk can be reduced by using electromagnetic methods [1]
Oil exploration is an expensive, high-risk operation. Offshore and remote area exploration is generally only undertaken by very large corporations or national governments. Typical shallow shelf oil wells (e.g. North Sea) cost US$10 – 30 million, while deep water wells can cost up to US$100 million plus. Hundreds of smaller companies search for onshore hydrocarbon deposits worldwide, with some wells costing as little as US$100,000.
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A prospect is a potential trap which geologists believe may contain hydrocarbons. A significant amount of geological, structural and seismic investigation must first be completed to redefine the potential hydrocarbon drill location from a lead to a prospect. Four geological factors have to be present for a prospect to work and if any of them fail neither oil nor gas will be present.
Hydrocarbon exploration is a high risk investment and risk assessment is paramount for successful project portfolio management. Exploration risk is a difficult concept and is usually defined by assigning confidence to the presence of the imperative geological factors, as discussed above. This confidence is based on data and/or models and is usually mapped on Common Risk Segment Maps (CRS Maps). High confidence in the presence of imperative geological factors is usually coloured green and low confidence coloured red. [2] Therefore, these maps are also called Traffic Light Maps, while the full procedure is often referred to as Play Fairway Analysis (PFA). [3] The aim of such procedures is to force the geologist to objectively assess all different geological factors. Furthermore, it results in simple maps that can be understood by non-geologists and managers to base exploration decisions on.
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Petroleum resources are typically owned by the government of the host country. In the United States, most onshore (land) oil and gas rights (OGM) are owned by private individuals, in which case oil companies must negotiate terms for a lease of these rights with the individual who owns the OGM. Sometimes this is not the same person who owns the land surface. In most nations the government issues licences to explore, develop and produce its oil and gas resources, which are typically administered by the oil ministry. There are several different types of licence. Oil companies often operate in joint ventures to spread the risk; one of the companies in the partnership is designated the operator who actually supervises the work.
Resources are hydrocarbons which may or may not be produced in the future. A resource number may be assigned to an undrilled prospect or an unappraised discovery. Appraisal by drilling additional delineation wells or acquiring extra seismic data will confirm the size of the field and lead to project sanction. At this point the relevant government body gives the oil company a production licence which enables the field to be developed. This is also the point at which oil reserves and gas reserves can be formally booked.
Oil and gas reserves are defined as volumes that will be commercially recovered in the future. Reserves are separated into three categories: proved, probable, and possible. To be included in any reserves category, all commercial aspects must have been addressed, which includes government consent. Technical issues alone separate proved from unproved categories. All reserve estimates involve some degree of uncertainty.
Proved oil and gas reserves are those quantities of oil and gas, which, by analysis of geoscience and engineering data, can be estimated with reasonable certainty to be economically producible—from a given date forward, from known reservoirs, and under existing economic conditions, operating methods, and government regulations—prior to the time at which contracts providing the right to operate expire, unless evidence indicates that renewal is reasonably certain, regardless of whether deterministic or probabilistic methods are used for the estimation. The project to extract the hydrocarbons must have commenced or the operator must be reasonably certain that it will commence the project within a reasonable time. [8]
The term 1P is frequently used to denote proved reserves; 2P is the sum of proved and probable reserves; and 3P the sum of proved, probable, and possible reserves. The best estimate of recovery from committed projects is generally considered to be the 2P sum of proved and probable reserves. Note that these volumes only refer to currently justified projects or those projects already in development. [9]
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Oil and gas reserves are the main asset of an oil company. Booking is the process by which they are added to the balance sheet.
In the United States, booking is done according to a set of rules developed by the Society of Petroleum Engineers (SPE). The reserves of any company listed on the New York Stock Exchange have to be stated to the U.S. Securities and Exchange Commission. Reported reserves may be audited by outside geologists, although this is not a legal requirement.
In Russia, companies report their reserves to the State Commission on Mineral Reserves (GKZ).[ citation needed ]
Petroleum engineering is a field of engineering concerned with the activities related to the production of hydrocarbons, which can be either crude oil or natural gas. Exploration and production are deemed to fall within the upstream sector of the oil and gas industry. Exploration, by earth scientists, and petroleum engineering are the oil and gas industry's two main subsurface disciplines, which focus on maximizing economic recovery of hydrocarbons from subsurface reservoirs. Petroleum geology and geophysics focus on provision of a static description of the hydrocarbon reservoir rock, while petroleum engineering focuses on estimation of the recoverable volume of this resource using a detailed understanding of the physical behavior of oil, water and gas within porous rock at very high pressure.
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.
An 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. Creating the wells can be an expensive process, costing at least hundreds of thousands of dollars, and costing much more when in hard to reach areas, e.g., when creating offshore oil platforms. The process of modern drilling for wells first started in the 19th century, but was made more efficient with advances to oil drilling rigs during the 20th century.
The Mumbai High Field, formerly called the Bombay High Field, is an offshore oilfield 176 km (109 mi) off the west coast of Mumbai, in Gulf of Cambay region of India, in about 75 m (246 ft) of water. The oil operations are run by India's Oil and Natural Gas Corporation (ONGC).
A salt dome is a type of structural dome formed when salt intrudes into overlying rocks in a process known as diapirism. Salt domes can have unique surface and subsurface structures, and they can be discovered using techniques such as seismic reflection. They are important in petroleum geology as they can function as petroleum traps.
North Sea oil is a mixture of hydrocarbons, comprising liquid petroleum and natural gas, produced from petroleum reservoirs beneath the North Sea.
Oil in place (OIP) (not to be confused with original oil-in-place (OOIP)) is a specialist term in petroleum geology that refers to the total oil content of an oil reservoir. As this quantity cannot be measured directly, it has to be estimated from other parameters measured prior to drilling or after production has begun.
The geology of the Falkland Islands is described in several publications. The Falkland Islands are located on a projection of the Patagonian continental shelf. In ancient geological time this shelf was part of Gondwana, which around 400 million years ago broke from what is now Africa and drifted westwards relative to Africa. Studies of the seabed surrounding the islands indicated the possibility of oil. Intensive exploration began in 1996, although there had been some earlier seismic surveys in the region.
A 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 is created in surrounding rock by the presence of high heat and pressure in the Earth's crust.
A petroleum geologist is an earth scientist who works in the field of petroleum geology, which involves all aspects of oil discovery and production. Petroleum geologists are usually linked to the actual discovery of oil and the identification of possible oil deposits, gas caps, or leads. It can be a very labor-intensive task involving several different fields of science and elaborate equipment. Petroleum geologists look at the structural and sedimentary aspects of the stratum/strata to identify possible oil traps or tight shale plays.
Petroleum 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. Extraction of petroleum can be dangerous and have led to oil spills.
Exploration for petroleum in the Arctic is expensive and challenging both technically and logistically. In the offshore, sea ice can be a major factor. There have been many discoveries of oil and gas in the several Arctic basins that have seen extensive exploration over past decades but distance from existing infrastructure has often deterred development. Development and production operations in the Arctic offshore as a result of exploration have been limited, with the exception of the Barents and Norwegian seas. In Alaska, exploration subsequent to the discovery of the Prudhoe Bay oilfield has focussed on the onshore and shallow coastal waters.
Proven reserves is a measure of fossil fuel energy reserves, such as oil and gas reserves and coal reserves. It is defined as the "[q]uantity of energy sources estimated with reasonable certainty, from the analysis of geologic and engineering data, to be recoverable from well established or known reservoirs with the existing equipment and under the existing operating conditions." A reserve is considered proven if it is probable that at least 90% of the resource is recoverable by economically profitable means.
The Sirte Basin is a late Mesozoic and Cenozoic triple junction continental rift along northern Africa that was initiated during the late Jurassic Period. It borders a relatively stable Paleozoic craton and cratonic sag basins along its southern margins. The province extends offshore into the Mediterranean Sea, with the northern boundary drawn at the 2,000 meter (m) bathymetric contour. It borders in the north on the Gulf of Sidra and extends south into northern Chad.
The Sarir Field was discovered in southern Cyrenaica during 1961 and is considered to be the largest oil field in Libya, with estimated oil reserves of 12 Gbbl (1.9 km3). Sarir is operated by the Arabian Gulf Oil Company (AGOCO), a subsidiary of the state-owned National Oil Corporation (NOC).
Heavy oil production is a developing technology for extracting heavy oil in industrial quantities. Estimated reserves of heavy oil are over 6 trillion barrels, three times that of conventional oil and gas.
A National Data Repository (NDR) is a data bank that seeks to preserve and promote a country's natural resources data, particularly data related to the petroleum exploration and production (E&P) sector.
The Bolivar Coastal Fields (BCF), also known as the Bolivar Coastal Complex, is located on the eastern margin of Lake Maracaibo, Venezuela. Bolivar Coastal Field is the largest oil field in South America with its 6,000-7,000 wells and forest of related derricks, stretches thirty-five miles along the north-east coast of Lake Maracaibo. They form the largest oil field outside of the Middle East and contain mostly heavy oil with a gravity less than 22 degrees API. Also known as the Eastern Coast Fields, Bolivar Coastal Oil Field consists of Tía Juana, Lagunillas, Bachaquero, Ceuta, Motatán, Barua and Ambrosio. The Bolivar Coast field lies in the Maracaibo dry forests ecoregion, which has been severely damaged by farming and ranching as well as oil exploitation. The oil field still plays an important role in production from the nation with approximately 2.6 million barrels of oil a day. It is important to note that the oil and gas industry refers to the Bolivar Coastal Complex as a single oilfield, in spite of the fact that the oilfield consists of many sub-fields as stated above.
Oil and gas reserves denote discovered quantities of crude oil and natural gas 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 are likely sub-commercial and may still be under appraisal with the potential to be technically recoverable once commercially established. Natural gas is frequently associated with oil directly and gas reserves are commonly quoted in barrels of oil equivalent (BoE). Consequently, both oil and gas reserves, as well as resource estimates, follow the same reporting guidelines, and are referred to collectively hereinafter as oil & gas.
Unconventional reservoirs, or unconventional resources are accumulations where oil & gas phases are tightly bound to the rock fabric by strong capillary forces, requiring specialised measures for evaluation and extraction.
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