Нефтяные и газовые скважины: история, добыча и экологические проблемы.

Well drilled to extract crude oil and/or gas

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 and if necessary equipped with extraction devices such as pumpjacks. Creating the wells can be an expensive process, costing at least hundreds of thousands of dollars, and costing much more when in difficult to access locations, e. g., offshore. The process of modern drilling for wells first started in the 19th century but was made more efficient with advances to oil drilling rigs and technology during the 20th century. Wells are frequently sold or exchanged between different oil and gas companies as an asset – in large part because during falls in the price of oil and gas, a well may be unproductive, but if prices rise, even low production wells may be economically valuable. Moreover, new methods, such as hydraulic fracturing (a process of injecting gas or liquid to force more oil or natural gas production) have made some wells viable. However, peak oil and climate policy surrounding fossil fuels have made fewer of these wells and costly techniques viable. However, a large number of neglected or poorly maintained wellheads is a large environmental issue: they may leak methane or other toxic substances into local air, water and soil systems. This pollution often becomes worse when wells are abandoned or orphaned – i. e., where wells no longer economically viable are no longer maintained by their (former) owners. A 2020 estimate by Reuters suggested that there were at least 29 million abandoned wells internationally, creating a significant source of greenhouse gas emissions worsening climate change.

The earliest known oil wells were drilled in China in 347 CE. These wells had depths of up to about and were drilled using bits attached to bamboo poles. The oil was burned to evaporate brine producing salt. By the 10th century, extensive bamboo pipelines connected oil wells with salt springs. The ancient records of China and Japan are said to contain many allusions to the use of natural gas for lighting and heating. Petroleum was known as burning water in Japan in the 7th century. According to Kasem Ajram, petroleum was distilled by the Persian alchemist Muhammad ibn Zakarīya Rāzi (Rhazes) in the 9th century, producing chemicals such as kerosene in the alembic (al ambiq), and which was mainly used for kerosene lamps. Arab and Persian chemists also distilled crude oil in order to produce flammable products for military purposes. Through Islamic Spain, distillation became available in Western Europe by the 12th century. Some sources claim that from the 9th century, oil fields were exploited in the area around modern Baku, Azerbaijan, to produce naphtha for the petroleum industry. These places were described by Marco Polo in the 13th century, who described the output of those oil wells as hundreds of shiploads. When Marco Polo in 1264 visited Baku, on the shores of the Caspian Sea, he saw oil being collected from seeps. He wrote that "on the confines toward Geirgine there is a fountain from which oil springs in great abundance, in as much as a hundred shiploads might be taken from it at one time." In 1846, Baku (settlement Bibi Heybat) the first ever well was drilled with percussion tools to a depth of for oil exploration. In 1846–1848, the first modern oil wells were drilled on the Absheron Peninsula north east of Baku, by Russian engineer Vasily Semyonov applying the ideas of Nikolay Voskoboynikov. Ignacy Łukasiewicz, a Polish pharmacist and petroleum industry pioneer drilled one of the world's first modern oil wells in 1854 in Polish village Bóbrka, Krosno County who in 1856 built one of the world's first oil refineries. In North America, the first commercial oil well entered operation in Oil Springs, Ontario in 1858, while the first offshore oil well was drilled in 1896 in the Summerland Oil Field on the California Coast. The earliest oil wells in modern times were drilled percussively, by repeatedly raising and dropping a bit on the bottom of a cable into the borehole. In the 20th century, cable tools were largely replaced with rotary drilling, which could drill boreholes to much greater depths and in less time. The record depth Kola Borehole used a mud motor while drilling to achieve a depth of over
Until the 1970s, most oil wells were essentially vertical, although lithological variations cause most wells to deviate at least slightly from true vertical (see deviation survey). However, modern directional drilling technologies allow for highly deviated wells that can, given sufficient depth and with the proper tools, actually become horizontal. This is of great value as the reservoir rocks that contain hydrocarbons are usually horizontal or nearly horizontal; a horizontal wellbore placed in a production zone has more surface area in the production zone than a vertical well, resulting in a higher production rate. The use of deviated and horizontal drilling has also made it possible to reach reservoirs several kilometers or miles away from the drilling location (extended reach drilling), allowing for the production of hydrocarbons located below locations that are difficult to place a drilling rig on, environmentally sensitive, or populated.

Before a well is drilled, a geologic target is identified by a geologist or geophysicist to meet the objectives of the well. For a production well, the target is picked to optimize production from the well and manage reservoir drainage. For an exploration or appraisal well, the target is chosen to confirm the existence of a viable hydrocarbon reservoir or to learn its extent. For an injection well, the target is selected to locate the point of injection in a permeable zone that may support disposing of water or gas and/or pushing hydrocarbons into nearby production wells. The target (the endpoint of the well) will be matched with a surface location (the starting point of the well), and a trajectory between the two will be designed. There are many considerations to take into account when designing the trajectory such as the clearance from any nearby wells (anti collision) or future wellpaths. When the well path is identified, a team of geoscientists and engineers will develop a set of presumed characteristics of the subsurface path that will be drilled through to reach the target. These properties may include lithology pore pressure, fracture gradient, wellbore stability, porosity and permeability. These assumptions are used by a well engineering team designing the casing and completion programs for the well. Also considered in the detailed planning are selection of the drill bits, Bottom hole assembly, and the drilling fluid Step by step procedures are written to provide guidelines for executing the well in a safe and cost efficient manner. With the interplay with many of the elements in a well's design, trajectories and designs often go through several iterations before the plan is finalized.

After drilling and casing the well, it must be 'completed'. Completion is the process in which the well is prepared to produce oil or gas. In a cased hole completion, small perforations are made in the portion of the casing across the production zone, to provide a path for the oil to flow from the surrounding rock into the production tubing. In open hole completion, often a 'sand screen' or 'gravel pack' is installed in the last drilled but uncased reservoir section. These maintain structural integrity of the wellbore in the absence of casing, while still allowing flow from the reservoir into the borehole. Screens also control the migration of formation sands into production tubulars, which can lead to washouts and other problems, particularly from unconsolidated sand formations. After a flow path is made, acids and fracturing fluids may be pumped into the well to fracture, clean, or otherwise prepare and stimulate the reservoir rock to allow optimal production of hydrocarbons into the wellbore. Usually the area above the producing section of the well is packed off inside the casing, and connected to the surface via a smaller diameter pipe called tubing. This arrangement provides a redundant barrier to leaks of hydrocarbons as well as allowing damaged sections to be replaced. Also, the smaller cross sectional area of the tubing gives reservoir fluids an increased velocity to minimize liquid fallback that would create additional back pressure, and shields the casing from corrosive well fluids. In many wells, the natural pressure of the subsurface reservoir is high enough for the oil or gas to flow to the surface. However, this is not always the case, especially in depleted fields where the pressures have been lowered by other producing wells, or in low permeability oil reservoirs. Installing a smaller diameter tubing may be enough to help the production, but artificial lift methods may also be needed. Common solutions include surface pump jacks, downhole hydraulic pumps or gas lift assistance. Many new systems in recent years have been introduced for well completion. Multiple packer systems with frac ports or port collars in an all in one system have cut completion costs and improved production, especially in the case of horizontal wells. These new systems allow casing to run into the lateral zone equipped with proper packer/frac port placement for optimal hydrocarbon recovery.

The production stage is the most important stage of a well's life: when the oil and gas are produced. By this time, the oil rigs and workover rigs used to drill and complete the well will have moved off the wellbore, and the top is usually outfitted with a collection of valves called a Christmas tree or production tree. These valves regulate pressures, control flows, and allow access to the wellbore in case further completion work is needed. From the outlet valve of the production tree, the flow can be connected to a distribution network of pipelines and tanks to supply the product to refineries, natural gas compressor stations, or oil export terminals. As long as the pressure in the reservoir remains high enough, the production tree is all that is required to produce the well. If the pressure depletes and it is considered economically viable, an artificial lift method mentioned in the completions section can be employed. Workovers are often necessary in older wells, which may need smaller diameter tubing, scale or paraffin removal, acid matrix jobs, or completion in new zones of interest in a shallower reservoir. Such remedial work can be performed using workover rigs – also known as pulling units, completion rigs or "service rigs" – to pull and replace tubing, or by the use of well intervention techniques utilizing coiled tubing. Depending on the type of lift system and wellhead a rod rig or flushby can be used to change a pump without pulling the tubing. Enhanced recovery methods such as water flooding, steam flooding, or CO2 flooding may be used to increase reservoir pressure and provide a "sweep" effect to push hydrocarbons out of the reservoir. Such methods require the use of injection wells (often chosen from old production wells in a carefully determined pattern), and are used when facing problems with reservoir pressure depletion or high oil viscosity, sometimes being employed early in a field's life. In certain cases – depending on the reservoir's geomechanics – reservoir engineers may determine that ultimate recoverable oil may be increased by applying a waterflooding strategy early in the field's development rather than later. Such enhanced recovery techniques are often called Secondary or "tertiary recovery".

The impacts of oil exploration and drilling are often irreversible, particularly for wildlife.