Oil well types, structure, construction and development phases.
An oil well is a mine roadway round section diameter mm 75-400, constructed without access to her person, intended for the production or exploration of oil and associated gas.
Oil production is one of the most important industries. Oil and products derived from natural resources that are the Foundation of modern life of every person on the planet, regardless of being developed directly in its native state or is imported. Extraction of this resource is carried out by means of drilling oil wells is a special mine workings in the form of a cylinder, narrow in diameter and very deep.
An oil well is one of the types of mines, with a round cross-section. The diameter of wells ranges from 75 to 400 mm. Feature generation in that it can’t penetrate the man, but, apart from wells, it also has the well and the mine, accessible to the workers. This hole is intended primarily for the extraction of oil, but also with their assistance of associated petroleum gasproduced in places deposits of “black gold”.
Most of the wells has a vertical structure, in rare cases, the drilling may be performed at a given angle.
The design of the oil well has three parts:
– the top – the mouth;
– lower slaughter;
– medium – barrelformed by going down the walls.
An oil well is a complex capital structure, whose construction is carried out in several stages:
Consistent drilling of rocks.
Removal of natural material resulting from drilling.
Additional work to strengthen the walls (held if necessary).
Direct extraction of oil from oil wells is also carried out in two ways:
– gush – if oil reservoirs have excess pressure, the hydrocarbons in the form of a fountain rise to the surface;
– injection into wells served by water, gas, mixtures of air and other substances and materials for the artificial creation of excess pressure.
Development of oil wells – long organizational process, requiring not only major investments but also of knowledge, skills and experience.
A distinctive feature of the oil well is the ratio of its diameter and length – the first parameter is always several times more. So, length is the distance from the ground the mouth to the bottom hole (the bottom part), measured on the axis of the barrel. The depth of oil wells is a projection of the length of the barrel on a vertical axis. If the development is carried out vertically, these indicators are identical, in other cases (inclined, curved boreholes) they differ from each other.
The first stage of oil production is considered in the design of future oil wells. Development design takes into account such requirements:
– ability to obtain free access to the bottom of the barrel all the necessary geophysical equipment;
– strong clamping of the walls of trunk, excluding its collapse;
– qualitative separation of passable layers, with the exception of possible blends of fossil and aquifers from the reservoir into the reservoir;
the existence of the possibility of sealing the mouth.
For breeds that are easily amenable to destruction by water, where often lies the oil, requiring additional strengthening of the trunks. In this case, the pattern of future oil wells varies slightly: close to the trunk added casing, concentrically located, i.e., their sizes may be different, but with a common center.
Construction – oil drilling happens in stages:
Drilling of the hole. Strikes well before the start of the resistant rocks, the average is 4-8 m. In the installed pipe and reinforcing it with rubble stone, poured concrete mortar, which fills up the space between the outside of the pipe and the soil. That is the direction.
The creation of the conductor. Represents a portion of the casing, which strengthened the next part of the well is new, deeper, but less wide pit. Its length ranges from 50 to 400 m, and the diameter is not more than 90 cm As in the first case, the space around is filled with cement for greater stability. The installation of the conductor allows you to block aquifers and soft types of rocks, whose presence complicates the mining process.
Setting intermediate casing. Create it in situations where there is no way to drill the well to the oil containing formations: there are complex areas or productive formations, that at this stage of production is not planned for development. Setting intermediate casing is analogous to a conductor, if necessary (too deep occurrence of the species) there can be several.
The installation of the production casing. It is the latest phase of drilling the casing string. Its task is to cover the productive formation and to ensure supply of “black gold” in the operating pipe. The space around it shall also be cemented (concrete ring), because it allows to avoid leakage of oil to other layers and to prevent possible infiltration of water directly into the reservoir.
After you create the well design is carried out directly formation opening for taking out the minerals. Almost 90 % of cases this is carried out by drilling to the sole productive of the reservoir. After at the bottom of the production casing and the concrete ring around it breaks some holes through which the well will go oil. For this purpose, special devices-punchers.
In the remaining 10% of cases develop the breed presented in a dense layer and strengthening of the bottomhole cement is not required. There is another option – not to lower the production casing to the sole of the reservoir, enough to make it up to her roof. This method is called an open face.
The choice of wells primarily influenced by geological conditions, which is the formation. Thus, for the development of oil fields use types of developments, which can be distinguished by the deviation angle of the barrel from its vertical axis:
– vertical oil wells – not more than 5 degrees;
– directional inclined oil wells – in excess of 5 degrees;
– horizontal oil wells – comprises about 90 degrees.
Horizontal oil wells have their own characteristics. So, strictly horizontal position from such workings does not exist, since to drill straight on the layers deposited under different bias, it is simply impossible. Although this definition is not entirely accurate from a scientific point of view (is not a strict straight line), it is most suitable for such type of development.
So much easier and more effective to drill along a path lying oil formation. In this regard, suggests a broader definition: a horizontal oil well is a structure in the form of an extended trunk, the drilling of which is carried out by a specific azimuth. The latter is calculated from the direction of the target layer, taking into account the maximum approximation to its occurrence.
Another type wells, multi-lateral and multilateral oil wells. These include production, having two or more barrels, i.e. the branch from the main. In the case where the “sleeve” is located above the productive formation, type of generation is called multi-stem (several points of penetration of the stratum). If the branch located in the reservoir, the well is considered to be multilateral (break through several, but at one point).
The rarest type of the well – Bush. In this case the mouth of the trunks located on land as close as possible to each other, and their trunks diverge under the earth at different angles. As a result the mouth are at different distances from each other, which in schematic form represents an upended hive.
Wells that are drilled to extract oil – they are also called operational oil wells – divided into the following categories:
– producing oil wells designed for the extraction of oil, associated petroleum gas or gas condensate,
– injection oil wells – used for injection (injection) in reservoirs of water (compressed gas, air, etc.).
In addition to the basic classification of wells (production and injection oil wells), the basis of which the direct appointment of production (it is given above), there is one more. So, for search, exploration and extraction of “black gold” is used well:
– reference wells – are used to study the composition of layers, age of the overlying rocks;
– parametric well – their tab required to calculate the prospects of the district in terms of its petroleum potential, the refinement of the geological features of the soil;
– structural well – constructed to define prospective areas, their immediate preparation for the development and production;
– search well – required to discover new deposits of minerals;
– exploration wells – help to study the size and structure of the productive strata, to assess the stocks of deposits, to obtain data for the design of future development wells;
– observation wells – allow you to control the carrying out of development;
– overlapping wells – their use begins at the cessation of work on the main trunk (wear, accident, etc.);
– special (water absorbing and other) well – needed to reset the fishing waters or the technical production, the elimination of outdoor fountains and other things.
All these types are successfully used in the oil industry.
The process of oil drilling caused by impacts on rocks, among which lies a fossil. In this regard, it is divided into:
– electric and other.
Today the industry is widely used only one method of development – mechanical, which may have different modes of drilling. Other methods continue to be used solely for experimental purposes.
Drilling is the mechanical method is divided into:
Percussion method of drilling oil wells is the use of the special tool – chisels. The latter is a drilling complex, consisting of a rope lock and shock rod. The bit is suspended on a rope, thrown into the unit, which is mounted directly on the drilling mast. The destruction of rocks running back and forth motions of the chisel, and drives him special drilling rig. During drilling, the bit rotates (turns), whereby the barrel and gets the shape of a cylinder.
In the process of whipping forms a destroyed rock, the removal of which from the trunk is carried out using jelonki. It is a long bucket, the bottom of which is a valve. Before cleaning the pit taking out of him a bit, then lower the bailer down and open the valve. When the bucket fills with water with bits of soil, buries the valve and the bucket rises to the top. After a sufficient purification of the trunk drilling continue.
Rotary method of drilling oil wells is also based on the use of chisels, but using a different method. The device goes deep into the mountain strata, experiencing simultaneously two effects: a vertical load and torque. Thus, the drill bit breaks the rock, crushes it using crushing, abrasion.
In turn, the rotary method has two varieties, which are determined by the location of the power unit on the device:
– rotary engine located on the earth’s surface, torque transmission is performed by the bit columns of drilling pipes;
– downhole motor is installed directly behind the bit, and provides only his movement, without the participation of the drill string.
In Russia, oil drilling produced mainly by the rotational method.
Oilfield development is a long and complex process. Before starting work on drilling wells, a thorough preparatory work, involving several stages: exploration needed to assess the prospects of development, assessment of the technical parameters of the planned wells, the sizing of the face and so on. In the preparation of project documentation takes into account the number of all objects to be developed, the sequence in which involves the extraction, determined by the drilling methods that allow to make the best use of the selected horizon.
She also well developed in the following sequence:
the development of oil wells. At this stage, the most intense production of “black gold”. The pressure in the reservoir is reduced to a minimum, watering also has the lowest rates. As necessary, the number of wells increases, the rate of recovery is maintained in the range of 10 %. The average exploration well lasts about 5 years.
ensuring the necessary level of production oil wells. Is achieved by maintaining this parameter in the range from 3 to 17 % (the rate is calculated individually for each layer and depends on the viscosity of the mineral). Stage duration ranges from one year to seven years, the number of wells gradually increased through the use of reserves, while depleted production closed. The last is caused by increase of water content – it increases to 65 %, increased oil recovery, to an average of 30-50 %.
the decline in production of oil wells. Oil recovery falls again to levels not exceeding 10 %. The number of backup wells tends to zero, the water content of oil increases to 85 %. Stage of decline – the most challenging when developing the well because it requires a lower pumping speed of the mineral. The average duration of this phase is 3 years and the development of promising layer during this time can reach 90 %.
the final stage of the development of oil wells. The selection of minerals does not exceed 1 %, water cut reaches 98 %. Oil production ends and wells are closed. The final stage is the longest, because the profitability of production is maintained even with such low production figures, and it is easy to extend it for a couple of decades.
The first in the world drilling wells for purposes of oil production carried out in 1846 in the village of Bibi-Heybat near Baku, part of the Russian Empire. The depth of oil wells was 21 m. the Well was exploratory.
In 1864 Russia’s first production well was drilled in the Kuban, in the village of Kiev, in the valley of the river Kudako.
The first American oil from the borehole to a depth of 15 m produced in 1857 in Enniskillen. However, most believe that the first American oil from industrial wells were obtained on 27 Aug 1859.
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