well construction

drilling craft

Today is a popular craft drilling activity! Drilling is applicable in various areas: the search for and extraction of minerals; study of geological properties of the rock; production blasting; artificial binding species (carburizing, freezing, bituminization); drainage of wetlands; laying underground pipelines; construction of pile foundations and more.

World progress is by leaps and bounds, and possibly soon in our lives will include other sources of energy besides petroleum and gas. Therefore, to delay the extraction of these minerals, then give up the riches that may soon lose their price.

It is no secret that our country occupies a leading place in the production of many minerals. It is difficult to overestimate the contribution to the economy, and hence in our well-being, which make drillers. Driller - it sounds harsh, but it proudly! Drillers are the people working in difficult conditions, as a rule, far from home and family. Therefore, this day is considered the most craft driller paid among workers specialties.

Advances in science and technology, as well as strict compliance with environmental requirements minimize the negative impact of drilling on the environment. Modern drilling - a complex of complex technical devices and machines. In the design and manufacture of drilling rigs is on the main slope safety and automation of drilling process. The number of labor-intensive operations is reduced, productivity is growing. As a result, increasing the qualification of the drilling personnel.

Drilling is not only a borehole, but also a whole range of services catering to many drilling and operating her work, among them:

- drilling team led by the head of the drill;

- Central Engineering and Technology Service (CITS);

- Chief Mechanic Department;

- Chief Power Engineer department;

- supply and others.

The joint work of many people making drilling feasible and effective.

Welcome to the site of the drill!

well construction

The concept of well construction

Drilling - a process well structures by breaking rocks. Wells mine workings called circular section being built without access to her people, the length of which is many times greater than the diameter.

The upper part of the well is called a mouth, the bottom - slaughter, the lateral surface - a wall and a space defined by a wall - the wellbore. well length - the distance from the mouth to the bottom of the barrel axis, and depth - the length of the projection on the vertical axis. The length and depth numerically equal only to vertical wells. However, they are not the same in inclined and deviated wells.

Elements of the well structure shown in Fig. 2. The initial portion I called the direction of the wells. As the wellhead is easily washed in the zone of rock must be strengthened. In connection with this direction is made as follows. First drilled hole - pit to the depth of stable rock (4. 8 m). Then it sets the necessary tube length and diameter, and the space between the walls of the pit and the tube is filled with rubble and cement mortar poured 2.

The downstream portions of the well - cylindrical. Now the direction of section is drilled to a depth of 50 to 400 m in diameter to 900 mm. This portion of the well is fixed casing 1 (consisting of the screwed steel pipe), which is called a conductor II. Annulus cement conductor. With the help of a conductor isolate intermittent, soft and fractured rocks, complicating the process of drilling. After the installation of the conductor is not always possible to drill a well to a depth of over complicating passage of new horizons, or because of the need of productive layers overlap, which is not planned to exploit this well. In such cases cement is set and another column III, called intermediate. If the reservoir, which is designed to develop well, lies very deep, the number of intermediate columns can be more than one. The last section IV wellbore production tubing is fixed.

Fig. 2. Well Structure: 1 - casing; 2 - cement stone; 3 - layer; 4 - perforation in the casing and the cement matrix; I - direction; II - conductor; III - an intermediate column; IV - a production string.

It is designed to lift oil and gas from the bottom to the wellhead or water injection (gas) into the reservoir to maintain pressure therein. To avoid oil and gas flows in the overlying formations, and water reservoirs space between the wall of the production tubing and the wellbore wall is filled with cement mortar. For extraction of oil and gas reservoirs using various methods of opening and downhole equipment. In most cases, the bottom of the production tubing located in a reservoir, shoot through (perforated) row of holes 4 in the wall of the casing and the cement sheath. The stable rocks bottomhole zone equipped with different filters, or not cemented casing string is lowered only to the producing formation of the roof, and its drilling out and operation without attaching produce wellbore. The wellhead depending on its purpose equipped armature (pillar head, valves, and the spider al.).

The main factors to justify the well design.

Selection and design rationale borehole is a critical starting point in the design and plays a crucial role in the success of the well to a depth with the best technical and economic characteristics, to ensure the optimal conditions of drilling and testing.

Under construction well understand the characteristics of the borehole, which determines the change in its diameter with depth, and the diameter and length of the casing. The input data for building structures are well coring physico-mechanical properties of rocks, the presence of the porous and unstable intervals, and, more importantly, the final diameter of the drill. well design affects all types of work that make up the drilling process, and determines the cost and quality performance of the geological setting.

When drilling into different types of minerals are subject to different well design, depending on the permissible diameter core. The final borehole diameter is determined by the minimum allowable diameter of the core specific minerals

In the search, exploration and development of oil and gas fields drilled support, parametric, structural, exploratory, operational, pressure, and other observation wells.

1) The reference wells are placed in areas not tested by drilling, and are used to study the composition and age of their rocks.

2) The parametric wells are placed in a relatively-studied areas in order to refine their geological structure and hydrocarbon potential.

3) Structural wells are drilled to identify promising areas and their preparation for exploratory drilling.

4) Searching wells are drilled in order to open new industrial oil and gas deposits.

5) Exploration wells are drilled in areas with established commercial oil and gas for the study of the size and structure of the deposit, to obtain the necessary input data for calculation of oil and gas as well as the design of its development.

6) production wells are placed in accordance with the circuit design and the reservoir are used to obtain oil and gas from the subsurface.

7) Injection wells are used when exposed to various agents operated reservoir (injection of water, gas, etc.).

8) Observation wells are drilled to oversee the development of deposits (the change in pressure, the position of oil-water and gas-oil contacts, etc.).

Also during the search, exploration and development of oil and gas fields drilled Kartirovochno, seismic, and other special wells.

Mainland OIL

GETTING STARTED WELL

well construction - a set of elements lining excavation with transverse dimensions immeasurably small compared to its depth and length, providing at the present technical and technological arms trouble-free, with the subsurface safety, economical construction hermetic spatially stable channel between the fluid-beds and the rest of the exposed geological section, as well as the surface, operating under the specified conditions of time and depending on purposes: to study geological someone cut, exploration and evaluation of oil and gas potential deposits, mining production, reservoir pressure maintenance, monitoring the regime of exploitation of the deposit, and others.

The gas-oil industry there is also a common methodological approach to assessing the quality of the design and construction of wells, including their design.

The basic elements of the well are the mouth, face, trunk, a casing, a filter, cement annulus.

mouth - is the beginning of the well formed by a short vertical pipe cemented - direction.

slaughtering - this is the bottom of the borehole.

Trunk - This excavation within which the casings and the borehole produced recess.

Filter - wellbore portion directly contacting with the oil or gas productive horizon. Filter string may be open hole section of the trunk, a special device with holes filled with gravel and sand, the portion of production casing or liner with holes or slits.

cement sheath - hardened grout pumped into the annulus between the barrel and the casing for the purpose of sealing.

cement sheath It is intended to secure insulation apart intervals geological section (including productive) for the entire period of construction, operation and ensure tight connection of casing the borehole walls to form a strong and permanent leakproof lining.

The system casing and cement rings make them lining well.

casing - is screwed together and lowered into the barrel casing to isolate trunk composing the rock. Distinguish first casing - the conductor, the last casing - the production string, including a shaft, intermediate casing strings, including flying detachment (liners).

casing for isolating wells of the barrel wall of the working space during the drilling and operation and provide the desired strength and integrity when subjected to internal and external influences primarily pressure. To produce the necessary isolation of the annular space remaining between the casing strings, it is filled with liquid cement mortar hardening over time.

Casing intended subdivided as follows.

Direction - the first column of tubes or one tube is designed for fastening the mouth part wells from erosion and collapse of the drilling fluid and to circulate the fluid. Direction, usually one. However, there may be instances well casing the two directions, when the upper part of the section represented loess soil, sand or bulk has other features. Usually the direction is lowered into a prepared pit, or hole, and concreted over the entire length. Sometimes the line is driven into the rock, as the pile.

distinguish mine (or Shaft) Direction and elongated direction. Mine is set, as a rule, in all cases, and its length is 3-10 m. Depending on the specific conditions may be set elongated direction or from one to several directions and in this case can be up to 100 m. Focus descends possible in clayey formation . The diameter of the column ranges from 245 to 1250 mm. Pipes used as destinations, the strength is not calculated and not pressurized.

Conductor - casing string intended for separation of the upper section of the interval of rock, isolated from fresh horizons contamination, installation equipment and blowout suspension subsequent casing strings.

The conductor according to the geological conditions set to an average depth of 100 m and a maximum depth of 600 m. The diameter of the conductor usually varies in the range 177-508 mm. He is pressurized as the cement sheath.

Mine direction and the conductor elements are mandatory well design.

Intermediate casing (There may be more than one) is used for separation of drilling conditions incompatible with zones intended to deepen the borehole depths.

Intermediate casing strings may be of the following types:

  • solid - covering the whole wellbore from the bottom to the mouth regardless of fastening the previous interval;
  • shanks - for fastening only the open hole interval overlapping with the previous casing by a certain amount;
  • flying detachment - Special intermediate casing strings that serve only to overlapping complications interval and have no connection with the previous or subsequent casing.

Sectional descent casing and the shank attachment holes are, firstly, a practical solution to the problem of descent of heavy casing and, secondly, the solution of the problem of simplifying the well design, reduced diameter casing, the gaps between the columns and walls of the well, reduce material consumption and plugging materials, an increase in drilling speed and reduce the cost of drilling.

production casing - last casing string, which is attached to isolate the well productive horizons from other breeds and extraction of oil or gas wells or for injection in a liquid or gas reservoirs. Sometimes the production string can be used (partially or completely) the last intermediate column.

Designing diameters of casing bits and begins with the production tubing and the method further upwards. Calculation diameter casing is being "inside" with the production tubing diameter. Based on the estimated production rate of the well and economic feasibility is selected diameter production casing. The diameter of the production tubing diameters defines a drilling casings for all wells, and the amount of construction determines the intermediate columns wellhead. The increase in the production string diameter allows the use of well production equipment allows to operate in a well multiple layers and facilitates the repair of the underground. On the other hand increase the production tubing diameter leads to an increase in metal casing, the volume of drilling and cementing. Increasing the load on the head of the column and its metal. All this leads to an increase in the construction cost of the well. Reducing the production casing diameter reduces the cost of its construction, but it increases the costs associated with the operation of the well. So the use of small equipment leads to an increase in the purchase of up to 2-3 times the cost. Complicated behavior of underground repair, which leads, as a rule, an increase in time-consuming and, therefore, and materials, and in some cases does not allow to make the necessary repairs.

Only erected the well can answer the question of whether there is in the area of ​​an oil or gas field and what is the value of commercial deposits of hydrocarbons.

The construction of the well, regardless of its destination (exploration, parametric, maintenance, etc.), includes the following main steps:

  1. The geological study of a place and preparation of the project of the well, which allow you to best accomplish the task.
  2. Mounting hardware for the highest quality and economical well construction.
  3. Wiring wellbore, providing high speed recesses at minimum cost.
  4. Deep geophysical and technological studies to examine in detail the geological section, thermodynamic parameters penetrated by the well layers, select rock samples and reservoir fluids for laboratory analysis.
  5. Mounting the barrel casing and cement, providing long trouble-free operation of the well as the engineering construction and its environmental safety.
  6. Production depth filter, which provides a qualitative and reliable hydrodynamic communication with the cavity of the producing formation and the production string in preventing penetration of the rock column and other contaminants hydrocarbons.
  7. Wellhead equipment, including, if necessary, the suspension string of tubing, providing a qualitative test wells and its subsequent continuous operation as an object of hydrocarbons.

When drilling into the well sequentially descends defined structure consisting of a casing. Each subsequent column is inserted into the previous one, and therefore has a smaller diameter all.

The bottom of the well is called the slaughter. After the cementing formed a new face, which is called "artificial slaughter." During operation, the slaughter precipitated impurities of the worn-out equipment or lost during underground repair tools, etc., that the measurements changes the depth of the well and a new point is called the "current slaughter."

If cased reservoir, the bottom of the shoe or the production string is always installed (after passing through the porous reservoir) in an impervious rock. This allows you to open the reservoir, to prevent its flooding, which in itself is a serious problem and can do well unproductive, ie, did not yield oil.

After creating a sealed structure in the well production casing opposite the producing formation, on a face down device (punch) which make holes in the casing and cement sheath and connects the reservoir and the wellbore. These holes are filled with a gas and the formation fluid (oil) supplied from the pressurized reservoir and fill the well.

to the well design requirements

Depending on the purpose of construction of wells can vary substantially, but always must satisfy certain general requirements which are as follows:

  • uncoupling sturdy passed rocks and their sealing, as follows from the requirement subsurface safety and environmental protection and is achieved by bolting strength and durability, the tightness of casing, and the annulus of annular spaces and also due to the isolation fluid-saturated horizons;
  • obtaining a maximum amount of geological and physical information necropsied wellbore section;
  • traceability of probable intercolumned or casing flow of fluids;
  • long trouble-free operation under the condition of safe operations at all stages of the life of the well;
  • structure must have a certain diameter casing that particularly relates to a production tubing;
  • be stable (does not change its initial characteristics for a long time or after certain processing operations);
  • effective fixation structure in the wellbore;
  • the possibility of an emergency well killing;
  • possibility of transformation of one species into another wellbore due to maximum uniformity of standard sizes of casing and the wellbore.

In addition to these, well design must meet certain technological requirements, the main ones are:

  • Good hydraulic characteristics (low resistance);
  • fullest possible use in the process of formation energy recovery production to the surface through the choice of the optimal diameter of the production tubing and the design face;
  • the possibility of all kinds of known and promising research downhole instrument;
  • conduct all production operations in the well, including on the impact on the productive horizon;
  • application of various methods using an effective operation of equipment, including heavy loads on the borehole wall (columns).

The development of well construction

The main parameters of the well structures: the number and diameter of the casing, the depth of their descent, the diameter of the bit, which are required for drilling under each casing, as well as the lifting height and the quality of cement slurry for them to ensure completeness of mud displacement.

The development of well construction is based on the following main geological, technical and economic factors:

  • geological features rock occurrence, their physico-mechanical characteristics, presence flyuidosoderzhaschih horizons, reservoir temperature and pressure, and the fracturing pressure of the rock traversed;
  • the intent and purpose of drilling;
  • intended method of well completion;
  • a method of drilling;
  • level of organization, technology, drilling technologies and geological study of the area of ​​drilling operations;
  • skill level drilling team and the organization of logistics;
  • methods and development of equipment, maintenance and repair of wells.

The objective geological factors include the anticipated and actual lithology, stratigraphy and tectonics cut power breeds with different permeability, strength, porosity, presence flyuidosoderzhaschih rock and reservoir pressure.

The geological structure of the rock cut in the design of the well structure counted as a constant factor.

During the development of deposits its initial reservoir characteristics will change, as the reservoir pressure and temperature affect the duration of operation, the selection rates of the fluids, the methods of stimulation and maintenance of reservoir pressure, the use of new types of impacts on productive horizons to better recovery of oil and gas from subsoil, so these factors must be considered when designing the well design.

wells construction must comply with the conditions of environmental protection and eliminates the possibility of contamination of reservoir water and crossflow of fluids not only during drilling and operation, but also after the completion of the work and the elimination of wells. In this connection it is necessary to provide for the proper and effective zonal isolation. This is one of the most important factors.

All the technical and economic factors - subjective and vary over time. They depend on the level and degree of perfection of all forms of organization, technique and technology of drilling in total. These factors influence the choice of well design, allow to simplify it, but are not decisive in the design. They vary widely and depend on the works of artists.

Thus, the design principles well designs must first be determined by geological factors.

Simple structure (the conductor and the production string) is not always rational. This primarily relates to a deep well (4000 meters or more), reveals a complex variety of deposits in which there are various, sometimes diametrically opposite in character and nature of complications.

Consequently, rational may be mentioned such a structure that corresponds to geological drilling conditions, allows for assignment of the well and other noted above factors, and creates conditions for drilling the intervals between the bindings in the shortest possible time. The latter condition is critical, since the practice of drilling clearly confirms that the less time spent on the drilling of bore interval between the bindings, the lower the number and severity of complications arising and lower the cost of the well wiring.

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