🏭 🧑🏿‍🤝‍🧑🏻 🚩 Well bottom: construction and cleaning 🕵🏿 ⛵️ 🕓

To understand what a bottom hole is, you need to have a general idea of the process, structural components, their functions.

A similar technology is very often used, since wells are used in various fields. This is a geological mine in which the length is greater than the diameter. Often such an artificial type system, including several constituent components, is created for water production.

Design features

Before you deal with the slaughter, you need to find out where it is located. A well is a geological mine. Its components:

the mouth is the very beginning;
wall - the surface inside, has the shape of a cylinder;
trunk - all the space inside;
the bottom is the bottom of the well.

In general, the well includes such elements:

Direction. This is the first part of the mouth, which includes loose rocks, they are easily eroded. To strengthen, make a wide well to the layer where harder rocks are located. Usually this is about 4 to 8 m. A pipe is placed in the hole, and the gap is filled with concrete.
Conductor. This is the part that follows the direction. The conductor is strengthened by a casing pipe, which consists of many smaller ones. The space between it and cement is also poured with cement.
The intermediate column. A section that passes through the direction, and a conductor to block weak or difficult layers, as well as those that are not planned to be developed in the future. If the well is very deep, then there may be several intermediate columns.
Production column. This is a section from the bottom to the mouth. It is through it that the material is transported.
Slaughter. This is the latest zone of the well. It is intended to extract the product from the layers. The layer itself has an upper and lower boundary (roof and sole).

These are the main components, without which there is not a single well.

Slaughter Features

The construction of the bottom of the wells is one of the main components of drilling. It performs such functions:

It maintains the mechanical strength of the productive layer, due to which it is possible to immerse the required equipment for bottomhole operations.
Maintains sufficient hydraulic permeability of the mechanism before slaughter.
It allows access to other reservoirs of productive type that were not originally planned to be used.
The ability to act on various adjacent layers or individual sections of the productive layer.
Maintain drainage of the entire formation in use.

Since the development conditions may be different, the design of the bottom hole can be of several types: open, with a filter, perforated, blocked.

Open face

An open type face is arranged so that the production casing reaches the beginning of the layer used. In this state, it is fixed with cement. After this, the layer is already cut with equipment with a smaller diameter. The trunk will remain open.

This design can be used in the following cases:

the exact boundaries of the used layer are clarified;
formation thickness is small;
the layer includes rocks that will not collapse;
the layer is homogeneous and does not include clay mass, which may collapse due to swelling;
there is no need to influence hotel sublayers.

Open face has the highest hydrodynamic type efficiency indicator compared to other types of structures. That is why the hydrodynamic drilling coefficients of other types are measured relative to the open face, which is taken per unit.

The downside is that it is not possible to develop separate zones of the reservoir or separately influence them. In addition, there is a possibility of collapse of the layer during pumping, due to the fact that the pressure inside it decreases. Therefore, open-hole wells are rarely used - in about 5% of cases.

Face capped by perforated liner

If it is planned to use this type of bottom, then the well is deepened to the bottom of the selected layer and fixed with a production string with perforated drilled type, which is at the level of the reservoir. After that, it is cemented to the place where the used layer begins.

The perforated area will remain open. This option does not have such disadvantages as reducing the working diameter, the risk of rock collapse. This method of borehole bottoming is used in the same cases as the open type.

Filter face

If a bottom with a filter is selected, the casing is placed to the upper edge of the used layer and filled with cement. A filter is placed on it in the reservoir, which has holes in the form of a circle or a slit. The areas between the filter and the pipe are closed with an oil seal.

Barriers of various designs are suitable. For example, they use the following:

Ring filter. It includes rings worn on a perforated tube. Between them there are tapes of such thickness that the required gap is formed, which is necessary for filtration.
Gravel filter. These are 2 concentric type perforated tubes. Between them is gravel with a size of 0.5-0.6 cm. It is he who is the filtering element.
Ceramic-metal filter. These are rings made of ceramic shot, which is baked under high pressure. The product is put on a perforated tube.

The latter kind of filters is the most effective, since the hydrodynamic resistance is low and has good cleaning ability.

In general, filter faces are used to protect the produced product from sand impurities during the development of layers where similar formations can occur.

Perforated face

This design option is considered the most common. He has such advantages:

Easy installation.
High quality insulation.
There is a possibility of further development of other layers.
It is possible to influence adjacent layers.
The cross section of the well remains unchanged for a long time.

To make a perforated face, you need to drill a hole from the selected mark. To the place of installation of the casing, everything is examined using special equipment. In the end, you can make the marks of the aquifer, and the result will be as accurate as possible.

When the pipe drops, it is cemented from the bottom to certain marks, and also perforated in the area of the formation used.

Cleaning: hydraulic method

An important working step is to clean the bottom of the well during its drilling. In this case, it is required to remove the slag by transporting it upstairs. If this is not done, then the accumulated masses will interfere with further deepening. And if there are too many of them, they can provoke a seizure of the drill, which will lead to an accident and destruction of the bottom of the well.

It is important to consider cleaning methods. It is carried out by various methods. One of them is hydraulic. That is, flushing the bottom of the well. This is the most common option.

It involves the use of fluid at the bottom of the well. Usually use industrial water, special means - saline, clay and non-clay, aerated. In addition, solutions of natural origin are involved. They are formed directly in the process of borehole bottom during its drilling.

If the rocks are weakly stable, then clay solutions are used during the rotation of the drill. They perform the following functions:

The rock is fixed in the walls of the well due to claying and the formation of increased hydrostatic pressure at the bottom of the well.
The aquifer is temporarily isolated.
The particles of the liberated rock are kept in suspension when fluid stops circulating.
Reduce fluid loss when it is supposed to pass through water-absorbing layers.
Significantly improve the conditions for cleaning the face and transporting sludge.

Aerated type fluids are used. This is necessary to reduce the hydrostatic pressure at the bottom of the well and the penetration of fluid into the layers. At the same time, aquifers are less clogged, and fluid loss is reduced.

Direct flush pattern

Direct flushing is very simple, but has a number of disadvantages. This includes increasing fluid costs, especially if the diameter of the well is large.

Due to the fact that you need to have a significant speed of the ascending stream, which provides the removal of sludge. In addition, there is an increase in the likelihood of an accident due to wall collapses that are made of unstable rock.

Reverse Flushing Scheme

The backwash is carried out due to the fact that the liquid is pumped or it is pumped out by a special pump. The equipment used is vacuum, centrifugal, piston, water-jet type or airlifts. With this washing method, the circulation of the solution is local or intra-well, complete or not.

Such a scheme has the following advantages:

the speed of the rising jet increases and the flow rate is small;
masses can be transported without a drill.

These nuances must be taken into account.

Cleaning: pneumatic method

With this cleaning method, air or gas is used instead of the solution. The latter is used while drilling oil wells. In gas-bearing regions, it is also used. This is due to the fact that it is forbidden to use air there, as this can lead to a fire. For example, exhaust gases from internal combustion engines can be used.

But air purging is a more common method. It is used even more often than washing. The pluses include the following:

no solution required;
no special equipment for cleaning the liquid is needed;
can be drilled in non-aquiferous areas, as well as in places with permafrost;
drilling speed becomes higher;
sanitary conditions for the brigade are better, especially in winter.

But this method also has disadvantages. The main thing is that if water gets into the well, accidents can be triggered. For example, a small water inflow leads to the fact that the sludge turns into a mass like dough, which sticks around the equipment. In more complex cases, the drilling depth decreases.

Cleaning: mechanical method

This method involves screw and impact methods. Moreover, the so-called types and drilling, and at the same time cleaning. Both methods are equally popular.

In the first case, a special screw conveyor is used, which is a hollow tube with a spiral tape. During its friction, the rock is destroyed and rises up due to the movement of the apparatus.

In the shock method, after rock destruction by the drilling rig, special mechanisms are used that are lowered into the well and the sludge is transported from it. Such equipment is called a bailer. It rises to the surface a large number of times and discards the collected material, which has a suspended state. For this, a little solution is added to the well.

Cleaning: combined method

The combined cleaning method involves the combination of a hydraulic or pneumatic method with a mechanical one. This option is considered more effective. Often it is used when the wells are in the form of columns, or they have a large diameter.

Well bottom: construction and cleaning