The wellhead is the intersection of the earth’s surface with the well. In this place, the production pipe comes to the surface, where the water intake devices and the pump are located. After completion of work on the arrangement of the water source, metal pipes are installed, the diameter of which is 12.7; 14.6 or 16.8 cm (these parameters are prescribed in GOSTs, which provides information about casing pipes). But if other sizes are used, this indicates that the pipes are not drill pipes. Inside, plastic pipes can be laid that guarantee the environmental friendliness of the produced water.
When plastic pipes are placed
The wellhead is sometimes arranged using exclusively plastic elements. What is true, if the depth does not exceed 50 m. Such products have a life of about half a century, and they are not afraid of corrosion, they are not covered by microorganisms, and no sediment appears inside. Pipes are highly resistant to chemicals and resistant to rock sediment or freezing soil.
The material for such pipes is polyethylene, and some products also have threads. PVC pipes are almost never found and are not used, as they are custom-made and soldered, which increases the cost of arranging the well.
Mouth construction
The wellhead should be designed for year-round use. Therefore, the arrangement of this part of the water source is one of the important stages in creating a water supply system for a house or even a village. Initially, a head should be installed at the mouth, which is a large metal pipe. The remaining work on the arrangement of this part of the well can be carried out after drilling is completed or later.
The wellhead is arranged using some components, namely:
- high capacity;
- steel pipe;
- submersible pump;
- automatic equipment;
- connecting elements.
Pumping equipment will be located in the tank. This part of the well is called a caisson. It will border the soil surface at the top point. This is the tip, it is needed to control the operation of the water supply system. The site is located at the wellhead.
Specialist advice
It is important to determine the right amount of such additional elements:
The caisson should be steel or plastic with a good layer of insulation and anti-corrosion coating. A proper installation allows you to protect the water supply system from freezing when the temperature drops.
Device features
The wellhead is arranged by removing soil around a metal pipe. After that, the caisson sinks to a depth. First, a head should be installed on the mouth - a pipe with a diameter that will be larger than the diameter of the first casing. The base of the head will need to be cemented.
When drilling a well, which will be operated year-round, a caisson should be mounted. The pumping equipment will be located in the tank. A caisson is something like a large barrel at 2 m. The diameter is 1 m. This device is installed on the head, while the container should be on the freezing line of the soil. Soil should be removed around the steel pipe, and the caisson should then be lowered.
In the bottom of the caisson, you need to make a hole with a diameter equal to the diameter of the head. Both elements are joined by welding. In the caisson, it will be necessary to install pumping equipment, then the communications are connected, the electricity supply is connected.
The caisson cover should block access to the source. As a result, you get an inspection well that provides access to the well. When choosing a caisson, you can purchase both a ground and an underground camera. On dry soils, it is recommended to use underground chambers. Elevated caissons will be relevant in other cases.
The upper part of the casing must be designed in a certain way so that surface water and dirt do not get inside. It is also necessary to ensure that the pressure line does not freeze, because it will have to be serviced by cleaning, and from time to time, repairs will also be required.
Mouth head
The exhaust pipe should have a head with a diameter larger than that of the upper casing. This part of the well not only prevents pollution, but also holds the submersible pump, undergoes pressure from the inside and outside. The heads can be made of:
The second are designed for shallow wells and differ in the quality and type of connecting fitting. Steel heads can withstand loads of up to 0.5 tons, plastic ones - about one centner.
The mouth cap provides for the presence of fasteners, a cover, and a flange (made of steel or plastic). The assembly also consists of a carbine and a rubber ring. The outer cover has not only leads, but also external eyebolts that are welded, and one of them is inside.
About pressure
One of the operations during the construction of the well is the development operation in order to create conditions for oil inflow. At the same time, the density of the clay solution gradually decreases - it is diluted with water, the hydrostatic pressure of the liquid column decreases. Manipulation continues until the clay solution is replaced.
With a decrease in pressure at the wellhead for oil, the last of the formation begins to flow through the perforations into the wellbore, displacing water, leaving the surface. In order to make the process safe and controlled, the mouth is closed by a lid. This requirement is especially important at high reservoir pressures. The cap is bolted to the casing flange. A production string of pipes is passed through the lid into the well, while pipes and valves are fastened from the outside. The assembly is called a fountain. And the outlet fitting in this system plays the role of a corridor through which oil is taken from the well. If the pressure at the mouth of the oil well is not enough, compressors are compressed to increase absorption and reduce investment in the installation.
Features of the binding of the mouth
The control equipment of the mouth is mounted on the drill pipe string, which allows you to control the flow of gas and liquid. This also prevents the risk of discharge of formation fluid from the pipe of the barrel.
Harnessing the wellhead involves screwing the wellhead to the upper drill pipe (it can be a swivel or fixed type). The head is connected to the steel manifold by means of movable articulated elbows using quick-disconnect couplings. The manifold is fixed by means of supports to the rig, which eliminates the vibration of the pipeline.
Sealing
Sealing the wellhead is carried out after stopping drilling. Next, you need to get the pipe coupling to the line of dies of the key, while the winch brake is fixed, and the pumps stop. The end valve must be opened and the position of the valves on the throttling unit checked. They need to be opened. The equipment of the wellhead provides for the winding of a ball valve. The winch brake must be locked. The tool is insured by the elevator. The preventer should be closed at this stage, as well as the ball valve. The valve should be closed on the flow line. It is important to monitor the pressure.