How to pull a casing from a well: rules for dismantling
When the column, which keeps the walls of the well in an unchanged state, ceases to fulfill its functions, the question inevitably arises of how to pull the pipe out of the well with the least expenditure of effort and finance. In this case, several methods are used. All of them involve the use of specialized equipment.
In our article, we describe in detail tried-and-tested methods for extracting casing from a water intake. The problems that can be encountered when pulling a pipe string from the trunk are given. Based on our recommendations, the task will be solved with the least effort and time.
The content of the article:
- What are casing pipes?
- When is casing removal necessary?
- What factors need to be considered?
- List of related problems
- Preparing to dismantle a borehole
- Methods for removing a pipe from a well
- Factory and home-made equipment
- Conclusions and useful video on the topic
What are casing pipes?
A well is the same well, only a very deep and small diameter. To strengthen the walls and ensure the tightness of the well structure, casing pipes are used. If there are several layers in the soil with water unsuitable for consumption, then the casing will not allow mixing them with clean drinking water.
As casing pipes made of metal, plastic and asbestos cement are used. The first of them are durable, well withstand mechanical stress. They are produced with a diameter of 114 to 508 mm. They are equipped with threads, which facilitates both their installation and dismantling.
The main disadvantages are the tendency to corrosion and high cost. They are used mainly for deep mines with a large water resource.
There are no shortcomings inherent in steel pipes, plastic products. The inner diameter of pipe PVC is from 80 to 200 mm. Products also have a thread, chemically resistant, light. Plastic pipes are buried no more than 60 m.
Asbestos-cement pipes have a diameter of 10 - 50 cm and a length of up to 500 cm. They are used less and less. They are fragile and unsafe for health.
When is casing removal necessary?
There are basically only three reasons for dismantling the casing from the well:
- There was a depressurization of the trunk, which happens due to poor-quality connection of the casing links or corrosion of the pipes by rust.
- A tool or equipment jammed hopelessly in the barrel, making it impossible to remove the old pump and install a new one.
- A change in the design of the tubular well is required: recess, transformation downhole filter etc.
The remaining cases are not a reason for extracting the structure. Sometimes you can save the situation by installing a polymer liner of a suitable diameter. If the cliff occurred at great depths, dismantling is simply impossible. Then it’s easier to drill a new source than to spend a lot of money on restoring the old one.
What factors need to be considered?
Usually a well is drilled in the area to a great depth, so removing the casing from it is not an easy task.
Before deciding on such an event, you need to clearly know the answers to the following 6 questions:
- what the casing is made of;
- product weight;
- at what depth is its base;
- how much time has passed since its inception;
- in what conditions it was operated;
- is there a good reason why it must be dismantled.
Perhaps ‚dismantling works will turn out to be so complicated, time-consuming and costly financially, that it would be more rational not to solve the issue of how to get the pipe out of the well more simply and quickly, but to abandon this idea in favor of deciding on a new water source.
List of related problems
In the process of removing the casing from the ground, you may encounter a number of unpleasant surprises. It is necessary to be prepared in advance for the fact that the prepared unit and winch will not cope with the task due to insufficient traction. Then you have to order a crane, and this will add problems: you need a ride ‚which will inevitably affect the landscape.
It should be taken into account that the pipe is possibly so tightened by soils that it is necessary to reduce the friction coefficient by drilling pits around the head and pouring a large amount of water into them. The pipe will come out of the moist earth much easier. A side effect of such actions is the probability of a collapse of the walls of the mine.
Insufficient rigidity of the extracted pipe.If it is made of asbestos cement, then its removal without damage is out of the question.
It will simply fall apart and come to the surface in the form of separate fragments, and the fragments will appear at the bottom of the well. It is better not to reuse such a shaft ‚if a pipe made of asbestos was removed from it, given that this material is far from safe.
Preparing to dismantle a borehole
Knowing about possible difficulties, you should thoroughly prepare for the process.
The first step is to determine the weight of the product, for which:
- measure the depth of the well ‚pipe diameter‚ wall thickness;
- open the directory and, focusing on the diameter and thickness of the walls, find the weight of 1 pog. m;
- multiply the found value by the depth of the mine and get the desired mass of the pipe.
This value will be the basis when choosing a winch for traction. If the figure is solid and the winch with such traction does not exist, then the only option is to order a crane. When deviations from the calculated value are insignificant, an ordinary winch is suitable.
Methods for removing a pipe from a well
Professionals have their own methods of pulling casing pipes: stretching followed by a break, flushing with pacing, twisting.
Stretch method for column extraction
To use this method you will need a tackle system or a jack. The force arising during tension is higher than the critical limit of plasticity of the material casing pipe. Therefore, the design may not withstand and burst.
The process algorithm is as follows:
- Around the mouth of the pipe they dig a trench about 1 m deep.
- A clamp is put on the pipe, and cables are attached to it, after which the structure is pulled a little.
- The clamp to which the cable is attached is moved lower and the same actions are repeated. This provides a smooth stretch.
- The upper edge of the casing is pulled until a break occurs. The fragment is removed from the mine, and the rest is captured with a special fishing tool and the process continues, or after replacing the damaged part of the barrel, the casing is replaced.
It is advisable to use the option for dismantling pipes having a large diameter and thick walls.
If the axis of the well has a vertical deviation, this extraction method cannot be used. For such complex work it is better to hire a drilling crew.
The hoist used for lifting must have a large carrying capacity. The best option is to use jacks. You should know that you do not have to rely on the further use of the extracted pipe.
If the casing does not come out of the soil due to the formation of a sand plug, a relatively simple method is used to extract it - flushing and stretching. To do this, you need a pump with a special flushing device. The pump head is connected to the top of the pipe.
Pressure should be minimal, but sufficient to circulate water. The column is washed ‚and after the sand goes‚ the pressure is increased. The body of the pipe is paced, scrolling it with the help of the rotor and loosening. All this is performed in parallel with the flushing. In this way, the coefficient of friction is reduced, and the string is easier to exit the well.
The ideal option when the pipe diameter allows not only to fix the pump in the upper part, but also lower the second one to the base of the column. The reverse water supply is started as soon as the edge of the flushing hose drops 300 cm below the shoe-clutch of the sediment column. The process continues until the sand congestion near the pipe is completely eliminated.
Sometimes when lifting the pipe to 10 m, it becomes impossible to remove it due to the strong sealing of the cork. In this case, there is only one way out - to take out individual fragments. Separately, it is necessary to dwell on the process of removing the pipe.
First, a piece of reinforcement with a diameter of about 18 mm is welded onto her body. This element is needed to secure the winch slings and begin to raise the casing riser.
For lifting it is necessary to apply a vertically directed pulling force. To do this, at the highest point of the extracted pipe, the unit is mounted, and a cable is thrown through it. When the winch drum rotates, torque is converted to traction.
The pipe is lightweight with a lever. Its end is brought under the welded reinforcement and, applying force, gradually pull the riser out of the ground.
Application of unwinding method
Using this method allows you to unscrew the elements of the casing and remove them from the well.
To apply the method, a tool stock is required:
- fishing crown;
- hammer drill;
- komululyati torpedoes.
A special left-handed fishing crown and a steel drill pipe are lowered into the shaft. By means of the rotor, the pipes are rotated counterclockwise.
After approximately 20 revolutions, the casing is paced, increasing the load to the maximum. If the catch pipe does not break, pacing and unwinding are repeated. The result of these efforts should be incomplete unscrewing of the joints.
If the thread could not be loosened even after a series of cycles, a special tool is launched, rotating which cause the pipes to oscillate due to friction and transmission of torque to the extracted riser.
Result: after turning the tool for 1 hour, the connection loosens. At the next stage, the upper rim of the column is captured and its fragment is unscrewed. To extract the unscrewed part of the pipe outward, exert a pulling force. The steps are repeated until the entire column is dismantled and all its elements are at the top.
When all efforts do not lead to success, they use the radical method - violation of the integrity of the structure by using cumulative torpedoes. As a result of their explosion, ring cuts appear on the pipe body at a given depth. It remains to cut off individual elements with a punch or other cutting tool.
All these works are within the scope of specialized organizations. Their cost is considerable, therefore, for the independent extraction of the pipe, the owners of country houses are looking for other ways.
Factory and home-made equipment
Professionals use factory-made equipment to extract the casing from a deep well.
It is characterized by such nominal parameters as pressure in MPa, stroke force - forward and reverse in tf, maximum torque in kN / m, maximum clamping or extraction force in tf, angle of rotation of clamps, mass in kg, dimensions in mm, range of diameters drawn pipes.
Hydraulic return cylinder rods combine supports equipped with a traverse on which the upper plate rests. To clamp the support column on this plate there is a special movable grip.Both fixed and movable grips are 3-wedge cams having an internal thread and placed in a cage.
Hydraulic cylinders are connected to the pumping station. In the event of an emergency, when there is not enough force to remove the pipe, a clamp wedging device is used. The tension may not be enough in the case when, due to unforeseen circumstances, additional frictional forces appear between the pipe body and the borehole walls.
The equipment is installed on the casing and clamp the latter using a movable gripper, and then raise it. The lift is equal to the stroke of the pistons. The next step is fixing the pipe with a fixed grip and returning the top plate to its original position. The pipe is removed by repeating these steps. In the process of extracting the riser, it is supported by a crane.
Using such equipment, casing pipes are pulled from the ground, the top of which is almost invisible, since the installation has a low pickup. Another advantage of the mechanism is the ability to raise steel pipes, whose sizes are in a wide range.
For the dismantling of pipes of small diameter at their site, suitable equipment can be manufactured independently. This will require 2 channels for racks, a drum for a cable, a bearing with a diameter of 40 mm inside, a cable, a handle.
Two supports are made with a height of about 1 m and a width of about 0.6 m. They have the shape of the letter T in the overturned form. A bearing is mounted on top of the posts, and an axis is passed through it. The drum and the handle are fixed on the axis.
They cover the pipe with a cable and begin to rotate the drum. The pipe gradually emerge from the ground. If a plastic product is to be dismantled, a special clamp is used.
As the pipe is removed, the cable is lowered lower. When the structure is of considerable length, a special device is used - a scribe to hold the column when moving the cable to a new position.
Conclusions and useful video on the topic
Video # 1. The author of the video filmed the process of removing the casing PVC pipe:
Video # 2. Tool and equipment for pulling casing:
Depending on financial capabilities and the availability of equipment, you can use any method to extract the pipe. It is important to be careful and not to neglect safety measures. Perhaps, after all the calculations, you decide that it is better to lay a new well.
If you had to drag the casing from the wellbore, tell us how you managed to remove it. Share information that site visitors can use in similar situations. Please write comments, ask questions, leave posts with your own opinion about the material we proposed and the related photos.