What is the rotary drilling method
Rotary Well Drilling: An Overview of Drilling Techniques and Essential Equipment
If a country house cannot be connected to the central water supply, then you need to organize an autonomous system. Most of the owners prefer to arrange it on the basis of the well, the development of which uses various methods. We will consider rotary drilling - a very promising but little known option.
Our article describes in detail the intricacies of rotor technology and the tools used. The advantages and disadvantages of this technique are examined and methods for its practical implementation are presented. Our tips are useful for prudent private property owners who want to oversee the work of drills.
The content of the article:
Definition of rotary drilling
First, let's analyze what rotary drilling is all about and what the alternatives are. Drill drilling is still considered to be one of the most common methods of drawing water.
However, screw technology does not allow rocky bedrock to pass through. The screw bit used in screw drilling cannot destroy limestone. But there often happens that you need to drill it because the layers above are not stable and sufficient for the operating flow rate.
Therefore, rotation technology, previously only used in mining, was introduced into the construction of private water intake systems. Its working element is somewhat in the borehole part of the well. A chisel is used to destroy coherent and incoherent soils and break up rocky bedrock.
The excavation of the destroyed rock is carried out with the help of a liquid that is fed to the area via a working column or annulus space.These are two different drilling methods, each of which is explained in detail below.
The diameter of the chisel exceeds the diameter of the working column, which allows:
- Reduction of the energy costs for the entire drilling process (the power is used here directly only for turning with the force of the drill bit in the face, and the friction losses of the work string against the borehole wall are minimized);
- Protect most elements of the working line from damage, as well as the walls of the borehole from destruction.
- Create drill holes with an impressive diameter (e.g. up to 70 cm) at extremely impressive depths.
In this way you can form aquifers with a depth of 300 meters or more, i.e. drill water inlets to supply summer houses and villages with water.
The definition: rotary drilling is thus such a way of developing a borehole, in which the force on the drill is transmitted in the area from the rotary drilling machine rotator through the working column. It consists of rods - narrow steel pipes that are connected one by one, changing the depths in the ground.
When cleaning the mine trunk and slaughtering it from the sludge, the water supplied under pressure is used. Thanks to this decision, there is no need to disassemble and assemble the drill string for core extraction as it is for core drilling.
The liquid injected into the mine immediately solves two important tasks: It clears the way for the drill to carry out further work and to produce the necessary flushing of the well in order to prepare the water intake for operation.
Advantages of rotation technology
What are the advantages of rotary drilling over possible alternatives? There are several of them.
FirstA lathe chisel can be used to create large-diameter wells that can fully meet the water needs of several households at the same time.
It's no secret that drilling is not an expensive process: it requires special equipment, and experienced drills need to control and manage the process. After all, drilling activities are licensed. Hence the high price.
The simultaneous amalgamation of several households to finance a common well for neighboring locations is a cost-effective undertaking. However, this requires a significant burden. In most cases, aquifers of quaternary sediments (sands) cannot supply them.
For collective operation, water should of course be absorbed on limestone. The groundwater obtained from this is characterized by greater water mobility and purity. The volume of precipitation does not have the slightest influence on the flow of the wells to the limestone. What can not be said about the wells in the sand.
Secondly, convince relatively low energy costs. The working element for rotary drilling is a chisel. But unlike auger and core drilling, the drilling tool does not interact with the walls of the borehole
That is, only one bit, the height of which is negligible in relation to the height of the entire drill string, is in direct contact with the ground. As a result, this method of forming wells is the fastest - up to 1000 linear meters per month!
ThirdCollective customers are attracted by the depth of the wells. Only the rotation method can be used to drill a well buried in native metamorphic and igneous rocks, from the cracks of which it is possible to pump water, the composition of which is most suitable for drinking purposes.
Most of the time, only service water is obtained from inlets less than 30 m deep; its composition is influenced by nearby bodies of water, rivers littered with rubbish, precipitation and only technical fluids that end up on the ground. The screw and core tube help to get just one such inlet.
In addition, rotary drilling allows you to go through development to full depth without having to switch to a different drilling method. For example, if a borehole is being developed with a screw and a boulder needs to be drilled, a push rope technique is used.
To do this, a screw cup is removed from the barrel and the drill is thrown in the face until a boulder is broken. Then slaughter is cleared by a bailer. It is used when it is necessary to bring water-saturated sand to the surface that is not cheesy in the core pipe.
Practice shows that wells drilled using the rotation method have a longer lifespan. Technologically, this is due to the fact that after the installation of the casing string forming the borehole walls, the annular space is further strengthened.
First, a vertical bracket is placed on the surface above the borehole to further secure the vertical members of the work line. The first link of this drilling shaft is equipped with a working element - a drill bit, which, depending on the rock category, can have a different format for drillability.
Drilling tool set
When you deepen the first link, the candle, the next, called the pole, will be mounted on it, and so on. The length of each such pipe block can vary between 20 and 50 m. To simplify the formation of the working column, each rod is equipped with a conical thread with a lock.
As a result, a drill is formed, which consists of:
- Work bit;
- Lead rod;
- Columns of ordinary rods connected to each other by couplings.
The working column is held with vortices, the rotation of which is carried out by the rotor. Depending on how deep you want to drill and the physical and mechanical properties of the soil, standard or weight bars are used to form the guide link.
The drive rod is typically a weighted tube because it has an important technological mission. Through them, a rinsing solution gets into the face of the chisel, whose job it is to wash out the crushed rock. And this in turn places demands on coupling connections, the task of which is to seal connections between links.
Do not forget that the liquid pressure is directly related to the height of the formed column (and not the pipe cross section). Even when water is used as the washing solution, the pressure increases by 1 atmosphere every 10 meters.
An example is worthwhile for comparison. The working pressure in the domestic pipeline network of the house is 10 atmospheres, and the most durable pipes are designed for a pressure of 20 atmospheres.
Only when home systems are stationary and not moving will the pressure be equal to the weight of the drill string on the drive rod. But it still has to transfer angular momentum and force to the teeth.
The following requirements are placed on couplings as structural elements of a drill string:
- must ensure the tightness of the rod connection and withstand a liquid pressure of up to 100 atmospheres (for cleaning the floor with a pressurized current);
- must be wear-resistant so as not to become unusable when rubbing against the walls of the well;
- must be able to transfer torque from the top of the work string down and ultimately to the drill bit.
It is imperative that the couplings are of the correct quality. If at least one of them cannot withstand the load and the working cord is broken, then it will be extremely difficult to bring the lower part together with the drill. In terms of capital expenditures, it is sometimes easier to drill a new well nearby than to get a shaft removed.
Water consumption when drilling
The fluid that is put on the face is usually ordinary water. Sometimes a solution containing drilling additives is fed into the borehole to stabilize the trunk that runs through loosely incoherent rocks (sand, gravel, gravel and pebble deposits). This is necessary because the housing is not in the first stages of penetration.
Water enters the outlet either under pressure in the actuator stem (and then pumps through annulus space) or by gravity through annulus space, and removal is already done through the working column with a suction pump.
These are two different rotary drilling technologies, the characteristics of which are explained below.
Whichever method is used, the fluid used everywhere in drilling must be cleaned (for further use).
Use the following devices to do this:
- Storage stall for drilling fluid. (If you are planning on drilling a shallow well, digits can be placed directly in the ground within a few tens, and ordinary water is used as the flushing liquid.) The barn acts as a battery for flushing liquid.
- Vibrosieve. The flushing solution lifted from the borehole contains gravel particles that must be removed. The most effective way is a mechanical one with vibrating screens.
- Sedimentation tank. After removing large particles of the rock, the liquid enters the sump to remove precipitating suspended particles. When using water as the washing liquid, a sump is sometimes built directly into the ground. In addition, hydrocyclone is used to separate liquid substances and separate sediments.
- Mud pump. It ensures the circulation of the washing solution.
- Gutter system. They are needed for the movement of water from the place of origin of the mine to the place of its purification.
Overall, the following mechanisms and equipment are required to develop a borehole using rotational technology:
- Tower or console for assembling the drill string from the rods and for dismantling at the end of drilling and a tackle system.
- engineProviding a rotation of a rotor.
- Fluid equipment. Mechanisms and devices for circulating and cleaning washing liquid (pump; vibrating sieve; collecting trays and / or hydrocyclone ;; a barn for storing washing liquid; system of pipes and gutters).
For the rotary drilling of shallow boreholes, the entire equipment set listed is very compact (for example, the bracket arm folds). This makes it easy to place drilling rigs in any convenient location for drilling and subsequent operation.
Two rotary drilling options
There are two types of rotary drilling technologies, depending on how irrigation fluid is supplied to the face:
- Direct feed;
- with reverse feed.
It should be noted that the liquid added to the face is not intended only for rinsing and removing gravel. It also cools the bit, which is very hot from friction. If the liquid is supplied directly, the pump generates its overpressure.
Water enters the face through the technological holes in the drill bit, "picks up" the crushed rock and then by gravity through the well (i.e. through annulus space in relation to the guide rod) enters the surface where it enters the Cleaning complex occurs (vibrating sieve, hydrocyclone).
The backfeed technology implies that the mud flows down by gravity and falls down the borehole, but the solution with comminuted material returns to the surface through the lead rod tube. In this case, the sludge pump generates a negative pressure.
Despite the apparent simplicity of both technologies, there are many more nuances than it might seem at first glance. It is therefore appropriate to examine each of these drilling technologies in more detail.
Direct flushing holes
This technology is sometimes referred to as "direct watercourse". It is advisable to use it in sandy, gravelly, gravelly soils. It is also used when the depth of the aquifer does not exceed 30 m. Here, additives are added to the liquid that increase its density and trunk stability.
Rotary drilling is characterized by a gradual decrease in the diameter of the borehole to be drilled. In other words, first the borehole with the largest diameter is drilled, then it is manure.The pipe and the annulus between the outer surface of the pipe and the wall of the well through technological holes are filled with cement mortar.
Further drilling is continued with a smaller chisel. Then casing again, and the new section is even smaller in diameter, and so on. The less "distracted" you need to be "distracted" by cementing the borehole, the higher the drilling productivity, which ultimately adds to the total cost of the process and the entire borehole.
In addition, too frequent jacketing will result in a large reduction in the effective diameter of the borehole (the diameter that opens the aquifer). The “direct watercourse” is characterized by the fact that the well cannot be encased up to 100 meters with this method of its formation.
The main pressure of the flushing liquid is generated by the pump in the drive stem. Annular space The liquid with elements made of crushed stone fills the space by gravity without destroying the borehole wall with excess pressure.
However, this drilling method has its disadvantages. In particular, open for too long The location causes finely dispersed clay particles to get into the aquifer, which can significantly reduce and slow down the flow of water into the aquifer.
These particles play the role of peculiar pore plugs and micro-channels in the rock through which water seeps. Therefore, the jacketing process performed during the drilling operation is required to maintain future productivity of the entire wellbore.
Flushing backward drilling
This method of controlling fluid flow is the best way to clean the cylinder and base.The pump here does not push the liquid into the ground, but, on the contrary, sucks it back, and this leads to the fact that the speed of the formation of the borehole with a chisel increases by an order of magnitude and many times compared to direct flushing.
The well itself is not contaminated with clay inclusions with a river of flowing washing liquid. After all, the pump sucks up everything that can be in it. Incidentally, additional additives no longer make any practical sense, so pure water is used as the same washing liquid.
To summarize the benefits of drilling with a reverse stream:
- The drilling speed increases by 15 times (compared to direct watercourse).
- The aquifer is not clogged with clay particles and muddy grains of sand from below unlocked well level;
- Due to the high-quality opening of the aquifer, the well does not have to be additionally prepared for operation. You can immediately install the inner case with a filter and pump it down with a pump.
- Simple (and therefore cheap) water is used as the working medium.
However, this method has a significant disadvantage. It requires the inclusion of expensive equipment, which ultimately leads to a significant increase in the cost of the entire drilling process as a whole.
For this reason, “reverse watercourse” drilling is only carried out in cases where the well is designed to be operated by several households at the same time. However, if the well is designed for individual operation, then it makes much more sense to use rotary drilling technology with direct watercourse.
Conclusions and useful video on the topic
Video # 1.Visual demonstration of the rotary drilling process in steps:
Video # 2. Analysis of Rotary Technology and Downhole Arrangement Principles:
Video # 3. Water circulation in rotary drilling:
The situation with the presence and depth of aquifers can be very different from place to place (but somewhere there are none at all, like on Madeira Island).
When planning a borehole and choosing the optimal rotary drilling method, existing maps of proven aquifers should be used. This will save you a lot of time and money.
Tell us about your experience developing a borehole with rotary technology. Share technological nuances useful to website visitors. Please leave comments in the block form below, post a photo, and ask questions about the subject of the item.
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