In recent years, construction has come out of a protracted crisis, the number of houses being built, industrial complexes, roads, and other infrastructure facilities is increasing. Accordingly, high-tech engineering methods are becoming more and more popular, which can reduce the time and labor costs.
General information
These include directional drilling. Wells are known to be either vertical (standard) or deviated. Moreover, the required deviation from the vertical / horizontal is small: only 2 degrees with standard drilling, more than 6 degrees with deep
drilling (artesian wells, oil or gas production).
Naturally, the presence of this deviation may be due not only to artificial, but also completely natural reasons. They are divided into several groups (geological, technical, technological). If you know all these factors thoroughly, you can accurately control the position of the well in space.
Accordingly, artificial deviation is understood to mean any “curvature” of the well channel that was originally conceived. It is important to understand that directional drilling involves strict control of the direction of movement of the drill throughout the work.
Features of drilling oil and gas wells
Particularly many difficulties are caused by such work in the aspect of the oil and gas industry. There, inclined drilling has to be carried out using special guide profiles. It is also important to remember that the upper pit is always (!) Made strictly vertical, and the deviation begins at lower horizons, in the planned azimuth.
Especially often, directional drilling is not used in field development, but only in exploration. It is much cheaper to check for the presence of “markers” by making a sufficiently long inclined pit than to immediately try to drill the rock to a sufficient depth vertically.
How is
directional drilling generally carried out
? The technology is relatively simple: first, the main pit breaks through, then, using bending devices, an oblique or horizontally directed drill is brought to the right place, with which an additional shaft is already being drilled. To accurately maintain the direction specified by the project, it is necessary to use “markers”, they are also beacons. In many cases, special cameras are used to visualize the drilling process.
Important notes
It should be noted that in some cases such wells are forced to make features of geological rocks. So, sometimes it is cheaper to pit above a place of some solid igneous rock than to punch it.
We also note that directional drilling also involves breaking through strictly horizontal pits. All wells produced by this method are divided into single and multilateral. In the latter case, several layers depart from the main trunk. A similar drilling method in the oil and gas industry is widely used in the following cases:
- At the opening of oil or gas strata, which lie between parallel discharges.
- If it turned out that the developed layer dramatically changes its direction.
- In the case when oil or gas horizons lie under salt domes (due to the difficulties of drilling through the latter).
- When it is necessary to bypass the collapse zones in the mines.
- Inclined (horizontal, in particular) drilling is indispensable if the productive layer lies under some body of water or on the seabed, under residential quarters or in detached buildings.
- On drilling racks and platforms located directly at sea, in 90% of cases this method of drilling pits is used.
- In addition, directional drilling is indispensable if you want to conduct a multilateral well in an area with a strongly crossed relief (ravines, hills, etc.).
A similar method is indispensable if for some reason (collapse,
tectonic rock
shift ) the shaft of the mine has shifted to the side, and therefore there is a need to bypass the problem place. This is also done if it is necessary to take a core sample from the main trunk, since it is impossible to do this in other ways.
Also, directional drilling is used when it is necessary to quickly extinguish a well that is lit up for some reason, as well as in cases where the lower part of the pit needs to be expanded for operational reasons. In a similar way, the drainage surface in old wells is increased when it is necessary to increase production volumes.
This is practiced when it is initially known that the field does not belong to the category of the rich, but it is required to quickly “milk” it. Then, “cluster” drilling is applied, with multiple and multiple withdrawal from the main pit side. If in this case we use standard methods, then the return on the field will be low, and the well will quickly be depleted.
By the method of directional drilling, primary pits are pierced through coal pastes, since in this situation they must first be freed from possible gas pockets. If this is not done, the probability of ignition and even explosion is already high during the operation of the well.
In all cases, downhole motors (turbodrills, occasionally - electric drills, screw motors) are used to break through the pit. The drilling method is rotary.
Main methods
The main method (both here and abroad) is the dynamic use of terrain features. And this is understandable, since perfectly flat plains and steppes are far from everywhere.
Typically, typical traces (profiles) are taken for the sample, which are built in advance, and for this, methods of mathematical modeling are used. It is important to note that the “standard” method can only be applied (!) To fields already being developed, all the features of which have long been known. The peculiarity of this method is that they do not try to control the curvature of the terrain, but adjust to it. Alas, at the same time, a significant drawback is manifested, which is expressed in a noticeable rise in the cost of drilling.
In the project profile, places with the maximum degree of curvature are marked without fail, since without this data it is not practical to draw up a finished project. In this case, a trained directional drilling engineer is responsible for the design.
Changing the layout of the drilling rig to adjust the bending of the well
The most common way when it comes to controlling the bend of the pit directly during punching. The method is good in that you do not have to use special equipment. Its disadvantage is a strong limitation of accelerated drilling.
The use of artificial diverters
For work of this type, curved sub, eccentric type nipples, wedges, and other deflecting devices are used. All devices are selected individually, depending on the specific situation and the type of terrain.
Shrub variety
An important method of directional drilling is cluster penetration of pits. At the same time, the beginning of all pits is at one point, and the end sections are where the layers of discovered deposits go.
The method is good in that it allows to significantly reduce the amount of installation work on the site, significantly reduce the number of required communication lines, including roads to the areas where work is performed, the need for water supply and power lines decreases. This type of drilling was first tested in the USSR, more precisely, in Azerbaijan, during installation work on the island of Artem.
The main disadvantages include the importance of preventing the intersection of the mouths of the mines. In addition, it is necessary to preserve the pits already operating by the time of the secondary drilling, as the fire safety rules require this. Finally, a huge drawback of cluster pits is the complexity of their subsequent maintenance and repair, and in marine conditions it is extremely difficult to eliminate breakouts.
In what conditions is cluster drilling used?
So in what cases is bush directional horizontal drilling used? The reasons for its use are divided into the following groups:
- Technogenic - drilling under buildings, including residential, other technical facilities.
- Technological - when it is likely that the development of a standard well will disrupt the operation of existing pits. The bush method is not so "traumatic" in this regard.
- Geological - when minerals occur in uneven formations at different horizons. In this case, directional drilling installations are the only option when it is necessary to establish production in the shortest possible time without spending phenomenal amounts of money on it.
- Orographic is the most common group of reasons, including the need to open a deposit located under the surface of the sea, lake, in the case of very rough terrain, as well as when laying pits from the base of offshore platforms, as well as overpasses.
- Climatic. In recent years, in many areas of the Far North, there has been a steady tendency to thaw permafrost, which is why specialists simply have to resort to the cluster method of drilling. Other methods are fraught with collapse of the lumen of the well.
Note that the maximum effect from the operation of cluster wells is observed in the conditions of marshy, often flooded areas. It is important to note that with directional drilling under the surface of water bodies, it is extremely important to have experienced personnel capable of properly using navigation equipment, without which penetration of a pit in such specific conditions becomes impossible.
Thus, jobs for directional drilling must necessarily include the search for technically savvy, educated personnel.
Important features of the method
Volumetric bushes are similar to pyramids or cones, the size of which, as you can understand, depends on the size and “fuzziness” of the field being developed. Accordingly, the number of punched holes is determined by technical capabilities. It is very important to understand that the determination of the size of the bush should be treated as responsibly as possible, since the area of the alienated territory depends on this indicator.
This is especially important when developing pits within the boundaries of a settlement. An important role in the operation of a finished well is played by the location of wellheads. It is not surprising that exactly directional drilling of gas pipelines in the last 15-20 years has become the main method widely used in practice.
Positive effects of cluster drilling
In general, this method significantly reduces the cost of organizing the extraction of mineral resources or the construction of industrial facilities, contributes to the volume of automation of all production operations and processes. More importantly, this approach helps protect the environment by minimizing environmental impacts.
The fact is that during the implementation of cluster drilling it becomes quite possible to completely collect drilling waste, preventing it from falling into groundwater, and also reduces the likelihood of a decrease in the level of the latter. This is often observed with standard drilling, as this results in the destruction of aquifers.
One bush contains at least two wells. As a rule, oil workers in our country practice grouping pits in 18-24 pieces, but in some cases their number exceeds 30. However, this is far from a record, since in foreign practice there are cases when 60 "could leave one mine processes ". In particular, the notorious BP company drilled 60 × 60 m on a small loose island ... immediately 68 pits. This allowed a sharp increase in the volume of oil received from one field.
So the drilling of directional and horizontal wells in the modern economy is extremely in demand precisely because of the conservation of material and financial resources.
Multilateral type of drilling
Currently, due to the depletion of many old deposits, the only reliable way to obtain minerals is the use of progressive production methods, which include multi-face drilling. Moreover, several new “processes” are immediately withdrawn from the main pit at a certain depth. Because of this, the area of the well in the productive horizon increases significantly, and the volume of extraction of minerals increases. In addition, at the same time, drilling volumes can be reduced in upper, unproductive horizons.
In our country, the first well of this type was drilled in 1953 in Bashkiria. But the pit, which took place directly in the thickness of the reservoir, could be made only at the end of the 50s. It happened in the Samara region. It was immediately revealed that the daily output of such wells is approximately 40% higher than that of cores made by the standard vertical method.
It was then that directional drilling began to develop in our country. Education in this specialty was introduced in all technical institutes of the country.
If the multilateral method is used, the total length of the pit in the formation increases significantly, and the drainage and filtration zone increases. This contributes not only to increase the return on the well, but also improves the quality of the product obtained during its operation. Such pits are divided into the following varieties:
- Inclined, branched type.
- Horizontally branched.
- The pits are radially directed.
In the latter case, directional drilling (horizontally directed drilling) is used for complex terrain and uneven concentration of production horizons. This method allows (while minimizing costs) to maximize the volume of mining.
Characteristics of multi-hole pits
As you might guess, oblique-branched pits consist of the main shaft of the shaft and the daughter processes extending from them located in different planes. The horizontally directed type itself is a variation of the species just described. The only difference is that the “shoots” depart from the main trunk in a strictly horizontal plane, at an angle of 90 degrees.
Accordingly, in radial pits, the main trunk also goes strictly vertically, and the additional ones - around the circumference, that is, in the radial direction. In recent years, branched wells are considered a very promising direction of drilling, since their use on an industrial scale allows us to solve many issues that arise in the aspect of underground development:
- The most efficient production of oil fields with uneven horizons. In this case, vertically directed drilling is not economically feasible, since the final cost is too large.
- Directionally directional drilling can significantly reduce the number of wells used. This leads to a reduction in the cost of the work, as well as minimizes the impact on the environment.
- When producing very viscous grades of oil that are pumped out at extremely deep depths.
- The same method is used when it is necessary to build a geothermal station that uses the energy of underground hot water.
Thus, the drilling of directional wells is a technique widely used in the modern oil and gas industry and the construction industry.