NO20131441A1 - Method of cleaning drilling fluid in rock sampling drilling and a cleaning unit - Google Patents

Description

The invention relates to a method for cleaning drilling fluid in rock sampling drilling, where a drilling machine is used, which has a hollow drill pipe, a bucket unit at the drill end of the drill pipe, a protective pipe that surrounds the part of the drill pipe that is close to the ground surface, so that there is empty space between the drill pipe and the protective pipe, and in the method, drilling fluid is fed into the drill pipe, which drilling fluid lubricates the drilling event, and the drilling fluid flows between the drill pipe and the borehole wall towards the borehole opening and at the same time transports solids formed during drilling. The invention further relates to a cleaning unit for the drilling fluid in sampling drilling.

In soil and rock sampling drilling, the aim is to obtain a core sample from the ground or bedrock over the length of the entire drilling depth or part of it, which core sample is generally rock material from the bedrock or in some cases also soil from the ground. The result of the sampling drilling is therefore a core sample taken from the borehole, which is arranged in sample boxes, for example for examination by a geologist. The hole generated in the actual drilling is a by-product, although it can also be exploited in some cases.

Sampling drilling differs from other basic drilling fields, such as oil drilling, charge drilling for blasting in the construction industry, drilled well or heat well drilling, drilling charge and pilot holes in an ore body in mining, drilling gas outflow holes in coal mines or holes formed in rescue operations. In all of these, the aim is to drill a hole in the ground or bedrock, which is used in different ways in each field. The result of the operation is consequently a hole obtained in the ground or bedrock, and the rock material obtained from the borehole is a by-product or rather waste which is not utilized in any way. In these boreholes, all the soil or rock material from the borehole is crushed and ground with the drill bit into a fairly fine material that is removed as soil or rock mud by the flow of drilling fluid. In sampling drilling, on the other hand, soil and rock material is ground away from the ground and bedrock with a tubular shovel only from a fairly small, circular area. Consequently, a core sample containing soil and rock material is located at each drilling depth inside the bucket and drill pipe, and this core sample is lifted in parts of suitable length up from the borehole and sorted for later investigations.

In sampling drilling, a cylindrical, hollow diamond blade placed on the end of a drill pipe is rotated and pressed with an appropriate force against the rock. The power needed to rotate and push the bucket and drill pipes is provided by a drilling machine that contains both a rotating unit and a power means that provides input power. Inside the drill pipe above the bucket unit, there is a separate core pipe that attaches to the rock sample, and with the help of this the rock sample can be lifted up from the hole using a device called a retriever and a winch. The core sample is lifted using the sampling drill field's special technology described above, which uses a core pipe, a generator and a winch. Deep drilling in rock is not possible without the use of drilling fluid. Water taken from nature near the drilling site is usually used as drilling fluid, or it is brought to the site in a tank or similar container. In some cases, a fluid other than water can be used as the drilling fluid.

Without drilling fluid, the tip of the diamond bit overheats and wears quickly. On the other hand, when the diamond bit is lubricated and cooled by drilling fluid, it lasts a very long time when used correctly. The drilling fluid also lubricates the rotation of the long drill pipe inside the rock and removes rock material that has been ground from the rock, i.e. rock mud, from the bucket and finally out of the borehole. Quite a bit of rock mud is formed in the case of sampling drilling, because the amount of rock material that is ground from the rock is much less than in other fields that use core drilling. Most of the rock material in the borehole remains in the rock material rod that forms as a result. Chemicals can, if necessary, be added to the drilling water, which further simplifies the drilling event and extends the life of the bucket, which is known in the art as such.

With current technology, the drilling fluid that lubricates the drilling event is normally taken from a lake, a ditch or other natural water source located near the drilling site. If necessary, water that collects in a previously drilled hole can also be used. The drilling fluid is fed at a suitable pressure inside the drill pipe and down the pipe, all the way down to the blade which rotates inside the rock. At the drilling bucket, the drilling fluid lubricates the drilling event, cools the bucket and removes rock material generated in the drilling, i.e. drilling mud. The drilling fluid and the rock mud it contains then flow back upwards outside the wall of the drill pipe. The fluid and the drilling mud it contains flows upwards between the drill pipe and the wall of the hole drilled in the rock, pushed by fluid reserve pressure acting behind it. At the same time, the fluid also lubricates the rotation of the drill pipe in the hole formed in the rock. If the rock is highly fractured or porous, some drilling fluid is absorbed into cracks and pores in the rock. This is illustrated in figure 4.

When the drilling fluid comes through the borehole drilled in the rock, and arrives at the soil layer between the rock and the ground surface, it moves inside the protective pipe sunk into the soil layer, the so-called soil pipe, up to the ground surface. With the help of the protective pipe, the large absorption of fluid into the soil material between the ground surface and the stone is avoided. The protective pipe extends slightly above the ground surface, and its end is located under or inside the drilling machine. This is shown in Figure 3.

With current technology, drilling fluid rising from the casing, and any chemicals it includes, and the solids, which are rock, soil, metal particles dislodged from the drilling equipment, and other fine solids, flow from the opening of the casing under the drill and beyond into the surrounding terrain.

As it rises from the ground, the drilling fluid is distinctly warm, even in winter. The drilling fluid rising from the protective pipe and flowing from under the machine to the terrain can in some places cause a muddy area which causes soiling of machinery, clothing and equipment and which hinders the movement of the work team, and further in winter freezing of the drilling fluid creates a risk of to slip, which are occupational safety risks. In winter, drilling can be carried out on the ice of a lake or frozen marsh, whereby the ice or the frozen surface of the marsh supports the drilling machine. The flow of drilling fluid into the area surrounding the machine melts the ice or frozen mud supporting the machine and can cause the machine to sink, which is also a major occupational safety risk.

Because the initial drilling fluid is usually taken from a natural water source, it must be heated immediately after it is taken from the water source when it is sub-zero outside, and a lot of energy is used for this. If the drilling fluid is not heated, at least at very low temperatures and with long water lines, there is a risk of the drilling fluid lines freezing. When a drilling fluid line freezes, the drilling operation is stopped immediately.

In some cases, chemicals must be added to the drilling fluid, which chemicals contribute to the drilling incident. After use, the fluid equipped with chemicals flows back into the environment, whereby in addition to continuously having to use quite a lot of additives, chemicals added to the fluid also end up in the environment. Although these chemicals are not considered dangerous to the environment with current knowledge, the applicant company is aware of the matter due to high environmental awareness.

Patent publication US2008/121589 describes a fluid cleaning device for cleaning drilling fluid so that the fluid can be reused in drilling. This has several successive precipitation basins, between which there are dam walls that become lower in successive precipitation basins. These dam walls are arranged so that turbulence in the pools is minimized. However, such an arrangement makes the removal of fine material from the drilling fluid difficult, and in sampling drilling the solids in the drilling fluid are mainly fine.

Patent publication EP 0047347 describes a closed circulation system for drilling fluid. However, the drilling operation described in the reference publication is related to drilling for coal deposits carried out in coal mines, which drilling only occurs underground and essentially in the horizontal direction. The aim is to drill a hole a few hundred meters long into a coal deposit, where the purpose of the hole is to remove methane gas in a controlled manner from a future extraction area. Consequently, the coal extraction carried out later in the vicinity of the hole will be safer. The technology described here comprises a complicated process auger sensor for drilling fluid, which device essentially enables the separation of explosive methane gas from the fluid and its safe removal. The described device is based on a very complicated technology, which uses successive sedimentation basins arranged in closed and gas-tight spaces, optimal boundaries for gas and fluid, which are at different levels in different basins, a screw conveyor used to remove stone material and centrifugal separation used for to remove finer rock material and various pumps, systems used to separate fluid, gas and rock material.

Patent publication WO 99/15758 describes the use of a closed drilling fluid circulation system. Here, the drilling only occurs in sea areas, for example in connection with oil drilling. The described technology includes a very complicated cleaning system located on the seabed, which system only performs the removal of coarse rock material. The aim of this is that the wear and tear on the pumps and other technology can be reduced, and the technology's reliability is improved under offshore conditions.

Patent publication US 5928519 describes the use of a closed drilling fluid circulation system in connection with underbalanced drilling (UBD) in oil and gas drilling. UBD drilling differs from normal oil drilling in that there is no overpressure in the drilling fluid in the borehole and the pipe system, but a negative pressure is provided in the drill pipe system with the help of suction that arises from the drilling fluid outlet side. In some cases, this provides definite advantages, such as the fact that the risk of weakening the oil deposit is reduced, and the risk of the drill pipe becoming stuck in the hole is reduced. Two different closed pressure containers are needed to circulate the drilling fluid, both of which contain complicated technology. One container has a higher pressure, and the other a lower pressure.

Patent publication US 5928519 describes the use of a closed drilling fluid circulation system in connection with oil drilling, where diesel, sludge/drilling mud and fine particles are separated from the drilling fluid. A closed circulation arrangement is presented here, where highly complex technology is used, including agitators, activated sludge tanks, soil and rock sludge washers, sludge dryers, intermediate sludge storage tanks, centrifugal/sling separators, fluid traps, fluid processing devices, diesel separators and tanks, pumps and conveyors. The methods described for recycling the drilling fluid require very complicated devices, where moving them from one place to another is practically impossible.

In general, with sampling drilling, the amount of drilling fluid used and the amount of fine solids formed during drilling is significantly less than with other rock drilling procedures. Consequently, there has traditionally been no reason to recycle the drilling fluid. Consequently, the methods of cleaning drilling fluid for recycling in other drilling processes are also quite difficult to apply to sampling wells.

An object of the invention is a solution in which the drawbacks and disadvantages associated with the known technique can be considerably reduced.

The object of the invention is achieved with a method and a cleaning unit which is characterized by the way presented in the independent claims. Some advantageous embodiments of the invention are presented in the dependent claims.

The main idea of the invention is to recover the drilling fluid used in sampling drilling by a drilling machine, when the drilling fluid comes out of the borehole, and to transport it to a separate cleaning unit. The cleaning unit has two or more precipitation basins, where solids are separated from the drilling fluid. The cleaned drilling fluid is returned to the drilling machine and

reused in sampling drilling.

The method according to the invention for cleaning drilling fluid in rock sampling drilling comprises using a drilling machine that has a hollow drill pipe, a cylindrical bucket unit at the drill end of the drill pipe, a protective tube that surrounds the part of the drill pipe that is close to the ground surface, so that there is empty space between the drill pipe and the protective pipe, and in the method, drilling fluid is fed into the drill pipe, which drilling fluid lubricates the drilling event, and the drilling fluid flows between the drill pipe and the borehole wall towards the borehole opening, and at the same time transports powder-like solids formed during drilling. Furthermore, the method has steps, where the drilling fluid coming from between the protective pipe and the drill pipe in the drilling machine, and which contains solids, is recovered with an arrangement in the drilling machine, the recovered drilling fluid is directed to a cleaning unit, which cleaning unit has at least two precipitation basins, where solids are separated from the drilling fluid, and the drilling fluid that has been cleaned in the cleaning unit, is led to the drilling machine and fed into the drill pipe. At least two of the precipitation basins are in series, i.e. the fluid to be purified passes in sequence from one basin to the next. Uncleaned drilling fluid is fed into the first precipitation basin, and purified drilling fluid is removed from the last precipitation basin. Between the precipitating basins there is a transfer connection which has an intake end and a discharge end. The inlet end takes fluid from the precipitation basin, and the discharge end releases the fluid into the next precipitation basin. The discharge ends of the transfer connection are closer to the bottom of the basins than the intake ends.

In one embodiment of the method according to the invention, drilling fluid mud containing solid matter which accumulates at the bottom of the precipitation basin is removed from the basin. The drilling fluid mud contains solids to a significantly greater extent than the untreated drilling fluid. In a second embodiment of the method according to the invention, the drilling fluid mud that collects at the bottom of the precipitation basin and contains solid matter is filtered and returned to the precipitation basin.

In a third embodiment of the method according to the invention, the drilling fluid in the cleaning unit is fed into the first precipitation basin through a nozzle, which nozzle has a neck part and a curved flange part, and the curved flange part is arranged so that the fluid flow essentially follows the flange part, and solids contained in the fluid detaches from the flow.

In a fourth embodiment of the method according to the invention, an ion-charged polymer mixture, ferrous sulfate, ferric sulfate or other chemical added to the drilling fluid, which contributes to the separation of solids from fluid, is used in the cleaning of the drilling fluid to enhance the process.

In a fifth embodiment of the method according to the invention, new drilling fluid is added to the drilling fluid circulation when necessary.

In a sixth embodiment of the method according to the invention, substances or chemicals that contribute to the drilling process are added to the drilling fluid before the drilling fluid is returned to the drill pipe.

In one embodiment of the method according to the invention, the cleaning unit is placed in one or more containers or other movable constructions. The construction's walls are thermally insulated, and a heating device can be installed therein.

The cleaning unit for drilling fluid in sampling drilling according to the invention has a connection for feeding impure drilling fluid into the cleaning unit, at least two precipitation basins, where solid matter contained in the drilling fluid is arranged to collect at the bottom of the basin, where it forms drilling fluid mud, and in the lower part of at least one precipitation basin, there is a valve arrangement for removing the drilling fluid mud containing solids from the precipitation basin, and between the precipitation basins there is a transfer connection for moving the drilling fluid between precipitation basins, and in the last precipitation basin in the series there is an outlet connection for removing the cleaned drilling fluid from the cleaning unit. The transfer connections have an intake end and a discharge end, and the discharge ends of the transfer connections are closer to the bottom of the precipitation basins than the intake ends. The cleaning unit is placed in one or more containers or similar structures that are intended to be moved.

In one embodiment of the cleaning unit according to the invention, the drilling fluid mud which has been discharged through the valve arrangement and containing solids is arranged to move through a filter arrangement to separate the solids.

In another embodiment of the cleaning unit according to the invention, the filter arrangement can be removed for replacement or cleaning, or it can be cleaned on site. In a third embodiment of the cleaning unit according to the invention, there is a point on the bottom of the precipitation basin which is lower than the rest of the bottom, in which the drilling fluid mud is arranged to collect. The valve arrangement is located at this point. In a fourth embodiment of the cleaning unit according to the invention, the drilling fluid which is separated from the drilling fluid mud with the filter arrangement is arranged to be transported back to the precipitation basin.

In a fifth embodiment of the cleaning unit according to the invention, there is a lower basin below the precipitation basin or basins, in which lower basin the drilling fluid separated from the drilling fluid mud by the filter arrangement or arrangements is arranged to be collected, and from which lower basin there is a transfer arrangement for to transfer the drilling fluid to the precipitation basin.

In a sixth embodiment of the cleaning unit according to the invention, the untreated drilling fluid fed into the first precipitation basin is arranged to be fed through a nozzle (611), which nozzle has a neck part and a curved flange part, and the curved flange part is arranged so that the fluid flow essentially follows the flange part, and the solids contained in the fluid detach from the flow.

In a seventh embodiment of the cleaning unit according to the invention, the discharge ends of the transfer connections between the precipitation basins are closer to the bottom of the basin than the intake ends, and the discharge ends are shaped to direct the drilling fluid substantially towards the bottom of the precipitation basin.

In an eighth embodiment of the cleaning unit according to the invention, an ion-charged polymer mixture, ferrous sulphate, ferric sulphate or other chemical which contributes to the separation of solids from fluid, is arranged to be added to the drilling fluid. In a ninth embodiment of the cleaning unit according to the invention, it has an arrangement for feeding substances that contribute to the drilling event into the drilling fluid before the drilling fluid is returned to the drilling process.

An advantage of the invention is that with its help occupational safety risks can be reduced in sampling drilling operations. The risk of slipping is reduced, because very little water, if any, flows under the drill. The drilling water causes a risk of slipping, except in winter when it freezes, also in summer, especially if slippery drilling assist chemicals are used in the fluid.

It also helps the drilling machine to move in the environment. Without recirculation of the drilling fluid, a lot of water flows out into the terrain surrounding the drilling machine, and the roads surrounding the machine inevitably become muddy within a short time. This leads to work safety risks when movement becomes more difficult, especially when the work crew has to carry equipment needed in drilling, such as drill pipe and rock samples, as they move around the machine. By recirculating the drilling fluid, these problems are reduced, because the area around the machine remains dry. Contamination of the work team's clothing and the internal parts of the machine is therefore also avoided.

A further advantage of the invention is that energy is saved with its help. With traditional technology, the drilling water must be continuously heated in winter to prevent the fluid lines from freezing. When using initial fluid taken from a ditch or lake with traditional technology, a lot of energy must be used to heat the fluid. Correspondingly, in the traditional method, very hot drilling water that returns from below the ground goes all the way into the ground after use, and the thermal energy it contains is lost. In winter, the heat of the drilling fluid that rises from the ground can be utilized by recycling, whereby a significant amount of energy is saved.

The invention further intensifies sampling drilling, because it reduces the risk of the drilling fluid lines freezing in winter. With the traditional technology, the drilling operation must be stopped immediately when the drilling fluid lines freeze, or when the water supply is interrupted in some other way, until water is again brought to the process. When applying the invention, even if the line for the initial replacement water were to freeze, the work team, due to the large amount of fluid in circulation, will have plenty of time to repair the lines without having to interrupt the drilling operation. If the drilling operation is interrupted for some reason, the initial drilling fluid with the traditional technology must still circulate continuously to no avail to prevent freezing, and the fluid must flow to be lost as unused. In some cases even all intermediate fluid reservoirs have to be drained to no avail due to the risk of freezing. Because the drilling fluid that rises from the ground is very hot in winter, this heat can be utilized in the case according to the invention, whereby interruptions in the drilling for other reasons can even be very long, without there being a risk of the fluid freezing.

An advantage of the invention is also that it saves water or other used drilling fluid. In some places, it can be difficult to find drilling water, or the water has to be piped to the drilling site even from far away. According to the invention, the same drilling fluid always circulates in the drilling operation, and it must only be added, for example, to compensate for evaporation and fluid absorbed into cracks in the rock or into the ground from the boundary of the protective pipe.

An advantage of the invention is nevertheless that the chemicals used do not flow into the environment in an uncontrolled manner. Chemicals that simplify the drilling operation must in some situations be added to the drilling fluid. According to the traditional technology, these chemicals continuously flow into the environment. Although, according to current knowledge, these chemicals are not harmful to the environment, it is better that substances are not released into the environment, which do not belong there. When using the invention, significantly less of these chemicals are also needed compared to the traditional technology. When the same drilling fluid is recycled, chemicals do not need to be used in the same amount as normal. When using the initial water, many chemicals that contribute to the drilling must be added, while on the other hand the water in circulation according to the invention, which has already been treated with chemicals, already contains the necessary chemicals.

An advantage of the invention is also that with its help a large part of the rock mud is recovered from the borehole. As of now, this mass has no practical use, but when it has begun to be collected in accordance with the invention, it can over time be used, for example, as a workplace-specific rock sludge sample. In addition, at some research sites, the drilling permit requires clean-up afterwards, and the invention simplifies this considerably.

In the following, the invention is described in detail. In the description, reference is made to the accompanying drawings, there

Figure 1 shows as an example a drilling machine,

Figure 2 shows, as an example, a cross-section of an arrangement according to the invention for collecting drilling fluid,

Figure 3 shows as an example a drill pipe and a protective pipe,

Figure 4 shows as an example a drill pipe,

Figure 5 shows as an example an arrangement according to the invention,

Figure 6 shows as an example the internal structure of a cleaning unit according to the invention, Figure 7 shows as an example a longitudinal cross-section of a cleaning unit according to the invention, Figure 8a shows as an example a nozzle used in an embodiment of the invention, Figure 8b shows the flows of fluid and solid caused by the nozzle in Figure 8a, and Figure 9 shows as an example an arrangement according to the invention for collecting drilling fluid. Figure 1 shows as an example a drilling machine 100 for sampling drilling. The drilling machine has a drill pipe 101 and a drilling unit 102, with which the movement needed for drilling is produced. The drilling machine has a frame that supports the constructions of the drilling machine. The frame has arrangements, with which the angle of the drill pipe and at the same time the angle of the drill hole are adjusted. In the case according to the figure is the drilling machine on the ground surface 103, but it can be located, for example, on a raft or in a mine. In sampling drilling, the aim is usually to obtain rock samples from the bedrock. The rock 105 is usually covered by a layer of soil 104. The drilling machine has an arrangement, with which drilling fluid is fed into the drill pipe. Points B, C and D are marked in the figure, which points are presented in more detail in figures 4, 3 and 2. Figure 2 shows an arrangement according to the invention for collecting drilling fluid as a cross-section. The arrangement has a drill pipe 101, a protective pipe 201, a collection collar 202 and a collection basin 203. The drill pipe is hollow, and the drilling unit rotates it. The protective pipe is around the drill pipe so that it extends substantially through the soil layer and its end towards the drilling machine is above the ground surface. The drilling fluid returning from the drilling process, which rises from a void between the protective pipe and the drill pipe, is collected by a collection collar located around the end of the protective pipe and directed to the collection basin. The collection basin is connected either to the machine or by a joint to the protective pipe. The collection basin is shaped and placed so that the drilling position can be moved at least in the commonly used drilling angles, i.e. at an angle of 30-90° in relation to the horizontal plane, and that the drilling fluid coming from the protective pipe ends up in the collection basin independently of the drilling position. The movement seam between the protective pipe and the collection basin can, if necessary, be tightened, for example, with a tensioner made from tarpaulin or a flexible rubber that enables the necessary range of movement of the drill bit and directs the drilling fluid coming from the protective pipe, at least almost all the way down into the collection basin. From the collection basin, the drilling fluid and the solids it contains, such as soil and rock mud, and any drilling additives, are led into a cleaning unit that can be moved in the terrain. Figure 9 shows a second example of an arrangement according to the invention for collecting the drilling fluid in a drilling machine. The arrangement has a protective pipe 903, a collection collar 904 and a collection basin 905. The collection collar has a hole 901 for the drill pipe. The water coming from the protective pipe is collected with the collection collar and directed to the collection basin. The collection basin has a pipe 902, with which the uncleaned drilling fluid is removed from the collection basin and led by arrangement into the cleaning unit. Figure 3 illustrates the location of the protective tube 201 in the sampling bore. The drill pipe 101 has been used to drill a sampling hole from the ground surface 103 through the soil layer 104 into the stone 105.1 in the case according to the figure, the protective tube extends through the soil layer and a little down into the stone. The fluid that rises between the wellbore wall and the drill pipe mostly passes between the protective pipe and the drill pipe and continues to rise. Figure 4 shows the drill end of the drill pipe 101 inside the rock 105. At the end of the drill pipe there is a cylindrical blade part 401 which, when it rotates, drills a rock core sample 402 from the rock. Inside the drill pipe is a core pipe 403 that the rock core sample goes inside. With the core tube, the rock core sample can be lifted to the ground surface and stored. The drilling fluid reaches the blade part between the core pipe and the inner wall of the drill pipe. In contrast to other drilling fields, only a little rock accumulates in the drilling fluid during sampling drilling, because the shovel used in drilling only grinds away a small part of the borehole area. The largest part of the rock material remains in the rock core sample that is generated as a result of the drilling operation, which rock core sample is traditionally lifted from the borehole with a core pipe according to known techniques. Figure 5 shows an arrangement according to the invention for cleaning and reusing drilling fluid in sampling drilling, which arrangement has a drilling machine 100 and a cleaning unit 501 to clean the drilling fluid. The drilling machine is used to drill a borehole to take samples from the bedrock. The drilling machine has a drill pipe 101 and a collection basin 203 which collects drilling fluid that comes from the borehole during drilling. From the collection basin, the drilling fluid is led with a pipe 502 for contaminated drilling fluid to the cleaning unit. If necessary, pressure is provided in the pipe with a pump 503. Because the drilling fluid does not contain a very large amount of solids, it is very fluid, and a pump is not necessarily needed in all cases to transfer the drilling fluid from the collection basin to the cleaning unit. If the drilling machine is higher in the terrain than the cleaning unit, the drilling fluid can flow along a sufficiently large pipe with the help of gravity. If necessary, a suitable pump is nevertheless used to ensure the transfer of the fluid.

The cleaning unit 501 can be a suitable construction, such as, for example, a container, a cart or a vehicle, inside which the device needed for the cleaning is placed. This container, cart or vehicle or other structure is on the other hand placed in the terrain near the drilling machine 100, and when the drilling site is moved, it can be moved together with the drilling machine either with the help of another vehicle or with its own power of movement. The cleaning unit has means by which its position can be adjusted as desired, even if the ground surface on which it stands is uneven. The cleaning unit either only contains a device that is needed for cleaning fluid or, in addition, also a device that is used to mix chemicals that are needed in the drilling process into the drilling fluid. Because the device needed for mixing chemicals is not used at every drilling site, it may be advantageous to place the device for mixing chemicals in its own separate portable container, cart or vehicle. Regardless of whether the device for mixing chemicals is placed in the same place as or in a different place than the device for cleaning drilling fluid, they are arranged so that, as needed, either they can either be used simultaneously or each of them separately. From the cleaning unit, the cleaned drilling fluid is brought to the drilling machine with a pipe 504 for cleaned drilling fluid. At the drilling machine, the purified drilling fluid is fed back into the drill pipe.

Although the drilling fluid circulating in the drilling process stays warm during the drilling operation even in winter due to the ground heat in the borehole and the friction created by the rotation of the drill bit and pipes, in winter there is a risk of the drilling fluid freezing, mostly in situations where the drilling operation is stopped for a long time. Therefore, the cleaning system for drilling fluid is located in a construction with walls that are thermally insulated, if it is used in wintry conditions. Sufficient heating is also arranged inside the structure, so that the fluids and devices it contains do not freeze when it is below freezing outside, if the drilling operation is interrupted.

Figure 6 shows the internal structure of a cleaning unit according to the invention. The cleaning device according to the invention has four precipitation basins: a first precipitation basin 604, a second precipitation basin 605, a third precipitation basin 606 and a fourth precipitation basin 607 and a lower basin 608 below these. There are at least two pools. The drilling fluid to be purified is led into the first precipitation basin by a nozzle 601. Between the precipitation basins there are transfer connections 610. To remove the purified drilling fluid from the purification unit there is an outlet connection 611. At the bottom of each precipitation basin there is a valve arrangement that can be used to release fluid mud that accumulates at the bottom of the precipitation basins, out of the precipitation basin. A filter assembly 609 for the drilling fluid mud is attached to the valve assembly. A lower basin discharge pipe 602 is connected to the lower basin, which discharge pipe has a pump 603.

The purification device's precipitation basins are shaped so that the solid contained in the fluid is separated from the fluid and sinks to the bottom of the precipitation basin and forms drilling fluid mud. The uncleaned drilling fluid is brought into the first precipitation basin 604 through a nozzle 601. This can for example be a nozzle of the Coanda type, with which the fluid part and the solid parts of the drilling fluid are set in motion in different directions. The solid is directed so that it ends up at the bottom of the first precipitation basin. From the first precipitation basin, the drilling fluid moves with a transfer connection 610 to the second precipitation basin 605. The transfer connection is positioned so that the drilling fluid is removed from the upper part of the precipitation basin. If necessary, several subsequent precipitation basins can be used, whereby the fluid is transferred to a new precipitation basin, where the same process occurs again. When several precipitating basins are used in succession, drilling mud and solids mostly accumulate in the first precipitating basin, and thereafter the drilling fluid may still be somewhat muddy. The amount of solids in the drilling fluid is reduced and the drilling fluid becomes clearer as it passes from one precipitation basin to another. Precipitation basins are placed in the cleaning unit in such a number that the drilling fluid in the last precipitation basin is sufficiently clean, so that it can be used again in drilling. In the example according to the figure, the precipitation basins are placed one after the other, but their position can also be different. They can be next to each other, one after the other or in several rows.

If necessary, a small amount of a polymer solution with a suitable ionic electrical charge, ferrous sulfate or ferric sulfate, which is widely used in connection with, for example, wastewater treatment and mud drying, can be added to the drilling fluid in the precipitation basin, which substances cause so-called coagulation and/or flocculation when mixed with water, i.e. an electrochemical reaction, where solids in the water bind together as larger particles that contribute to the separation of solids from the water and its flow to the bottom of the precipitation basin a drilling fluid mud.

A removable mechanical filter arrangement 609 based, for example, on filter cloth is placed below the precipitation basins, and with the help of this, most of the solids contained in the drilling fluid mud that has been removed from the bottom of the basin are separated from there. Most of the drilling fluid mud flows through the filter arrangement. Solid matter that remains inside the filter arrangement can be removed by removing the filter arrangement. The filter arrangement can either be disposable or so that it can be emptied of solids, washed and reused. The moist solid mass obtained with the help of the filter arrangement can, if necessary, be stored either in the filter itself or, for example, in a separate container, such as a plastic bottle, if the solid should in the future, for example, achieve a workplace-specific purpose in connection with sampling.

The drilling fluid separated from the drilling fluid mud by the filter arrangement 609 is poured into the lower basin 608, from which it is sometimes transferred back into the precipitation basin via the lower basin discharge pipe 602.1 example according to the figure, the pipe has a pump 603, and it leads to the first precipitation basin 604. If the filter arrangement can be cleaned and reused, the filter arrangement's filter cloth can be washed after the filter arrangement is emptied, for example with water contained in either the lower basin or the precipitation basin.

When the drilling fluid is sufficiently purified in the precipitation basins, chemicals that contribute to the drilling process are, if necessary, added therein in a chemical mixing device containing at least two subsequent basins. In the first pool, which can be smaller, a necessary amount of a desired chemical is mixed into the drilling fluid, and in the second pool, which can be larger, there is a sufficient intermediate storage for drilling fluid, so that the drilling operation can take place continuously, without interruption from the possible cyclical nature of the drilling fluid cleaning or chemical addition process. The device arranged to add chemicals is placed either in the same place as the cleaning device, or if necessary in its own separate place, which is transported to the drilling site only when necessary. In the example according to Figure 6, the third precipitation basin 606 can function as a chemical mixing basin and the fourth precipitation basin 607 as an intermediate storage for drilling fluid. When adding chemicals, the pH value of the drilling fluid is also measured, because the dosage of drilling assistance chemicals can depend on the pH value, and some chemicals do not mix with the drilling fluid or do not work in the desired way if the pH value is incorrect. The measured pH value of the drilling fluid can be changed as desired by adding chemicals that adjust the pH value of the drilling fluid.

The drilling machine sucks the drilling fluid it needs for drilling, for example either from the cleaning unit's last precipitation pool or from the chemical mixing device's last intermediate storage pool. Then the cleaned and treated drilling fluid is brought to the borehole, and it returns after being at the drill bucket along the borehole and the protective pipe back to the drilling machine, where it again flows to the collection basin waiting at the opening of the protective basin and starts a new treatment cycle.

Some of the drilling fluid is lost despite circulation, for example due to evaporation of the hot water, absorption into the fractured bedrock, losses occurring at the boundary between the casing and the rock, or losses occurring in connection with the removal of solids from the pool. This is compensated with a traditional method, by taking substitute initial fluid from a natural water source or from a previous borehole or a tank vehicle or the like. The new drilling fluid can be added in the drilling process at the drilling machine or the cleaning unit has an arrangement, for example a coupling, which is in connection with the precipitation basin, with which the new drilling fluid is added in the drilling fluid circulation.

Figure 7 shows a longitudinal cross-section of a cleaning unit 501 according to the invention, which has a cleaning device according to Figure 6. The cleaning device is placed inside a frame 704. The frame is sufficiently solid for transport and moving, and it has the necessary hatches, doors, ventilation openings and the like . The walls of the frame are sufficiently thermally insulated in relation to the cleaning unit's operating environment. For example, the walls of a cleaning unit intended for winter use are highly thermally insulated, but for a cleaning unit adapted for mining use, compactness and small size are more useful. Inside the frame it is also necessary

arrangements for the cleaning device's driving force. These are motors, batteries, cables and the like. Advantageously, all the cleaning unit's connections, the intake and outlet of drilling fluid, the addition of new drilling fluid, the electrical cables and the like, can be removed and protected when the cleaning unit is moved. The cleaning unit has adjustment means, such as adjustment legs, with which the position of the cleaning unit can be adjusted. With these adjustment means, the effort is made to maintain the designed position regardless of the slope of the terrain or the shape of the ground surface. This position is advantageously the horizontal position.

The drilling fluid to be cleaned is brought to the cleaning unit 501 by an inlet pipe 701 which is in contact with the nozzle 601. The nozzle may be a Coanda type nozzle. The inlet pipe has a suitable pressure, so that the fluid flow arrives at the nozzle at the correct speed. This pressure can be adjusted, for example, with valves.

The purification device's four precipitation basins: the first precipitation basin 604, the second precipitation basin 605, the third precipitation basin 606 and the fourth precipitation basin 607 are shaped to have a conical bottom or so that a part of the bottom is lower than the rest of the bottom, and the shape of the bottom rather against this section. The precipitation basins can be open or they can have a lid. Between the precipitation basins there is a transfer connection 610 to transfer drilling fluid from one precipitation basin to another. The transfer connection takes the drilling fluid from the upper part of the precipitation basin. The transfer connection inlet port determines the upper surface of the fluid in the precipitating pool, because the drilling fluid always flows to the next precipitating pool when the fluid surface rises to the inlet port. The intake openings of the transfer connections can be at different heights between different precipitation basins, whereby the fluid surfaces are at different heights in different precipitation basins. In the case shown in the figure, the transfer connection is a pipe that directs drilling fluid coming from the previous precipitation basin towards the bottom of the precipitation basin. The discharge end of the pipe is essentially lower than its intake end in the precipitation basin. Because the fluid flow through the transfer joint is quite slow, the solids contained in the drilling fluid have time to sink to the bottom of the precipitation basin.

At the bottom of the precipitation basins, substantially at their lowest point, there is a valve arrangement 703. This is in conjunction with the filter arrangement 609, so that the valve arrangement can, when necessary, be opened, and drilling fluid mud at the bottom of the precipitation basin, which contains a lot of solids , can be passed through the filter arrangement. The opening of the valve arrangement can be done manually or automatically. Because solids collect in different precipitating basins at different rates, for example, precipitating matter collects faster in the first precipitating basin 604 than in the fourth precipitating basin 607, the valve arrangements of the precipitating basins are opened at different times. The filter arrangements may also be different in different precipitation basins. The drilling fluid separated from the drilling fluid mud by the filter arrangement descends into the lower basin 608 which may be an open or closed container. From here, the drilling fluid is led back to the filtration pool. The fourth, last, precipitation basin 607 has an outlet connection 611 which is in connection with a discharge pipe 702 for purified drilling fluid, with which the drilling fluid is returned to the drilling machine.

Figures 8a and 8b show a nozzle 800 that uses the Coanda phenomenon. It has an inlet part 801, a neck part 803 and a curved flange part. In the Coanda phenomenon, a flow of fluids and gases occurring near a solid surface tends to follow the shape of the solid surface, even though the direction of the surface changes relative to the direction of the flow. When the nozzle is shaped in the right way, the direction of the fluid flow can be changed so quickly that the solids contained in the fluid are detached from the flow and effectively separated from the fluid. The inlet part is connected to the pipe that brings contaminated drilling fluid to the cleaning unit. The neck part is shaped so that the flow rate of the drilling fluid passing through it can be made so that the Coanda phenomenon occurs in the curved flange part, where the drilling fluid begins to follow the surface of the flange part. Consequently, the drilling fluid flow undergoes a rapid change of direction based on the Coanda phenomenon, where the solid contained in the drilling fluid effectively detaches from the fluid flow immediately upon arrival in the precipitation basin, and where the fluid's flow rate then rapidly decreases. The location of the nozzle is chosen so that the drilling fluid flow that is turned with the nozzle is close to the level of the fluid surface of the precipitation basin and essentially in the direction thereof. Depending on the case, the drilling fluid flow can also be slightly diagonally upwards or diagonally downwards in relation to the fluid surface. The direction of the solid particles is essentially towards the bottom of the precipitation basin. This is shown in Figure 8b, where the fluid flow follows the curved flange, and the solid particles are separated from the fluid flow. The flow occurring at the precipitation basin fluid surface is slow immediately after discharge from the nozzle. The fluid is transferred to a transfer connection located at the other edge of the precipitation basin, whereby solids that may still be present in the drilling fluid have time to sink further and are separated from the slow flow occurring on the upper surface of the fluid in the precipitation basin.

Some advantageous embodiments according to the invention are described above. The invention is not limited to the solutions described above, but the idea of the invention can be used in several ways within the scope of the claims.

Claims (18)

1. Method for cleaning drilling fluid in rock sampling drilling, where a drilling machine (100) is used which has a hollow drill pipe (101), a cylindrical vane unit (401) at the drill end of the drill pipe, a protective pipe (201; 903) surrounding the part of the drill pipe that is close to the base surface (103), so that there is an empty space between the drill pipe and the protective pipe, and in the method, drilling fluid is fed into the drill pipe, which drilling fluid lubricates the drilling event, and the drilling fluid flows between the drill pipe and the borehole wall towards the borehole opening, and at the same time transports solid matter formed during the drilling, characterized in that the method further has steps, where - drilling fluid containing solid matter coming from between the protective pipe and the drill pipe in the drilling machine is recovered with an arrangement in the drilling machine - the recovered drilling fluid is led to a cleaning unit (501) - the cleaning unit has two or several precipitation basins (604, 605, 606, 607) in series, where the solid is separated from the drilling fluid, and m between the precipitation basins there is a transfer connection which has an intake end and a discharge end, and the discharge end of the transfer connection is closer to the bottom of the precipitation basins than the intake ends, and - the drilling fluid that is cleaned in the cleaning unit is led to the drilling machine and fed into the drill pipe. 2. The method according to claim 1, characterized in that drilling fluid mud containing solid matter which collects on the bottom of the precipitation basin (604, 605, 606, 607) is removed from the basin. 3. The method according to claim 2, characterized in that the drilling fluid mud that has been removed from the bottom of the precipitation basin (604, 605, 606, 607) is filtered and returned to the precipitation basin. 4. The method according to any one of claims 1-3, characterized in that the drilling fluid is fed in the cleaning unit into the first precipitation basin through a nozzle (611), which nozzle has a neck part (803) and a curved enemy part, and the curved flange part is arranged so that the fluid flow essentially follows the flange part, and solid matter contained in the fluid detaches from the flow. 5. The method according to any one of claims 1-4, characterized in that an ion-charged polymer mixture, ferrous sulphate, ferric sulphate or other chemical added to the drilling fluid which contributes to the separation of solids from fluid, is used in the cleaning of the drilling fluid to enhance the process. 6. The method according to any one of claims 1-5, characterized in that new drilling fluid is added to the drilling fluid circulation when necessary. 7. The method according to any one of claims 1-6, characterized in that substances or chemicals that contribute to the drilling process are added to the drilling fluid before the drilling fluid is returned to the drill pipe. 8. The method according to any one of claims 1-7, characterized in that the cleaning unit (501) is placed in a container or another movable structure. 9. Cleaning unit (501) for drilling fluid in sampling drilling, characterized in that the cleaning unit is placed in one or more containers or similar movable constructions and the cleaning unit has - a connection (701) for feeding uncleaned drilling fluid into the cleaning unit - at least two precipitation basins (604, 605, 606 , 607), where solids contained in the drilling fluid are arranged to collect on the bottom of the pool as drilling fluid mud, and in the lower part of at least one precipitation pool there is a valve arrangement (703) for removing the drilling fluid mud containing solids from the precipitation pool and - between the precipitation pools there is a transfer connection (610) having an intake end and a discharge end, to transfer the drilling fluid between precipitation basins, and the discharge ends of the transfer connections are closer to the bottom of the precipitation basins than the intake ends, and in the last precipitation basin in the series there is an outlet connection (611) to remove the cleaned drill fly from the cleaning unit. 10. The cleaning unit (501) according to claim 9, characterized in that the drilling fluid mud containing solid matter which has been released through the valve arrangement (703) is arranged to pass through a filter arrangement (609) so that the solid matter can be removed. 11. The cleaning unit (501) according to claim 10, characterized in that the filter arrangement (609) can be removed for replacement and cleaning, or it can be cleaned on site. 12. The cleaning unit (501) according to any one of claims 9-11, characterized in that there is a point on the bottom of the precipitation basin (604, 605, 606, 607) which is lower than the rest of the bottom, and the valve arrangement (703) is located in this point. 13. The cleaning unit (501) according to any one of claims 9-12, characterized in that the drilling fluid separated from the drilling fluid mud by the filter arrangement (609) is arranged to be transported back to the precipitation basin (604, 605, 606, 607). 14. The cleaning unit (501) according to any one of claims 9-13, characterized in that below the precipitation basin or precipitation basins (604, 605, 606, 607) there is a lower basin (608), in which the drilling fluid that has been filtered from the drilling fluid mud with the filtration arrangement (609 ), is arranged to be collected, and from which lower basin there is a transfer arrangement to transfer drilling fluid to the precipitation basin. 15. The cleaning unit (501) according to any one of claims 9-14, characterized in that the uncleaned drilling fluid which is fed into the first precipitation basin, is arranged to be fed through a nozzle (611), which nozzle has a neck part (803) and a curved flange part, and the curved flange part is arranged so that the fluid flow substantially follows the flange part, and the solids contained in the fluid detach from the electricity. 16. The cleaning unit (501) according to any one of claims 9-15, characterized in that the discharge ends of the transfer connections (610) between the precipitation basins are shaped to direct the drilling fluid substantially towards the bottom of the precipitation basin. 17. The cleaning unit (501) according to any one of claims 9-16, characterized in that an ion-charged polymer mixture, ferrous sulfate, ferric sulfate or other chemical, which contributes to the separation of solids from fluid, is arranged to be added to the drilling fluid. 18. The cleaning unit (501) according to any one of claims 9-17, characterized in that it has an arrangement for feeding substances that contribute to the drilling event into the drilling fluid before the drilling fluid is returned to the drilling process.