TECHNICAL FIELD

Various example embodiments generally relate to a fluid drilling system. Some example embodiments relate to at least partially the fluid drilling system comprising a drill hammer.

BACKGROUND

Many types of fluid drilling systems are available for drilling a hole in the ground. A down-the-hole (DTH) drill is one example of available fluid drilling systems. The hole may be used for example, to gain an access to subterranean geothermal sources or other purposes. Capabilities of the fluid drilling systems to operate in a more optimal way may be however further improved.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. The scope of protection sought for various embodiments of the present disclosure is set out by the independent claims.

Example embodiments of the present disclosure increases borehole production efficiency by reducing energy consumption when drilling deep boreholes. This and other benefits may be achieved by the features of the independent claims. Further advantageous implementation forms are provided in the dependent claims, the description, and the drawings.

According to a first aspect, a fluid drilling system may comprise: a drill string; a drill hammer coupled to a lower end of the drill string; and a flow channel configured to lead a fluid to a bottom of a borehole; wherein the fluid comprising mixture of pressurized liquid and gas bubbles; and the fluid is configured to drive the drill hammer and to flush cuttings from the borehole.

According to an example embodiment of the first aspect, the pressurized liquid may comprise at least one of the following: pressurized water; and the gas bubbles may comprise at least one of the following: air, carbon dioxide and/or nitrogen bubbles.

According to an example embodiment of the first aspect, the gas bubbles may comprise micropores.

According to an example embodiment of the first aspect, the gas bubbles may have diameters D < 1 mm.

According to an example embodiment of the first aspect, the fluid may be configured to be made by adding the gas bubbles to the liquid before or after pressurizing the liquid.

According to an example embodiment of the first aspect, wherein pressure of the pressurized liquid may be 50-300 bar.

According to an example embodiment of the first aspect, wherein pressure of the pressurized liquid may be 150-200 bar.

According to an example embodiment of the first aspect, wherein the fluid comprising pressurized liquid and gas bubbles may be configured to be made by water oxygenation or aeration.

According to an example embodiment of the first aspect, wherein the flow channel may be configured to enable flow of the fluid along a central axis of the fluid drilling system.

According to an example embodiment of the first aspect, wherein a flow channel may be located inside the drill string and the drill hammer.

According to an example embodiment of the first aspect, wherein the drill hammer may comprise a drill bit for drilling the borehole, wherein the fluid may be configured to be directed through the drill bit.

According to an example embodiment of the first aspect, wherein the drill bit may comprise a drill bit face and the flow channel may be configured to be opened onto a drill bit face, wherein the fluid may be configured to be directed to flow through the flow channel.

According to an example embodiment of the first aspect, wherein the flow channel inside the drill bit may comprise at least one passage.

According to an example embodiment of the first aspect, wherein the drill hammer may be a fluid powered down-the-hole (DTH) hammer.

According to a second aspect, a method for drilling a hole using a fluid drilling system may comprise: a drill string; a drill hammer coupled to a lower end of the drill string; and a flow channel; wherein the flow channel may lead a fluid to a bottom of a borehole, wherein the fluid may comprise pressurized liquid and gas bubbles; and the fluid may drive the drill hammer and flush cuttings from the borehole.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and together with the description help to understand the example embodiments. In the drawings:

Fig. 1 illustrates a schematic drawing not drawn to scale, a fluid drilling system in which examples of disclosed embodiments may be applied; and

Fig. 2 illustrates an example of a method for drilling a hole using a fluid drilling system, according to an example embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps or operations for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

Example embodiments relate to a fluid drilling system comprising a drill string, a drill hammer coupled to a lower end of the drill string, and a flow channel configured to lead a fluid to a bottom of a borehole. More particularly, the fluid comprising mixture of pressurized liquid and gas bubbles, wherein the fluid is configured to drive the drill hammer and to flush cuttings from the borehole.

Many types of air and water drilling systems may be available for drilling a hole in the ground. The drilled hole may be used for example, to gain an access to subterranean geothermal sources or to other known purposes, such as wells. A down-the-hole (DTH) drill may be one example of available ground drilling systems. Previously ground source heat pumps (GSHPs) have been mostly used in single family homes, but a growing trend is to use GSHPs also in densely built city areas. According to an example embodiment, the challenge is to find technical solutions for GSHP systems in densely built city areas for multistory buildings. This may bring along new requirements and may expose the need to develop the time- proven GSHP installations to suit better the new city environment. Primarily the need may be to develop deeper borehole solutions for geothermal heat pump thermal energy collectors, as more heat energy may be required, and less ground surface may be available for them.

According to an example embodiment, a hole is drilled using a fluid drilling system^ where is used both liquid and gas. The fluid may comprise mixture of pressurized liquid and gas bubbles. The fluid may be configured to drive the drill hammer and to flush cuttings from the borehole. The fluid may be used for conducting energy to the drill hammer, as the liquid may not suffer from the groundwater hydrostatic counterpressure and may consume less energy than air drilling methods. The energy consumption difference may well double or triple when proceeding to greater depths. The gas lift effect of gas bubbles mixed into the liquid does improve cutting transport tremendously, further improving hammer performance.

According to an example embodiment, the fluid drilling system may be used to drill deep boreholes for example, to 400-800 meters or even deeper up to 5000 meters. This kind of drilling method may be very efficient for example, when boring to a hard bedrock.

According to an example embodiment, a fluid drilling system comprises a drill hammer for example, a DTH hammer. The hydraulic fluid powered drill hammer may have especially high efficiency for breaking rock into small flakes and dust, even in greater, virtually unlimited depth. The drill hammer may be one of the fastest ways to drill hard rock. In the fluid drilling system, the drill hammer may be located directly behind the drill bit. The drill string may have a drill channel through which the fluid required by the drill hammer may be fed. The drill channel may transmit the necessary feed force and rotation to the drill hammer and drill bit and fluids for the drill hammer and flushing of cuttings. The drill hammer may comprise a moving piston. The piston may strike the impact surface of the drill bit directly, while a drill hammer casing may give straight and stable guidance of the drill bit. This may mean that the impact energy may not have to pass through any joints at all. The impact energy therefore may not be lost in joints allowing for much deeper percussion drilling.

Figure 1 illustrates a schematic drawing not drawn to scale, a fluid drilling system 1 in which examples of disclosed embodiments may be applied. Figure 1 is only showing some elements and functional entities, whose implementation may differ from what is shown. It is apparent to a person skilled in the art that the drill system 1 may comprise also other functions and structures than those shown in Figure 1.

The embodiments are not, however, restricted to the drill system given as an example but a person skilled in the art may apply the solution to other drill systems provided with necessary properties.

Figure 1 illustrates a part of a fluid drilling system 1. According to an example embodiment the fluid drilling system 1 comprising a drill string 2 and a drill hammer 3 coupled to a lower end of the drill string 2. The drill hammer 3 may be a fluid operated DTH hammer. Obviously, the drill hammer 3 may, as concerns it basic idea, be a hammer other than a DTH hammer. The drill hammer 3 may comprise a fluid operated piston which is adapted to the cylinder of the drill hammer 3 movably back and forth.

The fluid drilling system 1 may further comprise a flow channel 5, which may be configured to lead a fluid 7 to a bottom of a borehole 8. The fluid 7 may be configured to drive the drill hammer 3 and to flush cuttings from the borehole 8.

In figure 1 , the fluid 7 is depicted by solid lines with terminating arrowheads depicting direction of flow. The fluid 7 may comprise mixture of pressurized liquid and gas bubbles. According to the example embodiment, the pressurized liquid comprises at least one of the following: pressurized water, additive, and/or any other suitable substance. The additive may be for example, vegetable oil, and/or biodegradable oil. The liquid may comprise pressurized water, wherein water may have been mixed with the additive like vegetable oil and/or biodegradable oil to lubricate the drill hammer 3. The gas bubbles may comprise at least one of the following: air, carbon dioxide, and/or nitrogen bubbles. According to the example embodiment, the gas bubbles having diameters D < 1 mm. According to the example embodiment, the gas bubbles comprising micropores. According to the example embodiment, the micropores having diameters D < 2 nm. The small gas bubbles may allow the drill hammer to operate smoothly. Too large gas bubbles may block the flow channel 5 or at least slow down flow of the fluid 7.

According to the example embodiment, the fluid 7 is made by adding the gas bubbles to the liquid before or after compressing the liquid. Thus, the liquid may be pressurized and gas bubbles may be added before it goes to the flow channel 5. This may be done on the ground with suitable equipment. For example, the liquid may be pressurized and after that the gas bubbles may be added to the liquid by pumping the gas through a nozzle to the liquid. According to another example, the gas may be added to the liquid by pumping the gas through a nozzle to the liquid and after that the liquid comprising gas bubbles may be pressurized.

According to the example embodiment, pressure P of the pressurized liquid is preferably about 50-300 bar. More preferable pressure P of the pressurized liquid is about 150-200 bar.

According to the example embodiment, the fluid 7 may comprise pressurized water and air bubbles. The fluid, comprising pressurized liquid and gas bubbles, may be made by water aeration or oxygenation. In the water oxygenation air may be pumped through a nozzle to the water.

According to the example embodiment, the gas bubbles added to the pressurized liquid may help to lift rock cuttings up to a surface. Thus, in the fluid 7 comprising a liquid and gas bubbles, the gas bubbles may work as a carrier to speed up flushing of the cuttings to the surface. The gas bubbles may also help to keep the drill bit holes open during drilling.

According to the example embodiment, the flow channel 5 is configured to enable flow of the fluid 7 along a central axis of the fluid drilling system 1. The fluid may flow through the fluid drilling system 1 and across a bit face 9. The fluid subsequently flows up the hole 8 flushing cuttings form the hole 8. According to the example embodiment, the flow channel 5 is located inside the drill string 2 and the drill hammer 3.

According to the example embodiment, the drill hammer 3 comprises a drill bit 4 for drilling the borehole 8, wherein the fluid 7 is configured to be directed through the drill bit 4. The flow channel 5 may be located inside the drill string 2, the drill hammer 3 and the drill bit 4. The fluid may flow through the drill string 2, the drill hammer 3 and the drill bit 4. According to the example embodiment, the drill bit 4 comprises a drill bit face 9 and the flow channel 5 is configured to be opened onto a drill bit face 9. According to the example embodiment, the flow channel 5 inside the drill bit 4 comprises at least one passage 6 which leads the fluid 7 to the bottom of the borehole 8, wherein the fluid 7 is configured to be directed to flow through the at least one passage 6. The flow channel 5 inside the drill bit 4 may split into several passages 6. The passages 6 may be open onto the bit face 9.

According to the example embodiment, the at least one passage 6 of the flow channel 5 in the drill bit 4 opens roughly parallel to the centre axis to the bottom of the borehole 8. This way, efficient flushing may be accomplished directly against the bottom of the borehole 8. The at least one passage 6 of the flow channel 5 in the drill bit 4 may open at an angle substantially different in relation to the centre axis, whereby flow in the direction of the hole bottom may be enhanced. There may also be a plurality of passages 6 of the flow channel 5 directed mutually in different directions.

Example embodiments of the present disclosure may offer a wide range of advantages, comprising low energy consumption, a cleaner environment, minimal hole deviation, smaller boreholes, deeper drilling capabilities, a high power output ratio, and minimal impact on the surrounding ground.

Figure 2 illustrates an example of a method for drilling a hole using a fluid drilling system, comprising a drill string 2, a drill hammer 3 coupled to a lower end of the drill string 2, and a flow channel 5.

At operation 200, the method may comprise the flow channel 5 leading a fluid to a bottom of a borehole 8, wherein the fluid 7 comprises pressurized liquid and gas bubbles.

At operation 210, the method may comprise the fluid 7 driving the drill hammer 3.

At operation 220, the method may comprise the fluid 7 flushing cuttings from the borehole 8.

Further features of the method directly result for example from the functionalities and parameters of the fluid drilling system 1 as described in the appended claims and throughout the specification and are therefore not repeated here. Different variations of the methods may be also applied, as described in connection with the various example embodiments.

A fluid drilling system may be configured to perform or cause performance of any aspect of the methods described herein. Any range or value given herein may be extended or altered without losing the effect sought. Also, any embodiment may be combined with another embodiment unless explicitly disallowed.

Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

The steps or operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the embodiments described above may be combined with aspects of any of the other embodiments described to form further embodiments without losing the effect sought.

The term 'comprising' is used herein to mean including the method, blocks, or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from scope of this specification.