DRILL PIPE FOR ROTARY DRILLING

Description

RELATED APPLICATION DATA

This application claims priority of U.S. Provisional Application No. 63/696,411, filed Sep. 19, 2024, which the entirety thereof is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a drill string element for use in rotary drilling or rotary percussive drilling.

BACKGROUND

Rotary drilling is extensively used in mining and civil engineering for making holes in the ground. In rotary drilling a drill bit in the form of a tricone is rotated at the end of a drill string to crush rock and thereby creating a hole. Sometimes, a piston is used in the drill string to act as a hammer to induce a percussive effect on the drill bit. This is called rotary percussive drilling and is, for many types of rock, more efficient than rotary drilling.

In rotary drilling, the tricone is connected to several different types of pipes, or tubes, to form a drill string. At the bottom of the hole, closest, and connected to, the tricone, is a bit sub. A starter sub or an extension sub can then be connected to the bit sub. The starter sub, or extension sub, is then connected to a drill pipe. Close to the top of the drill string a top sub adapter is connected to a drill pipe at one end and to a shock sub at the other end which forms the very top part of the drill string. In rotary percussive drilling, the bit sub is replaced by a RPS tool that induces the percussive effect on the tricone. In the following, the wording drill string element will be used as a general term. The wording drill string element includes drill pipes, various type of drill bits, such as tricones, claw bits, pick bits and fixed cutter drill bits, and additionally various types of subs that may form part of the drill string.

The drill string is driven by a drill rig, i.e. the drill rig applies force and rotation to the drill string. During drilling, when the drill bit progress further into the hole, the drill string needs to be extended by an additional piece of drill pipe.

Usually a carousel, holding multiple drill string elements, forms part of the drill rig. The uppermost drill string element is then loosened at its top and an additional drill string element, usually a drill pipe, taken from the carousel, is connected to it, thus becoming the uppermost drill string element. This loosening and fastening are done by a gripping tong that turns the drill string element to thread and unthread the drill string element. To facilitate the threading and unthreading, the outer surface of the drill string element is flattened on a certain location along the drill string element. The outer surface of the drill string element is flattened on diametrically opposite sides of the drill string element to form a pair of flats that ensures that the gripping tong gets a strong grip of the drill string element. In the following, a pair of diametrically opposed flats is simply called a flat. The tong is, during threading and unthreading, positioned on this flat to better be able to apply torque to the drill string element. The flat needs to have a certain axial extension and a certain diameter to be able to fit with the gripping tong. The gripping tong is part of the drilling rig and different drill rig manufacturers use gripping tongs of different sizes. This implies that drill string elements, having a certain type of flat, can only be used with a drilling rig having a gripping tong suitable for that specific drill string element.

It is common on drill sites to have drill rigs originating from different manufacturers. The drill site then needs to have several different types of drillstring elements in stock, one type for each drill rig manufacturer due to the need for the drill string element to have a flat that cooperates with the gripping tong of that specific drill rig.

Storing and handling a variety of different types of drill string elements is a logistic challenge. There is thus a need for improving the drill string elements that exist today to simplify handling and storing of drill string elements.

SUMMARY OF INVENTION

The present invention is related to a drill string element having at least two flats along the length of the drill string element. The at least two flats have different diameters, i.e. the surfaces of a first flat is located a different distance from a central axis of the drill string element compared to the distance the surfaces of a second flat is located from a central axis of the drill string element. This ensures that the drill string element can be used with drill rigs from at least two different manufacturers. One flat comprises two diametrically opposed flattened sections in the outer surface of the drill string element. Alternatively, the flattened sections are not diametrically opposed but each flattened section instead only covers a quadrant of the drill string element, when looking at the drill string element in a cross-section perpendicular to a longitudinal axis of the drill string element, and the two flattened sections are primarily positioned in two diagonally opposite quadrants so that there is one quadrant with no flattened section between the quadrants comprising a flattened section.

The two flats can be circumferentially rotated 90° relative to each other. When a gripping tong engages a flat wear of the drill string element occurs. By having the two sets of flats rotated relative to each other ensures that the wear is evenly spaced around the outer surface of the drill string element. Additionally, this strengthens the structural integrity of the drill string element compared to if the sets of flats had not been rotated relative to each other.

The two flats can be separated by at least 15 cm (6 inches). This ensures that wear occurring when engaging one of the flats does not overlap the wear caused when engaging the other flat. This improves the wear characteristics of the drill string element and ensures a longer lifetime of the drill string element.

The foregoing summary, as well as the following detailed description of the embodiments, will be better understood when read in conjunction with the appended drawings. It should be understood that the embodiments depicted are not limited to the precise arrangements and instrumentalities shown.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a drill string element in the form of a drill pipe according to a first embodiment of the invention.

FIG. 2 illustrates a drill string element in the form of a starter sub according to a second embodiment of the invention.

FIG. 3 illustrates a drill string element in the form of an extension sub according to a third embodiment of the invention.

FIG. 4 illustrates a cross-section of a drill string element with an alternative configuration of the flattened sections.

DETAILED DESCRIPTION

FIG. 1 illustrates a drill string element in the form of a drill pipe 1 according to the present invention. The drill pipe 1 has a main length section 10. Along the whole length of the drill pipe 1 a flushing channel 20 is positioned. The flushing channel 20 is centrally positioned on the inside of the drill pipe 1. At a forward end 30 of the drill pipe 1 a female thread is positioned. The female threaded forward end 30 is also called a box. The forward end 30 is the end of the drill pipe 1 that is closest to the bottom of the hole that is being drilled. The forward end 30 is usually connected to another piece of drill pipe, to a drill bit, to a starter sub or to an extension sub. At a rearward end 40 of the drill pipe 1 a male thread is positioned. The male threaded rearward end 40 is also called a pin. The rearward end 40 is the end of the drill pipe 1 that is furthest away from the bottom of the drill hole. The rearward end 40 is usually connected to another piece of drill pipe or to a shock sub.

Close to the rearward end 40 a first flat 50 is positioned. The first flat 50 consists of two diametrically opposite flattened sections at the outer surface of the drill pipe 1. The first flat 50 enables the threading and unthreading of the drill pipe 1 to another piece of the drill string using a gripping tong that is part of the drill rig. The first flat 50 has a diameter D_A.

Further towards the forward end 30 a second flat 51 is positioned. The purpose of the second flat 51 is the same as the purpose for the first flat 50 but it has a diameter D_B that is suitable for a gripping tong on a drilling rig made by another manufacturer than the first flat 50 is suitable for. Second flat 51 has both its pair of flattened surfaces rotated 90° relative the flattened surfaces of the first flat 50. The technical advantage of having the first flat 50 rotated relative to the second flat 51 is to reduce wear in critical areas. When engaging the gripping tong to a flat misalignment which causes wear on the outer surface of the drill pipe may occur. By having the first flat 50 rotated relative to the second flat 51 the wear on the outer surface of the drill pipe will be more evenly spaced out around the circumference of the drill pipe 1.

The first flat 50 is, in the longitudinal direction of the drill pipe 1, separated from the second flat 51 by a distance S. The distance S should be at least 15 cm (6 inches). The technical advantage of this is to not have the wear of the drill part from engaging a gripping tong to the first flat 50 overlapping the wear that occurs when engaging a gripping tong to the second flat 51. This improves the wear characteristics and lifetime of the drill pipe 1.

The flattened sections of the flats 50, 51 also lead to that the material in the drill pipe will be thinner than parts of the drill pipe without flats. By having the first flat 50 rotated relative to the second flat 51 the strength of the drill pipe 1 the strength of the drill pipe will be increased compared to if this relative rotation was not present.

Close to the forward end 30 similar third 52 and fourth flats 53 are positioned with diameters D_C and D_D, respectively. Fourth flat 53 is positioned closer to the forward end 30 than the third flat 52 is. Third flat 53 is intended for engagement of a gripping tong on a drilling rig of the same manufacturer as the first flat 50 is intended for. Diameters D_A and D_C are therefore identical. In the same manner the second flat 51 and the fourth flat 53 are intended for being engaged by a gripping tong from another different manufacturer of drilling rigs. Diameters D_B and D_D are therefore identical. In an alternative embodiment D_A and D_D are instead identical while D_B and D_C are also identical. The distance S between the third flat 52 and the fourth flat 53 should be at least 15 cm (6 inches) for the same reasons as given above for the distance between the first flat 50 and the second flat 51.

The third flat 52 can also advantageously be used for attaching the drill pipe to the carousel of a drilling rig. The carousel holds several drill pipes and is from where drill pipes are stored before they to be attached to the drill string.

The drill pipe 1 has a total length of about 7.6 m (25 feet) and has an outer diameter of about 22 cm. Normal lengths for drill pipe are between 6.1 and 10.7 m (20 to 35 feet). The diameter at the different flats is about 15 to 20 cm, depending on which drill rig it is to be used with. The axial extension of a flat is about 10 to 20 cm and may vary among all the flats on a drill pipe. The axial extension of a flat is set to accommodate the gripping tong and/or for positioning the drill pipe 1 on the carousel.

FIG. 2 illustrates a piece of drill string element in the form of a starter sub 101. The starter sub 101 is a specific type of drill pipe that is positioned close to the bottom of the drill string. It is attached at its forward end 130 to a drill bit, or to a bit sub, and to its rearward end 140 to a piece of drill pipe 1. The starter sub 101 is similar to the drill pipe 1 in most aspects and similar features will not be described again. Similar features have the same reference numerals as for the drill pipe 1 but with 100 added to the reference numeral.

The starter sub 101 differs from the drill pipe 1 in that flats for engagement by a gripping tong is not needed at the forward end 130.

Instead only a third flat 152 is positioned close to the forward end. This third flat is for attachment to the carousel that holds different types of drill string elements before they are attached to the drill string.

The starter sub 101 has a length of about 2.7 m (9 feet). All other dimensions are similar to the dimensions stated for the drill pipe 1.

FIG. 3 illustrates a piece of drill string element in the form of an extension sub 201. The extension sub 201 is another type of drill string element that is positioned close to the bottom of the drill string. It is attached at its forward end 230 to a drill bit, or to a bit sub, and to its rearward end 240 to a piece of drill pipe 1. The extension sub 201 is similar to the drill pipe 1 in most aspects and similar features will not be described again. Similar features have the same reference numerals as for the drill pipe 1 but with 200 added to the reference numeral.

The extension sub 201 differs from the drill pipe 1 in that flats for engagement by a gripping tong is not needed at the forward end 230.

Instead only a first flat 250 and a second flat 251 are positioned at the rearward end 240.

The extension sub 201 has a length of about 2.7 m (9 feet). All other dimensions are similar to the dimensions stated for the drill pipe 1.

FIG. 4 illustrates an alternative configuration of the flattened sections, on the outer surface of the drill string element, that constitutes a flat. It shows a cross-section, perpendicular to a longitudinal axis of a drill pipe 1, at a position where one flat is located. The flat comprises two flattened sections 61, 62. The flattened sections 61, 62 each primarily positioned in a single quadrant of the cross-section. Flattened section 61 is primarily positioned in a quadrant that is diagonally opposite the quadrant that the flattened section 62 primarily is positioned in. This alternative configuration can also be implemented on the starter sub 101, the extension sub 201 or any other type of drill string element.

All embodiments shown have on the rearward and/or the forward end two different types of flats. Alternatively, there is only one flat at the forward end and one flat at the rearward end if these are of different configuration, i.e. they have different diameters, to be able to function with at least two different types of drill rigs. Alternatively, there are only flats on either the forward end or at the rearward end if the flats at this end are of different configuration to be able to to function with at least two different types of drill rigs.

For all three embodiments disclosed two sets of flats are shown. This makes the specific piece of drill string element suitable for use with drill rigs made by two different manufacturers. Additional flats could be added to ensure that the specific piece of drill string element is usable with more than two types of drill rigs.

All embodiments disclosed are of different types of drill string elements that has a “box down/pin up” configuration. This is the configuration where the forward end has a female thread and the rearward end has a male thread. The invention is not limited to this configuration but is equally useful for “pin down/box up”, “box down/box up” or “pin down/pin up” configurations as long as the drill string element comprises multiple sets of flats with different configuration on the outer side of the drill pipe to ensure that the drill pipe can be used with at least two different types of drill rigs. If the drill string element is at either end of the drill string then it might have only a box or pin at either the forward or rearward end of the drill string element.

Although the present embodiment(s) has been described in relation to particular aspects thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present embodiment(s) be limited not by the specific disclosure herein, but only by the appended claims.