Borehole reamer

FIELD OF THE INVENTION

The present invention relates to a vibration damping reamer to be used in the stabilizing of a drilling tool during operation. The vibration damping reamer of the present invention is directed to an arrangement that will damp vibrations arising from use of the drill.

BACKGROUND OF THE INVENTION

Reamers have traditionally been employed in earth boring operations for the petroleum industry to provide two main functions:

• The first function that is provided by a reamer is to cut formations to enlarge the bored hole to the desired size, which may be the original size of the bit in the case where the drill bit wears to be under-gauged. However, even for new bits, reamers are employed to cut formations because the bit does not always drill a true bore hole and because of slight lateral shifting which is inherent in the drilling operation, which shifting leaves ledges and other distortions.

The second function of a reamer is to keep the drill stem in the centre of the hole, that is, the reamer acts as a stabilizer. Stabilizers are positioned above the drill bit to ensure that the drill bit and stabilizer assembly drill a straight hole of the desired diameter. Maintaining the drill stem centered has many beneficial effects, its primary one being minimizing unintentional hole-angle directional drilling.

A stabilizer thereby extends the life of the drill bit by maintaining the diameter of the hole to the original specification.

However, traditional reamers, such as described in WO 2004/029402, have not taken into account the vibrations that arise in the drilling assembly during use. Vibrations induced in the assembly may be lateral vibrations, that is, the assembly moves from side to side during operation; vibrations may also be axial with movement occurring generally vertically, or within the hole. Additionally, torsional vibrations occur resulting from the rotation of the assembly within the hole. Vibrations. Such vibrations may cause damage to the drill assembly reducing the life thereof.

The present invention provides the public with an alternative to existing reamers.

SUMMARY OF THE INVENTION

Therefore according to a first aspect of the present invention there is provided a vibration damping reamer for use in association with a drill stem and a drill bit in drilling a hole in a rock formation, said vibration damping reamer having:-

• a body having a through going bore for passage of drilling fluids there through; said body having a generally cylindrical upper part adapted from connection to a drill string and a generally cylindrical lowermost reamer part of diameter wider than said upper part, and
• said reamer part including plurality of wear surfaces located on an outer surface thereof that bear against a surrounding drill hole surface and a plurality of spaced apart axially extending spiral flutes cut into said outer surface; wherein said wear surfaces include two or more reaming bands axially spaced along the reamer part.

By arranging axially spaced reaming bands along the length of the cylindrical body, the reamer is thus is use, brought to bear against the drilled hole-wall at axially spaced positions. The surface of the reamer bears against the hole-wall thereby ensuring any vibrations induced in the tool are damped. The adoption of two or more bearing points, represented by the wear surfaces provides for stability in the position of the reamer and thereby the drill assembly.

Preferably, reaming bands axially spaced along the reamer part are separated by a region of reduced diameter.

Preferably, said wear surfaces studded with a plurality of hardwearing studs, for example carbide surface studs.

The vibration damping reamer of the present invention may be embodied as either a near bit vibration damping reamer in which the reamer part is adjacent the drill bit in use, or alternatively as a string reamer in which the reaming part is spaced along the drilling string from the drill bit.

Preferably, said spaced apart axially extending spiral flutes cut into said outer surface are cut at a high angle relative to thereby minimize the extent of helical movement in fluid moving in the flutes.

In a particularly preferred embodiment of the present invention the spaced apart axially extending spiral flutes cut into said outer surface are cut, and the distance between adjacent axially spaced wear surfaces are arranged such that, around the circumference of the reamer, a wear surface engages the surrounding hole wall at some point.

DESCRIPTION OF DRAWINGS

The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment in conjunction with the accompanying drawings. In the drawings:

• Figure 1 illustrates in perspective view, a vibration damping reamer constructed in accordance with the present invention;
• Figure 2 illustrates in side view the vibration damping reamer of figure 1;
• Figure 3 illustrates in side view a body of the vibration damping reamer during manufacture thereof;
• Figure 4 illustrates in side view a reamer part of the body of the vibration damping reamer during manufacture thereof; and
• Figure 5 illustrates a cross-sectional view of the partially constructed reamer shown in figure 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Shown in the drawings is vibration damping reamer 10 formed in accordance with the present invention. The reamer 10 is shown to advantage in perspective view in figure 1. The reamer 10 is used in association with a drill stem and a drill bit in drilling a hole in a rock formation. In the orientation shown a drill is located below the reamer 10. The geometry of the reamer 10 is such a drill bit would be located below the tool 10 with the top of the drill hole beyond the top of the page. The vibration damping reamer 10 includes a body 12 having a through going bore 14 for passage of drilling fluids there through. The bore 14 is of appropriate size to allow smooth passage of drilling fluids there through.

The body is divided into a generally cylindrical upper part 16 adapted for connection to a drill string (not shown) and a generally cylindrical lowermost reamer part 18 of diameter wider than the upper part 16. The upper part 16 has a smooth surface whereas the lowermost reamer part 18 has a complex surfaced described in detail below. The lowermost reamer part 18 terminates in an inwardly tapered bottom section 20. The diameter of the bottom section 20 is adjusted so as to be consistent with the size of drill bit to which the reamer 10 is attached.

The reamer part 18 includes an uppermost shoulder section 22 that allows the diameter of the tool as a whole to be increased from the narrower upper section 16 to the wider lower section 18.

As show in figure 3, during the construction of the tool of the present invention three bands axially spaced thereon distinguish the lower reamer section 18. An intervening band 26 separates upper and lower wear surfaces 24, 25. The intervening band 26 is lesser diameter than the wear surface 24, 25. Thus, as a result the wear surfaces 24, 25 extend radially outwardly of both the upper part 16 of the tool 10 and also the intervening band 26.

Five spiral flutes 28 are cut into the outer surface of the lower reamer part 16. As seen in the drawings the spiral flutes 28 are evenly spaced around the circumference of the tool 10. The spiral flutes 28 serve to collect drilling fluid and entrained rock material collected from a hole during a drilling operation and to deliver the material to the surface. It can also be observed from figure 5 that the spiral flutes 28 have a slightly squared off cross-section. It has been found in practice that such an arrangement provides for the smoothest transition of fluid through the flutes 28. Careful inspection of the drawings also reveals that the flutes 28 are cut at a relatively close angle to the vertical. Again this has been found in practice to yield the smoothest delivery of material from the cutting face to the surface.

In order to create the desired vibration damping effect the wear surfaces 24, 25 are each studded with an array of hardwearing carbide studs 30. The wear surfaces 24, 25 and studs 30 together form a pair of reaming bands axially spaced along the reamer part of the tool. The studs 30 represent the widest part of the tool 10 and, in use, engage the wall of the drilled holes and bear against the drill hole surface to thereby provide the vibration damping effect. The fact that the tool 10 is supported against the hole-face in two spaced apart locations provides a considerable mechanical advantage. By having two points of contact the tool is supported for more securely and the effect of vibration is easily reduced.

It is also important to note that the arrangement as shown in the drawings provides for substantially 360° contact between a reaming surface and the hole-wall. This arises because of the relative sizes of the wear surfaces and the spiral flutes 28. Thus, as can be observed in figure 2 a lower left hand stud 32 in one part of the upper wear surface 24 lies almost adjacent a stud 34 in the upper right hand corner of one part of the lower wear surface 25. Thus, in use, the wear surfaces are able to securely embed themselves in the wall of the drilled hole and thus substantially damp and vibrations that arise through use of the tool.

Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made there from within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

In any claims that follow and in the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the world "comprising" is used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.