Boring or penetrating the earth – With tool shaft detail – Helix or helically arranged structure
Reexamination Certificate
1999-06-14
2001-05-01
Lillis, Eileen D. (Department: 3673)
Boring or penetrating the earth
With tool shaft detail
Helix or helically arranged structure
C175S324000, C175S325400, C166S173000
Reexamination Certificate
active
06223840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to equipment for drilling operations.
2. Description of the Prior Art
In conventional drilling operations, mud or other drilling fluid is pumped down a hollow bore in the drill string and is ejected from the drill bit to lift the drill cuttings out of the bore-hole.
In an inclined well-bore it is been found that at a certain deviation or sail angle, some of the drill cuttings being transported back to the surface by the drilling fluid fall out of the main flow and settle on the lower portion of the bore-hole. These cuttings interfere with the drilling process and especially with the rotation of the rotating drill-pipe which also lies on the low side of the bore-hole.
The flow of returning drilling fluid which carries the cuttings is not uniform across the diameter of the bore-hole. On the low side of the bore-hole the flow is at a minimum and the capacity of the drilling fluid to transport drilling cuttings and solid particles is reduced.
To overcome this problem it is known to fit one or more cutting bed impellers to the drill-pipe. The impellers are integrally formed with a length of drill-pipe and comprise a body portion having a central longitudinal bore and a plurality of paddles in the form of single spiral blades which project radially outwardly from the body portion. These types of blade are similar in profile to those used on down-hole drilling stabilizers.
As the cutting bed impeller rotates with the drill-pipe, it disturbs and agitates the settled cuttings and other particles and moves them upwards into the path of the main flow of cutting fluid on the upper side of the bore-hole. Although these tools have proved reasonably effective they have been found to create extra down-hole torque.
SUMMARY OF THE INVENTION
According to the present invention there is provided a cutting bed impeller comprising a body portion and a plurality of paddles projecting outwardly from the body portion, at least one of the paddles comprising:
a radially outer face extending between a leading edge and a trailing edge in a normal direction of rotation of the impeller about an axis of rotation of the impeller;
a leading face; and
a trailing face, the radially outer face extending between the leading face and the trailing face, the leading face being inclined at a first angle to a first tangent to the radially outer face at the leading edge, the trailing face being inclined at a second angle to a second tangent to the radially outer face at the trailing edge, the second angle being less than the first angle.
Each paddle is preferably substantially straight.
A recess comprising a depression may be formed in the leading face of the paddle. Each recess is preferably from ¼″ to 2″ (6.4 to 51 mm) deep.
Preferably the cutting bed impeller comprises part of a drill string sub, rather than a complete length of drill-pipe. Preferably the wall thickness of the sub is reduced on one or both sides of the cutting bed impeller. This reduced thickness portion accommodates bending due to high side forces which may be generated on the sub.
The provision of the cutting bed impeller on a sub allows the tool to be run in conjunction with or immediately between bearing devices or torque reduction tools. This is not possible with a conventional cutting bed impeller, which is integrally formed with a length of drill-pipe.
The radially outer face of the paddles may be provided with replaceable wear elements. These wear elements may comprise nylon inserts fitted into openings in the radially outer faces of the paddles. The nylon inserts may be cylindrical and may fit within blind bores in the paddles. In another embodiment, the wear elements comprise wear pads which fit within slots formed through the paddles. Alternatively, the replaceable wear elements may comprise any appropriate shape or size of element of elements which may be used to protect the cutting bed impeller from abrasion with the wall of the bore-hole and/or which reduce the down-hole torque.
Preferably the wear elements comprise approximately 60% of the total area of the radially outer face of the or each paddle.
The recesses defined between respective paddles act as scoops to lift cuttings and solid particles from the lower portion of the bore-hole into the main flow of cutting fluid in the upper portion of the bore-hole. The effectiveness of the impeller is governed by the size of the clearance between the radially outer faces of the paddles and the bore-hole wall and the profile of the recess.
According to another aspect of the present invention there is provided a cutting bed impeller comprising a body portion and a plurality of paddles projecting from the body portion, replaceable wear elements being provided on the radially outer faces of one or more of the paddles.
Preferably, replaceable wear elements are disposed equidistantly around the circumference of the impeller to ensure an even bearing in the bore-hole. For example, they may be provided on oppositely disposed pairs of paddles.
A plurality of cutting bed impellers may be fitted to a drill string. The cutting bed impellers are preferably spaced apart at 90 m to 150 m (300 ft. to 500 ft.) intervals.
The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.
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patent: 5937957 (1999-08-01), Swietlik
Lee Jong-Suk
Lillis Eileen D.
Shaw Seyfarth
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