Borehole opener

Abstract

Borehole opener, particularly for enlarging this hole underneath a casing in the field of oil prospecting, comprising a body (2) of longitudinal axis (3), a duct (4) for drilling fluid, formed longitudinally in the body (2), and at least two hole-opening arms (5) which have an active part (7) equipped with cutting means (8), which are distributed symmetrically in the body (2) about the longitudinal axis (3), and which are arranged therein in such a way that they can be moved between a position of rest (9) in the body (2) and an active position (10) partially out of the body (2); in this hole opener in order to move it from the position of rest (9) to the active position (10), each arm (5) has a face (12), internal to the body (2), designed to be subjected directly, in the same way as an active face of a piston, to the pressure of the drilling fluid flowing through the body (2).

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]Applicants claim priority under 35 U.S.C. § 119 based upon Belgium Application No. 09900163 filed 9 Mar. 1999. <?insert-end id="INS-S-00001" ?>BACKGROUND OF THE INVENTION[0002]The present invention relates to a borehole opener, particularly for enlarging this hole underneath a casing in the field of oil prospecting, the hole opener comprising a body of longitudinal axis, a duct for drilling fluid, formed longitudinally in the body, and at least two hole-opening arms which have an active part equipped with cutting means, which are distributed symmetrically in the body about the longitudinal axis, and which are arranged therein in such a way that they can be moved between a position of rest in the body and an active position partially out of the body.BACKGROUND OF THE PRIOR ART[0003]Prospecting for oil of natural gas, for example, requires the probing of increasingly deep depths. What is more, it is desirable to drill with small diame...

AI Technical Summary

Benefits of technology

[0007]The object of the present invention is to overcome the problems set out hereinabove and to propose a hole opener with moving arms which is compact and robust and the mechanism of which involves a very small number of moving parts, these advantageously having to be easy to remove and replace in the event of an incident occurring during operation. What is more, the hole opener of the invention is to have a small bulk in the lengthwise direction, so that it can readily be installed very near a drill bit, in a drill string, between the drill bit and the aforementioned angled coupling.

Problems solved by technology

As a result, control over the equivalent density of the sludge formed by the drilling fluid and these particles of formation can rapidly be lost.

Hole openers known to date comprise mechanisms, of the hinge and pivot-pin type, which are rather delicate to be used at a high rate of advance and are too long to be placed between the drill bit and, in particular, an angled coupling well known to those skilled in the art and employed for directional drilling.

However, because of their asymmetric structure, these devices have an imbalanced behavior and because of this produce vibrational forces which are detrimental to the mechanisms to which they are coupled and to the condition of the bored hole.

What is more, because of this, these devices frequently cause unacceptable deviations in the bored holes.

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