Downhole Tool Coupling and Method of its Use

Abstract

A downhole tool coupling (10) comprises first (11) and second (12) downhole tool elements that are securable one to the other in a releasably locking manner by moving the tool elements from a longitudinally relatively less proximate, especially overlapping position into longitudinally relatively more overlap with one another. The first downhole tool element (11) supports a first inductive, capacitative and/or magnetic energy coupler (23) and the second downhole tool element (12) supports a second inductive, capacitative and/or magnetic energy coupler (24). The first and second energy couplers (23, 24) are moveable from an energetically uncoupled position when the tool elements (11, 12) are in the longitudinally relatively less overlapping position to an energetically coupled position when the first and second downhole tool elements (11, 12) overlap relatively more.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. application Ser. No. 13 / 905,257, filed 30 May 2013, which is incorporated herein by reference and which claims the benefit under 35 U.S.C. §119(a) to U.K. Appl. No. GB 1209805.9, filed 1 Jun. 2012.FIELD OF THE DISCLOSURE[0002]The invention relates to a downhole tool coupling, in particular of a kind that is suitable for coupling elements of logging toolstrings in downhole locations.BACKGROUND OF THE DISCLOSURE[0003]As is well known, prospecting for minerals of commercial or other value (including but not limited to hydrocarbons in liquid or gaseous form; water e.g. in aquifers; and various solids used e.g. as fuels, ores or in manufacturing) is economically an extremely important activity. For various reasons those wishing to extract such minerals from below the surface of the ground or the floor of an ocean need to acquire as much information as possible about both the potential commerci...

AI Technical Summary

Benefits of technology

[0048]Conveniently one or more shields surround the first and/or the second energy coupler so as to prevent contact between the energy couplers on insertion of the second energy coupler into the annulus of the first energy coupler.

[0049]The use of such shields means that the energy couplers can be completely proofed against ingress of e.g. borehole fluid or other contaminants that give rise to the drawbacks of wet

Problems solved by technology

This makes it hard to communicate with a logging tool that is conveyed a significant distance along the borehole.

An autonomous logging tool however is not normally capable of signalling correct deployment at its downhole location; nor is it usually capable of sending log data to a surface location in real-time; nor may it normally receive complex control commands from a surface location.

These mud pulses however amount to very narrow bandwidth, low bit-rate communications that are not at all suitable for conveying log data in real-time.

Moreover the mud pulses require energy to generate and can be ambiguous due to their propagation over many thousands of feet of the borehole depth.

Mud pulse signalling therefore is often of little help in the controlling of logging tools and the rapid acquisition of data.

As drilling a borehole takes significant time, typically days, slow data rates although a disadvantage are useable in this application.

However one difficulty associated with wireline logging tools is that it is not generally possible to maintain a connection during e.g. an LWD operation since the wireline presents an obstacle to jointing of the drill pipe at the surface.

Gathering data from the tool under such circumstances necessarily requires the movement of drill pipe.

The downhole environment is usually extremely harsh, partly because of significant fluid pressures that exist and also because various chemicals present in boreholes are not compatible with the use of electrical signals for data and power transmission.

This could be because the chemicals are for example chemically aggressive and thereby degrade connector terminals, or because they are electrically conducting or insu

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