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Antenna Alignment for an Inductive Coupler used for Downhole Wireless Connectors

IP.com Disclosure Number: IPCOM000252803D
Publication Date: 2018-Feb-13
Document File: 2 page(s) / 290K

Publishing Venue

The IP.com Prior Art Database

Abstract

In some downhole oil and gas installations there will be a need for connecting electric devices wirelessly by means of inductive couplers. For some of those applications, one part of the inductive coupler will be mounted to one of the well tube strings (e.g. the production tubing) and the other part of the inductive coupler to another well tube string (e.g. well casing or liner). Since the two tubing strings may move relative to each other, the two inductive coupler sections may move sufficiently away from each other to break the connection. To prevent loss of contact, either movement must be restricted or the system must be designed to tolerate the movement. This paper describes one method of preventing loss of contact even if the tubing strings move relative to each other

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Antenna Alignment for an Inductive Coupler used for Downhole Wireless Connectors November 2017

Summary In some downhole oil and gas installations there will

be a need for connecting electric devices wirelessly

by means of inductive couplers. For some of those

applications, one part of the inductive coupler will

be mounted to one of the well tube strings (e.g. the

production tubing) and the other part of the

inductive coupler to another well tube string (e.g.

well casing or liner). Since the two tubing strings may

move relative to each other, the two inductive

coupler sections may move sufficiently away from

each other to break the connection. To prevent loss

of contact, either movement must be restricted or

the system must be designed to tolerate the

movement.

This paper describes one method of preventing loss

of contact even if the tubing strings move relative to

each other.

Introduction In some oil and gas well installations, there is a need

of putting instruments in annular spaces outside of

the production tubing. Those annular spaces are not

always accessible by wiring from surface and

penetration of the tubing or casing strings are

generally not allowed or wanted.

Inductive couplers are in those cases an option used

for transferring power through the walls of a tube

and for data communication on the same or a

different inductive coupler.

An inductive coupler consists of two inductive

elements. The primary inductive element, hereafter

referred to as ‘transmitter antenna’, normally

consists of a wire coil with an alternating current

setting up an alternating magnetic field. The

secondary inductive element, hereafter referred to

as ‘receiver antenna’, will be exposed to those parts

of this magnetic field that is not lost by eddy

currents and other loss mechanisms related to the

physical construction of the inductive coupler.

‘Transmitter antenna’ denotes the antenna

transmitting power from a wired system powered

from a surface controller unit. ‘Receiver antenna’

denotes the other antenna being powered by the

alternating magnetic field set up by the transmitter

antenna. The alternating magnetic field seen by the

receiver antenna will generate an electric current

that can be used as an electric power source by the

electric annular instrumentation unit. Data

communication between the two sides will be done

either by an additional similar arrangement or by

modulating the alternating current in the power

transfer inductive coupler.

Normally, the receiver antenna will be installed first

in the well, as it is part of the casing string first being

installed in the wellbore. This part is often cemented

to the formation and will not move after it has been

cemented. Final longitudinal location in the well is

normally controlled and logged (tally), but there will

be small but significant variations caused by

differences in temperature and the weight of the

string.

The transmitter antenna is installed later as part of

the tubing string installation. Thi...