Full tensor gain compensated propagation measurements

Patent metadata

Field	Value
Publication number	US-9835755-B2
Application number	US-201414912893-A
Country	US
Kind code	B2
Filing date	Aug 21, 2014
Priority date	Aug 21, 2013
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

A method for obtaining full tensor gain compensated propagation measurements includes processing a full tensor voltage measurement to obtain a fully gain compensated tensor quantity. An electromagnetic logging tool including at least first and second axially spaced transmitters and at least first and second axially spaced receivers is rotated in a subterranean borehole. A plurality of voltage measurements are acquired while rotating to obtain a full tensor voltage measurement which is in turn processed to obtain the fully gain compensated tensor quantity.

First claim

What is claimed is:

1. A method for obtaining a full tensor gain compensated propagation measurement, the method comprising:
(a) rotating an electromagnetic logging tool in a subterranean borehole, the logging tool including at least first and second axially spaced transmitters and at least first and second axially spaced receivers, each of the transmitters and each of the receivers including a set of three collocated, linearly independent, antennas, at least one of the transmitters and receivers being non triaxial;
(b) acquiring a plurality of full tensor voltage measurements while rotating in (a), the full tensor voltage measurements obtained from a corresponding plurality of pairs of the transmitters and receivers; and
(c) causing a processor to process the plurality of full tensor voltage measurements to obtain a partially gain compensated full tensor quantity.

2. The method of claim 1 , wherein the processor is a downhole processor.

3. The method of claim 2 , further comprising:
(d) transmitting the partially gain compensated full tensor quantity to the surface; and
(e) causing a surface computer to invert the partially gain compensated full tensor quantity to obtain one or more properties of a subterranean formation.

4. The method of claim 2 , further comprising:
(d) causing the downhole processor to process the partially gain compensated full tensor quantity to obtain a partially gain compensated full tensor attenuation and a partially gain compensated full tensor phase shift.

5. The method of claim 1 , wherein diagonal terms of the partially gain compensated full tensor quantity are fully gain compensated and off diagonal terms of the partially gain compensated full tensor quantity are equal to a gain compensated cross term multiplied by a gain ratio.

6. A system comprising:
an electromagnetic logging tool having at least first and second axially spaced transmitters and at least first and second axially spaced receivers, each of the transmitters and each of the receivers including a set of three collocated, linearly independent, antennas, wherein the electromagnetic logging tool is configured to acquire a plurality of full tensor voltage measurements while rotating in a borehole, the full tensor voltage measurements being obtained from a corresponding plurality of pairs of the transmitters and receivers; and
a processor configured to process the plurality of full tensor voltage measurements to obtain an at least partially gain compensated full tensor quantity.

7. The system of claim 6 , wherein at least one of the transmitters and receivers are not triaxial.

8. The system of claim 6 , wherein the processor is a surface processor located in a surface computer, and wherein the system comprises a telemetry circuit configured to transmit the at least partially gain compensated full tensor quantity to the surface computer for inversion of the at least partially gain compensated full tensor quantity to obtain one or more properties of a subterranean formation.

9. The system of claim 6 , wherein the processor is a downhole processor and the processing of the plurality of full tensor voltage measurements to obtain an at least partially gain compensated full tensor quantity is performed downhole.

10. The system of claim 9 , wherein the downhole processor further obtains an at least partially gain compensated full tensor attenuation and an at least partially gain compensated full tensor phase shift based upon the at least partially gain compensated full tensor quantity.

11. The system of claim 6 , wherein diagonal terms of the partially gain compensated full tensor quantity are fully gain compensated and the off diagonal terms of the partially gain compensated full tensor quantity are equal to a gain compensated cross term multiplied by a gain ratio.

Assignees

• Schlumberger Technology Corp

Inventors

• Frey Mark
• Homan Dean M

Classifications

• E21B47/00 Primary

  Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) · CPC title

• G01V3/30

  operating with electromagnetic waves · CPC title

• G01V3/38 Primary

  Processing data, e.g. for analysis, for interpretation, for correction · CPC title

• G01V3/18

  specially adapted for well-logging · CPC title