Casing string monitoring using electromagnetic (EM) corrosion detection tool and junction effects correction

Patent metadata

Field	Value
Publication number	US-10234591-B2
Application number	US-201515118998-A
Country	US
Kind code	B2
Filing date	Apr 7, 2015
Priority date	Apr 10, 2014
Publication date	Mar 19, 2019
Grant date	Mar 19, 2019

Abstract

A corrosion monitoring method includes obtaining electromagnetic (EM) log, data along a casing string. The method also includes processing the EM log data to estimate casing thickness of the casing string as a function of position, where the processing includes correcting, for junction effects in the casing string.

First claim

What is claimed:

1. A corrosion monitoring method that comprises:
disposing an electromagnetic (EM) logging tool downhole;
generating a time-varying EM field along a casing string with a transmitter, wherein the transmitter is a coil or a solenoid;
recording a voltage induced by the EM field with a receiver, wherein the receiver is a coil or a solenoid;
constructing an EM data log with the recorded voltage; and
processing the EM data log to estimate casing thickness of the casing string as a function of position, wherein said processing comprises correcting for junction effects in the casing string, wherein the correcting for junction effects in the casing string comprises:
comparing results from a one-dimensional (1D) casing string model and a multi-dimensional casing string model to identify the junction effects; and
re-processing the EM log data using the 1D casing string model with the junction effects removed.

2. The method of claim 1 , wherein said correcting for junction effects in the casing string comprises employing a multi-dimensional casing string model.

3. The method of claim 2 , wherein said correcting for junction effects further comprises applying a multi-stage inversion with multiple stages, where a different casing string attribute or set of attributes is inverted for each stage while at least one other casing string attribute is fixed.

4. The method of claim 3 , wherein the multi-stage inversion comprises:
a first stage that inverts a junction location while a casing thickness is fixed; and
a second stage that inverts a casing thickness while junction location is fixed using values determined in the first stage.

5. The method of claim 4 , further comprising:
selecting EM log data at or near a casing junction for the first stage; and
selecting EM log data at or near a middle region of a casing section for the second stage.

6. The method of claim 4 , wherein the multi-stage inversion further comprises a third stage that inverts a junction location and a casing thickness using values determined in the first and second stages as initial values.

7. The method of claim 4 , wherein the multi-stage inversion further comprises performing multiple iterations of the multi-stage inversion, where initial values for attributes to be determined for each stage are based on a previous iteration.

8. The method of claim 1 , wherein said correcting for junction effects in the casing string comprises estimating junction positions directly from the EM log data, and inverting at least one other casing string attribute while a junction position attribute based on said estimating is fixed.

9. The method of claim 1 , wherein said correcting for junction effects in the casing string comprises calculating a first forward response using the multi-dimensional model and a second forward response using the 1D model, and wherein comparing results comprises comparing the first and second forward responses.

10. The method of claim 1 , wherein said correcting for junction effects in the casing string comprises using a one-dimensional (1D) model to identify one or more casing string attributes, and setting values for a multi-dimensional model based on the one or more casing string attributes determined using the 1D model.

11. The method of claim 1 , wherein said correcting for junction effects in the casing string comprises applying a layer-sliding inversion.

12. The method of claim 1 , wherein said correcting for junction effects in the casing string comprises applying a constraint condition that limits an amount of variance between casing thickness results of a one-dimensional (1D) casing string model and casing thickness results of a multi-dimensional casing string model.

13. A corrosion monitoring system that comprises:
an electromagnetic (EM) logging tool to collect EM log data along a casing string, wherein the EM logging tool comprises:
a transmitter, wherein the transmitter generates a time-varying EM field, wherein the transmitter is a coil or a solenoid; and
a receiver, wherein the receiver records a voltage induced by the EM field, wherein the receiver is a coil or a solenoid; and

a processing unit in communication with the EM logging tool, wherein the processing unit processes the EM log data to estimate casing thickness of the casing string as a function of position, wherein the processing unit corrects for junction effects in the casing string by:
comparing results from two different models to identify the junction effects; and
re-processing the EM log data using one of the different models with the junction effects removed.

14. The system of claim 13 , wherein the processing unit corrects for junction effects in the casing string by performing a multi-stage inversion with multiple stages, where a different casing string attribute or set of attributes is inverted for each stage while at least one other casing string attribute is fixed.

15. The system of claim 14 , wherein the multi-stage inversion further comprises a stage that inverts a junction location and a casing thickness using values determined in previous stages as initial values.

16. The system of claim 14 , wherein the processing unit performs multiple iterations of the multi-stage inversion, where initial values for attributes to be determined for each stage are based on a previous iteration.

17. The system of claim 13 , wherein said processing unit corrects for junction effects in the casing string based on a multi-dimensional casing string model.

18. The system of claim 13 , wherein said processing unit corrects for junction effects in the casing string by applying at least one of a layer-sliding inversion, and a constraint condition that limits an amount of variance between casing thickness results of a one-dimensional (1D) model and casing thickness results of a multi-dimensional model.

19. A corrosion monitoring method that comprises:
disposing an electromagnetic (EM) logging tool downhole;
generating a time-varying EM field along a casing string with a transmitter, wherein the transmitter is a coil or a solenoid;
recording a voltage induced by the EM field with a receiver, wherein the receiver is a coil or a solenoid
constructing an EM data log with the recorded voltage; and
processing the EM data log to estimate casing thickness of the casing string as a function of position, wherein said processing comprises correcting for junction effects in the casing string, wherein said correcting for junction effects in the casing string comprises:
employing a multi-dimensional casing string model;
applying a multi-stage inversion with multiple stages, where a different casing string attribute or set of attributes is inverted for each stage while at least one other casing string attribute is fixed, wherein the multi-stage inversion comprises a first stage that inverts a junction location while a casing thickness is fixed and a second stage that inverts a casing thickness while the junction location is fixed using values determined in the first stage;
selecting EM log data at or near a casing junction for the first stage; and
selecting EM log data at or near a middle region of a casing section for the second stage.

Assignees

• Halliburton Energy Services Inc

Inventors

• Wu Dagang
• Donderici Burkay

Classifications

• G01V3/28 Primary

  using induction coils · CPC title

• E21B47/092

  by detecting magnetic anomalies · CPC title

• G01N17/04

  Corrosion probes · CPC title

• E21B47/0006

  Fixed Constructions · mapped topic

• E21B47/00

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