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US-9223048-B2 · Dec 29, 2015 · US
Gain compensated directional propagation measurements
US9423525B2 · US · B2
| Field | Value |
|---|---|
| Publication number | US-9423525-B2 |
| Application number | US-201414325605-A |
| Country | US |
| Kind code | B2 |
| Filing date | Jul 8, 2014 |
| Priority date | Mar 29, 2014 |
| Publication date | Aug 23, 2016 |
| Grant date | Aug 23, 2016 |
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Abstract
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A method for obtaining gain compensated propagation measurements includes rotating an electromagnetic logging while drilling tool having at least one axial transmitter antenna, at least one transverse transmitter antenna, at least one axial receiver antenna and at least one transverse receiver antenna in a subterranean wellbore. Electromagnetic voltage measurements are acquired from the axial and transverse receiver antennas while rotating. The acquired voltage measurements are processed to compute harmonic voltage coefficients. Ratios of selected ones of the harmonic voltage coefficients are in turn processed to compute at least one gain compensated quantity including an axial cross term.
First claim
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What is claimed is: 1. A method for making downhole electromagnetic logging while drilling measurements, the method comprising (a) rotating an electromagnetic logging while drilling tool in a subterranean wellbore, the logging tool including at least one axial transmitter antenna, at least one transverse transmitter antenna, at least one axial receiver antenna, and at least one transverse receiver antenna; (b) acquiring a plurality of electromagnetic voltage measurements from the axial and transverse receiver antennas while rotating in (a); (c) processing the voltage measurements acquired in (b) to compute harmonic voltage coefficients; (d) processing a ratio of the harmonic voltage coefficients to compute at least one gain compensated quantity including at least one of an xz, zx, yx and zy value as defined in a coordinate system for the drilling tool. 2. The method of claim 1 , wherein the axial cross term is an xz coupling, a zx coupling, a yz coupling, a zy coupling, or a combination thereof. 3. The method of claim 1 , wherein the processing in (d) is performed by a downhole processor. 4. The method of claim 3 , further comprising: (e) transmitting the gain compensated quantity to a surface location; and (f) causing a surface computer to invert the gain compensated quantity to obtain one or more properties of a subterranean formation. 5. The method of claim 1 , further comprising: (e) processing the gain compensated quantity to compute a gain compensated phase shift and a gain compensated attenuation. 6. The method of claim 1 , wherein the harmonic voltage coefficients computed in (c) comprise DC, first harmonic sine, first harmonic cosine, second harmonic sine, and second harmonic cosine voltage coefficients. 7. The method of claim 1 , wherein the gain compensated quantity computed in (d) comprises at least one quantity proportional to an xz coupling, a zx coupling, a yz coupling, or a zy coupling. 8. The method of claim 7 , wherein the gain compensated quantity is computed using at least one of the following mathematical equations: CZX = V FHC _ 12 zx · V FHC _ 21 xz V DC _ 22 xx · V DC _ 11 zz CZX = V FHC _ 11 zx · V FHC _ 22 xz V DC _ 21 xx · V DC _ 12 zz CXZ = V FHC _ 21 zx · V FHC _ 12 xz V DC _ 11 xx · V DC _ 22 zz CXZ = V FHC _
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Classifications
using induction coils · CPC title
specially adapted for well-logging · CPC title
- G01V3/38Primary
Processing data, e.g. for analysis, for interpretation, for correction · CPC title
operating with electromagnetic waves · CPC title
using several coupled or uncoupled coils (G01V3/101 takes precedence) · CPC title
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- What does patent US9423525B2 cover?
- A method for obtaining gain compensated propagation measurements includes rotating an electromagnetic logging while drilling tool having at least one axial transmitter antenna, at least one transverse transmitter antenna, at least one axial receiver antenna and at least one transverse receiver antenna in a subterranean wellbore. Electromagnetic voltage measurements are acquired from the axial a…
- Who is the assignee on this patent?
- Schlumberger Technology Corp
- What technology area does this patent fall under?
- Primary CPC classification G01V3/38. Mapped technology areas include Physics.
- When was this patent published?
- Publication date Tue Aug 23 2016 00:00:00 GMT+0000 (Coordinated Universal Time) (B2). Legal status and post-grant events are not shown on this page.
- What related patents are in patentsdb?
- We list 8 related publications on this page (citations in our corpus or others sharing the same primary CPC).