U.S. patent application number 16/047893 was filed with the patent office on 2018-12-06 for rotatable sensors for measuring characteristics of subterranean formation.
The applicant listed for this patent is HALLIBURTON ENERGY SERVICES, INC.. Invention is credited to Burkay Donderici, Richard Thomas Hay.
Application Number | 20180347352 16/047893 |
Document ID | / |
Family ID | 54241027 |
Filed Date | 2018-12-06 |
United States Patent
Application |
20180347352 |
Kind Code |
A1 |
Hay; Richard Thomas ; et
al. |
December 6, 2018 |
ROTATABLE SENSORS FOR MEASURING CHARACTERISTICS OF SUBTERRANEAN
FORMATION
Abstract
Sensor assemblies are described for measuring isotropic,
anisotropic, or directionally dependent, characteristics of a
subterranean formation. Sensor assemblies can include sensors
deployed on a tool string. One or more of the sensors can be
rotatable relative to the tool string. Rotating one or more sensors
relative to the tool string can provide data about the subterranean
formation at multiple points around the tool string.
Inventors: |
Hay; Richard Thomas;
(Spring, TX) ; Donderici; Burkay; (Houston,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HALLIBURTON ENERGY SERVICES, INC. |
Houston |
TX |
US |
|
|
Family ID: |
54241027 |
Appl. No.: |
16/047893 |
Filed: |
July 27, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14429068 |
Mar 18, 2015 |
10053978 |
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PCT/US2014/032520 |
Apr 1, 2014 |
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16047893 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 47/024 20130101;
E21B 7/06 20130101; E21B 4/00 20130101; E21B 47/01 20130101; G01B
7/30 20130101; E21B 3/00 20130101; G01V 3/28 20130101; E21B 49/00
20130101 |
International
Class: |
E21B 49/00 20060101
E21B049/00; G01V 3/28 20060101 G01V003/28; G01B 7/30 20060101
G01B007/30; E21B 7/06 20060101 E21B007/06; E21B 47/01 20060101
E21B047/01; E21B 3/00 20060101 E21B003/00; E21B 47/024 20060101
E21B047/024 |
Claims
1. A method comprising: transmitting a first signal via a
transmitter coupled with a tool string in a subterranean formation;
receiving a second signal associated with the first signal via a
receiver coupled with the tool string, wherein the transmitter or
the receiver is rotating relative to the tool string, wherein at
least one of the transmitter or the receiver includes an antenna
having a first winding arranged in a first winding plane and a
second winding arranged in a second winding plane, the first
winding being tilted relative to the second winding; detecting an
angular position of the transmitter or the receiver as the
transmitter or the receiver rotates relative to the tool string;
and determining a characteristic of the subterranean formation at a
first position in the first winding plane and at a second position
in the second winding plane relative to tool string based, at least
in part, on the second signal and the angular position.
2. The method of claim 1, wherein determining the characteristic of
the subterranean formation at a position relative to the tool
string includes determining a resistivity of a region of the
formation at a distance from the tool string and in a direction
from the tool string.
3. The method of claim 2 wherein the receiver comprises a receive
antenna with a substantially perpendicular orientation relative to
a transmit antenna of the transmitter.
4. The method of claim 3 wherein the characteristic of the
subterranean formation is determined at a position lateral to the
tool string in a direction lateral to a direction of travel of an
end of the tool string based, at least in part, on the
substantially perpendicular orientation of the receive antenna
relative to the transmit antenna.
5. The method of claim 1 wherein the transmitter and the receiver
include the antenna having a first winding arranged in a first
winding plane and a second winding arranged in a second winding
plane.
6. The method of claim 1 wherein the transmitter and the receiver
rotate relative to the tool string.
7. The method of claim 6 further comprising controlling a speed of
a motor to rotate the transmitter and the receiver.
8. The method of claim 1, further comprising: receiving a third
signal associated with the first signal via a second receiver
coupled with the tool string at a position between the receiver and
the transmitter, wherein the transmitter or the second receiver is
rotating relative to the tool string; if the second receiver is
rotating relative to the tool string, detecting a second angular
position of the receiver as the second receiver rotates relative to
the tool string; using a first combination or a second combination
to determine the characteristic of the formation at a second
position relative to the tool string, the first combination
including the third signal and the first angular position, the
second combination including the third signal and the second
angular position; and creating a profile of the characteristic of
the formation based, at least in part, on the determination of the
characteristic of the formation at the first position and the
determination of the characteristic of the formation at the second
position.
9. An information-handling system comprising: a controller; and a
memory including machine-readable instructions that are accessible
by the controller for causing the controller to perform one or more
operations comprising: transmitting a first signal via a
transmitter coupled with a tool string in a subterranean formation;
receiving a second signal associated with the first signal via a
receiver coupled with the tool string, while the transmitter or the
receiver is rotating relative to the tool string, wherein at least
one of the transmitter or the receiver includes an antenna having a
first winding arranged in a first winding plane and a second
winding arranged in a second winding plane, the first winding being
tilted relative to the second winding; detecting an angular
position of the transmitter or the receiver as the transmitter or
the receiver rotates relative to the tool string; and determining a
characteristic of the subterranean formation at a first position in
the first winding plane and at a second position in the second
winding plane relative to tool string based, at least in part, on
the second signal and the angular position.
10. The information handling system of claim 9, wherein the
operation of determining the characteristic of the subterranean
formation at a position relative to the tool string includes
determining a resistivity of a region of the formation at a
distance from the tool string and in a direction from the tool
string.
11. The information handling system of claim 10 wherein the
receiver comprises a receive antenna with a substantially
perpendicular orientation relative to a transmit antenna of the
transmitter.
12. The information handling system of claim 11 wherein the
characteristic of the subterranean formation is determined at a
position lateral to the tool string in a direction lateral to a
direction of travel of an end of the tool string based, at least in
part, on the substantially perpendicular orientation of the receive
antenna relative to the transmit antenna.
13. The information handling system of claim 9 wherein the
transmitter and the receiver include the antenna having a first
winding arranged in a first winding plane and a second winding
arranged in a second winding plane.
14. The information handling system of claim 9 wherein the
transmitter and the receiver rotate relative to the tool
string.
15. The information handling system of claim 9 the one or more
operations further comprises controlling a speed of a motor to
rotate the transmitter and the receiver.
16. The information handling system of claim 9, wherein the one or
more operation further comprises: receiving a third signal
associated with the first signal via a second receiver coupled with
the tool string at a position between the receiver and the
transmitter, wherein the transmitter or the second receiver is
rotating relative to the tool string; if the second receiver is
rotating relative to the tool string, detecting a second angular
position of the receiver as the second receiver rotates relative to
the tool string; using a first combination or a second combination
to determine the characteristic of the formation at a second
position relative to the tool string, the first combination
including the third signal and the first angular position, the
second combination including the third signal and the second
angular position; and creating a profile of the characteristic of
the formation based, at least in part, on the determination of the
characteristic of the formation at the first position and the
determination of the characteristic of the formation at the second
position.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional of U.S. patent application Ser. No.
14/429,068 filed Mar. 18, 2015 (allowed), which is a national phase
entry under 35 USC .sctn. 371 of International Patent Application
No. PCT/US2014/032520 filed Apr. 1, 2014, the entireties of which
are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates generally to devices for use
in a wellbore in a subterranean formation and, more particularly to
sensor assemblies for measuring anisotropic characteristics of a
subterranean formation.
BACKGROUND
[0003] Various devices can be placed in a well traversing a
hydrocarbon bearing subterranean formation. Some devices can
include sensors capable of measuring attributes (e.g., resistivity)
of the subterranean formation. Measurements can be used to
determine characteristics (e.g., composition) of the subterranean
formation. In some operations, the number of measurements that can
be obtained is limited. Greater numbers of measurements can provide
more detailed analysis, which can lead to greater efficiency or
cost effective well operations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a diagram illustrating a drilling system,
according to one aspect of the present disclosure.
[0005] FIG. 2 is a diagram illustrating an example of a bottom hole
sensor assembly with rotatable antennas according to one aspect of
the present disclosure.
[0006] FIG. 3 is another diagram illustrating the bottom hole
sensor assembly of FIG. 2 according to one aspect of the present
disclosure.
[0007] FIG. 4 is a diagram illustrating an example of a bottom hole
sensor assembly with an orientation sensor according to one aspect
of the present disclosure.
[0008] FIG. 5 is a diagram illustrating an example of a bottom hole
sensor assembly with multiple receive antennas according to one
aspect of the present disclosure.
[0009] FIG. 6 is a diagram illustrating an example of a bottom hole
sensor assembly with receive antennas oriented at different tilt
angles according to one aspect of the present disclosure.
[0010] FIG. 7 is a diagram illustrating an example of a rotatable
sensor assembly according to one aspect of the present
disclosure.
[0011] FIG. 8 is a diagram illustrating an example of a bottom hole
sensor assembly with two motors according to one aspect of the
present disclosure.
[0012] FIG. 9 is a diagram illustrating an example of a rotatable
near-bit sensor assembly according to one aspect of the present
disclosure.
[0013] FIG. 10 is a diagram illustrating an example of a bottom
hole sensor assembly with sensor assemblies, each having three
formation sensors, according to one aspect of the present
disclosure.
[0014] FIG. 11 is a block diagram of a control system for a bottom
hole sensor assembly with rotatable sensors according to one aspect
of the present disclosure.
[0015] FIG. 12 is a block diagram of a control system for a
rotatable sensor assembly according to one aspect of the present
disclosure.
[0016] FIG. 13 is a flow chart illustrating an example method for
measuring anisotropic characteristics of a subterranean formation
according to one aspect of the present disclosure.
DETAILED DESCRIPTION
[0017] Certain aspects and examples of the present disclosure are
directed to sensor assemblies for measuring anisotropic, or
directionally-dependent, characteristics of a subterranean
formation. Sensor assemblies can include sensors deployed on a tool
string. One or more of the sensors can be rotatable relative to the
tool string. Rotating one or more sensors relative to the tool
string can provide data about the subterranean formation at
multiple zones around the tool string.
[0018] In one example, a rotatable antenna on a drill string may
rotate about the drill string for transmitting or receiving signals
to determine resistivity at various angles in the formation. The
rotation of the rotatable antenna, independent from any rotation of
the drill string, can provide resistivity readings at multiple
angles regardless of whether the drill string is rotating for
drilling. The multiple directional resistivity readings can
indicate boundaries of formation layers near the drill string. A
drill string operator may utilize the readings as navigation aids
in steering the direction of a new borehole being drilled for
optimal well bore placement with respect to the location of
boundaries, faults, calcite lens, or other natural or man-made
subterranean structures.
[0019] These illustrative examples are given to introduce the
reader to the general subject matter discussed here and are not
intended to limit the scope of the disclosed concepts. The
following describes various additional aspects and examples with
reference to the drawings in which like numerals indicate like
elements, and directional descriptions are used to describe the
illustrative aspects. The following uses directional descriptions
such as "above," "below," "upper," "lower," "left," "right,"
"downhole," etc. in relation to the illustrative aspects as they
are depicted in the figures, the downhole direction being toward
the toe of the well. Like the illustrative aspects, the numerals
and directional descriptions included in the following should not
be used to limit the present disclosure. Furthermore, the following
uses the term "or" to denote any combination of options separated
by the term "or", including combinations in which only one of the
options is utilized and combinations in which more than one (and in
some cases, all) of the options are utilized.
[0020] FIG. 1 schematically depicts an example of a well system 100
having a bottom hole sensor assembly 114. The well system 100 can
include a bore that is a wellbore 102 extending through various
earth strata. The wellbore 102 can extend through a hydrocarbon
bearing subterranean formation 110. A casing string 104 can extend
from the surface 106 to the subterranean formation 110. The casing
string 104 can provide a conduit via which formation fluids, such
as production fluids produced from the subterranean formation 110,
can travel from the wellbore 102 to the surface 106.
[0021] A tool string 112 within the wellbore 102 can extend from
the surface into the subterranean formation 110. In some aspects,
the tool string 112 can include a drill bit 116 introduced into the
well system 100 for drilling the wellbore 102 through the various
earth strata. In other aspects, the tool string 112 can be
introduced without the drill bit 116. As a non-limiting example of
a tool string 112 without a drill bit 116, the tool string 112 may
be part of a wireline tool utilized for downhole well operations.
The tool string 112 can include a bottom hole (or downhole) sensor
assembly 114. Although FIG. 1 depicts the bottom hole sensor
assembly 114 in section of the wellbore 102 that is substantially
vertical, the bottom hole sensor assembly 114 can be located,
additionally or alternatively, in sections of the wellbore 102 that
have other orientations, including substantially horizontal. In
some aspects, the bottom hole sensor assembly 114 can be disposed
in simpler wellbores, such as wellbores 102 without a casing string
104.
[0022] In some aspects, the tool string 112 can include a bent
housing 118. Examples of the bent housing 118 include a fixed bent
housing or an adjustable bent housing. The bent housing 118 can
provide steering for the drill bit 116. The bent housing 118 can
allow drilling to proceed ahead in a certain direction in response
to the tool string 112 rotating. Ceasing rotation of the tool
string 112 can allow the bent housing 118 to change the drilling
direction of the tool string 112. A motor 120 can rotate the drill
bit 116 while the tool string 112 slides ahead through the
formation 110 without the tool string 112 and bent housing 118
rotating. The tool string 112 can slide in the direction at which
the bent housing 118 is facing, often called the tool face, as the
motor 120 rotates the drill bit 116 on the bottom of the hole
without the tool string 212 and bent housing 118 rotating. Sliding
the tool string 112 can allow course adjustments in a drilling
path. Resuming rotation of the tool string 212 can cause the tool
string 212 to cease course adjustment and continue moving in the
adjusted direction.
[0023] Different types of bottom hole sensor assemblies 114 can be
used in the well system 100 depicted in FIG. 1. For example, FIG. 2
is a cross-sectional side view of an example of a bottom hole
sensor assembly 214 with rotatable antennas 216, 218 according to
one aspect. The bottom hole sensor assembly 214 can include a tool
string 212, a rotatable transmit antenna 216, a rotatable receive
antenna 218, a motor 222, a first angular position sensor 224, and
a second angular position sensor 225.
[0024] The rotatable transmit antenna 216 or the rotatable receive
antenna 218 can be rotatively coupled with the tool string 212. The
rotatable transmit antenna 216 or the rotatable receive antenna 218
can rotate relative to the tool string 212. The rotatable transmit
antenna 216 and the rotatable receive antenna 218 can together
measure a characteristic within a region of the formation 210. The
rotatable transmit antenna 216 can emit signals into the formation
210. The rotatable receive antenna 218 can detect responses in the
formation 210 to the emitted signals. A sensitive volume 226 can
define a region of the formation 210 in which the rotatable receive
antenna 218 can detect a relatively largest portion of the
responses to the signals emitted by the rotatable transmit antenna
216.
[0025] The rotatable transmit antenna 216 and the rotatable receive
antenna 218 can be induction-type antennas. The direction of the
signals emitted into or received from the formation 210 by an
induction-type antenna can depend on an orientation of an
equivalent dipole of the induction-type antenna. A tilt angle can
represent the deviation of the dipole orientation from an axial
direction of the tool string 212. The tilt angles of a pair of
induction-type antennas can affect the position of a sensitive
volume measured by the pair of induction-type antennas. For
example, the position of the sensitive volume 226 relative to the
tool string 212 can depend on the tilt angle of the rotatable
transmit antenna 216 and the tilt angle of the rotatable receive
antenna 218, as depicted in FIG. 2.
[0026] Examples of induction-type antenna include a solenoid, a
magnetometer, and a coil. A tilt angle of a solenoid antenna can be
produced by adjusting an elevation angle of a ferromagnetic core in
the solenoid. A tilt angle of a magnetometer antenna can be
produced according to the orientation at which the magnetometer
antenna is mounted onto or into the bottom hole sensor assembly
214. A tilt angle of a coil antenna can be produced by winding the
coil at an angle relative to the axial direction of the tool string
212. For example, the rotatable transmit antenna 216 can include a
wire winding 215 arranged in a plane of winding 217 that is
oriented approximately perpendicular to an equivalent dipole of the
wire winding 215, as depicted in FIG. 2. The rotatable receive
antenna 218 can include a wire winding 213 arranged in a plane of
winding 219 that is oriented approximately perpendicular to an
equivalent dipole of the wire winding 213, as depicted in FIG.
2.
[0027] Various relative arrangements of transmit and receive
antennas are possible. Transmit and receive antennas can be
perpendicular to each other, such that the tilt angle of a transmit
antenna and a receive antenna differ by substantially 90 degrees.
Transmit and receive antennas can be parallel to each other, such
that the tilt angle of a transmit antenna and a receive antenna are
substantially the same. It is also possible for the tilt angle of
one of the transmit antenna or the receive antenna to be
substantially equal to zero,
[0028] Although the bottom hole sensor assembly 214 is described
above as including a rotatable transmit antenna 216 and a rotatable
receive antenna 218, the bottom hole sensor assembly 214 can
alternatively or additionally include one or more other sensors
rotatable relative to the tool string 212. In some aspects, the
sensor rotatable relative to the tool string 212 can be an
azimuthal sensor or a sensor that is directionally dependent.
Non-limiting examples of azimuthal sensors include the
aforementioned antennas, as well as resistivity sensors, gamma ray
sensors, acoustic sensors, nuclear magnetic resonance sensors, and
density sensors. Notwithstanding the suitability of these azimuthal
sensors or other sensors, for the sake of simplicity and clarity,
aspects herein are primarily described with respect to antennas.
Also, although many aspects described herein include multiple
sensors rotatable relative to the tool string 212, in some aspects,
only one azimuthal sensor is rotatable relative to the tool string
212.
[0029] The motor 222 can be coupled with the rotatable transmit
antenna 216 or the rotatable receive antenna 218. In one example,
the rotatable transmit antenna 216 and the rotatable receive
antenna 218 can be coupled to a shaft 230 driven by the motor 222.
The rotatable transmit antenna 216 or the rotatable receive antenna
218 can rotate relative to the tool string 212 in response to the
motor 222 rotating. In some aspects, the motor 222 can be dedicated
for rotating the rotatable transmit antenna 216 or the rotatable
receive antenna 218. In other aspects, the motor 222 can also
provide other functions. In one example, the motor 222 can be
coupled with a drill bit portion of a drill string and provide
power for rotating drill bits without rotating the remainder of the
drill string.
[0030] The motor 222 can be any suitable form of torsion power
unit. Examples of torsion power units include a mud motor, a
turbine motor, an electric motor, a Tubodrill motor, a vane motor,
an air-powered motor, and a fluid-powered motor. In some aspects, a
torsion power unit can be a hydraulic powered motor powered by a
hydraulic pump. The pump can be powered by any suitable energy
source. Examples of suitable energy sources for such a pump include
electric power conveyed via a pipe (such as wired pipe or a pipe in
pipe system such as is available under the trade name
Reelwell.TM.), electric power from local power generation (such as
from a turbine-powered generator or other form of energy harvesting
device downhole), or electric power from an energy storage device
(such as batteries, rechargeable batteries, capacitors, or super
capacitors).
[0031] In some aspects, the angular position sensors 224, 225 can
be positioned for rotating respectively with the rotatable transmit
antenna 216 or the rotatable receive antenna 218. In one example,
the first angular position sensor 224 and the rotatable transmit
antenna 216 can be located on a shared housing that is rotatable
relative to the tool string 212. The first angular position sensor
224 can detect an orientation of the rotatable transmit antenna
216. For example, the first angular position sensor 224 may have a
a known rotational relationship with the rotatable transmit antenna
216 that allows the orientation of the rotatable transmit antenna
216 to be determined based on a known rotational location of the
first angular position sensor 224. The second angular position
sensor 225 can detect an orientation of the rotatable receive
antenna 218. The orientation of the rotatable transmit antenna 216
or the rotatable receive antenna 218 (or both) can indicate the
position of the sensitive volume 226 in the formation 210 relative
to the tool string 212 at a particular time.
[0032] In some aspects, the first angular position sensor 224 or
the second angular position sensor 225 can measure an orientation
or angular position of an antenna that is stationary relative to
the tool string 212. The first angular position sensor 224 or the
second angular position sensor 225 can additionally or
alternatively measure a changing orientation of an antenna that is
rotating relative to the tool string 212. In one example, the first
angular position sensor 224 can measure an orientation when the
rotatable transmit antenna 216 is rotating relative to the tool
string 212 in response to rotating the motor 222 and the second
angular position sensor 225 can measure an orientation of the
rotatable receive antenna 218 that is stationary relative to the
tool string 212 and not rotating with the motor 222.
[0033] The orientation detected by the angular position sensor 224
or 225 can indicate a radial direction of a reference point of an
antenna relative to an angular reference. The angular position
sensors 224, 225 can use any suitable angular reference for
indicating the orientation of the rotatable transmit antenna 216 or
the rotatable receive antenna 218. In some aspects, the angular
reference can be relative to gravity, a scribe line of the tool
string 212, another reference feature of the tool string 212, or a
northing, such as a true north or a magnetic north. In one example
of an angular reference relative to gravity, the first angular
position sensor 224 can measure the orientation of the rotatable
transmit antenna 216 relative to a top side of an inclined
borehole, which may also be referred to as a high side of the
borehole.
[0034] The angular position sensor 224 or 225 can include one or
more survey direction sensors. The angular position sensor 224 or
225 can use any suitable type or combination of survey direction
sensors. Examples of survey direction sensors include
accelerometers, magnetometers, and gyroscopes. In one example, an
angular position sensor 224 or 225 can include two accelerometers
orthogonally oriented along X-Y axes that are cross plane to the
longitudinal axis of the tool string 212. Each accelerometer can
detect a fraction of the earth's gravitational field according to
the orientation of the accelerometer. The values detected by the
accelerometers can indicate the orientation of the angular position
sensor 224 or 225, such as a deviation from a reference direction
of up or down. In another example, an angular position sensor 224
or 225 can include two magnetometers orthogonally oriented on the
X-Y axes. The magnetometers can measure the Earth's magnetic field
from different orientations to determine the direction of magnetic
north and the deviation of the angular position sensor 224 or 225
therefrom. In a further example, the angular position sensor 224 or
225 can include a gyroscope which measures the deviation of the
angular position sensor 224 or 225 from the spin axis of the earth
(e.g. true north) or a referenced direction. In some aspects, a
combination of survey direction sensors can be used together to aid
in further resolving horizontal and vertical planes relative to the
borehole. In one example, either a gyroscope or an X-Y magnetometer
arrangement may be complemented with an X-Y axis accelerometer
arrangement. In some aspects, additional survey direction sensors
of the same or different type can be included to provide additional
orientation information. In one example, a sensor that measures
along the Z-axis (e.g., along the longitudinal axis of the tool
string 212) may be included to reduce errors in resolving the
direction of the vertical or horizontal planes (or both) relative
to the down direction, such as in circumstances in which resolution
is poor on the X-axis, Y-axis, or both.
[0035] FIG. 3 is a cross-sectional side view of the bottom hole
sensor assembly 214 of FIG. 2 with rotated antennas 216, 218
according to one aspect. Rotating the motor 222 (such as depicted
by the counterclockwise arrow 228 in FIG. 3) can cause the
rotatable transmit antenna 216 or the rotatable receive antenna 218
to rotate relative to the tool string 212. Rotating the rotatable
transmit antenna 216 or the rotatable receive antenna 218 can shift
the position of the sensitive volume 226 of the formation 210
measured by the rotatable transmit antenna 216 and the rotatable
receive antenna 218. For example, the sensitive volume 226 can be
rotated from a position in the formation 210 above the tool string
212 (such as depicted in FIG. 2) to a position in the formation 210
below the tool string 212 (such as depicted in FIG. 3). The
sensitive volume 226 can be moved without rotation of the tool
string 212. Rotating the position of the sensitive volume 226
without rotating the tool string 212 can provide more data about
the formation 210 than would otherwise be provided without rotating
the tool string 212. In one example, resistivity information about
the formation 210 can be obtained at various points around the tool
string 212 while the tool string 212 is sliding for course
adjustment. The resistivity information can be presented to an
operator of the tool string 212 for indicating a proximity to a
boundary between water-bearing earth strata and hydrocarbon-bearing
earth strata.
[0036] In another example, rotating the position of the sensitive
volume 226 without rotating the tool string 212 can provide data
about the direction and distance to a subterranean man-made object
such as another well, another borehole, or a lost drill string. For
example, by detecting variations in the surrounding volume (such as
resistivity changes), the location of a man-made object (such as an
electrically conductive casing that has a lower resistivity than
the surrounding formation) may be determined.
[0037] In some aspects, the rotatable transmit antenna 216 or the
rotatable receive antenna 218 can be selectively rotatively coupled
with the tool string 212. In one example, the rotatable transmit
antenna 216 can be locked to the tool string 212 to prevent
rotation of the rotatable transmit antenna 216 relative to the tool
string 212. In some aspects, the rotatable transmit antenna 216 or
the rotatable receive antenna 218 can rotate relative to the tool
string 212 in a direction opposite to a direction in which the tool
string 212 rotates during drilling. An opposite direction of
rotation can allow a rate of rotation of the rotatable antenna 216,
218 relative to the formation 210 to be less than a rate of
rotation of the tool string 212 relative to the formation 210.
[0038] Although the bottom hole sensor assembly 214 is depicted in
FIGS. 2-3 with one rotatable transmit antenna 216 and one rotatable
receive antenna 218 rotated by one motor 222, other arrangements
are possible. For example, a bottom hole sensor assembly may
include a transmit antenna that is rotatable and a receive antenna
that is not rotatable or vice versa. A pair of antennas in which
only one of the antennas is rotatable may still provide a sensitive
volume that is rotatable relative to the tool string without
rotating the tool string. The bottom hole sensor assembly 214 can
include multiple receive antennas, multiple transmit antennas,
multiple motors, multiple angular position sensors, or any
combination thereof.
[0039] Although the bottom hole sensor assembly 214 is depicted in
FIGS. 2-3 with angular position sensors 224, 225 respectively
positioned on shared housings for rotating with the rotatable
transmit antenna 216 and the rotatable receive antenna 218, other
arrangements are possible. For example, in some aspects, the
angular position sensor 224 or 225 associated with an antenna can
include a survey direction sensor that is not rotating at the same
speed or direction as the antenna. In at least such arrangements,
the angular position sensor may also include an orientation sensor
that detects an orientation of the antenna relative to the object
containing the survey direction sensor. The orientation sensor can
detect an additional offset of the antenna from the orientation
measured by the survey direction sensor in order to determine the
orientation of the antenna relative to the angular reference. For
example, FIG. 4 is a back cross-sectional view of an example of a
bottom hole sensor assembly 314 with an orientation sensor 368
according to one aspect.
[0040] The bottom hole sensor assembly 314 can include a tool
string 312, a housing 356, and an angular position sensor 324. The
housing 356 can be rotatable relative to the tool string 312, such
as depicted by the curved arrow 328 depicted in FIG. 4. The tool
string 212 can include a bore 301. In some aspects, the bore 301
provides a flow path for fluids, such as drilling fluids or
production fluids, to flow through the tool string 212. In
additional or alternative aspects, motors, shafts, gears, or other
components for rotating the housing 356 relative to the tool string
212 can be positioned within the bore 301. (Some example
arrangements of such components are described below with respect to
FIG. 7). The housing 356 can carry an antenna 316. Rotating the
housing 356 relative to the tool string 312 can rotate the antenna
316 relative to the tool string 312. The angular position sensor
324 can provide information about an orientation of the antenna 316
relative to an angular reference that is separate from the tool
string 312. Non-limiting examples of the angular reference include
true north, magnetic north, and a downward direction corresponding
to a direction in which gravity of the earth exerts the greatest
pull.
[0041] The angular position sensor 324 can include a survey
direction sensor 325. The survey direction sensor can be positioned
on or in the tool string 312 rather than on the housing 356. The
survey direction sensor can detect an angular position of the tool
string 312 relative to the angular reference that is separate from
the tool string 312. The angular position sensor 324 can also
include an orientation sensor 368. The orientation sensor 368 can
detect an angular position of the antenna 316 relative to the
survey direction sensor 325. The orientation of the antenna 316
relative to the angular reference can be determined based on
readings from the orientation sensor 368 and the survey direction
sensor 325. For example, the angular offset of the antenna 316 from
the survey direction sensor 325 (measured by the orientation sensor
368) can be combined with the angular offset of the survey
direction sensor 325 from the angular reference (measured by the
survey direction sensor 325) to yield a total angular offset of the
antenna 316 from the angular reference. As an illustrative example,
the survey direction sensor 325 may be a gyroscope that detects
deviation of the tool string 312 from true north 399. The survey
direction sensor 325 may detect that the tool string 312 is
oriented at a 30-degree eastward deviation 397 from true north 399.
The orientation sensor 368 may detect that the antenna 316 is
oriented at a 60-degree eastward deviation 395 from the location of
the survey direction sensor 325 on the tool string 312. The
combined readings in such a scenario would indicate that the
antenna 316 is oriented at a total eastward deviation 393 of 90
degrees from true north 399.
[0042] In some aspects, the orientation sensor 368 can include
magnets 335, 345. The magnets 335, 345 can be arranged at regular
intervals around the circumference of the tool string 212. The
magnets 335, 345 can be arranged with dipoles aligned in a radial
direction of the tool string 212 on the X-Y plane. A zero-point
magnet 345 can have an inverted orientation relative to the
remaining magnets 335. For example, the zero-point magnet 345 can
be arranged with a South-North orientation in a radially inward
direction if the remaining magnets 335 are arranged with a
North-South orientation in a radially inward direction.
[0043] The zero-point magnet 345 can be aligned with (or at a known
offset from) the survey direction sensor 325. For example, the
zero-point magnet 345 can be aligned with or at a known offset from
a scribe line 327 of the tool string 312. The scribe line 327 may
identify a reference orientation position of the survey direction
sensor 325 relative to the tool string 312. For example, a zero
point of the survey direction sensor 325 can be at a known fixed
offset from the scribe line 327. In some aspects, the known fixed
offset from the scribe line 327 can be measured after the bottom
hole sensor assembly 314 is fully assembled.
[0044] The orientation sensor 368 can also include one or more
magnetometers 365 (such as a hall effect sensor). The magnetometer
365 can detect variations in magnetic field strength as the
magnetometer 365 moves between adjacent magnets 335, 345. For
example, the magnetometer 365 may detect spikes in magnetic field
magnitude each time the magnetometer 365 is aligned with a magnet
335, 345. The inverted alignment of the zero-point magnet 345 can
cause a spike in the opposite direction from the remaining magnets
335. The number of spikes since the opposite spike of the
zero-point magnet 345 can provide a general indication of how far
the magnetometer 365 has travelled past the zero-point magnet 345.
The difference in magnitude from the most recent spike can indicate
how far the magnetometer 365 has traveled from that spike and
provide more precise location information when the magnetometer 365
is between magnets 335, 345. In some aspects, a gyroscope or
interval timer can be used with the magnetometer 365 to provide
additional approximation of intermediate positions between magnets
335, 345 based on sensed rotation speed versus time.
[0045] Although the orientation sensor 368 is depicted in FIG. 4
with the magnets 335, 345 carried by the tool string 312 and the
magnetometers 365 carried by the housing 356, other arrangements
are possible. In some aspects, the magnetometers 365 are carried by
the tool string 312 and the magnets 335, 345 are carried by the
housing 356. In some aspects, a combination of magnets 335, 345 and
magnetometers 365 can be located on a combination of the tool
string 312 and a motor shaft coupled with the housing 356 to rotate
the housing 356 relative to the tool string 312. The motor shaft
can be located in the bore 301 and coupled to the housing 356 in
any suitable manner, including the example arrangement described
below with respect to FIG. 7. An arrangement in which an
orientation sensor 368 monitors rotation of the motor shaft can
provide an alternate or additional indication of the angular
position of the antenna based on a known relationship between
rotation of the motor shaft and rotation of the housing.
[0046] In some aspects, including an orientation sensor 368 can
reduce a cost of producing the bottom hole sensor assembly 314 by
reducing a number of survey direction sensors 325 used in the
bottom hole sensor assembly 314. In some aspects, positioning one
or more survey direction sensors 325 to rotate with each rotating
antenna 316 can reduce a complexity or increase an accuracy of the
bottom hole sensor assembly 314. For example, a survey direction
sensor 325 that rotates with an antenna 316 may directly provide
information about the orientation of the antenna 316 relative to an
angular reference. Directly obtaining orientation information may
reduce or eliminate inaccuracies from changes in alignment amongst
components arranged between the survey direction sensor 325 and the
antenna 316, such as may occur as a result of drill string twist,
threaded connection over-tightening during drilling, motor drive
train twist, gear play variations, or other misalignment
factors.
[0047] FIG. 5 is a cross-sectional side view of an example of a
bottom hole sensor assembly 414 with multiple receive antennas 418,
420 according to one aspect of the present disclosure. The bottom
hole sensor assembly 414 can include a tool string 412, a rotatable
transmit antenna 416, a first rotatable receive antenna 418, a
second rotatable receive antenna 420, and a motor 422.
[0048] The first rotatable receive antenna 418 and the second
rotatable receive antenna 420 can be located along the tool string
412 at different lengths from the rotatable transmit antenna 416.
The different lengths can cause the first rotatable receive antenna
418 and the second rotatable receive antenna 420 to align
differently with the rotatable transmit antenna 416. The difference
in alignment can allow the rotatable transmit antenna 416 to
produce a first sensitive volume 426 in the formation 410 with the
first rotatable receive antenna 418 and a second sensitive volume
428 with the second rotatable receive antenna 420. The first
sensitive volume 426 can be positioned at a different depth of
investigation than a depth of investigation of the second sensitive
volume 428.
[0049] In some aspects, the bottom hole sensor assembly 414 can
provide different depths of investigation simultaneously. For
example, the rotatable transmit antenna 416 may emit multiple
frequencies for obtaining multiple depths of investigation
concurrently. In some aspects, the bottom hole sensor assembly 414
can provide different depths of investigation successively. For
example, the bottom hole sensor assembly 414 may consistently
broadcast a frequency via the rotatable transmit antenna 416. The
bottom hole sensor assembly 414 may obtain a first depth of
investigation by activating the first rotatable receive antenna 418
without activating the second rotatable receive antenna 420. The
bottom hole sensor assembly 414 may obtain a second depth of
investigation by deactivating the first rotatable receive antenna
418 and activating the second rotatable receive antenna 420.
[0050] The rotatable transmit antenna 416, the first rotatable
receive antenna 418, and the second rotatable receive antenna 420
can rotate relative to the tool string 412 in response to rotation
of the motor 422. Rotating the first sensitive volume 426 and the
second sensitive volume 428 relative to the tool string 412 can
provide more diverse depths of investigation, improved vertical
resolution of data, compensation for variations in data, or any
combination thereof.
[0051] FIG. 6 is a cross-sectional side view of an example of a
bottom hole sensor assembly 514 with receive antennas 518, 520
oriented at different tilt angles according to one aspect. The
bottom hole sensor assembly 514 can include a rotatable transmit
antenna 516, a first rotatable receive antenna 518, and a second
rotatable receive antenna 520 positioned along a tool string
512.
[0052] The tool string 512 can have a downhole end 546. In some
aspects, a drill bit can be positioned at the downhole end 546. The
tool string 512 can travel in a direction through the formation
510. For example, the tool string 512 may travel in a substantially
horizontal direction, as depicted by the rightward arrow in FIG.
6.
[0053] The first rotatable receive antenna 518 can be oriented with
a plane of winding 519 positioned at a tilt angle that is
substantially perpendicular to a tilt angle of a plane of winding
517 of the rotatable transmit antenna 516. The perpendicular
orientation can produce a first sensitive volume 526 positioned
between the rotatable transmit antenna 516 and the first rotatable
receive antenna 518. The first sensitive volume 526 can provide
information about a portion of the formation 510 that is positioned
laterally to the tool string 512. For example, the first sensitive
volume 526 can be positioned below the horizontal direction of
travel of the tool string 512, as depicted in FIG. 6.
[0054] The second rotatable receive antenna 520 can have a plane of
winding 521 oriented at a tilt angle that is substantially parallel
to a tilt angle of the plane of winding 517 of the rotatable
transmit antenna 516. The parallel orientation can produce a second
sensitive volume 528 and a third sensitive volume 529. The second
sensitive volume 528 can include a portion 532 that extends beyond
the rotatable transmit antenna 516 and away from the second
rotatable receive antenna 520. For example, the second sensitive
volume 528 can include a portion 532 that extends ahead (e.g.,
depicted toward the right in FIG. 6) of the rotatable transmit
antenna 516. In some aspects, the second sensitive volume 528 from
a parallel orientation can extend ahead of the downhole end 546 of
the tool string 512. In one example, a parallel orientation can
provide information about a region that is ahead of a drill bit in
a drill string. In some aspects, positioning an antenna closer to
the downhole end 546 of the tool string 512 can increase a distance
ahead of the downhole end 546 that can be detected. For example,
the rotatable transmit antenna 516 can be positioned downhole of a
motor 522 that causes rotation of one or more antennas relative to
the tool string 512. The third sensitive volume 529 can include a
portion 533 that extends beyond the second rotatable receive
antenna 520 and away from the rotatable transmit antenna 516. For
example, the third sensitive volume 529 can include a portion 533
that extends behind (e.g., depicted toward the left in FIG. 6) of
the second rotatable receive antenna 520.
[0055] A perpendicular tilt angle orientation can provide a first
sensitive volume 526 that is smaller than a second sensitive volume
528 provided by a parallel tilt angle orientation. The smaller size
of the first sensitive volume 526 can provide readings with a
higher resolution than readings provided by the second sensitive
volume 528. The larger size of the second sensitive volume 528 can
provide readings that correspond to regions of the formation 510
that are further away from the tool string 512 than readings
provided by the first sensitive volume 526. Combining the shallower
readings of the first sensitive volume 526 and the deeper readings
of the second sensitive volume 528 can provide a profile of a
characteristic of the formation 510 radially around the tool string
512. A profile of a characteristic of the formation 510 can improve
interpretation or identification of boundaries of differing layers
in the formation 510.
[0056] FIG. 7 is a cross-sectional side view of an example of a
rotatable sensor assembly 650 according to one aspect. The
rotatable sensor assembly 650 can rotate a sensor relative to a
tool string 612 such as the rotatable sensors described above with
respect to FIGS. 2-6. The rotatable sensor assembly 650 can include
a body 652, a shaft 654, and a housing 656.
[0057] The body 652 can be part of a tool string 612. The body 652
may include coupling features 658a, 658b for connection with other
portions 660a, 660b of the tool string 612. For example, coupling
features 658a, 658b can be threaded surfaces.
[0058] The shaft 654 can be positioned within the body 652. The
shaft 654 can be supported relative to the body 652 by bearing
assemblies 662a, 662b. Bearing assemblies 662a, 662b can allow
shaft 654 to rotate relative to the body 652. In some aspects, the
bearing assemblies 662a,662b can restrict passage of fluid. In one
example, the bearing assemblies 662a, 662b seal a chamber 664
around the shaft 654. In another example, the bearing assemblies
662a, 662b allow some passage of fluid for lubrication of
components within the chamber 664. In some aspects, the shaft 654
can include an internal passageway 666. The passageway 666 can
allow fluid to flow through the shaft 654 from one end of the
chamber 664 to the other. For example, the passageway 666 may
provide a path for drilling fluids to reach and provide power to a
mud motor in a drilling operation.
[0059] The shaft 654 can be coupled to a motor, such as a motor 222
described above with respect to FIG. 2. In one example, the shaft
654 can be connected to a mud motor via a continuous velocity joint
668. In another example, the shaft 654 may be the rotor of the
motor. The shaft 654 can rotate in response to operation of the
motor. The shaft 654 can communicate torsional motion of the motor
to other objects. In some aspects, the shaft 654 can be linked with
a coupling 670 to communicate torsional motion to an object located
in an axial direction from the shaft 654. In one example, the shaft
654 can be linked by the coupling 670 to cause rotation of the
shaft 654 of another rotatable sensor assembly 650 for synchronized
rotation of the rotatable sensor assemblies.
[0060] The housing 656 can be torsionally coupled with the shaft
654 such that rotation of the shaft 654 causes rotation of the
housing 656. For example, the shaft 654 can be torsionally coupled
with the housing 656 via one or more gears 670a, 670b. The housing
656 can include a gear surface 672 for engaging the gears 670a,
670b. In one example, a gear 670a affixed to the shaft 654 can
engage a planetary gear 670b. The planetary gear 670b can be
affixed to a planetary shaft 674 that is supported by the body 652.
Although only one planetary gear 670b and one planetary shaft 674
is depicted in FIG. 7, multiple planetary gears 670b and planetary
shafts 674 can be positioned radially about the shaft 654. The one
or more planetary gears 670b can engage the gear surface 672 on the
housing 656 and the gear 670a affixed to the shaft 654 to transfer
rotational motion between the shaft 654 and the housing 656.
[0061] In some aspects, bearings 676 can be positioned between the
housing 656 and the body 652. The bearings 676 can be radial
bearings, axial bearings, or some combination thereof. A
combination of axial and radial bearings can allow the housing 656
to continue to rotate relative to the body 652 in the presence of
external loads applied on the housing that might otherwise impede
rotation. In some aspects, springs 678 or other biasing alignment
devices can be positioned with the bearings 676 to maintain the
bearings 676 in position under applied external loads.
[0062] The housing 656 can include a formation sensor 680, a body
angular position sensor 682, a shaft angular position sensor 684, a
survey direction sensor 686, an electronics package 688, and a
communications device 690. Although the housing 656 is depicted in
FIG. 7 with all of these components, in some aspects, one or more
of these components can be omitted from the housing 656.
[0063] The formation sensor 680 can detect characteristics of a
formation 610. For example, the formation sensor 680 can be a
rotatable transmit antenna 216 or a rotatable receive antenna 218
as described above with respect to FIG. 2. In some aspects, the
formation sensor 680 is a transceiver that can be switched between
a transmitting mode and a receiving mode. In some aspects, the
formation sensor 680 can be a directional sensor other than an
antenna for detecting resistance in the formation. Non-limiting
examples of such an alternative formation sensor 680 include a
gamma ray sensor, an acoustic sensor, a nuclear magnetic resonance
sensor, and a density sensor. All such sensors can be used
additionally or alternatively for sensing characteristics of the
formation or the direction and distance to sensed man-made objects
within the formation, such as another well bore, well bore tubular
or a lost in hole drill string. Although the rotatable sensor
assembly 650 is depicted in FIG. 7 with a single formation sensor
680, other arrangements are possible. In some aspects, the
rotatable sensor assembly 650 can include multiple formation
sensors 680 or multiple distance and direction ranging sensors.
These multiple formation sensors 680 or distance and ranging
sensors may be of the same or different types from one another.
[0064] The body angular position sensor 682 can detect an angular
position of the formation sensor 680 relative to the body 652 of
the rotatable sensor assembly 650. For example, the body angular
position sensor 682 may optically detect markers 692 positioned
around the circumference of the body 652. The marker 692 detected
at a particular time can indicate the angular position of the
formation sensor 680 relative to the body 652 at the particular
time.
[0065] The shaft angular position sensor 684 can detect an angular
position of the formation sensor 680 relative to the shaft 654 of
the rotatable sensor assembly 650. For example, the shaft angular
position sensor 684 may detect a magnetic field of one or more
magnets 694 coupled with the shaft 654 or a planetary shaft 674
(shown on coupled with a planetary shaft 674 in FIG. 7). The
strength of the magnetic field detected at a particular time can
indicate the angular position of the formation sensor 680 relative
to the shaft 654 at the particular time.
[0066] The survey direction sensor 686 can detect an angular
position of the survey direction sensor 686 relative to an angular
reference distinct from the rotatable sensor assembly 650. For
example, an angular position may be detected based on gravity, true
north, or magnetic north, such as by one or more accelerometers,
gyroscopes, or magnetometers. The strength or direction of readings
detected by one or more of these components at a particular time
can indicate an angular position or orientation of the survey
direction sensor 686 relative to the angular reference.
[0067] Positioning the survey direction sensor 686 on the housing
656 with the formation sensor 680 can cause the angular position
detected by the survey direction sensor 686 to directly correspond
to the angular position of the formation sensor 680. For example,
the angular deflection of the formation sensor 680 from the angular
reference can be equal to the angular deflection detected by the
survey direction sensor 686 or offset by a known amount
corresponding to the manner in which the survey direction sensor
686 and the formation sensor 680 are aligned relative to one
another on the housing 656.
[0068] In some aspects, the survey direction sensor 686 can be
located in a location other than the housing 656, such as elsewhere
in the tool string 612. In at least such arrangements the body
angular position sensor 682 or the shaft angular position sensor
684 can determine the angular position of the formation sensor 680
relative to the survey direction sensor 686, much as the
orientation sensor 368 (described above with respect to FIG. 4) can
determine the angular position of the antenna 316 relative to the
survey direction sensor 325. This angular position of the formation
sensor 680 relative to the survey direction sensor 686 can be
combined with the angular position of the survey direction sensor
686 to determine the orientation of the formation sensor 680
relative to the angular reference, much as the orientation of the
antenna 316 relative to the angular reference can be determined
based on readings from the orientation sensor 368 and the survey
direction sensor 325 (described above with respect to FIG. 4).
[0069] The electronics package 688 can send or receive information
to the various data producing sensors described above (e.g., the
body angular position sensor 682, the shaft angular position sensor
684, the survey direction sensor 686, the formation sensor 680, or
some combination thereof). The electronics package 688 may also
provide a centralized time keeping function for synchronizing or
synthesizing the timing of readings from the data producing
sensors. In some aspects, one or more of the data producing sensors
are integrated into the electronics package 688.
[0070] The electronics package 688 may include one or more
components of an information handling system. As used herein, the
term "information handling system" refers to a system including one
or more processors coupled with a non-transitory memory device.
Non-limiting examples of the memory device include RAM and ROM. The
memory device can store machine-readable instructions executable by
the one or more processors. When executed by a processor, the
instructions can cause the processor to perform functions, which
can include various of the functions described herein. As an
illustrative example, an information handling system can be
configured to perform functions described with respect to the
electronics package 688 in the preceding paragraph and elsewhere
herein. Furthermore, the term "information handling system" is not
limited solely to the electronics package 688 described with
reference to FIG. 7. Further non-limiting examples of information
handling systems include microcontrollers, analog electronics,
computing systems located at the surface, and combinations
thereof.
[0071] The electronics package 688 can also send or receive
information via the communications device 690. In one example, the
communications device 690 can be a toroid for providing short hop
communications over a wireless network to other devices in the
bottom hole assembly, such as the bottom hole sensor assembly 214
or at any intermediate point in a drill string. Other examples of
communications device 690 include an inductive coupler or a slip
ring.
[0072] The electronics package 688, the data producing sensors, and
the communications device 690 (or any combination thereof) can be
powered by any suitable power source. In one example, the power
source can be batteries included in the electronics package 688 in
the housing 656. In another example, the power source can be
located remotely from the housing 656 (such as elsewhere in a
bottom hole assembly) and transferred to the housing 656 by a slip
ring for communicating power from the body 652 to the housing
656.
[0073] FIG. 8 is a cross-sectional side view of an example of a
bottom hole sensor assembly 714 with two motors 722, 736 according
to one aspect. The bottom hole sensor assembly 714 can include a
first motor 722, a second motor 736, a first rotatable sensor
assembly 716, a second rotatable sensor assembly 718, a third
rotatable sensor assembly 720, a rotatable near-bit sensor assembly
738, and a drill bit 746 positioned along a tool string 712. In
some aspects, the first rotatable sensor assembly 716, the second
rotatable sensor assembly 718, and the third rotatable sensor
assembly 720 can each be similar to the rotatable sensor assembly
650 described above with respect to FIG. 7.
[0074] The first rotatable sensor assembly 716 can be coupled with
the first motor 722. The first motor 722 can cause the first
rotatable sensor assembly 716 to rotate independently of the tool
string 712 or the second motor 736. In one example, the second
motor 736 can rotate the drill bit 746. The first motor 722 can
allow the first rotatable sensor assembly 716 to be rotated at a
rate independent from a rate of rotation of the drill bit 746.
Independent rotation may allow a sweep rate of the first rotatable
sensor assembly 716 to be optimized, such as based on a rate of
penetration of a well being drilled.
[0075] The second motor 736 can be coupled with the second
rotatable sensor assembly 718, the third rotatable sensor assembly
720, the rotatable near-bit sensor assembly 738, and the drill bit
746. Coupling multiple rotatable sensor assemblies 718, 720, 738
with a common motor 736 can allow the rotatable sensor assemblies
718, 720, 738 to rotate in synchronization. Synchronized rotation
can allow simplified configurations of the bottom hole sensor
assembly 714, such as configurations with reduced numbers of motors
or angular position sensors.
[0076] One or more of the rotatable sensor assemblies 716, 718,
720, or 738 can include multiple sensors 780a, 780b. The multiple
sensors 780a, 780b can be tilted relative to one another such that
a different measurement can be made with the first sensor 780a than
with the second sensor 780b. In one example, the multiple sensors
780a, 780b can be windings of an antenna arranged in planes of
winding that are tilted relative to each other. A characteristic of
a subterranean formation can be determined both at a first position
in the first winding plane and at a second position in the second
winding plane based on respective orientations of the receive
antenna and the transmit antenna. In some aspects, the multiple
sensors 780a, 780b can be arranged substantially perpendicular to
each other.
[0077] Multiple sensors 780a, 780b in a rotatable sensor assembly
716, 718, 720, or 738 can provide a greater number of data points
for calculating formation characteristics. For example, crossed
antennas can provide more channels, i.e., measurements from a
distinct transmitter and receiver combination. Crossed antennas can
also allow synthesizing measurements from dipole angles that do not
exist physically, such as by performing a weighted average of the
responses from each of the crossed antennas.
[0078] The rotatable near-bit sensor assembly 738 can be different
from the rotatable sensor assembly 650 described above with respect
to FIG. 7. For example, FIG. 9 is a cross-sectional side view of an
example of a rotatable near-bit sensor assembly 838 according to
one aspect. The rotatable near-bit sensor assembly 838 can include
a body 852, a shaft 854, and an electronics housing or insert 856.
In some aspects, the rotatable near-bit sensor assembly 838 can be
located near a downhole end of a tool string to provide a rotatable
sensor for looking ahead of the downhole end of a tool string or
ahead of a drill bit in a drill string.
[0079] The body 852 can be coupled with the shaft 854. The shaft
854 can be rotatable by a motor. The shaft 854 can include a
passageway 866 through which drilling fluid can flow. The body 852
can have a hollow interior defining a chamber 864. The body 852 can
include coupling features 858 for connection with other tools, such
as a drill bit, other sensors, or a steering tool. In one example,
the coupling features 858 can be threaded surfaces. Drilling fluid
flowing through the shaft 854 can flow through the chamber 864 and
through the coupling features 858. The body 852 can include a
formation sensor 880 and a communications device 890.
[0080] The insert 856 can be installed into the chamber 864. The
insert can include a central bore 896. The bore 896 can provide a
path for drilling fluid to flow from the shaft 854 through the
coupling features 858. The insert 856 can include a sealed volume
898. The sealed volume 898 can contain an electronics package 888.
Installation of the insert 856 into the chamber 864 can establish
electronic communication between the electronics package 888 and
the formation sensor 880. Installation of the insert 856 into the
chamber 864 can establish electronic communication between the
electronics package 888 and the communications device 890. In some
aspects, the electronics package 888 can include one or more
angular position sensors 886 for determining an angular position of
the formation sensor 880. The electronics package 888 can transmit
information from the formation sensor 880 via the communications
device 890.
[0081] FIG. 10 is a cross-sectional side view of an example of a
bottom hole sensor assembly 914 with sensor assemblies 916, 918,
920, 938 each having three formation sensors 980a, 980b, 980c
according to one aspect. Sensor assemblies 916, 918, 920, 938 can
include any number of crossed sensors 980a, 980b, 980c.
Configurations with three crossed sensors 980a, 980b, 980c (such as
depicted in FIG. 10) can provide more channels and data points than
configurations with fewer crossed sensors 780a, 780b (such as
depicted in FIG. 8). In some aspects, while a configuration of
three crossed sensors 980a, 980b, 980c in the absence of rotation
can provide sufficient data for precise measurements, rotating one
or more of the sensor assemblies 916, 918, 920, 938 can provide
additional data for reducing noise or otherwise improving the
quality of information obtained from the rotatable sensor
assemblies 916, 918, 920, 938.
[0082] In some aspects, fewer than all of the sensor assemblies
916, 918, 920, 938 are rotatable. For example, a motor 922 coupled
with the sensor assemblies 916, 938 can cause the sensor assemblies
916, 938 to rotate while sensor assemblies 918, 920 remain
stationary. Reducing the number of rotating sensors can reduce the
complexity of the bottom hole sensor assembly 914 by reducing a
number moving parts. In some aspects, the rotating sensor
assemblies 916, 938 transmit and the stationary sensor assemblies
918, 920 receive. In other aspects, the stationary sensor
assemblies 918, 920 transmit and the rotating sensor assemblies
916, 938 receive. The bottom hole sensor assembly 914 can include
any combination of stationary or rotating sensor assemblies for
transmitting and receiving. In some aspects, a rotatable sensor
assembly (such as sensor assemblies 916, 938 depicted in FIG. 10)
can be locked to the tool string 912 to stop or prevent rotation
and temporarily convert the rotatable sensor assembly to a
stationary sensor assembly.
[0083] FIG. 11 is a block diagram of a control system 1000 for a
bottom hole sensor assembly with rotatable sensors according to one
aspect. The bottom hole sensor assembly can include a system
control center 1002, transmitters 1004a-n, receivers 1006a-m, a
data acquisition unit 1008, a data buffer 1010, a data processing
unit 1012, and a communication unit 1014, a time synchronizer 1020,
and a motor controller 1022.
[0084] The system control center 1002 can form all or part of an
information handling system, which may include or interface with
other information handling systems described herein. For example,
the system control center 1002 can include one or more processors
or analog electronics. The system control center 1002 can manage
the operation of other components in the control system 1000. A
signal within a frequency in range 1 Hz to 10 MHz can be generated
by the system control center 1002 and fed to a number of
transmitters 1004a-n (any number "n" of transmitters 1004a-n can be
included). In one example, the transmitters 1004a-n can include
transmit antennas that can emit electromagnetic waves into the
wellbore formation in response to currents passed through the
antennas. In some aspects, any of the transmitters 1004a-n can
include multiple transmit antennas connected to a single
transmitter via a demultiplexer that is controlled via the system
control center 1002. This may reduce the total number of
transmitters 1004a-n, the size of electronics, and complexity of
the control system 1000.
[0085] Receivers 1006a-m (any number "m" of receivers 1006a-m can
be included) can receive an electromagnetic wave signal from the
wellbore formation. In one example, the receivers 1006a-m include
antennas. The received signal can be directed to the system control
center 1002. Analogous to the transmitters 1004a-n with multiple
transmit antennas, multiple receive antennas can be connected to
the same receiver 1006a-m via a demultiplexer for efficiency.
Multiple frequencies may be transmitted and received at the same
time to increase functionality within a limited window of time. In
one example, square or other time waveforms can excite multiple
frequencies simultaneously at the transmitters 1004a-n. The
frequencies can be separated by filters at the receiving end in the
data acquisition unit 1008. Signals from each transmitter 1004a-n
can be received at all receivers 1006a-m and recorded. The time
synchronizer 1020 can include a clock or other device that can
provide a consistent time reference for tracking when the various
signals are emitted and received. The data buffer 1010 can store
received signals for processing. The data processing unit 1012 can
perform processing or inversion on the data to convert the signal
information into data about characteristics of the wellbore
formation. The inversion may be performed downhole, or in a
computer at the surface 1016 after the data is transferred to the
surface 1016. The communication unit 1014 can communicate the data
or results to the surface 1016, such as to a control system located
at the surface 1016. In one example, the data or results can be
utilized to direct the direction of a drill string in a drilling
operation, such as by providing information to a drill string
operator via a visualization device at the surface or by providing
information to an automated drill string guidance system. The
communication unit 1014 can additionally or alternatively
communicate the data or results to other tools downhole, e.g., to
improve various aspects of locating and extracting hydrocarbons.
The communication unit 1014 can include appropriate components or
combinations thereof for communicating by any suitable form of
telemetry, including but not limited to, any combination of
electronic pulses, analog signals, amplitude modulated patterns,
frequency modulated patterns, or electromagnetic waves, any of
which may conveyed by any combination of wired, wireless, or
mud-pulse transmissions.
[0086] The motor controller 1022 can control one or more motors
used for rotating any of the transmitters 1004a-n or receivers
1006a-m. The motor controller 1022 can form all or part of an
information handling system, which may include or interface with
other information handling systems described herein. The motor
controller 1022 can adjust the rate of rotation of the transmitters
1004a-n or receivers 1006a-m by controlling the rate of rotation of
the associated motor(s). In some aspects, the motor controller 1022
can stop the rotation at a particular point to orient one or more
of the transmitters 1004a-n or receivers 1006a-m in a particular
direction for measuring a particular region of interest in the
wellbore formation.
[0087] In some aspects, one or more of the transmitters 1004a-n or
the receivers 1006a-m can correspond to a rotatable sensor assembly
1028. For example, a rotatable sensor assembly 1028 can be the
rotatable sensor assembly 650 as described with respect to FIG. 7
above. FIG. 12 is a block diagram of a control system 1100 for a
rotatable sensor assembly 1028 according to one aspect. The control
system 1100 can form all or part of an information handling system,
which may include or interface with other information handling
systems described herein. The control system 1100 can include a
controller 1102, memory 1104, a survey direction sensor 1106, a
formation sensor 1108, a power source 1110, a shaft position sensor
1112, a communications device 1114, a housing position sensor 1116,
a time synchronizer 1118, and a rate controller 1120. Although the
control system 1100 for a rotatable sensor assembly 1028 is
depicted in FIG. 12 with all of these listed components, in some
aspects, one or more of these components can be omitted or
incorporated directly as part of the control system 1000 depicted
in FIG. 11.
[0088] The controller 1102 can form all or part of an information
handling system, which may include or interface with other
information handling systems described herein. For example, the
controller 1102 can include a processor. The memory 1104 can store
machine-readable instructions accessible by the controller 1102.
The memory 1104 can store data retrievable after a well operation
is completed. Storing data in memory 1104 can reduce an amount of
data that is communicated to the surface during operation. The
formation sensor 1108 can receive signals from the wellbore
formation and provide related data to the controller 1102. For
example, the formation sensor 1108 can be the formation sensor 680
described above with respect to FIG. 7.
[0089] The power source 1110 can provide electric power for the
various electronics of the control system 1100. The power source
1110 can be any suitable power source, including batteries, a slip
ring or other connection to a wire or other conduit to another
power source at the surface or in the tool string, or a generator
driven by drilling fluids or the differential rotation between the
bottom hole assembly and the sensor housing (such as an
alternator).
[0090] In some aspects, the memory 1104 can also store data to be
organized and analyzed. For example, as formation sensors 680
rotate, the orientation of the azimuthal measurement can be binned
in the memory 1104 and divided up into directional bins versus time
or depth (or both). The hole depth may be known at the time of the
azimuthal measurement or later added based on depth versus time
data, which may be measured at the surface. The binned data can be
used to correlate the measurement versus a depth and orientation.
In this manner, an angular profile of the formation characteristics
around the circumference of a tool string or bore hole can be
measured while the azimuthal formation sensor 680 rotates.
[0091] The survey direction sensor 1106 can provide information
about the orientation of the formation sensor 1108 to the
controller 1102. The shaft position sensor 1112 can provide
information to the controller 1102 about the position of the
formation sensor 1108 relative to a rotating shaft (such as shaft
654 described above with respect to FIG. 7) that causes the
formation sensor 1108 to rotate. The housing position sensor 1116
can provide information to the controller 1102 about the angular
position relative to a tool string of a housing (such as housing
656 described above with respect to FIG. 7) supporting the
formation sensor 1108. In some aspects, the survey direction sensor
1106 may provide direct information about the orientation of the
formation sensor 1108, similar to the manner described above with
respect to FIGS. 2-3, in which the angular position sensors 224 or
225 can be positioned for rotating respectively with the rotatable
transmit antenna 216 or the rotatable receive antenna 218 to
indicate an angular position thereof. In some aspects, the survey
direction sensor 1106 may provide indirect information about the
orientation of the formation sensor 1108 that can be supplemented
by information from the shaft position sensor 1112 or the housing
position sensor 1116, similar to the manner described above with
respect to FIG. 5, in which data from the survey direction sensor
325 can be combined with data from the orientation sensor 368 to
determine an angular position of the antenna 316.
[0092] The time synchronizer 1118 can include a clock or other time
reference device. The time synchronizer can provide a common time
scale for the controller 1102 for synthesizing the various
measurements received from the various components. The controller
1102 can control a rate of rotation of the formation sensor 1108
via the rate controller 1120. For example, the rate controller 1120
can control the rotation rate of a motor rotating the formation
sensor 1108. The rate controller 1120 can form all or part of an
information handling system, which may include or interface with
other information handling systems described herein.
[0093] The communications device 1114 can communicate information
to or from the controller 1102. For example, the communications
device 1114 can communicate information from the controller to the
surface or to another tool in the tool string. One example of the
communications device 1114 is a toroid for short hop
communications, as discussed above with respect to FIG. 7. The
toroid can wrap circumferentially around a carrier of the toroid.
In some aspects, the communications device 1114 can communicate
synthesized information or raw data about the formation sensor 1108
to the system control center 1002 (described above with respect to
FIG. 11) as information about one or more of any of the
transmitters 1004a-n or receivers 1006a-m.
[0094] FIG. 13 is a flow chart illustrating an example method 1200
for measuring anisotropic characteristics of a subterranean
formation according to one aspect. The method can utilize a bottom
hole sensor assembly as described herein, such as the bottom hole
sensor assembly 214 described above with respect to FIGS. 2-3 or
variations thereof, such as described with respect to other figures
herein.
[0095] In block 1210, a first signal is transmitted via a transmit
antenna. For example, the rotatable transmit antenna 216 can
transmit the signal into the formation 210. In block 1220, a second
signal associated with the first signal is received via a receive
antenna. The first signal can be transmitted or the second signal
can received as the transmit antenna or the receive antenna is
rotating relative to the tool string. For example, the rotatable
receive antenna 218 can receive a signal from the sensitive volume
226 of the formation 210 that corresponds to a response of the
formation 210 to the first signal transmitted by the rotatable
transmit antenna 216. The rotatable transmit antenna 216 or the
rotatable receive antenna 218 may be rotating as the signals are
transmitted or received.
[0096] In block 1230, an angular position of the transmit antenna
or the receive antenna is detected as the transmit antenna or the
receive antenna rotates relative to the tool string. For example,
the angular position sensor 224 or 225 can detect the angular
position in block 1230.
[0097] In block 1240, the second signal and the angular position
can be used to determine a characteristic of the subterranean
formation at a position relative to the bottom hole assembly. For
example, the second signal can indicate a resistivity of the
formation 210 in the sensitive volume 226 and the angular position
can indicate the location of the sensitive volume 226 relative to
the tool string 212.
[0098] In some aspects, signals from multiple transmitter and
receiver pairs can be used in combination in determining the
characteristic of the subterranean formation. Determination may be
carried out by performing simulations with a formation
characteristic value to produce modeled signals, computing a
difference between the modeled signals and signals from the
transmitter and receivers, and adjusting the formation
characteristic value until a least difference is achieved. The
formation characteristic value corresponding to the least
difference may be accepted as final interpretation of the formation
characteristic measured by the signals of the transmitter and
receiver pairs.
[0099] In some aspects, a bottom hole assembly can be provided
including a tool string and an azimuthal sensor rotatively coupled
with the tool string such that the azimuthal sensor is rotatable
relative to the tool string. In some aspects, a method can include
rotating an azimuthal sensor relative to a tool string.
[0100] In some aspects, a bottom hole assembly, downhole system, a
tool, or a method is provided according to one or more of the
following examples. In some aspects, a tool, an assembly, or a
system described in one or more of these examples can be utilized
to perform a method described in one of the other examples.
Example #1
[0101] Provided can be a downhole assembly, comprising a tool
string; a directionally-dependent transmitter coupled with the tool
string; and a directionally-dependent receiver coupled with the
tool string, wherein at least one of the directionally dependent
receiver and the directionally dependent transmitter is rotatable
relative to the tool string.
Example #2
[0102] Provided can be the downhole assembly of Example #1, further
comprising at least one angular position sensor arranged with a
known rotational relationship with the at least one of the
transmitter or the receiver rotatable relative to the tool string.
The receiver may receive signals having signal information. The at
least one angular position sensor may detect an angular position of
at least one of the transmitter or the receiver. The signal
information and the angular position may be indicative of a
characteristic of a subterranean formation at a position relative
to the tool string.
Example #3
[0103] Provided can be the downhole assembly of any of Examples
#1-2, further comprising a communication unit communicatively
coupled with the receiver and the at least one angular position
sensor. The communication device may be communicatively coupled
with the receiver for transmitting the signal information. The
communication device may be communicatively coupled with the at
least one angular position sensor for transmitting the angular
position.
Example #4
[0104] Provided can be the downhole assembly of any of Examples
#1-2, further comprising a motor coupled with at least one of the
transmitter or the receiver, wherein the transmitter or the
receiver is rotatable relative to the tool string in response to
the motor rotating.
Example #5
[0105] Provided can be the downhole assembly of any of Examples
#1-4, further comprising a second motor and a drill bit rotatable
in response to the second motor rotating, wherein the motor coupled
with the transmitter or the receiver is rotatable independently of
the second motor.
Example #6
[0106] Provided can be the downhole assembly of any of Examples
#1-4, wherein the transmitter or the receiver is positioned uphole
of the motor.
Example #7
[0107] Provided can be the downhole assembly of any of Examples
#1-4, wherein the transmitter or the receiver is positioned
downhole of the motor.
Example #8
[0108] Provided can be the downhole assembly of any of Examples
#1-2, further comprising a motor and a drill bit rotatable in
response to the motor rotating, wherein the transmitter or the
receiver is positioned at the drill bit or adjacent to the drill
bit.
Example #9
[0109] Provided can be the downhole assembly of any of Examples
#1-2, wherein the transmitter or the receiver is rotatable relative
to the tool string in a direction opposite to a direction of
rotation of the tool string.
Example #10
[0110] Provided can be the downhole assembly of any of Examples
#1-2, wherein the transmitter is rotatable relative to the tool
string and the receiver is rotatable relative to the tool
string.
Example #11
[0111] Provided can be the downhole assembly of any of Examples
#1-10, further comprising a motor coupled with the transmitter and
the receiver, wherein the transmitter and the receiver are
rotatable together relative to the tool string in response to the
motor rotating.
Example #12
[0112] Provided can be the downhole assembly of of any of Examples
#1-10, wherein the at least one angular position sensor includes a
first angular position sensor and a second angular position sensor,
the downhole assembly further comprising a first motor coupled with
the transmitter, wherein the transmitter is rotatable relative to
the tool string in response to the first motor rotating and the
first angular position sensor is arranged with a first known
rotational relationship with the transmitter; and a second motor
coupled with the receiver, wherein the receiver is rotatable
relative to the tool string in response to the second motor
rotating and the second angular position sensor is arranged with a
second known rotational relationship with the receiver. The first
angular position sensor may detect an angular position of the
transmitter relative to the tool string. The second angular
position sensor can detect an angular position of the receiver
relative to the tool string.
Example #13
[0113] Provided can be a system comprising a tool string; a
transmitter rotatable relative to the tool string; a first angular
position sensor arranged with a first known rotational relationship
with the transmitter; a receiver rotatable relative to tool string;
a second angular position sensor arranged with a second known
rotational relationship with the receiver; and an information
handling system communicatively coupled with at least the receiver,
the information handling system comprising a processor and a memory
device coupled with the processor, the memory device containing a
set of instructions that, when executed by the processor, cause the
processor to determine a characteristic of a subterranean formation
relative to the tool string based, at least in part, on outputs
received from the receiver, the first angular position sensor, and
the second angular position sensor. The first angular position
sensor may detect an angular position of the transmitter. The
second angular position sensor may detect an angular position of
the receiver. Said outputs may include a signal received by the
receiver, the angular position of the transmitter, and the angular
position of the receiver.
Example #14
[0114] Provided can be the system of Example #13, further
comprising a motor torsionally coupled with at least one of the
transmitter or the receiver for rotating the torsionally coupled
antenna or antennas; and a motor controller communicatively coupled
with the motor and the information handling system, wherein the set
of instructions contained in the memory device of the information
handling system further comprise instructions that, when executed
by the processor, cause the processor to instruct the motor
controller to control a speed of the torsionally coupled antenna or
antennas by controlling a speed of the motor.
Example #15
[0115] Provided can be the system of Example #13, wherein the
receiver comprises a receive antenna oriented substantially
parallel to a transmit antenna of the transmitter and at least one
of the transmit antenna or the receive antenna is tilted with
respect to a longitudinal axis of the tool string, wherein the set
of instructions contained in the memory device of the information
handling system further comprise instructions that, when executed
by the processor, cause the processor to determine the
characteristic of the subterranean formation at a position ahead of
an end of the tool string based, at least in part, on the parallel
orientation of the receive antenna and the transmit antenna.
Example #16
[0116] Provided can be the system of Example #13, wherein the
receiver comprises a receive antenna oriented substantially
perpendicular to a transmit antenna of the transmitter, wherein the
set of instructions contained in the memory device of the
information handling system further comprise instructions that,
when executed by the processor, cause the processor to determine
the characteristic of the subterranean formation at a position
lateral to the tool string in a direction lateral to a direction of
travel of an end of the tool string based, at least in part, on the
perpendicular orientation of the receive antenna and the transmit
antenna.
Example #17
[0117] Provided can be the system of Example #13, wherein at least
one of the transmitter or the receiver includes an antenna having a
first winding arranged in a first winding plane and a second
winding arranged in a second winding plane, the first winding being
tilted relative to the second winding, wherein the set of
instructions contained in the memory device of the information
handling system further comprise instructions that, when executed
by the processor, cause the processor to determine the
characteristic of the subterranean formation at a first position in
the first winding plane and at a second position in the second
winding plane based, at least in part, on respective orientations
of the receiver and the transmitter.
Example #18
[0118] Provided can be a method comprising transmitting a first
signal via a transmitter coupled with a tool string in a
subterranean formation; receiving a second signal associated with
the first signal via a receiver coupled with the tool string,
wherein the transmitter or the receiver is rotating relative to the
tool string; detecting an angular position of the transmitter or
the receiver as the transmitter or the receiver rotates relative to
the tool string; and determining a characteristic of the
subterranean formation at a position relative to tool string based,
at least in part, on the second signal and the angular
position.
Example #19
[0119] Provided can be the method of Example #18, wherein using the
second signal and the angular position to determine a
characteristic of the subterranean formation at a position relative
to the tool string includes determining a resistivity of a region
of the formation at a distance from the tool string and in a
direction from the tool string.
Example #20
[0120] Provided can be the method of any of Examples #18-19,
further comprising receiving a third signal associated with the
first signal via a second receiver coupled with the tool string at
a position between the first receiver and the transmitter, wherein
the transmitter or the second receiver is rotating relative to the
tool string; if the second receiver is rotating relative to the
tool string, detecting a second angular position of the receiver as
the second receiver rotates relative to the tool string; using a
first combination or a second combination to determine the
characteristic of the formation at a second position relative to
the tool string, the first combination including the third signal
and the first angular position, the second combination including
the third signal and the second angular position; and creating a
profile of the characteristic of the formation based, at least in
part, on the determination of the characteristic of the formation
at the first position and the determination of the characteristic
of the formation at the second position.
[0121] The foregoing description of the aspects, including
illustrated examples, of the disclosure has been presented only for
the purpose of illustration and description and is not intended to
be exhaustive or to limit the disclosure to the precise forms
disclosed. Numerous modifications, adaptations, and uses thereof
will be apparent to those skilled in the art without departing from
the scope of this disclosure.
* * * * *