U.S. patent application number 14/763519 was filed with the patent office on 2016-01-07 for automatic wellbore survey evaluation.
The applicant listed for this patent is SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Darren Lee Aklestad, Clinton D. Chapman, Randolph R Hansen, Ross Lowdon, Jan Morley, Wayne J. Phillips, Richard V.C. Wong, Han Yu.
Application Number | 20160003028 14/763519 |
Document ID | / |
Family ID | 51625465 |
Filed Date | 2016-01-07 |
United States Patent
Application |
20160003028 |
Kind Code |
A1 |
Aklestad; Darren Lee ; et
al. |
January 7, 2016 |
Automatic Wellbore Survey Evaluation
Abstract
A method for automatically evaluating a survey of a subterranean
wellbore includes receiving downhole navigation sensor measurements
and automatically evaluating surface sensor data obtained at
substantially the same time as the navigation sensor measurements
to determine whether or not the navigation sensor measurements were
obtained during satisfactory wellbore survey conditions. The
navigation sensor measurements are evaluated to determine whether
or not they meet certain predetermined conditions necessary for
obtaining a satisfactory survey. A survey recommendation is
automatically generating based on the automatic evaluations
performed.
Inventors: |
Aklestad; Darren Lee; (Katy,
TX) ; Chapman; Clinton D.; (Missouri City, TX)
; Wong; Richard V.C.; (Houston, TX) ; Yu; Han;
(Sugar Land, TX) ; Phillips; Wayne J.; (Houston,
TX) ; Morley; Jan; (Houston, TX) ; Hansen;
Randolph R; (Sugar Land, TX) ; Lowdon; Ross;
(Katy, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHLUMBERGER TECHNOLOGY CORPORATION |
Sugar Land |
TX |
US |
|
|
Family ID: |
51625465 |
Appl. No.: |
14/763519 |
Filed: |
March 24, 2014 |
PCT Filed: |
March 24, 2014 |
PCT NO: |
PCT/US2014/031546 |
371 Date: |
July 26, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61806356 |
Mar 28, 2013 |
|
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|
Current U.S.
Class: |
702/6 |
Current CPC
Class: |
E21B 44/00 20130101;
E21B 47/022 20130101; E21B 47/024 20130101 |
International
Class: |
E21B 47/024 20060101
E21B047/024; E21B 47/022 20060101 E21B047/022 |
Claims
1. A method for surveying a subterranean wellbore, the method
comprising: (a) deploying a drill string in the subterranean
wellbore, the drill string including one or more navigation sensor
sets; (b) performing survey preparation operations to promote
satisfactory wellbore survey conditions based upon a position of
the drill string within the wellbore and specific requirements of
the navigation sensor sets for taking and communicating a survey;
(c) causing the downhole navigation sensor sets to obtain
navigation sensor measurements; (d) automatically evaluating
surface sensor measurements obtained at substantially the same time
as the navigation sensor measurements to determine whether or not
the navigation sensor measurements were obtained during
satisfactory wellbore survey conditions; (e) automatically
evaluating the navigation sensor measurements to determine whether
or not the navigation sensor measurements meet certain
predetermined conditions necessary for obtaining a satisfactory
survey; and (f) automatically generating a survey recommendation
based on said automatic evaluations performed in (d) and (e).
2. The method of claim 1, wherein the survey preparation operations
comprise (i) lifting the drill string such that the drill bit is
off bottom and (ii) holding the drill string rotationally
stationary with respect to the subterranean wellbore.
3. The method of claim 1, wherein the navigation sensor
measurements comprise accelerometer measurements and magnetometer
measurements.
4. The method of claim 1, wherein the surface sensor measurements
comprise at least one of hook load sensor measurements, traveling
block position and velocity measurements, surface torque and
rotation rate measurements of the drill string, and bit and hole
depth measurements.
5. The method of claim 4, wherein the surface sensor measurements
verify satisfactory wellbore survey conditions when (i) at least
one of the hook load sensor measurements and the bit and hole depth
measurements indicate that the drill bit is off-bottom, (ii) the
traveling block position and velocity measurements indicate that a
velocity of the traveling block is about equal to zero, and (iii)
the drill string torque and rotation rate measurements indicate
that a rotation rate of the drill string is about equal to
zero.
6. The method of claim 4, wherein the surface sensor measurements
verify satisfactory wellbore survey conditions when the bit and
hole depth measurements indicate that a distance between the
navigation sensors and magnetically hot casing components is
greater than a predetermined threshold.
7. The method of claim 1, wherein said automatic evaluation in (e)
comprises at least one of the following: (i) processing the
navigation sensor measurements to compute a total acceleration and
comparing the total acceleration with a reference value of earth's
gravitational field, (ii) processing the navigation sensor
measurements to compute a total magnetic field and comparing the
total magnetic field with a reference value of the earth's magnetic
field, (iii) processing the navigation sensor measurements to
compute a magnetic dip angle and comparing the magnetic dip angle
with a reference value of earth's magnetic dip angle, (iv)
co-processing the total acceleration, the reference value of the
earth's gravitational field, the total magnetic field, the
reference value of the earth's magnetic field, the magnetic dip
angle, and the reference value of the earth's magnetic dip angle to
obtain a survey confidence value.
8. The method of claim 7, wherein the automatic evaluation in (e)
verifies that the predetermined conditions were met for obtaining a
satisfactory survey when (i) the total acceleration is
substantially equal to the reference value of earth's gravitational
field, (ii) the total magnetic field is substantially equal to the
reference value of the earth's magnetic field, and (iii) the
magnetic dip angle is substantially equal to the reference value of
earth's magnetic dip angle.
9. The method of claim 1, wherein the survey recommendation
comprises an automatic survey acceptance when the automatic
evaluation in (d) verifies that the navigation sensor measurements
were obtained during satisfactory wellbore survey conditions and
the automatic evaluation in (e) verifies that the navigation sensor
measurements meet the predetermined conditions necessary for
obtaining a satisfactory survey.
10. The method of claim 1, further comprising: (g) automatically
employing measurement correction processes to improve quality of
the navigation sensor measurements.
11. A method for automatically evaluating a survey of a
subterranean wellbore, the method comprising: (a) receiving
downhole navigation sensor measurements; (b) receiving surface
sensor measurements made at substantially the same time as the
navigation sensor measurements; (c) automatically evaluating the
surface sensor measurements to determine whether or not the
navigation sensor measurements were obtained during satisfactory
wellbore survey conditions; (d) automatically evaluating the
navigation sensor measurements to determine whether or not the
navigation sensor measurements meet certain predetermined
conditions necessary for obtaining a satisfactory survey; and (e)
automatically generating a survey recommendation based on said
automatic evaluations performed in (c) and (d).
12. The method of claim 11, wherein the navigation sensor
measurements comprise tri-axial accelerometer measurements and
tri-axial magnetometer measurements.
13. The method of claim 11, wherein the surface sensor measurements
comprise at least one of the following: hook load sensor
measurements, traveling block position and velocity measurements,
surface torque and rotation rate measurements of the drill string,
and bit and hole depth measurements.
14. The method of claim 13, wherein the surface sensor measurements
verify satisfactory wellbore survey conditions when (i) at least
one of the hook load sensor measurements and the bit and hole depth
measurements indicate that the drill bit is off-bottom, (ii) the
traveling block position and velocity measurements indicate that a
velocity of the traveling block is about equal to zero, and (iii)
the drill string torque and rotation rate measurements indicate
that a rotation rate of the drill string is about equal to
zero.
15. The method of claim 13, wherein the surface sensor measurements
verify satisfactory wellbore survey conditions when the bit and
hole depth measurements indicate that a distance between the
navigation sensors and magnetically hot casing components is
greater than a predetermined threshold.
16. The method of claim 11, wherein said automatic evaluation in
(c) comprises at least one of the following: (i) processing the
navigation sensor measurements to compute a total acceleration and
comparing the total acceleration with a reference value of earth's
gravitational field, (ii) processing the navigation sensor
measurements to compute a total magnetic field and comparing the
total magnetic field with a reference value of the earth's magnetic
field, and (iii) processing the navigation sensor measurements to
compute a magnetic dip angle and comparing the magnetic dip angle
with a reference value of earth's magnetic dip angle.
17. The method of claim 16, wherein the automatic evaluation in (c)
verifies that the predetermined conditions were met for obtaining a
satisfactory survey when (i) the total acceleration is
substantially equal to the reference value of earth's gravitational
field, (ii) the total magnetic field is substantially equal to the
reference value of the earth's magnetic field, and (iii) the
magnetic dip angle is substantially equal to the reference value of
earth's magnetic dip angle.
18. The method of claim 11, wherein the survey recommendation
comprises an automatic survey acceptance when the automatic
evaluation in (b) verifies that the navigation sensor measurements
were obtained during satisfactory wellbore survey conditions and
the automatic evaluation in (c) verifies that the navigation sensor
measurements meet the predetermined conditions necessary for
obtaining a satisfactory survey.
19. The method of claim 1, further comprising: (e) automatically
employing measurement correction processes to improve quality of
the navigation sensor measurements.
20. A system for automatically evaluating a wellbore survey, the
system comprising: a plurality of surface sensors deployed on a
drilling rig; a computer processor in electronic communication with
the surface sensors, the processor configured to automatically (a)
receiving downhole navigation sensor measurements, (b) receive
sensor measurements from the surface sensors; (c) evaluate the
surface sensor measurements to determine whether or not the
navigation sensor measurements were obtained during satisfactory
wellbore survey conditions; (d) evaluate the navigation sensor
measurements to determine whether or not they meet certain
predetermined conditions necessary for obtaining a satisfactory
survey, and (e) generate a survey recommendation based on said
automatic evaluations performed in (c) and (d).
Description
FIELD OF THE INVENTION
[0001] Disclosed embodiments relate generally to systems and
methods for surveying a subterranean wellbore and particularly to a
method for automatically accepting and evaluating a wellbore
survey.
BACKGROUND INFORMATION
[0002] Wellbore surveying measurements are commonly obtained at
some interval while drilling. For example, static surveying
measurements may be obtained at 30 to 120 foot intervals when a new
pipe stand is added to the drill string. The location at which a
static survey is obtained is commonly referred to as a survey
station. Dynamic surveying measurements may also be obtained at a
much higher frequency while drilling (e.g., at 10 second
intervals). Such static and dynamic surveying measurements commonly
include borehole inclination and borehole azimuth measurements that
describe the current direction of drilling. Borehole inclination is
an angular measurement that describes the deviation of the borehole
from vertical while borehole azimuth is an angular measurement that
describes the deviation of the borehole from a reference direction
(e.g., magnetic or true north) in the horizontal plane.
[0003] The process of acquiring acceptably accurate surveys
generally involves meeting several criteria while making the
measurements. For example, specific operations may be completed to
ensure that satisfactory conditions exist to minimize potential
errors. Moreover, the acquired survey measurements are often
analyzed to ensure data quality compliance. In present drilling
operations, such activities are conducted manually by various rig
personnel. Manual operations can be time consuming and inefficient
as well as prone to human errors. Therefore, there is room in the
art for improved borehole surveying methods.
SUMMARY
[0004] A method for automatically evaluating survey of a
subterranean wellbore is disclosed. The method includes receiving
downhole navigation sensor measurements and automatically
evaluating surface sensor data obtained at substantially the same
time as the navigation sensor measurements to determine whether or
not the navigation sensor measurements were obtained during
satisfactory wellbore survey conditions. The navigation sensor
measurements may also be evaluated to determine whether or not they
meet certain predetermined conditions necessary for obtaining a
satisfactory survey. A survey recommendation is automatically
generated based on the automatic evaluations performed.
[0005] The disclosed embodiments may provide various technical
advantages. For example, the disclosed embodiments provide
automated acceptance of wellbore surveys. Such automation enables a
survey to be quickly and reliably accepted or rejected based on
various predetermined acceptance (or rejection) criteria thereby
potentially improving survey quality and saving rig time. The
disclosed embodiments may provide a high confidence level in that
they automatically evaluate both the state of the drill string
(i.e., whether or not it is in a predictable state suitable for
acquiring a survey) and the quality of the navigation sensor
data.
[0006] This summary is provided to introduce a selection of
concepts that are further described below in the detailed
description. This summary is not intended to identify key or
essential features of the claimed subject matter, nor is it
intended to be used as an aid in limiting the scope of the claimed
subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a more complete understanding of the disclosed subject
matter, and advantages thereof, reference is now made to the
following descriptions taken in conjunction with the accompanying
drawings, in which:
[0008] FIG. 1 depicts an example drilling rig on which disclosed
embodiments may be utilized.
[0009] FIG. 2 depicts a lower BHA portion of the drill string shown
on FIG. 1.
[0010] FIG. 3 depicts one disclosed embodiment of a system for
automatic wellbore survey acceptance.
[0011] FIG. 4 depicts a flow chart of one disclosed method
embodiment for obtaining wellbore survey.
DETAILED DESCRIPTION
[0012] FIG. 1 depicts a drilling rig 10 suitable for using various
method and system embodiments disclosed herein. A semisubmersible
drilling platform 12 is positioned over an oil or gas formation
(not shown) disposed below the sea floor 16. A subsea conduit 18
extends from deck 20 of platform 12 to a wellhead installation 22.
The platform may include a derrick and a hoisting apparatus (also
referred to as a block or a traveling block) for raising and
lowering a drill string 30, which, as shown, extends into borehole
40 and includes a bottom hole assembly (BHA) 50.
[0013] In the depicted embodiment, BHA 50 includes a drill bit 32
and one or more downhole navigation sensors 70. The navigation
sensors 70 may be deployed substantially anywhere in the BHA 50,
for example, in a measurement while drilling (MWD) tool, a logging
while drilling (LWD) tool, a steering tool, a near-bit sensor sub,
and the like. The drill string may further include multiple
navigation sensors deployed, for example, in a steering tool
located near the bit 32 and an MWD tool located well above the bit.
A navigation sensor set commonly includes a set of tri-axial (three
axis) accelerometers and a set of tri-axial magnetometers as
described in more detail below with respect to FIG. 2. However, the
disclosed embodiments are not limited in this regard as a
navigation sensor set may include alternative accelerometer and/or
magnetometer arrangements and may additionally and/or alternatively
include gyroscopic sensors. The BHA 50 may further include
substantially any other suitable downhole tools such as a downhole
drilling motor, a downhole telemetry system, a reaming tool, and
the like. The disclosed embodiments are not limited in regards to
such other tools.
[0014] While not depicted the drilling rig may include a rotary
table or a top drive for rotating the drill string 30 (or other
components) in the borehole. The rig may further include a swivel
that enables the string to rotate while maintaining a fluid tight
seal between the interior and exterior of the pipe. During drilling
operations mud pumps draw drilling fluid ("mud") from a tank or pit
and pump the mud through the interior of the drill string 30 to the
drill bit 32 where it lubricates and cools the bit and carries
cuttings to the surface. Such equipment is well known to those of
ordinary skill in the art and need not be discussed in further
detail herein.
[0015] The drilling rig may also include various surface sensors
(not illustrated on FIG. 1) for measuring and/or monitoring rig
activities. These sensors may include, for example, (i) a hook load
sensor for measuring the weight (i.e., the load) of the string on
the hoisting apparatus, (ii) a block position sensor for measuring
the vertical position and/or velocity of the travelling block (or
the top of the pipe stand) in the rig as various components are
raised and lowered in the borehole, (iii) a drilling fluid pressure
sensor for measuring the pressure of drilling fluid pumped
downhole, (iv) a drilling fluid flow-in sensor for measuring the
flow rate of drilling fluid into the drill string, and (iv) a
surface torque sensor for measuring the torque applied by the top
drive or rotary table. Such surface sensors are also well known in
the industry and need not be discussed in detail.
[0016] It will be understood by those of ordinary skill in the art
that the deployment illustrated on FIG. 1 is merely an example.
While FIG. 1 depicts a drill bit 32, the disclosed embodiments are
not limited in this regard, as surveys may also be acquired on open
end drill pipe (e.g., during reaming or other non-drilling
operations). It will be further understood that disclosed
embodiments are not limited to use with a semisubmersible platform
12 as illustrated on FIG. 1. The disclosed embodiments are equally
well suited for use with any kind of subterranean drilling
operation, either offshore or onshore.
[0017] FIG. 2 depicts the lower BHA portion of drill string 30
including drill bit 32 and navigation sensors 70. As described
above with respect to FIG. 1, the navigation sensors 70 may include
tri-axial accelerometer and magnetometer sensor sets. Suitable
accelerometers and magnetometers may be chosen from among
substantially any suitable commercially available devices known in
the art. FIG. 2 further includes a diagrammatic representation of
the tri-axial accelerometer and tri-axial magnetometer sensor sets.
By tri-axial it is meant that each sensor set includes three
mutually perpendicular sensors, the accelerometers being designated
as A.sub.x, A.sub.y, and A.sub.z and the magnetometers being
designated as B.sub.x, B.sub.y, and B.sub.z. By convention, a right
handed system is commonly designated in which the z-axis
accelerometer and z-axis magnetometer (A.sub.z and B.sub.z) are
oriented approximately parallel with the borehole as indicated
(although disclosed embodiments are of course not limited by such
conventions). Each of the accelerometer and magnetometer sets may
therefore be considered as determining a plane (the x and y-axes)
and a pole (the z-axis along the axis of the BHA). Those of
ordinary skill will readily appreciate that navigation sensor sets
measure the orientation of the tool axis (which is not generally
exactly parallel with the borehole axis) and may require correction
(e.g., a sag correction) to obtain a better estimate of the
borehole orientation.
[0018] FIG. 3 depicts one disclosed embodiment of a system 80 for
automatically evaluating a wellbore survey. The system may be
implemented at the rig site, for example, on a local computer
system 85. The system may include a plurality of rig sensors 82,
such as the surface sensors referred to with respect to FIG. 1, for
obtaining measurements pertaining to the rig activity. The rig
sensors may be in electronic communication with the computer system
85 such that the sensor measurements may be transferred to the
computer system where they may be used to evaluate rig activity
while obtaining a survey. The system may further include a
plurality of downhole sensors 90 such as the navigation sensors 70
referred to with respect to FIG. 1. The downhole sensors 90 may
also be in electronic communication with the computer system, for
example, via a telemetry link such as wired drill pipe, mud pulse
telemetry, electromagnetic telemetry, and the like. The computer
system 85 is configured to process data from the rig sensors and
the downhole sensors to automatically generate a survey report 95.
The survey report 95 may include a survey acceptance along with
accepted borehole inclination and borehole azimuth values.
Alternatively, the survey report 95 may include a survey rejection
along with the corresponding reasons for that rejection.
[0019] It will be understood that system 80 is not necessarily
located entirely at the rig site. For example, the computer system
85 may be located offsite and may communicate with the rig sensors
82 and the downhole sensors 90 via substantially any known means
(e.g., wirelessly or via internet or intranet communication
channels). The disclosed embodiments are not limited in these
regards. Nor are they limited to any particular hardware
implementation of the system 80.
[0020] FIG. 4 depicts a flow chart of one disclosed method
embodiment 100 for obtaining a wellbore survey. At 102 various
operations may be performed in preparation for the survey operation
to promote optimal (or satisfactory) wellbore survey conditions.
Borehole navigation measurements are acquired at 104. Surface
sensor data is evaluated at 106 to verify that satisfactory
conditions existed at the time the survey measurements were
acquired in 104. The navigation sensor measurements are evaluated
at 108 according to certain dynamic criteria to ensure high data
quality. Measurement correction processes may be optionally
employed at 110 to improve survey quality. At 112 a recommendation
(or report) is automatically generated regarding survey quality and
subsequent actions such as accepting or rejecting the survey,
continuing drilling, obtaining another survey, etc.
[0021] As is known to those of ordinary skill in the art, wellbore
surveys are commonly obtained at some predetermined interval while
drilling the well (e.g. at 30 to 120 foot intervals when adding a
new pipe stand to the drill string). Measurement while drilling
(MWD) surveys commonly include three-axis accelerometer and
three-axis magnetometer measurements from which a borehole
inclination and a borehole azimuth may be computed. Borehole
inclination is a measure of the deviation of the direction of
drilling from vertical while borehole azimuth is a measure of the
deviation of the direction of drilling (in the horizontal plane)
from magnetic (or true) north. In order to improve survey accuracy,
navigation sensor measurements (survey measurements) are commonly
made when the sensors are stationary and in the absence of magnetic
interference. The disclosed embodiments may be utilized with either
static or dynamic surveys.
[0022] Preparation operations may be performed at 102 to increase
the likelihood that that satisfactory conditions exist when the
survey measurements are made. For example, the drill string may be
lifted off-bottom thereby enabling torsional and compressional
energy in the string to be released. Likewise, the top drive (or
rotary table) and block may be held stationary such that the
sensors are stationary and free of rotational and axial motion. The
pumps may be turned off or turned on depending on the particular
rig and BHA configuration.
[0023] Navigation sensor measurements (e.g., accelerometer and
magnetometer measurements) may be obtained at 104 and transmitted
to the surface (e.g., via a conventional telemetry channel). The
measurements may be time stamped downhole. Alternatively, a time at
which the measurements were made may be directly measured or
inferred from various surface measurements. The accelerometer
measurements may include tri-axial measurements including A.sub.x,
A.sub.y, and A.sub.z measurements while the magnetometer
measurements may also include tri-axial measurements including
B.sub.x, B.sub.y, and B.sub.z measurements as described above with
respect to FIG. 2. Alternatively, the accelerometer and
magnetometer measurements may be processed downhole to obtain
borehole inclination, borehole azimuth, toolface, magnetic dip,
total gravitational field, and total magnetic field which may be
transmitted to the surface.
[0024] The surface sensor data may be automatically evaluated at
106 to verify that satisfactory conditions existed at the time the
survey measurements were acquired in 104. For example, the hook
load sensor data may be evaluated to ensure that the drill bit was
off-bottom at the time the navigational sensor measurements were
made (drill bit and hole depths may also be compared to determine
if the rig is off-bottom). The block position sensor data may be
evaluated to ensure that the block velocity was zero (or near
zero). The torque sensor data may be evaluated to ensure that the
rotate rate of the drill string was zero (or near zero). Moreover,
the drilling fluid pressure sensor data or flow-in sensor data may
be evaluated to ensure that the pumps were on or off depending on
the rig. The bit and hole depth measurements may also be evaluated
to determine the proximity of the navigation sensors to a
magnetically hot casing string or casing shoe. The distance between
the sensors and magnetically hot casing components is desirably
greater than some predetermined threshold.
[0025] The accelerometer and magnetometer measurements may be
automatically evaluated at 108 to verify that the measurements meet
certain predetermined conditions for obtaining a survey of
satisfactory quality. For example, the accelerometer measurements
may be processed to compute a total acceleration that may be
compared with a reference gravitational field to ensure that the
total acceleration is equal to the magnitude of the earth's
gravitational field (within predetermined limits). Likewise, the
magnetometer measurements may be processed to compute a total
magnetic field that may be compared with a reference value of the
earth's magnetic field to ensure that the total magnetic field is
equal to the magnitude of the earth's magnetic field (within
predetermined limits). Moreover, the magnetometer measurements may
be further processed to compute a magnetic dip angle that may be
compared with a reference value at the drilling location to ensure
that measured magnetic dip angle is equal to the magnetic dip angle
of the earth's gravitational field (within predetermined
limits).
[0026] The total acceleration may be computed, for example, as
follows:
A= {square root over (A.sub.x.sup.2+A.sub.v.sup.2+A.sub.z.sup.2)}
(1)
[0027] where A represents the total acceleration and A.sub.x,
A.sub.y, and A.sub.z represent the x-, y-, and z-axis accelerometer
measurements. In the absence of drill string vibrations, the total
acceleration should equal the earth's gravitational acceleration.
The total magnetic field may be computed, for example, as
follows:
B= {square root over (B.sub.x.sup.2+B.sub.v.sup.2+B.sub.z.sup.2)}
(2)
[0028] where B represents the total magnetic field and B.sub.x,
B.sub.y, and B.sub.z represent the x-, y-, and z-axis magnetometer
measurements. In the absence of external magnetic interference
(e.g., from magnetic drill string components or magnetic ores in
the formation), the total magnetic field should equal the earth's
magnetic field. The magnetic dip angle may be computed, for
example, as follows:
MDip=B.sub.x cos(TF)sin(Inc)+B.sub.y sin(TF)sin(Inc)+B.sub.z
cos(Inc) (3)
[0029] where TF represents the toolface angle (high side angle) and
Inc represents the borehole inclination. The toolface angle and
borehole inclination may be computed from the tri-axial
accelerometer measurements, for example, as follows:
TF = arc tan ( A y A x ) = arc cos ( A x A x 2 + A y 2 ) = arc sin
( A y A x 2 + A y 2 ) ( 4 ) Inc = arc tan ( A x 2 + A y 2 A z ) ( 5
) ##EQU00001##
[0030] The evaluation at 108 may alternatively and/or additional
include co-processing the total acceleration, the reference value
of the earth's gravitational field, the total magnetic field, the
reference value of the earth's magnetic field, the magnetic dip
angle, and the reference value of the earth's magnetic dip angle to
obtain a survey confidence value which may in turn be compared with
a reference confidence value. For example, the survey may be
accepted when the computed confidence value is greater than or
equal to the reference confidence value and rejected when the
computed confidence value is less than the reference confidence
value.
[0031] The reference gravitational field of the earth and the
reference magnetic field of the earth (including both the magnitude
and direction (or dip)) are commonly known, for example, from
previous geological survey data (e.g., as available from the U.S.
Geological Survey). However, for some applications it may be
advantageous to measure the gravitational and magnetic fields in
real time on-site at a location substantially free from magnetic
interference, e.g., at the surface of the well or in a previously
drilled well. Measurement of the gravitational and magnetic fields
in real time may be advantageous in that it may account for time
dependent variations (e.g., the earth's magnetic field is known to
vary with time). However, at certain sites, such on an offshore
drilling rig, it may not be possible to locate a magnetically clean
measurement site or site free from external vibrations). In such
instances, it may be preferable to utilize previous geological
survey data in combination with suitable interpolation and/or
mathematical modeling (i.e., computer modeling) routines known in
the art.
[0032] It will be understood that the evaluation in 108 may be
performed downhole by a downhole processor. For example, the total
acceleration, the total magnetic field, the magnetic dip angle,
and/or or the confidence value may be computed downhole and
compared with corresponding reference values stored in downhole
memory. In such an embodiment, the navigation sensor measurements
may be transmitted to the surface along with an indication of
survey acceptance or rejection. Alternatively, navigation sensor
measurements may be transmitted to the surface only upon acceptance
of the measurements. In such an embodiment, a rejection may trigger
the navigation sensors to automatically make new measurements.
[0033] It will further be understood that the evaluation in 108 may
result in partial acceptance and/or a partial rejection of the
navigation sensor data. For example, the quality of the
accelerometer data may be acceptable thereby resulting in an
acceptable borehole inclination measurement while at the same time
the quality of the magnetometer data may unacceptable resulting in
an unsatisfactory borehole azimuth measurement.
[0034] Measurement correction processes may be optionally employed
at 110 to improve survey quality (navigation sensor data quality).
Such measurement correction processes may include, for example, sag
corrections to correct for misalignment of the drill string with
the borehole and multi-station analysis to correct for magnetic
interference in the drill string.
[0035] A survey recommendation (or report) may be automatically
generated at 112. For example, if the evaluations performed at 106
and 108 indicate that the survey is of satisfactory quality, the
survey may be automatically accepted and a recommendation for
drilling to continue may be given. Alternatively, if one (or both)
of the evaluations performed at 106 and 108 indicate that the
survey result is questionable, the survey may be rejected and a
recommendation for conducting another survey may be given. The
reasons for rejection may also be noted to alert rig personnel. For
example, the survey may be rejected (or flagged for further review)
if one of the rig sensors indicates at 106 that the conditions were
not satisfactory at the time the survey measurements were obtained.
Alternatively, the survey may be rejected if the survey
measurements do not satisfy the above described predetermined
conditions (as evaluated in 108).
[0036] Automatic acceptance or rejection of dynamic survey data may
employ a similar methodology. For example, single axis (z-axis)
accelerometer and magnetometer data may be automatically compared
with reference obtained from the previous static survey.
[0037] Although automatic wellbore survey acceptance and certain
advantages thereof have been described in detail, it should be
understood that various changes, substitutions and alterations may
be made herein without departing from the spirit and scope of the
disclosure as defined by the appended claims.
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