U.S. patent application number 13/500085 was filed with the patent office on 2012-08-02 for magnetic ranging system for controlling a drilling process.
Invention is credited to Mathias Francke, Jorgen Hallundb.ae butted.k.
Application Number | 20120193144 13/500085 |
Document ID | / |
Family ID | 41820332 |
Filed Date | 2012-08-02 |
United States Patent
Application |
20120193144 |
Kind Code |
A1 |
Hallundb.ae butted.k; Jorgen ;
et al. |
August 2, 2012 |
MAGNETIC RANGING SYSTEM FOR CONTROLLING A DRILLING PROCESS
Abstract
The invention relates to a ranging system (1) for controlling a
drilling process downhole. The ranging system has a longitudinal
direction and comprises a drilling tool (2) for drilling a first
borehole (3), the drilling tool having a tool axis (4) and
comprising a magnetic field source (5) in the form of an
electromagnet generating a magnetic field (6) and having a magnetic
field source axis (7) which is substantially parallel to the tool
axis. Moreover, the ranging system comprises a sensing tool (8)
arranged in a second borehole (9) for measuring the magnetic field
by means of at least two sensor units (10), which sensor units are
arranged at a distance (D) from each other along an axis of the
sensing tool.
Inventors: |
Hallundb.ae butted.k; Jorgen;
(Graested, DK) ; Francke; Mathias; (Virum,
DK) |
Family ID: |
41820332 |
Appl. No.: |
13/500085 |
Filed: |
October 29, 2010 |
PCT Filed: |
October 29, 2010 |
PCT NO: |
PCT/EP2010/066443 |
371 Date: |
April 4, 2012 |
Current U.S.
Class: |
175/45 |
Current CPC
Class: |
E21B 47/0228 20200501;
E21B 7/04 20130101 |
Class at
Publication: |
175/45 |
International
Class: |
E21B 47/02 20060101
E21B047/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2009 |
EP |
09174667.7 |
Claims
1. A ranging system (1) for controlling a drilling process
downhole, the ranging system having a longitudinal direction and
comprising: a drilling tool (2) for drilling a first borehole (3),
the drilling tool having a tool axis (4) and comprising a magnetic
field source (5) in the form of an electromagnet generating a
magnetic field (6) and having a magnetic field source axis (7)
which is substantially parallel to the tool axis, and a sensing
tool (8) arranged in a second borehole (9) for measuring the
magnetic field by means of at least two sensor units (10) wherein
the sensor units are arranged at a distance (D) from each other
along an axis of the sensing tool.
2. A ranging system according to claim 1, wherein each sensor unit
comprises at least one magnetometer (20).
3. A ranging system according to claim 1, wherein the magnetic
field source axis is substantially coincident with the tool
axis.
4. A ranging system according to claim 1, wherein the sensing tool
is submerged into the well by a wireline.
5. A ranging system according to claim 1, wherein the magnetometers
are arranged in the same plane in the sensor unit.
6. A ranging system according to claim 5, wherein the magnetometers
measure the magnitude and direction of the magnetic field, such as
the magnitude and direction of a local magnetic field vector.
7. A ranging system according to claim 1, wherein the second
borehole is an existing borehole.
8. A ranging system according to claim 1, wherein the sensor unit
and/or the drilling tool is driven by a driving unit (11).
9. A ranging system according to claim 1, further comprising a
positioning tool for determining the position of the sensing tool
in the second borehole or the position of the drilling tool in the
first borehole.
10. A ranging system according to claim 1, wherein the sensing tool
has means (12) for controlling and/or measuring the velocity or
position of the sensing tool.
11. A ranging system according to claim 1, wherein the magnetic
field source has a through hole (13), allowing fluid for driving a
drilling head (14) of the drilling tool to pass through the
magnetic field source.
12. A ranging system according to claim 1, further comprising a
downhole calculation unit (15) for processing magnitude and
direction measurements of the magnetic field measured by the
sensing tool.
13. A ranging system according to claim 1, further comprising a
second drilling tool, the sensing tool being arranged in or in
connection with the second drilling tool so that the first drilling
tool comprises the magnetic field source and the second drilling
tool comprises the sensing tool.
14. A method for using the ranging system according to claim 1,
comprising the steps of: drilling the first borehole in one
drilling direction, inserting the sensing tool into the second
borehole, measuring the magnitude and direction of the magnetic
field while drilling, calculating a position of the drilling tool
relative to the sensing tool while drilling, and calculating the
direction of the drilling head,
15. A method according to claim 14, further comprising the step of:
adjusting the drilling direction based on the calculated direction
and relative position of the drilling tool.
16. Use of the ranging system according to claim 1 downhole.
Description
TECHNICAL FIELD
[0001] The present invention relates to a ranging system for
controlling a drilling process downhole. The ranging system has a
longitudinal direction and comprises a drilling tool for drilling a
first borehole, the drilling tool having a tool axis and comprising
a magnetic field source in the form of an electromagnet generating
a magnetic field and having a magnetic field source axis. In
addition, the ranging system comprises a sensing tool arranged in a
second borehole for measuring the magnetic field by means of a
sensor unit.
BACKGROUND
[0002] When drilling into the formation of an existing well or
borehole, it is very important to know the distance to the existing
well or borehole while drilling. In some cases, the purpose is to
meet the existing well or borehole at a certain position and, in
other cases, the purpose is to drill a new borehole at an exact
distance to the existing borehole or well, while ensuring that the
distance between the two is substantially the same along a certain
stretch.
[0003] Known tools comprise different solutions to determine this
distance. The tools are used to detect magnetic fields for the
purpose of determining the distance. Some tools use current in a
wire in the existing borehole while others use a magnet rotating in
the drilling head.
[0004] In prior art tools, such as the one described in US
2008/0041626, the magnet in the drilling head needs to rotate in
order for the sensor to be able to detect the magnetic field and
thus the distance of the drilling head in relation to a known
position. Sometimes, however, the drilling heads stops, making it
impossible to detect the magnetic field and thus determine the
distance and the drilling direction of the drilling head.
Furthermore, in order to conduct measurements, the drilling process
has to be stopped to allow the magnet to be rotated and the tool to
be slid back and forth further than the interwell separation, i.e.
further than 5-10 meters.
[0005] In regard to these tools and tools using current in a wire
in an existing borehole, the magnetic field sensing device is
positioned in the drilling tool. Since the drilling head of the
drilling tool is driven by high-pressurised fluid delivered through
the drill string, transmission of data from the measurements
conducted by the sensing device is very difficult. These tools
produce waves in the fluid as a means of communicating data, which
is a very slow means of communication and may moreover inhibit the
drilling process.
DESCRIPTION OF THE INVENTION
[0006] It is an object of the present invention to wholly or partly
overcome the above disadvantages and drawbacks of the prior art and
provide an alternative ranging system able to determine the
distance between the drilling tool and an existing well or borehole
and even the three-dimensional position and orientation of the
drilling head in order to control the drilling tool while
drilling.
[0007] It is an additional object to provide an improved ranging
system capable of determining the distance to an existing borehole
or well, even when the drilling tool or the drilling string is not
rotating.
[0008] The above objects, together with numerous other objects,
advantages, and features, which will become evident from the below
description, are accomplished by a solution in accordance with the
present invention by a ranging system for controlling a drilling
process downhole, the ranging system having a longitudinal
direction and comprising: [0009] a drilling tool for drilling a
first borehole, the drilling tool having a tool axis and comprising
a magnetic field source which is an electromagnet generating a
magnetic field and having a magnetic field source axis, and [0010]
a sensing tool arranged in a second borehole for measuring the
magnetic field by means of at least two sensor units, wherein the
sensor units are arranged at a distance from each other along an
axis of the sensing tool.
[0011] When the sensor units are arranged at a distance from each
other along an axis of the sensing tool, the electromagnet does not
have to move in order to make sufficient measurements to be able to
calculate the position of the magnet relative to the sensing tool.
When it is necessary to move the magnet, an imprecise distance
between two sets of measurements may occur as a result; however,
this is not the case when two sensor units are arranged at a fixed
mutual distance. Furthermore, when having an electromagnet in
relation to a permanent magnet, it is not necessary to rotate the
magnet. Consequently, the calculation of the position of the magnet
and thus the drilling tool is simplified, since the magnetic field
is the same in relation to a rotating permanent magnet, rotating to
change the field.
[0012] In one embodiment, the magnetic field source axis may be
substantially parallel to the tool axis.
[0013] The magnetic field source axis may also be substantially
coincident with the tool axis.
[0014] The sensor units may each comprise a three axis magnetometer
for measuring the magnitude and direction of the magnetic
field.
[0015] Moreover, the magnetometers may be arranged in the same
plane in the sensor unit.
[0016] According to one embodiment, the second borehole may be an
existing borehole.
[0017] In another embodiment, the sensor unit and/or the drilling
tool may be driven by a driving unit.
[0018] The ranging system may further comprise a positioning tool
for determining the position of the sensing tool in the second
borehole or the position of the drilling tool in the first
borehole.
[0019] This sensing tool may also have means for controlling and/or
measuring the position of the sensing tool.
[0020] The magnetic field source may have a through hole, allowing
fluid for driving a drilling head of the drilling tool to pass
through the magnetic field source.
[0021] The ranging system may also comprise a calculation unit for
processing magnitude and direction measurements of the magnetic
field measured by the sensing tool.
[0022] In addition, the ranging system may comprise a second
drilling tool, and the sensing tool may be arranged in or in
connection with the second drilling tool so that the first drilling
tool comprises the magnetic field source and the second drilling
tool comprises the sensing tool.
[0023] The invention further relates to a method for using the
ranging system according to the invention, comprising the steps of:
[0024] drilling the first borehole in one drilling direction,
[0025] inserting the sensing tool into the second borehole, [0026]
measuring the magnitude and direction of the magnetic field, and
[0027] calculating a position of the drilling tool relative to the
sensing tool, wherein the steps of measuring and calculating occur
while drilling the first borehole.
[0028] In one embodiment, the steps of measuring and calculating
are performed simultaneously with drilling the first borehole,
meaning that the steps of measuring and calculating are performed
at least once an hour, preferably at least once every 0.5 hour,
more preferably at least once every 10 minutes.
[0029] Furthermore, the method may comprise the step of calculating
the direction of the drilling head.
[0030] In addition, the method may comprise the step of adjusting
the drilling direction based on the calculated relative position of
the drilling tool in relation to the sensing tool.
[0031] In addition, the method may comprise the step of adjusting
the drilling direction based on the calculated direction and
relative position of the drilling tool.
[0032] Finally, the invention relates to any use of the ranging
system according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The invention and its many advantages will be described in
more detail below with reference to the accompanying schematic
drawings, which for the purpose of illustration show some
non-limiting embodiments and in which
[0034] FIG. 1 shows a cross-sectional view of a ranging system
according to the invention arranged in two boreholes downhole,
[0035] FIG. 2 shows a partly cross-sectional view of the drilling
tool,
[0036] FIG. 3 shows the magnetic field source in perspective,
and
[0037] FIG. 4 shows the sensing unit.
[0038] All the figures are highly schematic and not necessarily to
scale, and they show only those parts which are necessary in order
to elucidate the invention, other parts being omitted or merely
suggested.
DETAILED DESCRIPTION OF THE INVENTION
[0039] The present invention relates to a ranging system 1 for
controlling a drilling process downhole, the ranging system having
a longitudinal direction. When drilling a borehole, it is very
important to be able to control the drilling direction and to know
the orientation of the drilling head to ensure that the borehole is
positioned at the predetermined position. When using steam assisted
gravity drainage (SAGD) to extract the oil out from the ground, two
boreholes must be drilled being substantially parallel, along
almost all of their horizontal extension to ensure that the steam
penetrates the formation along almost the entire horizontal
extension of the boreholes.
[0040] The ranging system comprises a drilling tool 2 for drilling
a new borehole near an existing borehole as shown in FIG. 1. The
drilling tool 2 comprises a drilling head 14 for drilling a first
borehole into the formation, and it further comprises a magnetic
field source 5 generating a magnetic field 6, which can be detected
by a sensing tool 8 arranged in a second borehole in order to
determine the distance between the drilling tool 2 and the sensing
tool 8 while drilling and to determine the orientation of the
drilling head.
[0041] The ranging system 1 may also be used while drilling two new
boreholes. When drilling two boreholes at substantially the same
time, the magnetic field source 5 is arranged in one drilling tool
2 and a sensor unit 10 of the sensing tool 8 is arranged in, or in
connection with, another drilling tool 2. By processing the
measurements conducted by the sensor unit 10, the drilling
direction of the drilling tools 2 can be adjusted to ensure that
the distance between the two boreholes remains substantially the
same. In order to ensure that the boreholes are positioned in the
predetermined position, one of the drilling tools 2 may comprise a
positioning tool which is able to determine the position of the
drilling tools in relation to the starting point or another known
position.
[0042] In FIGS. 1 and 2, the drilling tool 2 has a tool axis 4 and
the magnetic field source 5 has a magnetic field source axis 7
which is substantially coincident with the tool axis 4. The
magnetic field source 5 may be any suitable electromagnet. By using
an electromagnet, the poles can switch, and the sensor units 10 are
thereby able to conduct measurements where the contribution from
the earth magnetic field is effectively cancelled out.
[0043] Furthermore, rotating the drilling string, and thereby the
magnetic field source, does not have any substantial effect on the
measurements, which means that useful measurements can be made
while drilling and even when the drilling tool is not rotating. As
shown in FIG. 4, the sensing tool comprises at least two sensor
units 10 arranged at a distance D from each other along an axis of
the sensing tool. This means that independent measurements of the
magnetic field can be made simultaneously, i.e. there is no need
for moving the magnet along the tool axis and thus stop drilling
while conducting the measurements. In prior art tools, the
conducting of measurements is dependent on the magnetic field
source rotating and sliding while conducting the measurements.
Thus, in prior art tools, measurements can only be performed when
the drilling process is stopped.
[0044] If the drilling tool 2 and thereby the drilling process
stops, for instance if the drilling tool 2 has broken down, the
sensing tool 8 of the present invention is still capable of sensing
the magnetic field 6 and thus of continuing to conduct
measurements.
[0045] As shown in FIG. 4, the sensing tool 8 comprises at least
two sensor units 10. Thus, the sensor tool 8 comprises at least two
magnetometers, enabling it to calculate the exact position of the
drilling head 14 in relation to the sensing tool as well as the
direction in which the drilling head 14 is drilling. Each
magnetometer measures the local magnitude and direction of the
magnetic field 6 and thus provides independent vector measurements
without having to move the magnet in relation to the sensors, as is
the case in the prior art. When having several sensor units 10,
sufficient measurements can be conducted to calculate the position
of the drilling tool in relation to the sensing tool 8 without
having to stop the drilling process. The first vector corresponding
to the magnitude and direction of the magnetic field 6 measured in
a first sensor unit and the second vector corresponding to the
magnitude and direction of the magnetic field 6 measured in a
second sensor unit are used to calculate the position of the magnet
in the drilling tool. The measurements in the two sensor units 10
are conducted at the same time and, as the distance between the
sensor units is known, the position of the magnet can be
calculated.
[0046] When the sensing unit has detected that the distance from
the drilling tool to the sensing tool is increased or decreased,
the drilling direction of the drilling head 14 can be adjusted so
that the direction is the intended direction or so that the
distance to a second borehole is the same as the predetermined
distance, meaning that the first and second boreholes thus become
parallel again.
[0047] The sensing tool may comprise even more sensing units.
Having three or even four sensor units instead of only the two
mentioned above will increase the accuracy of the calculated
position as well as the direction of the magnetic source and thus
the drilling tool. The method described above still applies when
using more than two sensor units.
[0048] When having an electromagnet as the magnetic field source,
the magnet does not have to rotate in order to produce useful
measurements as the electromagnet is instead pulsed. The direction
of the magnetic field is thus the same relative to the rest of the
drill string, simplifying the calculation of the position of the
magnet substantially. Even though the electromagnet is rotated, its
rotational axis can be coincident with the rotational axis of the
drilling tool, thus not affecting the direction of the magnetic
field.
[0049] In FIG. 1, the sensing tool 8 comprises a driving unit 11
for driving the tool in the longitudinal direction of the second
borehole 9. The sensing tool 8 may comprise means 12 for adjusting
the position of the sensing tool, enabling the sensing tool to move
back and forth in the borehole to be within the desired range of
the drilling tool. The desired range is the range within which the
sensing tool 8 has a distance to the magnet of the drilling tool 2,
enabling measurements of good enough quality to accurately and
precisely calculate the position of the drilling tool in relation
to the sensing tool.
[0050] The drilling tool 2 may also comprise a driving tool if the
drilling process is not performed by means of coiled tubing or
drill pipes.
[0051] In FIG. 1, the first borehole 3 is the borehole to be
drilled, and the second borehole 9 is an existing borehole, but the
second borehole may also be a well or another kind of hole in the
formation. The second borehole 9 may be a vertical part of a well
which the drilling tool drilling the first borehole deliberately is
to collide with or deliberately is to avoid while drilling.
[0052] The drilling tool 2 typically runs on a high-pressurized
fluid. As can be seen in FIGS. 2 and 3, the magnetic field source 5
has a through hole 13, allowing the fluid to pass through the
magnetic field source 5 without losing energy. This is especially
convenient when the drilling tool 2 is driven by pressurised fluid
through drill pipes or coiled tubing.
[0053] In order to calculate the distance between the drilling head
14 and the sensing tool 8 and the orientation of the drilling head
based on the measurements, the ranging system 1 comprises a
calculation unit 15 for processing magnitude and direction
measurements of the magnetic field 6 measured by the sensor unit
10. The calculation unit 15 is placed in the sensor unit 10.
Detailed Description of the Calculation Method
[0054] The position, r, of the magnet relative to the sensor is
calculated as the solution to a minimisation problem. The
expression for the field, B, of a magnetic dipole in vector
notation is:
B = .mu. 4 .pi. ( 3 ( d r ) r r 5 - d r 3 ) ##EQU00001##
where .mu. is the permeability, d is the dipole vector being
substantially coincident with the magnetic field source axis 7, r
is the position vector, and r is the distance, i.e. the length of
the position vector. This can be rearranged into:
- .mu. 4 .pi. d = r 3 ( B - 3 2 r 2 ( r B ) r ) . ##EQU00002##
[0055] If two field-vector measurements, B.sub.1 and B.sub.2, are
made at the same time in two different places, r and r+s, the
dipole vector, being the same for both measurements, can be
eliminated from the above equation and the following expression
emerges:
r 3 ( B 1 - 3 2 r 2 ( r B 1 ) r ) = r + s 3 ( B 2 - 3 2 r + s 2 ( (
r + s ) B 2 ) ( r + s ) ) ##EQU00003##
where r is the only variable and s is the relative position between
the two measurements. The position of the magnet with respect to
the sensor unit, r, can be found by minimisation of a residual
based on the equation above, the expression being:
r = arg min r d 1 - d 2 , where ##EQU00004## d 1 = r 3 ( B 1 - 3 2
r 2 ( r B 1 ) r ) ##EQU00004.2## and ##EQU00004.3## d 2 = r + s 3 (
B 2 - 3 2 r + s 2 ( ( r + s ) B 2 ) ( r + s ) ) .
##EQU00004.4##
[0056] After finding the relative position of the magnet, the
dipole vector can be calculated directly by insertion into the
equation for d.
[0057] All of the calculations described above are performed by the
processing unit 15 situated in the sensor tool 8 immediately after
the measurements are available, and are subsequently transmitted to
the surface. Thus, the information about direction and relative
position of the drilling head 14 is available to the drilling
operator almost instantly, and any needed actions can be performed
without further delay.
[0058] Thus, there is no heavy data communication or time-consuming
post-processing involving personnel for making interpretations of
the data.
[0059] The method using the ranging system comprises the steps of:
[0060] drilling the first borehole in one drilling direction,
[0061] inserting the sensing tool into the second borehole, [0062]
measuring the magnitude and direction of the magnetic field, and
[0063] calculating a position of the drilling tool relative to the
sensing tool, wherein the steps of measuring and calculating are
performed while drilling the first borehole.
[0064] The steps of measuring and calculating are performed
simultaneously with drilling the first borehole, meaning that the
steps of measuring and calculating are performed at least once an
hour, preferably at least once every 0.5 hours, more preferably at
least once every 10 minutes. It is also possible to do this more
often, such as several times per second.
[0065] In order to ensure that the borehole is drilled in the
predetermined position, either the drilling tool 2 or the sensing
tool 8 may also have a positioning tool.
[0066] By fluid or well fluid is meant any kind of fluid which may
be present in oil or gas wells downhole, such as natural gas, oil,
oil mud, crude oil, water, etc. By gas is meant any kind of gas
composition present in a well, completion, or open hole, and by oil
is meant any kind of oil composition, such as crude oil, an
oil-containing fluid, etc. Gas, oil, and water fluids may thus all
comprise other elements or substances than gas, oil, and/or water,
respectively.
[0067] By a casing is meant any kind of pipe, tubing, tubular,
liner, string, etc. used downhole in relation to oil or natural gas
production.
[0068] In the event that the tools are not submergible all the way
into the casing, a downhole tractor can be used to push the tools
all the way into position in the well. A downhole tractor is any
kind of driving tool capable of pushing or pulling tools in a well
downhole, such as a Well Tractor.RTM..
[0069] Although the invention has been described in the above in
connection with preferred embodiments of the invention, it will be
evident for a person skilled in the art that several modifications
are conceivable without departing from the invention as defined by
the following claims.
* * * * *