GB2526824A

GB2526824A - Determination of initial tool orientation

Info

Publication number: GB2526824A
Application number: GB1409866.9A
Authority: GB
Inventors: Bjã Rn Tornstein Bruun; Erik Nyrnes
Original assignee: Statoil Petroleum ASA
Current assignee: Equinor Energy AS
Priority date: 2014-06-03
Filing date: 2014-06-03
Publication date: 2015-12-09
Anticipated expiration: 2034-06-03
Also published as: CA2893361A1; GB2526824B; NO344400B1; NO20150710A1; GB201409866D0; CA2893361C

Abstract

A method of determining the initial orientation of a tool 6 to be moved from a drilling site along a wellbore in the earth comprises defining a drilling site coordinate system which is fixed relative to said drilling site; defining a tool coordinate system which is fixed relative to said tool; providing at least one marker 20, 22 on said drilling site defining at least one drilling site reference point which is fixed relative to said drilling site coordinate system; providing at least one marker 20 on said tool defining at least one tool reference point which is fixed relative to said tool coordinate system; determining the positions of said drilling site and tool reference points using a measuring device 24 such as a 3D laser scanner; and using said determined positions to perform a coordinate transformation between said drilling site and tool coordinate systems in order to determine the orientation of said tool.

Description

Determination of initial tool orientation

FIELD OF THE INVENTION

The invention relates to the determination of initial tool orientation, for example determining the initial orientation of an instrument package to be moved along a wellbore.

BACKGROUND OF THE INVENTION

As of today onsite calibration and initialization of tools, using accelerometers, magnetic and gyrosoopic sensors, are mainly done using sensors in the tool, and to some extent physical models. For some tools oresighting" techniques are used when movement of the drilling vessel (for example an onshore or offshore drilling platform, a floating or fixed platform or a boat) does not allow for tool initialization using the tool sensors. The method aligns the tool to a reference point (foresight") on the drilling site, to determine an approximate azimuth direction for initialization purposes. As the reference point position is not dynamically updated, the method has drawbacks when used on a moving drilling vessel, such as a floating drilling unit in high seas.

The following two patents relate to apparatuses for initializing wellbore survey tools: US 8,305,230, in the name of Gyrodata Incorporated, an apparatus for initialization of gyro tools using satellite navigation systems. The apparatus includes the use of a mechanically coupled mounting portion to give the tool a predetermined orientation to a directional reference system.

US 2013/01 27631, in the name of Gyrodata Incorporated, describes an apparatus for transferring orientation from a directional reference frame to a tool. The apparatus uses mechanical couplings to a directional reference system and to the tool to transfer orientations.

Existing technology is known which uses measurements of the earth's magnetic field or measurements of the earth's rotation rate to estimate initial tool orientation. The earth's magnetic field is measured by means of magnetometers or magnetic compassing. The earth's rotation rate is measured by gyroscopes. Both methods utilizing the earth's magnetic field and the earth's rotation rate become gradually more inaccurate as latitude increases, making them unreliable for use in arctic regions.

Using measurements of the earth's rotation rate to find the initial tool orientation is troublesome and inaccurate when performed on a vessel with large and frequent movements, such as an offshore drilling unit in high seas.

The patented Gyrodata technology, not yet fully developed, comprises mechanical coupling of the tool to a directional reference frame, or a device transferring orientation from a directional reference frame to the tool, making it cumbersome to handle the tool or/and the transferring device.

SUMMARY OF THE INVENTION

The invention provides a method of determining the initial orientation of a tool as set out in the accompanying claims.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows the relationship between three different coordinate systems; Figure 2 shows the transformation of a point P between three coordinate systems using scale, translation and rotation; FigureS shows components of a system for performing translations; Figure 4 shows a system for performing translations using markers and reflectors; and Figure 5 shows a further system for performing translations using markers and reflectors.

DESCRIPTION OF PREFERRED EMBODIMENTS

Each feature disclosed or illustrated in the present specification may be incorporated in the invention, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.

Figure 1 is a schematic diagram showing the surface of the earth 2, and a drilling rig 4, which may be a floating rig, located on the surface of the earth 2. The drilling rig 4 may move relative to the earth 2. A wellbore survey tool 6 is positioned on the rig 4 and moves with the rig 4. We define three 3D coordinate systems, namely: a) an earth coordinate system 8, which is fixed relative to the earth 2; b) a rig or drilling site coordinate system 10, which is fixed relative to the rig 4 and which moves with the rig 4; and c) a tool coordinate system 12 Figure 2 shows how a point P may be transformed between the three coordinate systems 8, 10 and 12.

We describe methods of determining initial tool orientation, which may include dynamically updated reference points. The reference points are known, fixed positions in a given coordinate system.

We describe a method for determining the orientation of a tool relative to a fixed reference frame, determined by a loca or global fixed coordinate system, such as WGS 84 (a 3D coordinate reference system often used with OPS systems), UTM (a 2D coordinate system often used for map planes) or a locally defined coordinate system (field specific), instantly or as a function of time.

The term tool may herein include any instrument package to be moved along a wellbore trajectory, for instance as a part of a wireline unit or bottomhole assembly.

The method involves the transformation between coordinate systems moving relative to the fixed reference frame using dynamically updated reference points on the drilling unit.

Using satellite receivers, radio navigation systems or positioning data from the vessel's DPS (dynamic positioning system), the current positions of the signal receivers or antennas can be found relative to the fixed reference system.

Using three or more reference points, a site specific coordinate system for the moving site, for example a drilling site, can be defined. Using surveying techniques, such as photogrammetric or traditional geodetic techniques involving theodolites and electronic distance measuring devices, the position of the antennas/receivers can be determined in the site specific coordinate system utilizing direction and distance measurements.

A first three dimensional coordinate transformation consisting of scaling, translation and rotation elements, can then be defined using the time synchronized dual positions of the antennas/receivers in both the locally defined and fixed coordinate system, which can be used to transform positions defined in the local coordinate system to current positions in the fixed coordinate system.

Figure 3 shows components of a system used to perform translations. A survey tool 6 carries a frame 14, which in turn carries markers 20.

Two types of markers are used. Markers 20 are able to receive and reflect incoming signals, and are also able to transmit signals. The transmitted signals may be optical, acoustic or electromagnetic. Markers 22 are able to receive and reflect incoming signals, but do not transmit signals. Also shown in Figure 3 is a main measuring device 24.

Figure 4 shows a system in which markers 20 and 22 are used to identify the reference points in the rig/drilling site or tool specifc coordinate systems. The markers 20 and 22 can include characteristic patterns, e.g. printed patterns or physical shaped objects.

Alternatively markers can include certain geometric shapes, or transmitters, receivers or reflectors of acoustic or electromagnetic signals. The markers are attached to the reference points, so the reference points can be easily detected by a main measurement device 24.

Figure 5 shows an alternative arrangement which uses two main measurement devices 24 and three markers 20 attached to a survey tool 6, together with additional markers and 22.

The main measurement 24 for measuring distances and/or directions can for instance be a theodolite, a 3D laser scanner, a device utilising a photogrammetric principle, or a device utilising electromagnetic or acoustic signals. The main measurement device 24 can include computer software and hardware to automatically identify the various markers 20 and 22.

When using markers 20 or 22 consisting of characteristic patterns, the main measurement device determines the distance and direction to the markers by recognizing the marker's shape or pattern, either automatically or by manually detection. If the markers and the main measurement device 24 utilise electromagnetic or acoustic signals, a time synchronized signal transmitted from either the marker or the main measurement device is used to determine the distance and/or direction between the main measurement device 24 and the marker 20 or 22.

Measurements of distance and! directions between markers can also be performed and included in the coordinate transformation calculations.

The markers placed in the drilling unit coordinate system may be geometrically distributed around the drilling site, to provide optimal accuracy performance in coordinate transformations.

Defining two or more additional reference points on the drilling tool, a third local tool coordinate system can be defined. By utilizing direction and distance measurements between reference points in the site specific coordinate system and reference points in the tool specific coordinate system, a second transformation consisting of scale, translation and rotation elements can be defined, which can be used to transform positions in the tool coordinate system into positions of the site specific coordinate system. The method can also include physically orienting the tool so that it points in one or more predetermined reference directions.

The direction and distance measurements needed for the second transformation are measurements made between the main measurement device 24 and the markers placed in the drilling tool coordinate system (ie those shown attached to frame 14 in the examples in the figures) and markers placed in the site specific coordinate system.

Additionally measurements can be made directly between markers in both coordinate systems.

One or more of the drilling tool reference point markers can be placed on physical drilling tool attachments 30 pointing in a specified direction relative to the tool coordinate system. The attachments 30 can be pointing in various directions, and have varying lengths making the actual marker positions distanced from the drilling tool body. The attachments 30 can for instance be rod shaped and mounted on the body of the drilling tool 6.

Combining the two transformation calculations the current orientation of the tool 6 relative to the fixed reference frame can be calculated. Although we describe the use of three coordinate systems in the present method, the same procedure can be applied for any number of coordinate system transformations. An example where more than three coordinate systems may be used is on a drilling rig which has heave compensation. On such a rig a stabilised portion of the rig is arranged to move relative to the rest of the rig in order to reduce the effects of sea movement I heave. In this case separate coordinate systems may be used for the stabilised portion of the rig and the rest of the rig, A coordinate system transformation may be performed between the two systems. In general, the method uses at least two coordinate systems.

During measurements and calculations the drilling tool has to be placed in a fixed position and orientation relative to the site specific coordinate system, for the orientation calculations to be valid. In other words, the tool has to be still relative to the site specific coordinate system when measurements are taken.

The calculation can be done utilizing a device or network to transfer orientations to the tool software or external software, either as direct orientations or corrections to tool determined orientations. Otherwise a time synchronization device can be used to match time stamps from the tool with time stamps of the signal receiver or software time at the time of calculation, for retrospective calculation of orientations, which can be transferred to the tool as corrections to tool determined orientations. Calculated corrections to tool determined orientations will be valid also when tool has been moved from its initial fixed position.

The method may use real time/dynamically updated reference points at the rig site for finding tool orientation.

The method may use more than one reference point for topside determination of tool direction.

The method may determine three dimensional tool orientation topside by means of reference points.

The method may use three dimensional tool orientation found by means of dynamically updated reference points to initialize or correct tool determined orientation.

The method may use three dimensional topside determined orientations or corrections to tool determined orientations to update and/or quality control tool orientations determined by the tool downhole.

The method may utilize redundant direction and distance measurements to reduce the uncertainty of the calculated tool orientation, and may use statistical adjustment methods, such as the method of least squares.

Existing technology is unreliable at high latitudes and in conditions of strong heave and movements of the rig. This leads to increased time spent on initialization and calibration of tools, and decreased accuracy of tool initialization and calibration.

Compared to existing technology, the invention provides a more accurate tool orientation and reduced time consumption.

The orientation of drilling/surveying tools are traditionally established by stationary measurements performed at discrete survey stations downhole. As an example some surveying tools, such as continuous tools run on wireline, measure small incremental changes in wellbore direction along the wellbore path, starting at a reference point with known direction. The orientation of the reference point is usually established by stationary earth rate measurements. This approach has its limitations: 1) Because the accuracy of the stationary measurements is inversely proportional to the cosine of the geographical latitude, the directional accuracy degrades strongly with increasing latitude, making the reference point uncertain, and consequently, the measured position of the well trajectory also becomes uncertain. 2) Stationary measurements are sensitive to movements, caused by for instance wave motions in high seas.

By using methods described here, a more accurate reference orientation can be established at the rig-site instead of downhole in a faster way than existing technology.

If the tool is aligned along the vertical, or close to the vertical, relative to the direction of gravity or to the direction of the vertical axis of the site specific coordinate system, the orientation of the tool (for instance gyro toolface) can be determined by using only one marker attached to the tool and one marker in the site specific coordinate system.

Claims

CLAIMS: 1. A method of determining the initial orientation of a tool to be moved from a drilling site along a wellbore in the earth, the method comprising: defining a drilling site coordinate system which is fixed relative to said drilling site; defining a tool coordinate system which is fixed relative to said tool; providing at least one marker on said drilling site, defining at least one drilling site reference point which is fixed relative to said drilling site coordinate system; providing at least one marker on said tool, defining at least one tool reference point which is fixed relative to said tool coordinate system; determining the positions of said drilling site and tool reference points; and using said determined positions to perform a coordinate transformation between said drilling site and tool coordinate systems in order to determine the orientation of said tool.
2. A method as claimed in claim 1, which further comprises: defining an earth coordinate system which is fixed relative to the earth; determining the positions, at a specific instant in time, of at least three drilling site reference points relative to said earth coordinate system; and using the determined positions of said at least three drilling site reference points to perform a coordinate transformation to transform positions defined in said site coordinate system to positions defined in said earth coordinate system.
3. A method as claimed in claim 1 or 2, which further comprises: determining the positions of said at least one tool reference point relative to said site coordinate system; and using the determined positions of said at least one tool reference point to perform a coordinate transformation to transform positions defined in said tool coordinate system to positions defined in said site coordinate system.
4. A method as claimed in any preceding claim, wherein said markers include at least one optical marker.
5. A method as claimed in claim 4, wherein said at least one optical marker is provided with a printed pattern.
6. A method as claimed in any preceding claim, wherein said markers include at least one acoustic marker arranged to send or receive an acoustic signal.
7. A method as claimed in any preceding claim, wherein said markers include at least one electromagnetic marker arranged to send or receive an electromagnetic signal.
8. A method as claimed in any preceding claim, wherein said tool is provided with at least one attachment which is fixed relative to said tool coordinate system, and wherein at least one of said markers is provided on said attachment.
9. A method as claimed in claim 8, wherein said attachment is an elongate member which defines a specified direction in said tool coordinate system.
10. A method as claimed in any preceding claim, which comprises using an optical measuring device to determine the position of at least one of said markers.
11. A method as claimed in claim 10, wherein said optical measuring device is a theodolite or 3D laser scanner.
12. A method as claimed in any preceding claim, wherein the or each drilling site reference point has a corresponding signal receiver for receiving signals from a positioning system, and wherein said position of the or each drilling site reference point is determined by calculating the positions of said signal receivers.
13. A method as claimed in any preceding claim, wherein the orientation of said tool is determined relative to said earth coordinate system.
14. A method as claimed in any preceding claim, wherein the orientation of said tool is determined at a fixed instant in time.
15. A method as claimed in any preceding claim, wherein the orientation of said tool is determined as a function of time