Communications – electrical: acoustic wave systems and devices – Underwater system
Reexamination Certificate
2001-07-23
2004-03-02
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Underwater system
Reexamination Certificate
active
06700835
ABSTRACT:
CONTENTS
Background of the invention.
Description of the related art.
Manual, diver-assisted metrology.
ROV-assisted metrology.
An overview of embodiments of the invention in a general context.
I: A “full Smartwire” device embodiment.
II: A “full Smartwire” method embodiment.
III: A “light” Smartwire device embodiment.
IV: A “mapping” method embodiment.
V: A “positioning” method embodiment.
Summary of the invention.
Brief description of the drawings.
Specification of a preferred embodiment of the invention, (with reference numerals referring to the drawings and the set of claims).
III: A “light”-Smartwire device embodiment.
II: A “Smartwire” method embodiment.
I: A “full” Smartwire device embodiment.
The subsea operation using the full device.
IV: A “mapping” method embodiment.
V: A “positioning” method embodiment.
Mathematical outline of the metrology calculations.
Computer implementation
Robustness of measurements.
Displacement along the pipe or hub.
Multiple hubs on a manifold.
Claims.
Abstract.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ROV-supported metrology device and a method for precision measurements of relative position and orientation of two or more objects (connection points) at the seabed, e.g. measuring distance and relative orientation of two pipe terminations subsea; two pipe flanges which are to be connected. To give an example, pipelines which are laid out ready on the seabed, shall be connected to a subsea manifold which becomes lowered to the seabed in a separate operation, see FIG.
2
. The manifold has pipeline receptors/hubs which are to be connected with the pipeline terminations via hard-piped so-called tie-in jumpers or spoolpieces. The position for the manifold on the seabed must be within a predefined area, but it is infeasible to predetermine this position precisely enough to allow for rigid prefabricated jumper spools made in steel. The pipelines shall be connected to the manifold's hubs via hard-piped jumper spools which must be tailored according to the local separations and relative orientations. Installation of flexible jumpers are not considered.
2. Description of the Related Art
Manual, Diver-assisted Metrology
Manual equipment for metrology of manifold and pipeline relative orientation and separation exists. Such measurements are made by divers on the site and later reproduced using the same equipment in a jig at a surface vessel or onshore. End pieces with the desired orientation and separation are arranged in the jig, and then a jumper spool is welded to the end pieces and tested. Thereafter the jumper spoolpiece is lowered down and placed between the manifold and the pipeline, and connected.
Disadvantages of Manual Metrology
Manual metrology performed by divers is inaccurate, time-consuming and expensive. Diver assistance is not feasible for the entire depth range considered, often more than 300 meters, down to more than 1500 meters. Generally, the use of diver assistance may be discouraged due to the general health hazard connected with offshore diving.
ROV-assisted Metrology
A system for ROV-assisted diverless metrology of subsea installations and subsequent hard-piping connection between a production manifold and pipelines, is described in
Offshore Technology Conference
, 1996
: OTC
8134: Sanjay K. Reddy et al: “
Diverless Hard
-
Pipe Connection Systems for Subsea Pipelines and Flowlines
”. The measurement system “Pre-Measurement Tool”, PMT, comprises a “Measurement Tool”, MT, with a landing/alignment pin arranged for a measurement receptacle on the termination to be measured. The MT is provided with a length metering cable, two inclinometers and horizontal and vertical angle readouts for the taut-cable orientation. A “Measurement Pin”, MP, with a landing pin arranged for a receptacle on the other termination to be measured is to be connected via the cable, all shown in FIGS. 5 and 10 of the article OTC 8134. The cable is drawn from the MT and hooked onto the MP by means of an ROV. The ROV then reads off the horizontal relative azimuth and vertical inclination of the cable relative to the MT. The ROV camera must be moved into position to view the inclinometers of the MT. The reading of the scales is conducted by an operator on the surface via the ROV camera.
Disadvantages of the Known ROV Metrology
The camera reading procedure is a separate source of error, as a parallax error will arise because of the orientation between the ROV camera and the scales to be viewed. Another problem with the existing diverless system is the time-consuming ROV-manoevering procedure to get the camera in position for reading off the angles. This measuring must be conducted at both terminations, thus doubling the effort of measuring the orientation of the two separations. The readings are, as with the diver-assisted method, mimicked at the surface in a “manifold end/pipeline end construction jig” having receptacles at either end for the PMT tools MT and MP, and height and inclination adjustment for the receptacles. Jumper spool endpieces are then mounted at either receptacle and a spool pipe with the desired length and orientation is then welded between the jumper spool endpieces sitting in the construction jig. The resulting jumper spoolpiece is then lowered and connected accordingly.
In addition to the parallax problems, another problem has been described as inconsistent pull force of the PMT tool, a pull which depends on the ROV hot stab pressure.
Thus it is desirable to have a system which overcomes the inaccuracy of reading the angles.
It is desirable to have a metrology system which overcomes the slow measurement procedure of the existing systems. It is also highly desirable to have a method and a device being independent of divers. It is also desirable to have a metrology system being independent of the the pull force of the hot stab of the ROV.
In addition, it is desirable to have a metrology system also being capable of conducting local mapping of the seabed and structures around a local reference system defined by e.g. a manifold frame which has been arranged at the seabed. It is equally desirable to have a system being capable of setting out markers, e.g. marker buoys, for indicating the future position for equipment which shall be arranged at the seabed in a reference system being relative to e.g. a manifold frame at the seabed. Arranging passive markers at the seabed according to one method of the invention eliminates the need for maintenance of transponder arrays.
The existing system requires that the wire is extended between two receptacle points before the angles are measured. The existing system is not capable of being used for determining positions on the seabed relative to one existing receptacle at e.g. a manifold's termination without having a first ROV to hold and tension the wire, and a second ROV to read off the angles at the receptacle's end of the wire. Thus it is desirable to have a metrology system capable of mapping and determining positions on the seabed relative to one existing receptacle at e.g. a manifold termination in one single tensioning-and-measuring operation with one single ROV.
An Overview of Embodiments of the Invention in a General Context
The invention is embodied both in a device and several methods for subsea metrology. There are several modes of operating different preferred embodiments of the invention:
I: A “full Smartwire” device embodiment;
II: A “Smartwire” method embodiment;
III: A “light” Smartwire device embodiment;
IV: A “mapping” method embodiment.
V: A “positioning” method embodiment.
On I and II: “Full Smartwire” Device and Smartwire Method Embodiment
A “full Smartwire” device and Smartwire method embodiment of the invention may be described with reference to
FIG. 1
c
and
FIG. 1
e
: An ROV may generally carry two metrology units. A so-called “reference” metrology unit is attatched to e.g. a manifold's (or a pipeline's) termination, e.g. a hub. A so-called “base” metrology unit is carried to a basically independent pipeline termi
Sparrevik Per
Walker Andy
Ward Nic
Den Norske Stats Oljeselskap A.S.
Foley & Lardner
Pihulic Daniel T.
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