Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Submerging – raising – or manipulating line of pipe or cable...
Reexamination Certificate
1999-10-13
2001-09-18
Bagnell, David (Department: 3673)
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Submerging, raising, or manipulating line of pipe or cable...
C015S104062, C073S064560, C137S317000, C405S170000, C405S158000
Reexamination Certificate
active
06290432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to a diverless process for tapping a pressurized subsea pipeline without removing the pipeline from service. This diverless process utilizes specialty clamping equipment, tapping equipment and remote operating vehicles for operating at water depths beyond that accessible by divers.
2. Prior Art
Various kinds of underwater pipeline work have been carried out using divers equipped with various tools. Deep water conditions entail high subsea pressure and dangerous conditions. Manned or diver equipped operations are not suitable if the pipeline is at a depth which is inaccessible by divers.
Remote operating vehicles perform visual and operational functions that are more limited than those functions performed by divers. To compensate for this limitation, processes must be developed to adapt the available technology to the work requirements. These processes are typically referred to as “diverless”. Developed diverless processes are easily adapted for use using divers and/or control from the sea surface in diver accessible water depths.
It has been proposed in the past to utilize a diverless underwater pipe tap system. De Sivry et al. (U.S. Pat. No. 4,443,129) discloses an example of a diverless underwater pipe tap system including a lifting device to engage and displace the pipe, a working platform installed vertically above the tapping region and various tools used to carry out operations including concrete stripping, ovality or roundness measurement, and a tapping operation. De Sivry et al. contemplates cutting out a section of the pipeline. There is no disclosure or suggestion of a tap procedure while the pipeline is under pressure and de Sivry would not be suitable for such an operation.
Likewise, various hot tap machines for tapping into a pipeline while the pipeline is pressurized have been disclosed. Reneau et al. (U.S. Pat. No. 4,223,925) discloses one example of a hot tap machine for an underwater pipeline. It is advantageous to perform work on the pipeline without interrupting the flow of liquids or gases therethrough.
It is also known to provide a remote operated subsea vehicle (ROV) controlled from the surface which includes thrusters or other mechanisms for propelling it through the water in response to a source of power at or controlled from the surface.
Brooks et al. (Re27,745) illustrates an example of a submersible wireline robot unit that may be controlled remotely.
None of the foregoing would be suitable for deep water conditions where the external subsea pressure is extreme.
Given that the life spans of certain deep water oil and gas developments will be coming to an end in the near future, there will be an increasing number of existing pipelines which have excess transport capacity, thereby leaving excess pipeline infrastructure in deep water locations.
If production from new fields can be tied into existing pipelines, then the investment in the pipeline can be spread out over more than one development. A diverless hot tap capability would allow the extension of pipelines from new fields to be connected to existing pipelines. This will reduce the overall length of the pipeline required to support a new field.
It would also be possible to lay new trunk lines into areas in order to support multiple future field developments which would use lateral pipelines without having to pre-install connection facilities and valves at predetermined locations along the pipeline.
Additionally, in deep water oil and gas developments, the cost of the pipeline infrastructure is estimated to be the majority of the cost of all of the installed subsea equipment.
As an alternative to diverless hot tap systems, it would be possible to take an existing line out of service, cut a section of the pipeline and bring it to the surface, install a valve, lower the section back to the bottom and reconnect with a suitable jumper. Such an approach is not only time-consuming but requires the pipeline to be out of service. It would also be possible to pre-install blind branch connection facilities in the pipeline for future tie-ins. A disadvantage is that a great number of branch facilities would have to be installed to cover all possible future tie-in locations, a procedure that would be both time-consuming and expensive.
Notwithstanding the foregoing, there remains a need for a diverless process of tapping a deep water subsea pipeline under high pressure without removing the pipeline from service.
SUMMARY OF THE INVENTION
The present invention is directed to a diverless process for tapping a deep water, pressurized subsea pipeline without removing the pipeline from service.
During the initial stages of the process, a pipeline will be located and a preliminary visual condition inspection will be conducted through use of cameras. Cameras would be incorporated in a remote operating vehicle which is known in various configurations. The pipeline will be inspected in the area of interest and a pipe section will be identified. If the pipe contains a longitudinal weld or seam, the location of the seam will be identified. It is preferred, but not required, to select a location where a weld seam is not cut out with the hole being bored into the pipe during the tapping operation. For seamless pipe, this step is ignored. Additionally, a location will be identified away from any circumferential weld so that no section of the hot tap fitting will be over a circumferential field weld joint.
Soil will be excavated from underneath the pipeline at the chosen location to allow unrestricted installation of the tools. The remote operating vehicle will be utilized to remove soil from underneath the pipeline and create a hole or an exposed area. The pipeline will be cleaned using a brush and/or a low pressure water jet powered by the remote operating vehicle.
Once the foregoing preliminary procedures have been completed, a measurement tool will be lowered from the surface on to the pipeline in order to check circumferential roundness or ovality of the pipeline while simultaneously checking the straightness of the pipeline. The measurement tool will be powered by the remote operating vehicle.
A pair or more of pipe lift frames will be lowered from the surface to straddle the pipeline, the lift frames spaced as appropriate, along the pipeline axis, and on opposing sides of the hot tap location. Each pipe lift frame will include a pair of platforms containing screw or hydraulic mechanisms, located on each side of the pipeline, which are used to position and raise or lower a pipeline lifting tong.
Between the pair of platforms is a transverse beam from which extends the pipe tong. Each pipe tong may be positioned transversely to the axis of the pipeline and lowered onto the pipeline using the hydraulic system from the remote operating vehicle or a mechanical screw. Each lift platform may also include a mud mat which is adjustable with respect to the lift frame.
The lift frames will position the pipeline to a desired height in an even and incremental sequence by the aforementioned mechanical or hydraulic mechanisms contained in each of the platforms thereby creating an upward net force. The mechanisms are powered by the remotely operated vehicle (ROV) in the same manner as the aforementioned tong and its associated manipulation mechanism. Subsequently, the pipe tongs are mechanically locked onto the pipeline in an elevated position.
After lifting the pipeline in preparation for installation of the hot tap fitting clamp assembly, around the pipeline, the measurement tool will again be utilized to check the circumferential roundness or ovality and straightness of the pipeline.
In the event the pipeline contains a longitudinal weld and it is deemed necessary to remove the protruding surface of the weld, a weld bead removal tool will be lowered from the surface and landed onto the pipeline. The remote operating vehicle will be docked into the weld bead removal tool and hydraulic and control connections will be made. The weld bead removal tool w
Cross Donald W.
Decker Larry
Exley Gern D.
Hicks David J.
McCoy Richard W.
Bagnell David
Head Johnson & Kachigian
Mayo Tara L.
Williams Field Services Gulf Coast Company, L.P.
LandOfFree
Diverless subsea hot tap system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Diverless subsea hot tap system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diverless subsea hot tap system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2442124