Subsea Pipeline Tie-in/Piggable Wye Tie-in

Subsea Pipeline Tie-in

Subsea flowlines are used for the transportation of crude oil and gas from subsea wells, manifolds, off-shore process facilities, loading buoys, S2B (subsea to beach), as well as re-injection of water and gas into the reservoir. Achieving successful tie-in and connection of subsea flowlines is a vital part of a subsea field development.

1.  Vertical tie-in systems

Vertical connections are installed directly onto the receiving hub in one operation during tie-in. Since the Vertical Connection System does not require a pull-in capability, it simplifies the tool functions, provides a time efficient tie-in operation and reduce the length of Rigid Spools.

Vertical tie-in systems

Stroking and connection is carried out by the the Connector itself, or by the ROV operated Connector
Actuation Tool (CAT) System.

Vertical Tie-in assisted by V-CAT
2.  Horizontal tie-in systems

Horizontal Tie-in may be used for both firstend and second-end tie-in of both flowlines, umbilicals and Jumper spools. The termination head is hauled in to the Tie-in point by use of a subsea winch. Horizontal Tie-in may be made up by Clamp Connectors operated from a Tie-in tool, by integrated hydraulic connectors operated through the ROV, or by non-hydraulic collet connectors with assistance from a Connector Actuation Tool (CAT) and ROV. Horizontal connections leave the flowline/umbilical in a straight line, and is easy to protect if overtrawling from fishermen should occur.
Horizontal tie-in systems
Each tie-in and connection point requires some form of subsea base structure. This base may be on a single well structure, a template, a manifold, or other individual structure such as a Riser Base, a Pipeline End Manifold (PLEM), a Pipeline End Termination (PLET) or an In-line Tee.

Horizontal tie-in

Piggable Wye Tie-in

Piggable wyes have been used extensively in deepwater oil and gas pipeline operations to allow cleaning and inspection pigs and intelligent pigs access through main lines and the laterals that tie into them. Being able to run these state-of-the-art pigs through the wye improves the operating efficiency and the long-term integrity of the pipeline system. Although wyes improve operations on some levels, there are cases when operators need to run pigs counter to the normal flow direction in the lines. This presents no problem in a pipeline with no piggable wyes, but the internal profile at the wye fitting juncture does not permit reverse flow pigging.

Traditional piggable wye operations

Operators of oil and gas pipelines wage a constant battle against the harmful effects of internal corrosion, paraffin, and condensate accumulation. Commonly accepted practice dictates that the operator run pipeline pigs through the line. The pipeline product flow pushes these cleaning devices through the length of the line. The pig maintains contact with the internal wall of the pipe, pushing hydrates, paraffin, condensate, and other potentially harmful agents in advance of its passage through the pipeline. Corrosive elements are removed from the line at its termination point, enhancing the long-term integrity of the pipeline.

Pigging a single line is a straightforward process, requiring only that the pig be launched from one end and pushed the length of the line using a liquid or gas medium as the propelling force until it is captured in the pig receiver at the end of its journey. However, pigging lateral line tie-in connections requires that the operator pre-plan the installation of a piggable wye fitting in the main line during the construction process. A piggable wye is a Y-shaped fitting that has two inlets, one for each incoming pipeline, and a single outlet that merges the flow of the two converging pipelines. The two lines converge in the Y at an intersecting angle of 30°. This basic wye configuration was originally tested in the 1980s and has proven to be a reliable design.

Piggable wye

Bi-directional pigging

A recently developed product now allows pigs to run forward or backward through a wye. The Director Wye has the unique ability to accommodate reverse flow pigging. This new direction in piggable wye technology uses an internal diverter sleeve that is actuated from the exterior of the wye. The diverter can be actuated by an ROV or diver. The internal diverter sleeve rotates within the mainline bore of the wye to direct the pig.

The open position permits normal pigging operations that originate through the main line and/or the lateral line that converges into the single main line downstream of the wye. When the internal sleeve of the Director Wye is rotated to the closed position, the barrel of the sleeve closes the access port within the wye from the lateral line to the main line. Conventional pigging can still be conducted through the main line in the closed position, but the diverter sleeve allows a pig to run in the reverse flow direction through the main line as well. With the lateral line bore closed, the pig cannot jam in the juncture of the wye and cannot inadvertently enter the bore of the lateral line.

The directional wye achieves bi-directional pigging through the main line


The Dual Director Wye

The Director Wye had no more entered the market than an operator asked if the design could be modified to permit bi-directional pigging through both the main line and the lateral legs of the wye. The Dual Director Wye accomplishes this feat through the addition of a mirror-image internal diverter sleeve in the lateral leg of the fitting.

Like its predecessor, the Dual Director can be used as a standard wye with both diverter sleeves in the open position. When the main line diverter is operated to shut off access to the lateral opening, the Dual Director also permits bi-directional pigging through the main line. The differentiating feature of the Dual Director is that if the mainline sleeve closes the main line and the lateral line sleeve is open, bi-directional pigging can be accomplished through the lateral line. The design of the dual internal diverter sleeves and the actuation system is the same for both the Director Wye and Dual Director Wye.

The dual directional wye permits bi-directional pigging through both the main line and the lateral legs of the wye




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