Arrangement for preventing collection of debris and cuttings on the top of a riser closure device
An arrangement and a method for preventing collection of debris on or for removing debris, such as cuttings, from the top of a closed riser sealing device ( 215 ) in a subsea riser ( 1 ). The arrangement comprises a flushing line and at least one flushing fluid inlet ( 294 ) to direct a jet of flushing fluid into said riser ( 1 ). The inlet ( 294 ) directs flushing fluid into a space in the riser ( 1 ) immediately above said closing element. The invention also relates to a swirl element ( 351 ) located immediately above the riser sealing device ( 215 ) and being rotationally coupled to a drillstring ( 11 ).
1 . An arrangement comprising:
a riser defining a longitudinal bore;
a riser sealing element;
wherein the riser sealing element has a closed position, the closed position either closing the longitudinal bore around a string arranged within the riser or completely sealing the longitudinal bore;
wherein the arrangement is adapted to prevent collection of debris on or for removing debris from the top of the riser sealing element when the riser sealing element is in the closed position;
a flushing line and a plurality of fluid flushing inlets into the longitudinal bore, the plurality of fluid flushing inlets directing a jet of flushing fluid into the longitudinal bore immediately above the closed riser sealing element wherein the flushing line branches off from a boost line extending along the riser; and
wherein the plurality of fluid flushing inlets are connected to a distribution line, which distribution line is branched off from the boost line.
2 . The arrangement of claim 1 , wherein the plurality of fluid flushing inlets directed at an acute angle relative to the circumference of the riser.
3 . The arrangement of claim 1 , wherein the plurality of fluid flushing inlets for are arranged around the circumference of the riser and immediately above the closed riser sealing element.
4 . The arrangement of claim 1 , wherein the distribution line is a ring line encircling the riser.
5 . The arrangement of claim 1 , wherein the plurality of fluid flushing inlets are set at an acute angle relative to the longitudinal axis of the riser.
6 . The arrangement of claim 1 , further comprising a debris agitating device in the form of a fluid directing element shaped to direct particles towards the periphery of the riser.
7 . The arrangement of claim 6 , wherein the fluid directing element is conical.
8 . The arrangement according to claim 1 , wherein the debris comprises cuttings.
9 . The arrangement of claim 1 , wherein the external line is a boost line.
10 . An arrangement for preventing collection of debris on or for removing debris from the top of a closed riser sealing device in a subsea riser, comprising a swirl element located immediately above the riser sealing device, the swirl element being rotationally coupled to a drill string but being allowed to slide axially with respect to the drill string.
11 . The arrangement of claim 10 , wherein the swirl element is equipped with an elastic material part providing friction against the drill string and the elastic material part having a sufficient flexibility to let varying diameters of a drill pipe pass through.
12 . The arrangement according to claim 10 , wherein the swirl element has a weight that holds the swirl element against the riser sealing element, or that is mechanically attached to the riser sealing element in a way that allows the swirl element to rotate.
13 . The arrangement of claim 10 , wherein the swirl element is attached to a fluid directing element.
14 . The arrangement of claim 10 , wherein the swirl element comprises at least one fin.
15 . A method for preventing collection of debris on or for removing debris from the top of a closed closing element in a subsea riser, wherein the debris is agitated by a jet of fluid being injected into a space in the riser immediately above the closing element, to stir up any debris from the top of the closing element, wherein the fluid to produce the jet is injected through a flushing line that branches off from an external line extending along the riser, wherein the agitation is assisted by a swirl element rotationally coupled to a drill string.
16 . The method of claim 15 , wherein the jet is directed at an acute angle relative to the circumference of the riser.
17 . The method of claim 15 , wherein a jet is injected into the riser at multiple locations along the circumference of the riser.
18 . The method of claim 15 , wherein the external line is a boost line.