Patent EA-001885-B1 (EA)
Title: Process for seabed bore drilling using one riser
Inventor: THOMAS PIERRE-ARMAND
IPC: E21B33/076
Filed: 1999-08-10
Abstract: 1. A process for seabed bore drilling using one riser, the free end of which is fixed to a semi-submerged platform, adopted for oil deposit operation from a cluster of well-boring points, characterized in that the platform is anchored for keeping it unmovable in the area above the deposit, the riser is mounted connecting the platform to the seabed for drilling in the first point, the free end of the riser from the first point is disengaged and kept it submerged, the free end of the riser is moved to connect to a second point for well drilling keeping the platform unmovable and start drilling in the second point. 2. The process as claimed in claim 1, wherein the step of moving the free end of the riser relative to the seabed involves the previous establishment of at least one fixed point on the seabed, positioning means of traction between the free end of the riser and the or each fixed points and pulling the free end of the riser using the means of traction to move the free end of the riser relative to the seabed to the second point. 3. The process as claimed in claim 2, wherein three nonaligned fixed points are anticipated to which the means of moving the free end are connected providing moving the end under the action of three non axial forces. 4. The process as claimed in claim 2, wherein when moving the free end of the riser relative to the seabed the end is connected to at least one mooring, the other end is fixed to the seabed at such points, that the first and the second drilling points are in positioned in one or each sector of circumference described by one or each mooring. 5. The process as claimed in claim 4, wherein the free end of the riser is connected to two moorings fixed to the seabed on both sides of the segment limited by the first and the second drilling points, the length of moorings is selected so that said segment is along the axis of biconvex sector formed by crossing of two sectors of circumference described by moorings. 6. The process as claimed in claims 2 to 5, wherein the means of traction the free end of the riser are transported to the seabed using a submersed means and after delivering to the seabed they are fixed to one or each corresponding point from one side and are fixed to the free end of the riser on the other side. 7. The process as claimed in claims 2 to 6, wherein one or each fixing point is provided with a device capable to move over the seabed and having means to fix to the seabed in one or each fixing point, said means is moved to the seabed at a distance from the drilling point, selected as a fixing point to the selected point, and at that point the device is anchored. 8. The process as claimed in claims 2 to 6, wherein one or each fixing point is marked on the seabed before the platform is anchored above the deposit, and one or each fixing points are positioned under the platform. 9. The process as claimed in claim 8, wherein a plurality of fixing points are selected and connected with ties on the seabed between two fixing points around the zone of the seabed where a cluster of drilling points is positioned. 10. The process as claimed in any of the preceding claims, wherein a means of retrieving the free end of the riser to its initial position is provided between the free end of the riser and the seabed. 11. The process as claimed in claim 10, wherein the free end of the riser is returned by the means of retrieving to the center of the drilling points. 12. The process as claimed in claim 10 or 11, wherein the means of retrieving comprises a rope sliding in a case positioned and fixed in the riser, the rope is fixed to the seabed and to the platform, and the free end of the riser is retrieved to the point of fixing the rope to seabed by pulling the rope in the case from the platform.