Drilling system and method of submarine drilling rig

1. A drilling system of a submarine drilling rig, comprising: a barge, an umbilical cable, a submarine device and a drilling device;

wherein the barge is loaded with an electric-hydraulic control device and a mud treatment device; the electric-hydraulic control device and the mud treatment device are respectively connected to the submarine device through the umbilical cable, and the barge is used as a mud and cement circulation base station as well as a control center;

the submarine device comprises a submarine traveling device, a coiled tubing roller, a derrick, a centralized valve seat, an iron roughneck, a wellhead device and a casing rack, wherein the coiled tubing roller, the derrick, the centralized valve seat, the iron roughneck, the wellhead device and the casing rack are loaded to the submarine traveling device; the centralized valve seat is connected to the umbilical cable for shunting mud, cement and electrical signals conveyed by the umbilical cable; the coiled tubing roller is used to store and release coiled tubing; the derrick is installed above the wellhead device, respectively matched with the iron roughneck and the casing rack for replacing drill bits and conveying and withdrawing casings; and

the drilling device is connected to the coiled tubing for performing drilling operations.

2. The drilling system of a submarine drilling rig according to claim 1 , wherein the submarine traveling device is provided with at least two groups of track wheels.

3. The drilling system of a submarine drilling rig according to claim 2 , wherein the derrick comprises a drilling derrick and a casing running derrick, the drilling derrick is provided with an injection head for receiving coiled tubing from the coiled tubing roller and conveying coiled tubing to the wellhead device, and the casing running derrick is provided with a casing installation and dismantling device for grabbing a casing from the casing rack for casing running operations.

4. The drilling system of a submarine drilling rig according to claim 2 , wherein the casing installation and dismantling device is electrically driven.

5. The drilling system of a submarine drilling rig according to claim 2 , wherein the drilling device comprises a downhole drilling permanent magnet motor and a drill bit, and an end of the downhole drilling permanent magnet motor is connected to the coiled tubing to drive the drill bit to perform drilling operations.

6. The drilling system of a submarine drilling rig according to claim 1 , wherein the submarine traveling device comprises a water filling and draining buoyancy tank and a power positioning device;

the water filling and draining buoyancy tank is used to achieve floating and sitting at the bottom by filling with water and draining; and

the power positioning device is used to provide power for the submarine traveling device to drive the submarine traveling device to travel and position the submarine traveling device.

7. The drilling system of a submarine drilling rig according to claim 6 , wherein the derrick comprises a drilling derrick and a casing running derrick, the drilling derrick is provided with an injection head for receiving coiled tubing from the coiled tubing roller and conveying coiled tubing to the wellhead device, and the casing running derrick is provided with a casing installation and dismantling device for grabbing a casing from the casing rack for casing running operations.

8. The drilling system of a submarine drilling rig according to claim 6 , wherein the casing installation and dismantling device is electrically driven.

9. The drilling system of a submarine drilling rig according to claim 6 , wherein the drilling device comprises a downhole drilling permanent magnet motor and a drill bit, and an end of the downhole drilling permanent magnet motor is connected to the coiled tubing to drive the drill bit to perform drilling operations.

10. The drilling system of a submarine drilling rig according to claim 1 , wherein the derrick comprises a drilling derrick and a casing running derrick, the drilling derrick is provided with an injection head for receiving coiled tubing from the coiled tubing roller and conveying coiled tubing to the wellhead device, and the casing running derrick is provided with a casing installation and dismantling device for grabbing a casing from the casing rack for casing running operations.

11. The drilling system of a submarine drilling rig according to claim 10 , wherein the casing installation and dismantling device is electrically driven.

12. The drilling system of a submarine drilling rig according to claim 10 , wherein the drilling device comprises a downhole drilling permanent magnet motor and a drill bit, and an end of the downhole drilling permanent magnet motor is connected to the coiled tubing to drive the drill bit to perform drilling operations.

13. The drilling system of a submarine drilling rig according to claim 1 , wherein the casing installation and dismantling device is electrically driven.

14. The drilling system of a submarine drilling rig according to claim 13 , wherein the drilling device comprises a downhole drilling permanent magnet motor and a drill bit, and an end of the downhole drilling permanent magnet motor is connected to the coiled tubing to drive the drill bit to perform drilling operations.

15. The drilling system of a submarine drilling rig according to claim 1 , wherein the drilling device comprises a downhole drilling permanent magnet motor and a drill bit, and an end of the downhole drilling permanent magnet motor is connected to the coiled tubing to drive the drill bit to perform drilling operations.

16. The drilling system of a submarine drilling rig according to claim 15 , wherein an output end of the downhole drilling permanent magnet motor is connected to the drill bit.

17. The drilling system of a submarine drilling rig according to claim 1 , wherein the submarine traveling device and the coiled tubing roller are driven by a hydraulic motor or driven electrically.

18. The drilling system of a submarine drilling rig according to claim 17 , wherein the centralized valve seat and the iron roughneck are placed in a closed watertight caisson.

19. The drilling system of a submarine drilling rig according to claim 17 , wherein the submarine traveling device and the coiled tubing roller are driven by a hydraulic motor or driven electrically.

20. A drilling method of a submarine drilling rig, comprising the following steps of:

loading an umbilical cable, a submarine device and a drilling device to a barge and transporting to a designated sea area;

placing down the submarine device and the drilling device to a seabed by the barge, and controlling a submarine traveling device by an electric-hydraulic control device to move to a designated position;

starting a mud treatment device to perform mud circulation treatment during drilling and casing running operations;

controlling, by the electric-hydraulic control device, a casing installation and dismantling device to grab a casing from a casing rack to complete surface layer casing running; then controlling an iron roughneck to complete drill bit replacement; then controlling a downhole drilling permanent magnet motor to drive a drill bit to complete drilling operations; and

controlling, by the electric-hydraulic control device, the mud treatment device to convey cement through the umbilical cable to complete cementing operations.