SEDIMENT CORE-DRILLING PROCESS FOR SUBMARINE WIRE-LINE CORING DRILL RIG

• US 20200131853A1
• Filed: 12/31/2019
• Published: 04/30/2020
• Est. Priority Date: 08/13/2018
• Status: Active Grant

• Current Assignee: Hunan Sea Bull Geological Exploration Company Limited
• Original Assignee: Hunan University of Science and Technology
• Inventors: WAN, Buyan, JIN, Yongping, HUANG, Xiaojun, WANG, Jialiang
• Granted Patent: US 10,927,606 B2
• Time in Patent Office: Days
• CPC Class Codes: E21B 21/001 specially adapted for underwater drilling dual gradient drilling E21B21/082
• CPC Class Codes: E21B 25/18 the core receiver being specially adapted for operation under water
• CPC Class Codes: E21B 7/124 with underwater tool drive prime mover, e.g. portable drilling rigs for use on underwater floors

Abstract

Disclosed is a sediment core-drilling process for a submarine wire-line coring drill rig, including 1) lowering the drill rig; 2) drilling in a pressure-suction mode; 3) drilling in a rotation-pressure-suction mode; 4) cutting sediment cores; 5) recovering a core inner tube; 6) cleaning bottom of hole; 7) punching before adding a drill pipe; 8) lowering another core inner tube; 9) adding the drill pipe; 10) punching after adding the drill pipe; 11) repeating the steps 2)-10) until a given hole depth is reached; 12) recovering the drill pipe and a wire-line coring outer tube drilling tool; 13) recovering the submarine wire-line coring drill rig. The core-drilling process provided herein is suited to working conditions without mud lubrication and mud protection for hole wall. This invention has advantages of low disturbance and high efficiency in coring and is suitable for remote operation.

Claims

1. A sediment core-drilling process for a submarine wire-line coring drill rig, comprising:

(1) arranging a plurality of drill pipes and a plurality of inner tubes on a storage rack of a drill rig;

placing an inner tube that is hollow into an outer tube drilling tool;

lifting the drill rig into the sea;

leveling and supporting the drill rig by leveling-feet below the drill rig after the drill rig arrives at a surface of seabed sediments;

(2) switching a reversing valve to allow an inlet of a rodless cavity of a seawater suction cylinder to communicate with an inner hole of a drill pipe;

keeping the drill rig to drill in a pressure-suction mode;

passing force from a drilling power head to the drill pipe and the outer tube drilling tool to drive a thin-walled annular cutting blade at a font of the inner tube to cut into seabed sediments at a speed of 20±

2 mm/s; and

drawing seawater from the drill pipe by the seawater suction cylinder, wherein a volume of the drawn seawater is equal to a volume of a sediment core sample in the inner tube;

(3) switching on the drilling power head when a propulsive force of the drilling power head is not enough to drive the thin-walled annular cutting blade to cut into the seabed sediments at a reasonable speed only by pressure;

drilling and cutting into the seabed sediments under the conditions that the outer tube drilling tool is driven by the drill pipe to rotate and the inner tube is kept from rotating;

(4) raising the drilling power head to take the drill pipe, the outer tube drilling tool and the inner tube up to a position where the inner tube is able to be removed;

cutting sediment cores;

(5) using a winch to lower an extractor;

recovering the inner tube containing the sediment core sample to the drill rig;

separating an active drill pipe of the drilling power head from the drill pipe which is arranged below the active drill pipe;

raising the active drill pipe to a highest position;

placing the inner tube containing the sediment core sample on the storage rack of the drill rig;

(6) reconnecting the active drill pipe to the drill pipe which is arranged below the active drill pipe;

switching the reversing valve to allow a water outlet of a pump to communicate with the inner hole of the drill pipe;

switching on the pump and the drilling power head;

cleaning a bottom of the drilled hole by using the outer tube drilling tool to wipe stairs at the bottom of the drilled hole, wherein the stairs are formed since the inner tube protrudes from the outer tube drilling tool;

(7) using the pump to repeatedly perform punching;

wherein the punching is performed by raising the drilling power head to take the drill pipe and the outer tube drilling tool up 1.5-2.0 m from the bottom of the drilled hole followed by staying for 20-30 s and returning to the bottom of the drilled hole;

the punching is performed for 2-3 times when a drilling depth is less than 10 m, 3-4 times when the drilling depth is 10-30 m, or more than 5 times when the drilling depth is more than 30 m; and

a pump flow rate of the pump is 50-80 L/min during a downwards punching, and 100-150 L/min during an upwards punching;

(8) separating the active drill pipe from the drill pipe;

raising the active drill pipe to the highest position;

lowering another inner pipe that is hollow into the outer tube drilling tool;

(9) adding another drill pipe;

(10) using the pump to repeatedly perform punching, wherein the punching is performed for 1-2 times when the drilling depth is less than 10 m, 2-3 times when the drilling depth is 10-30 m, or 4 times when the drilling depth is more than 30 m;

the pump flow rate of the pump is 100-150 L/min during the downwards punching and the upwards punching;

(11) performing one or both of the steps (7) and (10) as needed;

determining if the core-drilling reaches a given hole depth;

if yes, proceeding to next step;

if no, repeating the steps (2)-(10);

(12) recovering the drill pipe and the outer tube drilling tool; and

(13) recovering the drill rig;

wherein the drill pipes, the inner tubes, the drill rig and the outer tube drilling tool are suitable for submarine wire-line coring;

the sediment core-drilling process adopts a coring apparatus, which comprises the drill rig, the plurality of drill pipes, the plurality of inner tubes and the outer tube drilling tool;

the drill rig is provided with the pump, the seawater suction cylinder and the reversing valve;

the pump is specifically a high pressure seawater washing pump;

the water outlet of the pump and the inlet of the rodless cavity of the seawater suction cylinder are communicated with an inner hole of the active drill pipe on the drilling power head of the drill rig via the reversing valve;

the reversing valve is switchable as needed to allow the inner hole of the drill pipe to communicate with the water outlet of the pump or the inlet of the rodless cavity of the seawater suction cylinder;

a rod cavity of the seawater suction cylinder is communicated with external seawater;

a top end of a first piston rod of the seawater suction cylinder is connected to a top end of a second piston rod of a propulsion cylinder of the drill rig via hinges;

an upper part of the inner tube is provided with a bearing combination which prevents a rotational motion of the outer tube drilling tool from being transmitted to the inner tube;

the thin-walled annular cutting blade is provided at a bottom of the inner tube;

the inner tube and the outer tube drilling tool are matched in a way that a part of the inner tube protrudes out from a center hole of the outer tube drilling tool, and the inner tube and the center hole of the outer tube drilling tool are arranged with clearance.

2. The sediment core-drilling process of claim 1, wherein in step (2), the drilling is performed in a pressure-suction mode at a drilling speed of 20±

2 mm/s.

3. The sediment core-drilling process of claim 1, wherein in step (3), the drilling power head starts to rotate when a propulsive force of the drilling power head is 60-80% of its own maximum propulsive force or is 3-4 tons;

and the drilling power head rotates at a rotational speed of 30-150 r/min and performs the drilling at a drilling speed of 20±

2 mm/s.

4. The sediment core-drilling process of claim 1, wherein in step (5), the winch lowers the extractor at a lowering speed of 18-25 m/min;

and the winch and the extractor are lifted to raise the inner tube at an ascending speed of 30-40 m/min.

5. The sediment core-drilling process of claim 1, wherein in step (6), the outer tube drilling tool cleans the bottom of the drilled hole at a speed of 20-25 m/min;

and the pump functions for 1-2 min at a pump flow rate of 50-80 L/min.

6. The sediment core-drilling process of claim 1, wherein in step (3), after the drilling power head starts to rotate, if a propulsion force of the drilling power head is reduced to less than 2 tons or less than 40% of its own maximum propulsive force, the drilling power head stops rotating and at this point the drilling switches back to the pressure-suction mode in step (2).