Construction method for butt joint of offshore pipelines

Abstract

The invention discloses a construction method for offshore pipeline butt joint. The construction method comprises the following steps that whether a drill bit of a directional drill drills to an unearthed point or not is determined; when the drill bit drills to an unearthed point, preliminarily detecting an unearthed area of the drill bit by using magnetic detection equipment; a channel reserved by a drill rod of the directional drill is inflated by an air compressor at the starting point of the directional drill; when bubbles emerge from the head of the drill bit, a diver dives to find the accurate position of the drill bit and marks the drill bit; the drill bit continuously drills forwards until the drill bit is exposed out of the sea level; dragging a pipe dragging head of the bottom dragging laying pipe to an area near a drill bit from the other side far away from the directional drill, and hoisting by a crane on a barge connecting platform; the butt joint of the bottom dragging laying pipe and the drill bit is completed on the barge connecting platform, and then the connected bottom dragging laying pipe and the drill bit are placed at designated positions. According to the construction method for offshore pipeline butt joint, the butt joint operation can be rapidly completed.

Description

Technical Field

[0001] The invention relates to the field of laying of offshore water pipelines, in particular to a construction method for offshore pipeline docking. Background Art

[0002] In the process of laying water pipelines across the channel to the island in the sea, when different construction techniques are used for submarine pipeline laying, since two techniques are used to lay the water pipelines from both sides of the coast respectively, when the pipeline laying construction reaches the designated docking position, it is necessary to carry out offshore docking operations. Due to the complex seabed terrain and surrounding environmental conditions, it is difficult to achieve fast and accurate pipeline docking operations during offshore pipe laying.

[0003] Taking a submarine water pipeline project in Dongtou District, Wenzhou City as an example, the pipeline is laid by a combination of directional drilling and bottom dragging. When the pipeline is docked at sea, the directional drill is always about 15 meters below the seabed mud surface when drilling from the starting point on the coast. Only when the directional drill drills to the excavation point can the towing pipe head of the bottom drag tube be connected to the drill bit of the directional drill. Finally, the pipeline on one side of the bottom drag is dragged back with the directional drill bit to realize the laying of the pipeline.

[0004] Due to the long distance of the tidal flat section in the pipeline laying area, the large tidal range, the short construction period, and the crossing of the main channel, and the existence of submarine optical cables and aquaculture areas in the laying area, it is necessary to accurately locate the unearthed point of the directional drill bit. Since the directional drilling construction distance of this project is relatively long, about 2.8km, the accuracy of the drill rod positioning device of the directional drilling equipment itself has a certain deviation. The directional drill bit may be distributed below the seabed mud surface when it reaches the unearthed point. Conventional detection instruments are difficult to accurately determine the unearthed point of the directional drill bit, making the docking of the pipeline more difficult.

[0005] Since this project is an offshore pipeline laying construction, there are waterways and aquatic aquaculture areas in the sea area surrounding the pipeline laying, and the waterway is uninterruptedly navigable. The laying area is a tidal flat sea area with relatively turbid water quality and a lot of silt on the seabed. When the drill bit reaches the excavation point, if the drill bit continues to drill directly from the silt surface, the position is difficult to locate in a short time (if no other measuring equipment is used, and only the directional drill's own positioning system is used for positioning, the positioning is inaccurate and the error is large; if other measuring equipment is used, it can also be detected, but due to the large range, it takes about 2 to 3 days, which results in a large warning area and a long closure time), causing unforeseen impacts and dangers on the waterway passage and the aquaculture area (due to the difficulty in controlling the initial drilling accuracy of the drill bit, it is safer to reach the excavation point below the silt surface). Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a construction method for offshore pipeline docking. In view of the situation that when a directional drill and bottom dragging combination pipe laying construction is used, the excavation point of the drill bit is located below the seabed mud surface, which makes it difficult for detection instruments to accurately detect. The excavation point of the directional drill bit can be found quickly and accurately to achieve pipeline docking, thereby avoiding the impact of long-term construction on waterway traffic and offshore aquaculture areas due to the search for the drill bit.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: A construction method for offshore pipeline docking comprises the following steps: Step 1: Determine whether the drill bit of the directional drill has drilled to the excavation point; Step 2: When the drill bit reaches the excavation point, use magnetic detection equipment to preliminarily detect the excavation area of ​​the drill bit; Step 3: At the starting point of directional drilling, the air compressor inflates the reserved channel of the drill pipe of the directional drilling; when bubbles emerge from the head of the drill bit, the diver dives to find the exact position of the drill bit and marks it; Step 4: The drill bit continues to drill forward until it emerges from the sea level; the pipe-laying head of the bottom-drag pipe is dragged from the other side away from the directional drill to the area near the drill bit, and then lifted by the crane on the barge connection platform; Step 5: Complete the docking of the bottom-drag pipe and the drill bit on the barge connection platform, and then lower the connected bottom-drag pipe and the drill bit to the designated position.

[0008] In step 1, it is determined whether the drilling has reached the excavation point by means of mud pressure, thrust, and drill pipe length; when the drill bit reaches the excavation point, the drill bit is located in the mud layer above the seabed and below the seabed mud surface, and the distance between the drill bit and the seabed mud surface is 1 m to 2 m.

[0009] In step 2, when the drill bit reaches the excavation point and is located above the seabed and below the seabed mud surface, the barge connection platform conducts multiple round-trip measurements in accordance with the initially determined sea area of ​​the pipeline and perpendicular to the direction of the pipeline, with a measurement line spacing of 15m, and records the data information of each measurement.

[0010] In step 2, before detection, the magnetic detection device keeps a distance from the barge connection platform, the GPS locator is connected to the magnetic detection device, and the receiver of the GPS locator is fixedly installed at the towing point of the magnetic detection device.

[0011] In step 2, before the magnetic detection device detects, a buoy is tied to the towline of the magnetic detection device.

[0012] In step 3, when the air compressor is inflated, the drill bit slowly drills in and penetrates the mud layer and extends out of the mud surface on the seabed.

[0013] In step 3, when the diver dives, he further determines the distance and direction from the drill bit to the water surface, obtains the precise position of the drill bit, and at the same time ties a lifting belt to the drill bit.

[0014] In step 3, the specific time of inflation is determined according to the pressure during drilling, and inflation begins when the drilling is about to emerge from the seabed mud layer.

[0015] In step 5, after the drill bit is docked with the pipe head of the bottom-drag laying pipe and placed, the directional drill is used to pull back the bottom-drag laying pipe and guide the bottom-drag laying pipe to the position of the right directional drill to complete the pipeline laying.

[0016] A construction method for offshore pipeline docking comprises the following steps: The present invention provides a construction method for offshore pipeline docking, which has the following technical effects: 1) In view of the complex environmental conditions such as the presence of aquaculture areas and waterways at sea, and when the drill bit of the directional drill reaches the excavation point, the drill bit of the directional drill drills out of the seabed surface, but because it is still in the mudflat area and there is a certain thickness of silt on it, the present application, based on the positioning of the directional drill itself, relies on the magnetic field generated by the magnetic detection equipment to perform multiple round trip measurements along the pipe laying direction. On the one hand, the area where the drill bit is located can be preliminarily obtained, and the positioning range of the drill bit can be reduced; on the other hand, through the measurement of the magnetic detection equipment, the running trajectory of the directional drill bit can be further understood, the position of the final excavation point can be determined, and the accuracy of the excavation point of the directional drill bit below the silt surface can be further improved.

[0017] 2) Based on the positioning of the magnetic detection equipment, the air compressor is used to inflate the reserved channel of the drill rod of the directional drill with high pressure at the starting point of the directional drill. The bubbles in the drill bit of the directional drill can directly and accurately locate the excavation point of the drill bit of the directional drill, which can greatly shorten the positioning of the excavation point of the drill bit of the directional drill and improve the connection efficiency between the pipe head of the bottom drag pipe laying and the drill bit of the directional drill.

[0018] 3) After the directional drill bit confirms the excavation point and trajectory, the pipe-laying head of the bottom-drag pipe laying and the drill bit of the directional drill are respectively salvaged and hoisted to the barge connection platform, and the directional drill and the pipe-laying head are quickly connected on the platform, reducing the risk of offshore pipeline docking.

[0019] 4) In the prior art, when the drill bit reaches the excavation point, if the construction environment of the project is not very complex, there is no waterway or aquaculture area, and the drill bit is in the mud, the drill rig directly drills out of the mud interface, and relies on the directional drill's own positioning device system and divers to explore and determine the excavation point of the pipeline, which takes 2 to 3 days; the use of this method can greatly shorten the time, and the position of the pipeline can be determined and docked within 1 day, reducing the impact of the surrounding complex environment; especially in the face of complex environments such as tunnels and aquaculture areas, the effect is particularly obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a schematic diagram of the drill bit of the directional drill in the present invention drilling to the excavation point (the seabed mud layer is not drawn).

[0021] Figure 2 for Figure 1 Detail of the drill bit at the excavation site.

[0022] Figure 3 This is a schematic diagram of using an air compressor to blow bubbles in the present invention (the seabed mud layer is not shown).

[0023] Figure 4 This is a schematic diagram of the docking of the bottom drag-laid pipe and the drill bit in the present invention (the seabed mud layer is not shown).

[0024] Figure 5 It is a schematic diagram of directional drilling back towing bottom towing pipe laying in the present invention (the seabed mud layer is not shown).

[0025] In the figure: barge connection platform 1, directional drill 2, drill bit 3, drill rod 4, magnetic detection equipment 5, float 6, bottom drag pipe 7, pulley 8, ground a, sea level b, seabed surface c, entry point d, exit point f, docking point g, seabed mud surface v. DETAILED DESCRIPTION

[0026] like Figure 1-4 As shown, a construction method for offshore pipeline docking includes the following steps: Step 1: The drill bit 3 of the directional drill 2 determines whether it has reached the excavation point based on mud pressure, thrust, drill rod length, etc. When the drill bit 3 reaches the excavation point, the drill bit 3 is located above the seabed surface c and in the mud layer below the seabed mud surface v. The distance between the drill bit 3 and the seabed mud surface v is 1 m to 2 m. At this time, the magnetic detection equipment (magnetometer) is used to detect the excavation position of the drill bit 3.

[0027] Step 2: In order to reduce the impact of magnetic objects such as the generator at the barge connection platform 1 (survey ship) on the detection accuracy of the magnetometer, a professional survey ship is used, and the magnetometer is placed 20 meters away from the stern of the survey ship. The GPS locator is connected to the magnetometer, and the plane position is located by the GPS locator. In order to reduce the positioning error of the measurement data, the GPS receiver is fixedly installed at the towing point of the magnetic detection equipment 5 (magnetometer); in order to prevent the magnetic detection equipment from sinking to the bottom of the sea, a floating ball 6 is tied near the cable of the magnetometer.

[0028] Step 3: The survey vessel conducts multiple round trip measurements in the initially determined sea area of ​​the pipeline and perpendicular to the pipeline route, with a survey line spacing of 15m, and records the data information of each measurement.

[0029] Step 4: Use magnetic detection equipment to determine the preliminary position information of the drill bit 3, and preliminarily determine that the drill bit 3 is within the range of the magnetic detection area L (area L range is 10~15m); the drill bit 3 mainly relies on the magnetic detection equipment under the silt layer. After determining its preliminary position, the drill bit 3 slowly drills and passes through the silt layer and extends out of the seabed silt surface v. At the same time, at the starting point of the directional drilling 2, the air compressor inflates the reserved channel of the drill pipe 4 of the directional drilling; When bubbles emerge from the head of the drill bit 3 of the directional drill 2, the diver dives to find the drill bit 3, further determines the distance and direction from the drill bit to the water surface, obtains the precise position of the drill bit 3, and at the same time ties a lifting belt to the drill bit 3 to facilitate the subsequent lifting and docking of the drill bit 3.

[0030] In step 4, the specific time of inflation is determined according to the pressure during drilling, and inflation begins when the drilling is about to emerge from the seabed mud layer.

[0031] Step 5: The drill bit 3 of the directional drill at the starting point continues to drill forward until the drill bit 3 is exposed above the sea level b. After the pipe head of the bottom-drag laying pipe 7 is towed by the tugboat to the area near the drill bit 3, the pipe head of the bottom-drag laying pipe 7 is lifted by the crane on the barge connection platform 1, and the drill pipe, drilling tools, transfer gear and bottom-drag laying pipe 7 (main pipeline) are connected on the barge connection platform 1. The connected bottom-drag laying pipe 7 and the drill bit 3 are placed at the designated position by the crane on the barge connection platform 1. The docking is thus completed.

[0032] After the drill bit 3 is docked with the pipe head of the bottom-drag laying pipe 7 and placed, the directional drill 2 returns to drag the bottom-drag laying pipe 7 and leads the bottom-drag laying pipe 7 to the position of the right directional drill 2 to complete the pipeline laying.

Claims

1. A construction method for offshore pipeline docking, characterized in that: The following steps are involved: Step 1: Determine whether the drill bit (3) of the directional drill (2) has drilled to the excavation point; Step 2: After the drill bit (3) reaches the excavation point, a magnetic detection device (5) is used to preliminarily detect the excavation area of ​​the drill bit (3); Step 3: At the starting point of the directional drilling (2), an air compressor is used to inflate the reserved channel of the drill rod (4) of the directional drilling (2); when bubbles emerge from the head of the drill bit (3), a diver dives to find the exact position of the drill bit (3) and marks it; Step 4: the drill bit (3) continues to drill forward until the drill bit (3) is above the sea level; the pipe-laying head of the bottom-drag pipe-laying (7) is dragged from the other side away from the directional drill (2) to the area near the drill bit (3), and then lifted by the crane on the barge connection platform (1); Step 5: The bottom-drag laying pipe (7) and the drill bit (3) are connected on the barge connection platform (1), and then the connected bottom-drag laying pipe (7) and the drill bit (3) are placed down to the designated position.

2. A construction method for offshore pipeline docking according to claim 1, characterized in that: In step 1, it is determined whether the drilling has reached the excavation point by means of mud pressure, thrust and drill rod length; when the drill bit (3) reaches the excavation point, the drill bit (3) is located in a silt layer above the seabed and below the seabed silt surface, and the distance between the drill bit (3) and the seabed silt surface is 1m to 2m.

3. A construction method for offshore pipeline docking according to claim 1, characterized in that: In step 2, after the drill bit (3) reaches the excavation point, when the drill bit (3) is located above the seabed surface and below the seabed mud surface, the barge connection platform (1) performs multiple round trip measurements in accordance with the initially determined sea area of ​​the pipeline and perpendicular to the direction of the pipeline, with a measurement line spacing of 15m, and records the data information of each measurement.

4. A construction method for offshore pipeline docking according to claim 1, characterized in that: In step 2, before the magnetic detection device (5) detects, the magnetic detection device (5) and the barge connection platform (1) are kept at a distance, a GPS locator is connected to the magnetic detection device (5), and a receiver of the GPS locator is fixedly installed at the towing point of the towing cable of the magnetic detection device (5).

5. A construction method for offshore pipeline docking according to claim 1, characterized in that: In step 2, before the magnetic detection device (5) detects, a buoy (6) is tied to the towline of the magnetic detection device (5).

6. A construction method for offshore pipeline docking according to claim 1, characterized in that: In step 3, when the air compressor is inflated, the drill bit (3) slowly drills in and penetrates the mud layer and protrudes out of the mud surface on the seabed.

7. A construction method for offshore pipeline docking according to claim 1, characterized in that: In step 3, when the diver dives, he further determines the distance and direction from the drill bit to the water surface, obtains the precise position of the drill bit (3), and at the same time, ties a lifting belt to the drill bit (3).

8. A construction method for offshore pipeline docking according to claim 1, characterized in that: In step 3, the specific time of inflation is determined according to the pressure during drilling, and inflation begins when the drilling is about to emerge from the seabed mud layer.

9. A construction method for offshore pipeline docking according to claim 1, characterized in that: In step 5, after the drill bit (3) is docked with the pipe head of the bottom-drag laying pipe (7) and placed, the directional drill (2) is pulled back to drag the bottom-drag laying pipe (7) and guide the bottom-drag laying pipe (7) to the position of the right directional drill (2) to complete the pipeline laying.

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