阅读说明：本技术 一种深水单点系泊中水浮筒回收下放系统及方法 (system and method for recycling and putting down reclaimed water buoy in deep water single-point mooring ) 是由 张人公 高原 高超 刘耀江 苗春生 林守强 孙锟 郑申奎 邓善博 张云鹏 于 2019-01-28 设计创作，主要内容包括：本发明涉及一种深水单点系泊中水浮筒回收下放系统及方法,该方法包括：锚系处理船上的吊机将中水浮筒回收索具下放入水至中水浮筒上的卸扣附近,ROV辅助将中水浮筒回收索具与卸扣连接；FPSO下放ACT链,ROV连接锚系处理船上的绞车至ACT链,绞车回收ACT链及第一上锚缆至甲板,拆除ACT链；绞车继续回收第一上锚缆,直至中水浮筒浮出水面；将中水浮筒回收索具连接至锚系处理船上的吊机,进行中水浮筒吊装；将中水浮筒吊装回收上船并固定后,拆除中水浮筒,并存放至中水浮筒储存支架上。本发明能够实现在FPSO在位不停产的情况下进行作业,工作量大大减少,提高了施工效率及可靠性,减少了油田的产量损失；利用ROV辅助下水作业,减少了施工成本。(the invention relates to a system and a method for recovering and lowering a reclaimed water buoy in deep water single-point mooring, wherein the method comprises the following steps: a crane on the anchor system treatment ship puts the reclaimed water buoy recovery rigging into water to be close to a shackle on the reclaimed water buoy, and the ROV is used for connecting the reclaimed water buoy recovery rigging with the shackle in an auxiliary manner; the FPSO lowers the ACT chain, the ROV connects a winch on the anchor system processing ship to the ACT chain, the winch recovers the ACT chain and a first upper anchor cable to a deck, and the ACT chain is dismantled; the winch continues to recover the first upper anchor cable until the reclaimed water buoy floats out of the water surface; connecting the reclaimed water buoy recovery rigging to a crane on the anchoring system treatment ship to hoist the reclaimed water buoy; and after the reclaimed water buoy is hoisted, recovered and loaded on the ship and fixed, the reclaimed water buoy is detached and stored on the reclaimed water buoy storage bracket. The invention can realize the operation under the condition that the FPSO is not stopped in place, greatly reduces the workload, improves the construction efficiency and reliability and reduces the yield loss of the oil field; and the ROV is used for assisting in launching operation, so that the construction cost is reduced.)

1. a deepwater single-point mooring reclaimed water buoy recovery and lowering system is characterized by comprising an anchor system treatment ship (4), an ROV, a reclaimed water buoy recovery rigging (3), a cable joint limiting device (6) and a reclaimed water buoy storage support (7);

a crane and a winch are arranged on the anchoring system processing ship (4);

the crane is used for lowering the reclaimed water buoy recovery rigging (3) into water to the vicinity of a shackle (131) on a reclaimed water buoy (13), and connecting the reclaimed water buoy recovery rigging (3) to the shackle (131) with the aid of an ROV; and the hoisting and recovering device is used for connecting the reclaimed water buoy (13) to the reclaimed water buoy recovery rigging (3) to hoist and recover the reclaimed water buoy (13) after the reclaimed water buoy (13) floats out of the water surface;

The winch is used for being connected to an ACT chain rigging (111) on an ACT chain (11) through the assistance of an ROV to recover the ACT chain (11) and a first upper anchor cable (121);

The cable joint limiting device (6) is used for fixing an upper anchor cable upper cable joint (123) of the first upper anchor cable (121) so as to remove the connection between the ACT chain (11) and the first upper anchor cable (121);

and the middle water buoy storage bracket (7) is used for storing the detached middle water buoy (4).

2. Deep water single point mooring greywater buoy retrieval lowering system according to claim 1, characterised in that the greywater buoy retrieval rigging (3) comprises a first annular harness (31), a first ROV hook (35), a second annular harness (33), and a tie-up strap (32);

One end of the first annular hanging strip (31) is connected with the first ROV hook (35), and a hard guide rod is arranged on the first annular hanging strip (31) along the length direction of the first annular hanging strip;

one end of the second annular hanging strip (33) penetrates through the first ROV hook (35) to be sleeved on the first annular hanging strip (31) and the hard guide rod, and is bound and fixed through the binding strip (32).

3. Deep water single point mooring greywater buoy retrieval lowering system according to claim 2, characterised in that the greywater buoy retrieval rigging (3) further comprises a third loop harness (34) connected to the other end of the second loop harness (33); the binding band (32) is made of a material which is easy to break by pulling.

4. the deepwater single-point mooring normal water buoy recovery lowering system as claimed in claim 2, further comprising a normal water buoy floating ball rigging (5), wherein the normal water buoy floating ball rigging (5) comprises a second ROV hook (51), a main connecting rope (52) connected with the second ROV hook (51), and a plurality of floating balls (53) connected with the main connecting rope (52).

5. The deepwater single-point mooring normal water buoy recovery lowering system as claimed in claim 1, further comprising a normal water buoy lowering rigging (9) for cooperating with a crane to lower the normal water buoy (13) into water; the reclaimed water buoy lowering rigging (9) is mounted on the shackle (131) in a return cable mode.

6. A method for recovering and lowering a deepwater single-point mooring reclaimed water buoy is characterized by comprising the following steps:

s1, connection of the reclaimed water buoy recovery rigging (3):

s11, connecting the reclaimed water buoy recovery rigging (3) with a crane hook on an anchoring treatment ship (4), and lowering the reclaimed water buoy recovery rigging (3) into water by using a crane to be close to a shackle (131) on a reclaimed water buoy (13);

S12, connecting the reclaimed water buoy recovery rigging (3) with the shackle (131) by using ROV assistance;

s2, recovering ACT chain (11) and first upper anchor cable (121):

S21, lowering the ACT chain (11) by an FPSO (2), connecting a winch on the mooring system processing vessel (4) to an ACT chain rigging (111) on the ACT chain (11) by an ROV, recovering the ACT chain (11) and the first upper anchor cable (121) to a deck by using the winch on the mooring system processing vessel (4), fixing an upper anchor cable upper cable joint (123) of the first upper anchor cable (121) on the mooring system processing vessel (4) by using a cable joint limiting device (6), and dismantling the ACT chain (11);

s22, the winch continues to recover the first upper anchor cable (121) until the middle water buoy (13) floats out of the water surface;

s3, connecting the reclaimed water buoy recovery rigging (3) to a crane on the anchoring treatment ship (4) for hoisting a reclaimed water buoy;

S4, after the reclaimed water buoy (4) is hoisted, recovered and fixed on the ship, the reclaimed water buoy (4) is detached and stored on the reclaimed water buoy storage support (7).

7. the deepwater single-point mooring greywater buoy retrieval lowering method as claimed in claim 6, characterized in that the greywater buoy retrieval rigging (3) comprises a first annular harness (31), a first ROV hook (35), a second annular harness (33), a third annular harness (34), and a lashing strap (32), the lashing strap (32) being made of a material that is easily torn and broken;

one end of the first annular hanging strip (31) is connected with the first ROV hook (35), and a hard guide rod is arranged on the first annular hanging strip (31) along the length direction of the first annular hanging strip;

One end of the second annular sling (33) penetrates through the first ROV hook (35) to be sleeved on the first annular sling (31) and the hard guide rod, and is bound and fixed through the binding belt (32);

The other end of the second annular hanging strip (33) is connected with the third annular hanging strip (34);

the step S11 includes:

connecting the end of the first endless sling (31) remote from the first ROV hook (35) to a crane hook on the mooring handling vessel (4);

the step S12 includes:

Connecting the third looped strap (34) with the first ROV hook (35) through the shackle (131) using an ROV;

A crane recovery sling, which pulls and breaks a binding belt (32) bound between the first annular sling (31) and the second annular sling (33), so that the second annular sling (33) moves along a hard guide rod to pass through the first ROV hook (35);

the crane continues to recover the hanging strip, the second annular hanging strip (33) is installed in the shackle (131), and after the installation is completed, the crane is lifted upwards to tighten the knot of the second annular hanging strip (33) on the shackle (131);

Removing the connection of the third looped strap (34) to the first ROV hook (35) with an ROV.

8. the deepwater single-point mooring reclaimed water buoy recovery lowering method as claimed in claim 7, further comprising a reclaimed water buoy floating ball rigging (5), wherein the reclaimed water buoy floating ball rigging (5) comprises a second ROV hook (51), a main connecting rope (52) connected with the second ROV hook (51), and a plurality of floating balls (53) connected with the main connecting rope (52);

Further included after step S12 is:

S13, the main connecting rope (52) is bound along a hanging strip of a crane and then put into water, the second ROV hook (51) is connected with the third annular hanging strip (34) through an ROV, and the hanging strip is recovered by the crane;

the step S3 further includes:

deck operators salvage the reclaimed water buoy floating ball rigging (5) and pull back to the anchoring system treatment ship (4).

9. The deepwater single-point mooring normal water buoy recovery lowering method as claimed in claim 6, further comprising, before step S1:

S0, the ROV carries hydraulic polishing brush into water to clean marine life on the shackle (131).

10. The deepwater single-point mooring normal water buoy recovery lowering method as claimed in claim 6, further comprising, after step S4:

S5: -recovering the first lower anchor line (151), replacing and laying the second lower anchor line (152):

S51, a crane lifts the connecting plate (14) connected between the first upper anchor line (121) and the first lower anchor line (151), the lower anchor line upper cable joint (153) of the first lower anchor line (151) or the upper anchor line lower cable joint (124) of the first upper anchor line (121) is placed in a cable joint limiting device (6) to be fixed, and the connection between the first upper anchor line (121) and the first lower anchor line (151) and the connecting plate (14) is removed;

S52, removing the cable joint stopper (6), starting to retrieve the first lower anchor line (151) until the part of the heavy chain (16) passes through the shark jaw, and fixing the heavy chain (16) using the shark jaw;

s52, removing the connecting plate (14) connected between the heavy chain (16) and the first lower anchor line (151), and connecting the heavy chain (16) and the second lower anchor line (152);

S53, a crane lifts the connecting plate (14) between the counterweight chain (16) and the second lower anchor cable (152) and puts water into the connecting plate;

s54, laying the second lower anchor cable (152);

S6: installing and lowering the reclaimed water buoy (13):

S61, lifting a guide pile when laying the lower anchor cable upper cable joint (153) of the second lower anchor cable (152), installing a cable joint limiting device (6) at the guide pile by deck operators, fixing the lower anchor cable upper cable joint (153) by using the cable joint limiting device (6), and detaching the connection between a winch and the lower anchor cable upper cable joint (153);

s62, connecting the second lower anchor line (152) and the second upper anchor line (122) with a connecting plate (14) respectively;

s63, pulling back a winch belt by a winch of the second upper anchor cable (122), and pulling the connecting plate (14) to a preset position in the ship;

s64, mounting a reclaimed water buoy mounting bracket (8) by deck workers according to the position of the connecting plate (14);

s65, deck operation personnel install a reclaimed water buoy lowering rigging (9) on the shackle (131) in a return cable mode, and hang the reclaimed water buoy (13) from the reclaimed water buoy storage bracket (7) to the reclaimed water buoy mounting bracket (8);

s66, connecting the reclaimed water buoy (13) with the connecting plate (14) by deck operators;

s67, hoisting the reclaimed water buoy (13) by a crane, removing the reclaimed water buoy mounting bracket (8) by deck workers, and lowering the reclaimed water buoy (13) into water by using the crane matched with a winch of the second upper anchor cable (122);

s68, after the top of the reclaimed water buoy (13) enters water, removing the connection between the reclaimed water buoy lowering rigging (9) and a crane hook from a deck, and drawing back the reclaimed water buoy lowering rigging (9);

S7, laying a second upper anchor cable (122);

S71, the mooring system processing ship (4) starts to lay the second upper anchor line (122) until the upper anchor line connector (123) of the second upper anchor line (122) reaches the stern;

s72, fixing the upper anchor cable upper cable joint (123) by using the cable joint limiting device (6), connecting the ACT chain (11) with the second upper anchor cable (122), removing the cable joint limiting device (6), and lowering the upper anchor cable upper cable joint (123) by using a crane for assistance;

S8: an ACT chain (11) is laid and fixed;

S81, placing the ACT chain (11) until the tail end of a chain ring of the ACT chain (11) approaches the stern, fixing the ACT chain (11) by using shark pincers, connecting the ACT chain (11) with a lifting cable (10) on an FPSO (2), continuing to place the ACT chain (11) until the load is completely transferred to the FPSO (2), and removing the connection between a crane hook and an upper cable joint (123) of the upper lowering anchor cable by using an ROV underwater;

s82, the FPSO (2) recovers the lifting cable (10) until the ACT chain (11) passes through the ACT chain hole on the FPSO (2), and the chain stopper is closed.

Technical Field

the invention relates to a mooring system, in particular to a system and a method for recovering and lowering a reclaimed water buoy in deep water single-point mooring.

background

an internal turret single point mooring system is a single point mooring system widely used in floating production, storage and offloading vessels (FPSO) and may typically comprise 6-12 anchor legs which are identical in their structural configuration. Mooring anchor legs for deepwater (water depth of more than 300 m) generally comprise an adjusting chain (ACT chain), an upper anchor cable, a reclaimed water buoy, a connecting plate (a triangular plate or a four-corner plate), a lower anchor cable, a heavy chain, a lying cable, anchor piles and the like. Different from a common shallow water mooring system, the deep water mooring system is divided into an upper anchor cable and a lower anchor cable by one anchor cable in an anchor leg component and is connected through a middle water buoy. In each component of the anchor leg, the upper anchor cable and the lower anchor cable are in a state of repeated contraction and stretching for a long time, the probability of damage is relatively maximum after years of operation, when the damage reaches a certain degree, the maximum safe load value borne by the anchor cables is lower than the safe load value required in the design of a single-point mooring system, and a new anchor cable needs to be replaced to ensure the safety of the FPSO. In addition, the design life of a single point mooring system is typically 10-20 years, and after the end of the life, if the oil field reserves are still in production beyond the estimated reserves at the beginning of the development, the entire single point mooring anchor leg needs to be replaced to ensure production safety during the life of the FPSO, including the replacement of the upper and lower anchor lines.

In the replacement work of the FPSO anchor cable in place, the reclaimed water buoy is connected between the upper anchor cable and the lower anchor cable, so that the protective recovery and the lowering of the reclaimed water buoy are important components in the anchor leg recovery and lowering procedures. Before the anchor cable is recovered, a recovery rigging connected with a reclaimed water buoy is needed to be arranged underwater. At present, an operator usually completes the installation of the reclaimed water buoy recovery rigging in a saturated diving mode, and the operation mode increases the construction cost, has low working efficiency, has higher requirement on the operator and is unsafe.

Disclosure of Invention

the invention aims to solve the technical problem that in order to overcome the defects in the prior art, the invention provides a system and a method for recovering and lowering a deepwater single-point mooring reclaimed water buoy, which can operate under the condition that an FPSO (floating production storage and offloading) does not release on site, and can assist in the launching operation by using an ROV (remote operated vehicle) in the operation process, so that the construction cost is reduced.

The technical scheme adopted by the invention for solving the technical problems is as follows: the method comprises the following steps of constructing a deepwater single-point mooring reclaimed water buoy recovery and lowering system, wherein the deepwater single-point mooring reclaimed water buoy recovery and lowering system comprises an anchor system treatment ship, an ROV, a reclaimed water buoy recovery rigging, a cable joint limiting device and a reclaimed water buoy storage support;

a crane and a winch are arranged on the anchor system processing ship;

The crane is used for lowering the reclaimed water buoy recovery rigging into water to the position close to a shackle on the reclaimed water buoy and connecting the reclaimed water buoy recovery rigging to the shackle by the aid of an ROV (remote operated vehicle); the reclaimed water recovery rigging is connected to the reclaimed water buoy for hoisting and recovering the reclaimed water buoy after the reclaimed water buoy floats out of the water surface;

the winch is used for being connected to an ACT chain rigging on an ACT chain through the assistance of an ROV to recover the ACT chain and the first upper anchor cable;

The cable joint limiting device is used for fixing an upper anchor cable upper cable joint of the first upper anchor cable so as to be convenient for detaching the connection between the ACT chain and the first upper anchor cable;

And the reclaimed water buoy storage bracket is used for storing the disassembled reclaimed water buoy.

In some embodiments, the mid water buoy recovery rigging comprises a first loop-shaped harness, a first ROV hook, a second loop-shaped harness, and a tie-up strap;

one end of the first annular sling is connected with the first ROV hook, and a hard guide rod is arranged on the first annular sling along the length direction of the first annular sling;

One end of the second annular hanging strip penetrates through the first ROV hook sleeve to be arranged on the first annular hanging strip and the hard guide rod, and is bound and fixed through the binding strip.

in some embodiments, the mid water buoy recovery rigging further comprises a third looped sling connected to the other end of the second looped sling; the binding band is made of materials which are easy to be pulled and broken.

in some embodiments, the system further comprises a mid-water buoy floating ball rigging, wherein the mid-water buoy floating ball rigging comprises a second ROV hook, a main connecting rope connected with the second ROV hook, and a plurality of floating balls connected with the main connecting rope.

in some embodiments, the system further comprises a reclaimed water buoy lowering rigging used for cooperating with a crane to lower the reclaimed water buoy into water; the middle water buoy lowering rigging is mounted on the shackle in a return cable mode.

The invention also provides a method for recovering and lowering the reclaimed water buoy in the deep water single-point mooring, which comprises the following steps:

s1, connection of a reclaimed water buoy recovery rigging:

s11, connecting the reclaimed water buoy recovery rigging with a crane hook on an anchoring treatment ship, and lowering the reclaimed water buoy recovery rigging into water to the vicinity of a shackle on a reclaimed water buoy by using a crane;

s12, connecting the reclaimed water buoy recovery rigging with the shackle by using ROV assistance;

S2, recovering ACT chain and first upper anchor line:

s21, lowering the ACT chain by an FPSO, connecting a winch on the anchor system processing ship to an ACT chain rigging on the ACT chain by an ROV, recovering the ACT chain and the first upper anchor cable to a deck by using the winch on the anchor system processing ship, fixing an upper anchor cable connector of the first upper anchor cable on the anchor system processing ship by using a cable connector limiting device, and dismantling the ACT chain;

S22, the winch continues to recover the first upper anchor cable until the middle water buoy floats out of the water surface;

s3, connecting the reclaimed water buoy recovery rigging to a crane on the anchoring treatment ship for hoisting a reclaimed water buoy;

and S4, hoisting and recovering the reclaimed water buoy, loading the reclaimed water buoy onto a ship, fixing the reclaimed water buoy, and then removing the reclaimed water buoy and storing the reclaimed water buoy onto a reclaimed water buoy storage support.

In some embodiments, the greywater buoy retrieval rigging comprises a first looped strap, a first ROV hook, a second looped strap, a third looped strap, and a tie strap made of a material susceptible to rupture by pulling;

One end of the first annular sling is connected with the first ROV hook, and a hard guide rod is arranged on the first annular sling along the length direction of the first annular sling;

one end of the second annular hanging strip penetrates through the first ROV hook sleeve to be arranged on the first annular hanging strip and the hard guide rod, and is bound and fixed through the binding strip;

the other end of the second annular hanging strip is connected with the third annular hanging strip;

the step S11 includes:

connecting an end of the first looped strap remote from the first ROV hook to a crane hook on the mooring handling vessel;

the step S12 includes:

Connecting the third looped strap through the shackle to the first ROV hook using an ROV;

A crane recovery hanging strip, wherein the binding strip bound between the first annular hanging strip and the second annular hanging strip is pulled and broken, so that the second annular hanging strip moves along a hard guide rod to pass through the first ROV hook;

The crane continuously recovers the hanging strip, the second annular hanging strip is installed in the shackle, and after the installation is finished, the crane is lifted upwards to tighten the knot of the second annular hanging strip on the shackle;

removing the connection of the third looped sling with the first ROV hook using an ROV;

in some embodiments, the system further comprises a reclaimed water buoy floating ball rigging, wherein the reclaimed water buoy floating ball rigging comprises a second ROV hook, a main connecting rope connected with the second ROV hook, and a plurality of floating balls connected with the main connecting rope;

Further included after step S12 is:

s13, the main connecting rope is bound along a hanging strip of a crane and then put into water, the second ROV hook is connected with the third annular hanging strip through an ROV, and the hanging strip is recovered by the crane;

the step S3 further includes:

deck operators salvage the reclaimed water buoy floating ball rigging and pull back to the mooring system treatment ship.

In some embodiments, before step S1, the method further includes:

and S0, the ROV carries hydraulic polishing brush into water to clean marine life on the shackle.

In some embodiments, after step S4, the method further includes:

S5: recovering the first lower anchor cable, replacing and laying the second lower anchor cable:

s51, a crane lifts the connecting plate connected between the first upper anchor cable and the first lower anchor cable, the lower anchor cable upper cable joint of the first lower anchor cable or the upper anchor cable lower cable joint of the first upper anchor cable is placed in a cable joint limiting device to be fixed, and the connection between the first upper anchor cable and the connecting plate as well as the connection between the first lower anchor cable and the connecting plate are removed;

s52, removing the cable joint limiting device, beginning to recover the first lower anchor cable until part of the counterweight chain passes through the shark jaw, and fixing the counterweight chain by using the shark jaw;

s52, detaching a connecting plate connected between the heavy chain and the first lower anchor cable, and connecting the heavy chain and the second lower anchor cable;

s53, hoisting a connecting plate between the counterweight chain and the second lower anchor cable by a crane and putting into water;

S54, laying the second lower anchor cable;

S6: installing and lowering the reclaimed water buoy:

s61, lifting a guide pile when laying the cable connector on the lower anchor cable of the second lower anchor cable, installing a cable connector limiting device at the guide pile by deck operators, fixing the cable connector on the lower anchor cable by using the cable connector limiting device, and removing the connection between a winch and the cable connector on the lower anchor cable;

S62, connecting the second lower anchor cable and the second upper anchor cable with a connecting plate respectively;

S63, pulling back a winch belt by a winch of the second upper anchor cable, and pulling the connecting plate to a preset position in the ship;

s64, mounting a reclaimed water buoy mounting bracket by deck workers according to the position of the connecting plate;

s65, deck operating personnel install a reclaimed water buoy lowering rigging on the shackle in a return cable mode, and hang the reclaimed water buoy from the reclaimed water buoy storage support to the reclaimed water buoy installation support;

s66, connecting the reclaimed water buoy with the connecting plate by deck operators;

S67, hoisting the reclaimed water buoy by using a crane, removing the reclaimed water buoy mounting bracket by deck workers, and putting the reclaimed water buoy into water by using the crane to match with a winch of the second upper anchor cable;

S68, after the top of the reclaimed water buoy enters water, removing the connection between the reclaimed water buoy lowering rigging and the crane hook from the deck, and drawing back the reclaimed water buoy lowering rigging;

s7, laying a second upper anchor cable;

S71, the anchoring system processing ship starts to lay the second upper anchor line until the upper anchor line connector of the second upper anchor line reaches the stern;

s72, fixing the upper anchor cable connector by using the cable connector limiting device, connecting the ACT chain with the second upper anchor cable, removing the cable connector limiting device, and lowering the upper anchor cable connector by using a crane in an auxiliary manner;

S8: laying and fixing an ACT chain;

s81, releasing the ACT chain until the tail end of the chain ring of the ACT chain is close to the stern, fixing the ACT chain by using shark pincers, connecting the ACT chain with a lifting cable on an FPSO, continuing to release the ACT chain until the load is completely transferred to the FPSO, and utilizing an ROV to remove the connection between a crane hook and an upper cable joint of the released anchor cable underwater;

S82, the FPSO recovers the lifting cable until the ACT chain passes through the ACT chain hole on the FPSO, and the chain stopper is closed.

The implementation of the invention has at least the following beneficial effects: the reclaimed water buoy recovery rigging is put into water to the vicinity of the shackle on the reclaimed water buoy through a crane on an anchor system treatment ship, and the reclaimed water buoy recovery rigging is connected with the shackle by using ROV assistance; the FPSO lowers the ACT chain, the ROV is used for connecting a winch on the anchor system processing ship to the ACT chain, the winch is used for recovering the ACT chain and a first upper anchor cable to a deck, and the ACT chain is dismantled; the winch continues to recover the first upper anchor cable until the middle water buoy floats out of the water surface; connecting the reclaimed water buoy recovery rigging to a crane on the anchoring system treatment ship to hoist the reclaimed water buoy; and after the reclaimed water buoy is hoisted, recovered and loaded on the ship and fixed, the reclaimed water buoy is detached and stored on the reclaimed water buoy storage bracket. The invention can realize the maintenance or replacement operation of the anchor leg under the condition that the FPSO does not stop production in place and does not release, thereby avoiding the release, the tieback and other work of the FPSO, greatly reducing the workload, improving the construction efficiency and the reliability, and reducing the yield loss and the output value loss of the oil field; the ROV is used for assisting the launching operation in the operation process, the installation, the release and other work of the rigging are completed, the saturated diving operation of operators is not needed, the construction cost is reduced, and the operation efficiency and the operation safety are improved.

drawings

the invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic structural diagram of an anchor leg of a deep water single point mooring system in some embodiments of the invention;

FIG. 2 is a schematic illustration of the structure of a reclaimed water buoy recovery rigging in some embodiments of the present invention;

FIG. 3 is a schematic illustration of the structure of a mid water buoy float rigging in some embodiments of the present invention;

FIG. 4 is a schematic illustration of the structure of a reclaimed water buoy recovery rigging and a reclaimed water buoy floating ball rigging after installation in some embodiments of the present invention;

FIG. 5 is a schematic illustration of the FPSO and mooring line processing vessel being transferred through an ACT chain in some embodiments of the invention;

FIG. 6 is a schematic view of a cable connector stop device according to some embodiments of the present invention;

FIG. 7 is a schematic view of the engagement of a cable connector stop device with a cable connector according to some embodiments of the present invention;

FIG. 8 is a schematic illustration of the structure of a greywater buoy storage cradle in some embodiments of the present invention;

FIG. 9 is a schematic structural view of a bracket half of a mid-water buoy mounting bracket in some embodiments of the invention;

figure 10 is a schematic view of the arrangement of the mid water buoy mounting bracket in cooperation with the mid water buoy in some embodiments of the present invention.

Detailed Description

for a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

fig. 1 is a schematic structural diagram of a deep water single-point mooring system according to some embodiments of the present invention, which may generally include an FPSO (Floating Production Storage and Offloading) 2 and a plurality of anchor legs 1 of the same structural form connected to the FPSO 2. Anchor leg 1 may generally comprise an ACT chain (alignment chain) 11, an upper anchor line (first upper anchor line 121 or second upper anchor line 122), a mid-water buoy 13, a lower anchor line (first lower anchor line 151 or second lower anchor line 152), a counterweight chain 16, a lying line 17, and several attachment plates 14. The upper anchor cable and the lower anchor cable are generally composed of a steel cable and cable joints (an upper cable joint and a lower cable joint, respectively) respectively located at two ends of the steel cable. The connecting plates 14 are used for connecting adjacent anchor cables and anchor chains, and can be in the form of triangular plates or square plates. The reclaimed water buoy 13 is arranged at the joint of the upper anchor cable and the lower anchor cable, the upper anchor cable, the lower anchor cable and the reclaimed water buoy 13 can be connected through a connecting plate 14, and the upper anchor cable and the lower anchor cable are connected to the connecting plate 14 through respective cable connectors (an upper cable connector of the upper anchor cable and a lower cable connector of the lower anchor cable).

as shown in fig. 4, the reclaimed water buoy 13 is usually provided with a shackle 131 thereon, and the shackle 131 is usually a wide shackle arranged at the top of the reclaimed water buoy 13 to facilitate the hoisting of the reclaimed water buoy 13. As shown in fig. 5, the ACT chain 11 is typically provided with an ACT chain rigging 111 thereon to facilitate connection to a winch for ACT chain retrieval or lowering.

Referring to fig. 1-10, the deepwater single-point mooring reclaimed water buoy recovery lowering system of the invention may comprise an anchor system processing vessel 4, a reclaimed water buoy recovery rigging 3, a cable joint limiting device 6, a reclaimed water buoy storage bracket 7, and an ROV (Remote Operated Vehicle).

the mooring system treatment vessel 4 is provided with a crane and a winch, and the sling of the crane and the winch belt of the winch can both adopt steel wire ropes. Among these, the crane usually has two hooks: the main hook (big hook) and the auxiliary hook (small hook) can be selected to be hoisted and recovered according to the situation. The winch can be used for lowering or recovering anchor cables (upper anchor cables, lower anchor cables and the like) or anchor chains (ACT chains, adjusting chains and the like).

the reclaimed water buoy recovery rigging 3 can be connected with a shackle 131 on the reclaimed water buoy 13 for hoisting and recovering the reclaimed water buoy 13. The cable joint stop means 6 may be used to secure cable joints of the upper and lower anchor lines to the mooring handling vessel 4 to facilitate removal or installation of the upper and lower anchor lines. The reclaimed water buoy storage bracket 7 can be used for temporary storage after the reclaimed water buoy 4 is detached.

preferably, the method for recovering and lowering the deepwater single-point mooring reclaimed water buoy in one preferred embodiment of the invention comprises the following steps:

S1, connection of the reclaimed water buoy recovery rigging 3:

and S11, connecting the reclaimed water buoy recovery rigging 3 with a crane hook 41 on the anchoring treatment ship 4, and lowering the reclaimed water buoy recovery rigging 3 into the water to the position near the shackle 131 at the top of the reclaimed water buoy 13 by using the crane.

and S12, connecting the reclaimed water buoy recovery rigging 3 with the shackle 131 by using an ROV (remote operated vehicle) for assistance.

s2, FPSO2 retrieve ACT chain 11 and first upper anchor line 121:

S21, an FPSO2 lowers an ACT chain 11, an ROV connects a winch on an anchor system processing ship 4 to an ACT chain rigging 111 on the ACT chain 11 for load transmission, anchor leg load is transmitted to the winch on the anchor system processing ship 4 through the FPSO2, as shown in figure 5, then the ACT chain 11 and a first upper anchor cable 121 are recovered to a deck through the winch on the anchor system processing ship 4, an upper anchor cable connector 123 of the first upper anchor cable 121 is temporarily fixed on the anchor system processing ship 4 through a cable connector limiting device 6 matched with a stern guide pile, and the ACT chain 11 is detached.

specifically, the mooring processing vessel 4 may be first displaced close to the FPSO2, and then the ACT chain 11 may be lowered and connected for ease of operation.

s22, the winch on the mooring handling vessel 4 continues to retrieve the first upper mooring line 121 until the mid-water buoy 13 is floating out of the water to near the stern of the mooring handling vessel 4.

and S3, connecting the reclaimed water buoy recovery rigging 3 to a crane on the anchoring treatment ship 4 for hoisting the reclaimed water buoy.

and S4, hoisting and recovering the reclaimed water buoy 4 to be loaded on the ship and fixing, then detaching the reclaimed water buoy 4 and storing the reclaimed water buoy on the reclaimed water buoy storage bracket 7.

Thus, the protective recovery of the greywater buoy 13 is achieved.

Specifically, in step S3, before the reclaimed water buoy 13 is hoisted, parameters such as the operation radius of the crane, the effective hoisting height, the operation sea state, the weight of the reclaimed water buoy, and the like need to be calculated, analyzed and verified. In the process of recovering the reclaimed water buoy 13 to the deck, the ship position of the recovery anchor system processing ship 4, the anchor cable catenary and the tension of the first upper anchor cable 121 are controlled, so that the reclaimed water buoy 13 is safely and efficiently recovered to the deck.

in step S4, after the reclaimed water buoy 13 is recovered to the ship, the deck operator may temporarily fix the reclaimed water buoy 13 by using three tail ropes or other fixing means, and then remove the pin shaft connected between the reclaimed water buoy 13 and the connecting plate 14. The pin shaft is usually designed as a screw, when the pin shaft is detached, the safety pin is firstly detached from the nut, then the pin shaft is detached and taken down, the reclaimed water buoy 13 is hoisted and moved to the reclaimed water buoy storage support 7 for storage after the detachment is finished, and the design of the reclaimed water buoy storage support 7 does not interfere with the recovery path of the anchor cable.

The cable joint limiting device 6 is used for fixing cable joints of upper and lower anchor cables, is convenient for dismounting or mounting the cable joints, and can be matched with a stern guide pile and the like for fixing the cable joints. As shown in fig. 6-7, in some embodiments, the cable splice restraint 6 may include a restraint body 61, and a semi-circular catch plate 62 removably disposed on the restraint body 61. For the upper cable connector 121 of the anchor cable as an example, the semicircular clamping plate 62 is butted with the limiting main body 61 to form a closed circle, the closed circle clamps and fixes the conical part of the upper cable connector 121 of the anchor cable, so as to limit the upper cable connector 121 of the anchor cable, and the upper cable connector 121 of the anchor cable can be fixed on a deck and the like by matching with a stern guide pile and the like.

to better address the connection problem of the greywater buoy recovery rigging 3 during deepwater non-submergence operation, as shown in fig. 2, the greywater buoy recovery rigging 3 in a preferred embodiment of the present invention may comprise a first loop-shaped harness 31, a first ROV hook 35, a second loop-shaped harness 33, a third loop-shaped harness 34, and a tie-up strap 32. Wherein one end of the first looped strap 31 is connected to the first ROV hook 35 and the other end is connectable to the crane hook 41. The first annular sling 31 is provided with a hard guide rod along the length direction thereof, and the first annular sling 31 and the hard guide rod can be fixed by binding and other modes. One end of the second annular sling 33 passes through the first ROV hook 35 to be sleeved on the first annular sling 31 and the hard guide rod and is bound and fixed by the binding belt 32. The binding band 32 may be made of a material such as gray adhesive tape or nylon cord, which is easily broken by pulling, and the second ring-shaped hanging strip 33 may be moved along the hard guide bar after the binding band 32 is broken by pulling. The other end of the second loop strap 33 is connected to a third loop strap 34. The third looped straps 34 are typically wide and thick to allow safe hoisting of the greywater buoy; the width and thickness dimensions of the second endless sling 33 are small to facilitate connection with the first ROV hook 35. In addition, in order to avoid the winding of the second annular hanging strip 33 along the drift of water flow, two vertical strips at the middle section of the second annular hanging strip 33 can be fixed together by adopting a binding strip and the like, and hanging rings for connection are reserved at the head end and the tail end of the two vertical strips.

accordingly, the step S11 includes:

the end of the first loop harness 31 remote from the first ROV hook 35 is connected to a crane hook 41 on the mooring handling vessel 4. In this step, the crane hook 41 can be operated with a crane hook.

the step S12 includes:

S121, connecting the third annular hanging strip 34 with the first ROV hook 35 through the shackle 131 by using an ROV;

S122, the crane recovery crane sling 42 pulls and breaks the binding band 32 bound between the first annular sling 31 and the second annular sling 33, and the second annular sling 33 moves along the hard guide rod to pass through the first ROV hook 35;

S123, the crane continuously recovers the crane sling 42, the second annular sling 33 is installed in the shackle 131, and after the installation is completed, the crane is lifted upwards to tighten the knot of the second annular sling 33 on the shackle 131;

and S124, releasing the connection between the third annular sling 34 and the first ROV hook 35 by using the ROV.

if the shackle 131 is not perpendicular to the bottom surface of the mid-water buoy, before step S121, the method may further include:

and S120, righting the shackle 131 by using the ROV to enable the shackle to be vertical to the bottom surface of the reclaimed water buoy 13.

it will be appreciated that in the second embodiment, the greywater buoy retrieval rigging 3 may also comprise only the first loop strap 31, the first ROV hook 35, the second loop strap 33, and the tie strap 32, without the need to comprise the third loop strap 34. Accordingly, step S121 in the above steps is: connecting the end of the second loop strap 33 remote from the first loop strap 31 with the ROV through the shackle 131 to the first ROV hook 35; step S124 is: the second endless sling 33 is disconnected from the first ROV hook 35 by means of the ROV.

in other embodiments, the tie wrap 32 may not be made of a material that is easily broken by pulling, and the tie wrap 32 may be unfastened by the ROV in step S122.

Preferably, as shown in fig. 3, the deepwater single-point mooring reclaimed water buoy recovery lowering system further comprises a reclaimed water buoy floating ball rigging 5, wherein the reclaimed water buoy floating ball rigging 5 is connected with the reclaimed water buoy recovery rigging 3 and is used for floating the reclaimed water buoy recovery rigging to prevent the rigging from being wound with the upper anchor cable and the lower anchor cable along with the water flow drifting. The mid-water buoy floating ball rigging 5 can comprise a second ROV hook 51, a main connecting rope 52 connected with the second ROV hook 51, and a plurality of floating balls 53 connected with the main connecting rope 52. Wherein the second ROV hook 51 can be connected with the greywater buoy recovery rigging 3 with the aid of an ROV. One end of the main connecting rope 52 connected with the second ROV hook 51 is connected with at least two floating balls through an auxiliary connecting rope 54. The other end of the main connecting rope 52, which is far from the second ROV hook 51, is also connected with a floating ball 53, and at least one floating ball 53 can be connected through an auxiliary connecting rope 54. The main connecting rope 52 and the auxiliary connecting rope 54 can be made of light materials such as nylon ropes.

correspondingly, after the step S12, the method further includes:

s13, the main connecting rope 52 on the reclaimed water buoy floating ball rigging 5 is tied along the hanging strip of the crane, and then water is put in, the second ROV hook 51 on the reclaimed water buoy floating ball rigging 5 is connected with the third annular hanging strip 34 (in the second embodiment, it can also be connected with the second annular hanging strip 33) by using an ROV, and the hanging strip is recovered by the crane.

in the step, the main hook of the crane can be selected when the crane is lowered so as to eliminate the buoyancy influence of the floating ball. The main connecting rope 52 is bound along the sling of the crane and then put into water, so that the main connecting rope can be prevented from being wound with the sling of the crane during the putting. The main connecting rope 52 and the hanging strip of the crane can be bound by materials which are easy to pull and break, such as gray adhesive tape and small nylon ropes, so that the main connecting rope is directly broken when the crane is lifted and recovered, and the connection between the floating ball rigging 5 of the mid-water buoy and the crane can be released. In other embodiments, the main connecting line 52 may be tied to the crane sling without using a material that is easily torn and broken, and then untied with an ROV after lowering the water.

the step S3 further includes:

deck operators salvage the reclaimed water buoy floating ball rigging 5 and pull back to the mooring system treatment vessel 4.

Specifically, when the reclaimed water buoy 13 is recovered to a distance of about 5 to 10m from the stern of the mooring system treatment vessel 4, a deck operator can salvage the reclaimed water buoy floating ball rigging 5 and the reclaimed water buoy rigging 3 by using a long rod or other tools, pull the reclaimed water buoy floating ball rigging 3 back to the mooring system treatment vessel 4, then release the connection between the reclaimed water buoy floating ball rigging 5 and the reclaimed water buoy recovery rigging 3 on the deck, hook the reclaimed water buoy recovery rigging 3 to a crane, and perform reclaimed water buoy hoisting. When the hook is used for hoisting, the second annular hanging strip 33 can be hooked to a crane.

In some embodiments, the deepwater single-point mooring mid-water buoy retrieval lowering system may further comprise a hydraulic sanding brush that may be lowered into the water carried by the ROV to clean marine life on shackle 131.

accordingly, step S1 is preceded by:

s0, the ROV carries hydraulic polishing brush into water to clean marine life on the shackle 131.

In some embodiments, before step S0, the method may further include: the mooring treating vessel 4 is displaced to a predetermined position. For example, the mooring processing vessel 4 may be displaced to near above the greywater buoy 13.

After the recovery of the reclaimed water buoy 13 is completed, the recovery and replacement of the lower anchor cable may be performed, and accordingly, after the step S4, the method may further include:

s5: retrieve first lower anchor line 151, replace and lay second lower anchor line 152:

S51, the crane lifts connecting plate 14 connected between first upper anchor line 121 and first lower anchor line 151, places lower anchor line upper cable joint 153 of first lower anchor line 151 into cable joint retainer 6, temporarily fixes lower anchor line upper cable joint 153, and removes the connection between first upper anchor line 121 and first lower anchor line 151 with connecting plate 14.

in other embodiments, the upper anchor line lower cable connector 124 of the first upper anchor line 121 may be placed in the cable connector position-limiting device 6, and the upper anchor line lower cable connector 124 may be temporarily fixed.

S52, removing the cable joint stopper 6, starting to retrieve the first lower anchor line 151 until the partially distributed heavy chain 16 passes the shark jaw and using said shark jaw to secure the heavy chain 16, slowly transferring the load from the first lower anchor line 151 to the shark jaw.

s52, removing the connecting plate 14 connected between the counterweight chain 16 and the first lower anchor line 151, swinging and bending the counterweight chain 16 behind the shark jaw by using a crane on the mooring processing vessel 4, and then connecting the counterweight chain 16 to the second lower anchor line 152.

s53, the hoist lifts the attachment plate 14 connected between the counterweight chain 16 and the second lower anchor line 152 over the stern and down into the water, transferring the load to the second lower anchor line 152.

And S54, laying a second lower anchor cable 152. When the anchor chain is laid, whether the anchor chain is twisted or not can be observed at a mud landing point by using the ROV.

and then, the lower anchor cable is recovered, replaced and laid. Next, the installation and the lowering of the middle water buoy 13 can be performed, and accordingly, after the step S5, the method further includes:

S6: installing and lowering the reclaimed water buoy 13:

and S61, lifting the guide pile when the cable is laid on the lower anchor cable upper cable joint 153 of the second lower anchor cable 152, installing a cable joint limiting device 6 at the guide pile by deck operators, fixing the lower anchor cable upper cable joint 153 by utilizing the cable joint limiting device 6 in cooperation with the guide pile, and detaching the connection between a winch on the anchor system processing ship and the lower anchor cable upper cable joint 153.

S62, connecting second lower anchor line 152 and second upper anchor line 122 to attachment plate 14, respectively.

specifically, lower anchor line upper cable joint 153 of second lower anchor line 152 and upper anchor line lower cable joint 124 of second upper anchor line 122 are respectively connected to connection plate 14.

S63, the winch of the second upper anchor line 122 pulls back the winch belt, pulling the attachment plate 14 to a predetermined position in the vessel.

and S64, installing the reclaimed water buoy installation bracket 8 by deck workers according to the position of the connecting plate 14.

s65, the deck worker installs the mid-water buoy lowering rigging 9 on the shackle 131, and hangs the mid-water buoy 13 from the mid-water buoy storage bracket 7 to the mid-water buoy mounting bracket 8, as shown in fig. 10.

s66, the deck operator connects the reclaimed water buoy 13 with the connecting plate 14.

Specifically, deck operators can connect the reclaimed water buoy 13 with the connecting plate 14 by using tools such as a jack and a lever block.

s67, hoisting the reclaimed water buoy 13 by the crane, removing the reclaimed water buoy mounting bracket 8 by deck workers, and putting the reclaimed water buoy 13 into water by using the crane matched with a winch of the second upper anchor cable 122; in addition, the monitoring can also be performed by using an ROV.

And S68, releasing the hook of the crane after the water enters the top of the middle water floating cylinder 13.

preferably, in step S65, the mid-water buoy lowering rigging 9 can be installed on the shackle 131 by using a return cable (double connection), so that after the lowering of the mid-water buoy 13 is completed, the connection between the mid-water buoy lowering rigging 9 and the crane hook is released on the deck, and then one side of the rigging 9 is released, so that the whole rigging 9 can be pulled back to restore the original shape of the mid-water buoy. By adopting the connection mode of the return cable, the unhooking operation of the lowering rigging 9 of the reclaimed water buoy can be completed by the deck, so that the ROV is prevented from entering the water, the operation is simple, and the efficiency is high.

the reclaimed water buoy mounting bracket 8 is used for fixing the reclaimed water buoy 13 so as to facilitate the mounting operation of the reclaimed water buoy 13. The design of the greywater buoy mounting bracket 8 is required to facilitate the operations of dismantling and mounting the greywater buoy 13, and removal after the installation of the greywater buoy 13 and the connection plate 14 is completed. As shown in fig. 9-10, the greywater buoy mounting bracket 8 may comprise two detachably mating bracket halves 81. The two bracket halves 81 can be butted with each other to fix the reclaimed water buoy 13, and the reclaimed water buoy mounting bracket 8 can be removed from the reclaimed water buoy 13 after being disassembled from each other. Each bracket half 81 may include a base 815, a connecting rod 813, a support plate 812, and a semi-circular snap ring 811. A base 815 is arranged at the lowest part of the greywater buoy mounting bracket 8 for supporting the standing position of the greywater buoy mounting bracket 8, which may be placed horizontally on a deck or the like for the fixation of the greywater buoy 13 on the deck or the like. The semicircular snap rings 811 are arranged at the topmost part of the reclaimed water buoy mounting bracket 8, the two semicircular snap rings 811 are mutually butted to form a closed circular ring, and the closed circular ring is mutually matched with the upper cylindrical part of the reclaimed water buoy 13 to achieve the limiting effect on the reclaimed water buoy 13. The diameter of the semicircular snap ring 811 may be slightly larger than the diameter of the upper cylindrical portion of the reclaimed water buoy 13 to facilitate the lowering of the reclaimed water buoy 13. The supporting plate 812 is disposed below the semicircular snap ring 811, and is in abutting fit with the lower tapered portion of the reclaimed water buoy 13, for supporting and fixing the reclaimed water buoy 13. The semicircular snap ring 811 may be vertically provided with a mounting rib 816 downward, and the support plate 812 is provided obliquely downward inside the mounting rib 816. Connecting rods 813 are connected between the top of the base 815 and the bottom of the support plate 812, respectively, for assisting in supporting the greywater buoy 13. A plurality of reinforcing ribs 814 can be arranged between the base 815 and the connecting rod 813 to improve the strength of the bracket. In some embodiments, each rack half 81 may be supported by two spaced apart bases 815; two support plates 812 are arranged on each bracket half 81 at intervals and used for supporting the reclaimed water buoy 13; each base 815 is connected to the support plate 812 by a vertically disposed connecting rod 813. The four supporting plates 812 of the reclaimed water buoy installing support 8 can be arranged at even intervals with 90-degree included angles. A plurality of reinforcing ribs 814 can also be arranged on the two connecting rods 813 to increase the strength.

as shown in connection with fig. 8-9, the greywater buoy storage bracket 7 is similar in construction to the greywater buoy mounting bracket 8, the greywater buoy storage bracket 7 being formed by two bracket halves 81, either detachably connected or integrally connected. It will be appreciated that for increased versatility, the mid-water buoy storage bracket 7 and the mid-water buoy mounting bracket 8 may be of the same structural design, i.e. they may each consist of two detachably arranged bracket halves 81.

the reclaimed water buoy mounting bracket 8 is convenient for operations such as dismounting, mounting and removing the reclaimed water buoy 13, so that deck personnel can easily dismount and mount the pin shaft, and can perform fine adjustment through the jack and the lever block to completely mount the pin shaft into the pin hole; and can also reduce the matching precision requirement when the reclaimed water buoy 13 and the connecting plate 14 are detached and installed.

after the lowering of the normal water buoy 13 is completed, the laying of the second upper anchor line 122 and the ACT chain 11 may be performed, and accordingly, after step S6, the method may further include:

S7, laying a second upper anchor cable 122;

S71, starting to lay the second upper anchor line 122 by using the winch on the mooring processing vessel 4 until the upper anchor line connector 123 of the second upper anchor line 122 reaches the stern;

S72, fixing the upper anchor cable connector 123 at the stern by using the guide piles and the cable connector limiting device 6, connecting the ACT chain 11 with the second upper anchor cable 122, removing the cable connector limiting device 6, and lowering the upper anchor cable connector 123 by using the crane for assistance;

s8: laying and fixing an ACT chain 11;

S81, lowering the ACT chain 11 by a winch on the anchor system processing ship 4 until the end cross ring of the chain ring of the ACT chain 11 is close to the stern, fixing the ACT chain 11 by a shark jaw, connecting the ACT chain 11 with a lifting cable 10 (such as a dyneema cable) on an FPSO2, continuing to lower the ACT chain 11 until the load is completely transferred to an FPSO2, and connecting an ROV underwater removal crane hook with an upper cable connector 123 of a lower anchor cable;

s82, the FPSO2 retrieves the hoist cable 10 until the ACT chain 11 passes through the ACT chain aperture in the FPSO2, closing the chain stopper. And then, replacing the anchor leg and the anchor cable.

According to the system and the method for recovering and lowering the reclaimed water buoy in the deepwater single-point mooring, the ROV is used for assisting the launching operation in the operation process, the installation, the release and other work of the rigging are finished, the saturated diving operation of operators is not needed, the construction cost is reduced, the operation efficiency and the operation safety are improved, the maintenance or the replacement operation of the anchor leg can be carried out under the condition that the FPSO is not released in situ without production stop, the work of the FPSO such as release, return connection and the like is avoided, the workload is greatly reduced, the construction efficiency and the reliability are improved, and the yield loss and the output value loss of an oil field are reduced.

it is to be understood that the above-described respective technical features may be used in any combination without limitation.

the above examples only express the preferred embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention; it should be noted that, for those skilled in the art, the above technical features can be freely combined, and several changes and modifications can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention; therefore, all equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.