CN101710242A - Method for monitoring anchoring line of deep-sea terrace - Google Patents

Abstract

The invention belongs to the technical field of offshore oil and natural gas exploitation equipment safety monitoring and risk control, and relates to a method for monitoring anchoring line of deep-sea terrace. The method comprises the following steps: (1) installing a displacement transducer on the position of height of gravitational center of the terrace to monitor the motion displacement U0 of the terrace main body in real time, arranging a strain transducer on the anchoring line to monitor the strain of the anchoring line in real time and transmitting the monitoring data to a central computer; (2) calculating and analyzing whether the anchoring line appears relaxed-tensioned state; (3) calculating and analyzing dynamic tension; (4) comparing the calculated dynamic tension with the fracture tension of the anchoring line, judging whether the tension of the anchoring line is within the safe range, if not, implementing adjustment; (5) if needing adjustment, commanding the adjustment value of the anchoring line to each anchor gear, starting and controlling each anchor gear, adjusting the length of the anchoring line, and calculating whether the adjusted length of the anchoring line meets the requirement, if not, repeating the step. The invention can realize control on state and tension of the terrace anchoring line, can enhance the safety level of the terrace system and can reduce occurrence of grave accidents.

Description

Method for monitoring anchoring line of deep-sea terrace

Technical field

The invention belongs to marine oil and gas exploitation equipment safety monitoring and risk control technical field, relate to a kind of method for monitoring anchoring line of deep-sea terrace.

Background technology

At present, in the deep-sea of the depth of water more than 1000 meters, found abundant oil and natural gas, exploitation for oil and natural gas, adopt classical Spar platform or truss-like Spar platform at present, as depicted in figs. 1 and 2, planting the relevant vitals of structural safety therewith is the mooring line, its effect is that structure is fixed in the deep-sea, in case the mooring line breaks down or ruptures, whole plateform system will lose operation function generation havoc, " fatal crass " major disaster accident occur.

The present invention proposes monitoring and the control technology security-related, can monitor the degree of tightness and the tension state of mooring line, and implement Tension Control, do not rupture, guarantee the safety of mooring line to guarantee the mooring line with the mooring line.

The Spar platform is a typical deep-sea platform, mainly by main platform body, mooring line, upper module, and anchor foundation form.Under wind wave action, main platform body significantly moves up and down.When main platform body was significantly moved downwards, the mooring line tension reduced fast, and the mooring line is crooked lax; When main platform body is upwards significantly moved fast, the tensioning of mooring line.In the process of mooring line relaxation-tensioning, the mooring line produces and impacts, and very large tension force occurs, can cause the mooring line to break, and the mooring line length phase relaxes-the tensioning process, can cause the fatigure failure of mooring line.

Therefore, reducing the mooring line and impact tension force, avoid the fatigure failure of mooring line, is the important technique measure that guarantees mooring line safety.

For this reason, need implement monitoring and forecast to the state of mooring line, and adopt suitable technical measures to control, make the mooring line be in suitable tightness, avoid the mooring line lax-tensioning state significantly to occur for the state and the tension force size of mooring line.

Summary of the invention

The present invention proposes a kind of method for monitoring anchoring line of deep-sea terrace in order to solve the safety problem that anchoring line of deep-sea terrace exists.The mooring line method for supervising that the present invention proposes is monitored and is adjusted platform mooring line states in real time, makes the mooring line tension remain on the safe range of permission, for the safety of anchoring line of deep-sea terrace provides safeguard.

The present invention proposes following technical scheme: a kind of method for monitoring anchoring line of deep-sea terrace comprises the following steps:

(1) installation position displacement sensor on position, platform height of C.G. place, monitoring platform main body moving displacement U in real time ₀, on the mooring line, lay strain transducer, monitor the strain of mooring line in real time, and Monitoring Data is sent to central computer;

(2) according to formula

Whether computational analysis mooring line occurs relaxing-tensioning state, in the formula,

U _StBe the static extention amount of mooring line, Λ is the ratio of wave frequencies and platform heave natural frequency, and ξ is the dimensionless damping ratio,

C _EquBe the ratio of damping of considering mooring line and seawater, M be the deep water platform sole mass with and the added mass of entrained water sum, λ ₀Be platform heave natural frequency,, judge that then lax-tensioning state takes place to be changed if inequality is set up;

(3) according to the computing formula T of dynamic tension _d=EA ε, the analytical calculation dynamic tension, in the formula, E is the mooring linear elastic modulus, and A is a mooring line cross-sectional area, and ε is the strain of any point on the mooring line, and this strain calculates or is obtained by the strain transducer monitoring that is laid on the mooring line;

(4) with the dynamic tension that calculates and the disrumpent feelings warp tension ratio of mooring line, judge whether the mooring line tension is in safe range, and tension force criterion is Mooring line distortion criterion is: U ₀Sin ω t-U sin (ω t-φ) 〉=U _St, in the formula, T _bBe the disrumpent feelings tension force of mooring line, ω is a wave frequencies, and t is a time parameter, and φ is systematic steady state response phase angle, and one of two formulas more than satisfying are promptly implemented to adjust;

(5) adjust if desired, then the adjusted value with the mooring line sends instruction to each windlass, starts and controls each and play the chain machine, adjusts the length of mooring line, and according to inequality U ₀Sin ω t-U sin (ω t-φ)＜U _StCalculate adjusted mooring line length and whether meet the requirements,, then repeat this step, set up until inequality if inequality is false, in the formula,

$U=\frac{U_0}{\sqrt{{(1-{\mathrm{\Λ}}^2)}^2+{\left(2\mathrm{\ξ\Λ}\right)}^2}},$ $\mathrm{\φ}={\mathrm{tg}}^{-1}\frac{2\mathrm{\ξ\Λ}}{1-{\mathrm{\Λ}}^2}.$

The present invention is applied on the production vessel of deep-sea, enforcement is monitored the main platform body motion state, lax-tensioning state analysis, the tension force of mooring line forecast, realize the control to platform mooring line states and tension force, can improve the security level of plateform system, reduce the generation of major accident.

Description of drawings

Fig. 1 platform-mooring system vertical view;

Fig. 2 platform-mooring system synoptic diagram;

Fig. 3 mooring system Tension Control process flow diagram;

Fig. 4 mooring system tension force calculation flow chart.

Embodiment

Main platform body is the right cylinder of a vertical suspension in water, and integral diameter is greatly about 20-35 rice scope, and huge body interior adopts vertical water proof bulkhead and horizontal deck to be separated into multilayer, many cabin structures, and has function separately.Mooring system is made up of mooring hawser, chock, a chain machine and seafloor foundation, the location and the kinematic constraint of main implementation platform main body.To the forecast and the control of platform mooring line impact tension force, embodiment is as follows:

1, installation position displacement sensor on position, platform height of C.G. place, the U of monitoring platform main body motion in real time ₀Value; Simultaneously arrange strain transducer on the mooring line, the strain of monitoring mooring line is arrived central computer by dynamic data collection system with platform motion displacement and mooring line strain data aggregation;

2, with image data as known conditions, be input in real time in the program, whether occur relaxing-tensioning state according to formula (1) computational analysis mooring line:

$\frac{\sqrt{{\left(2\mathrm{\ξ\Λ}\right)}^2{[{\left(2\mathrm{\ξ\Λ}\right)}^2-(1-{\mathrm{\Λ}}^2){\mathrm{\Λ}}^2]}^2}}{{(1-{\mathrm{\Λ}}^2)}^2+{\left(2\mathrm{\ξ\Λ}\right)}^2}\≥\mathrm{\μ}---\left(1\right)$

In the formula,

U _StStatic extention amount for the mooring line depends on the platform original state, U ₀For the displacement of main body under action of wave force, obtain by sensor monitors; Λ is the ratio of wave frequencies and platform heave natural frequency, and ξ is the dimensionless damping ratio,

C _EquBe the ratio of damping of considering mooring line and seawater, M be the deep water platform sole mass with and the added mass of entrained water sum, λ ₀For platform heave natural frequency, for concrete deep water platform, the C here _Equ, M and λ ₀All determine.

According to the parameter of following formula (1) and given mooring system, can judge the mooring line and whether can in lax-tension regions, change, thereby determine whether to produce temporary impact load.

3, according to mooring line relaxation-tensioning state judged result, if taking place, lax-tensioning state changes, then need the tension force of further computational analysis mooring line.The computing formula of dynamic tension is

T _d＝EAε (2)

In the formula, E is the mooring linear elastic modulus, and A is a mooring line cross-sectional area, and ε is the strain of any point on the mooring line, and this strain calculates or obtained by the sensor monitors that is laid on the mooring line.

Dynamic tension and mooring line rupture pull force that following formula is calculated compare, and judge whether the mooring line tension is in safe range.

4, with gained mooring line tension and mooring displacement of the lines amplitude input computer control system, whether need to adjust the mooring line length from tension force and lax-two aspect synthetic determinations of tensioning state.Criterion is:

Tension force criterion: $T_d\≥\frac{T_b}{2}---\left(3\right)$

Mooring line distortion standard: U ₀Sin ω t-U sin (ω t-φ) 〉=U _St(4)

T _dBe the instantaneous dynamic tension that formula (2) calculates, ω is a wave frequencies, and t is a time parameter, and φ is systematic steady state response phase angle, T _bDisrumpent feelings tension force for the mooring line.One of two formulas more than satisfying are promptly implemented to adjust.

5, adjust if desired, then the adjusted value with the mooring line sends instruction to each windlass, starts and controls each and play the chain machine, adjusts the length of mooring line, and according to inequality U ₀Sin ω t-U sin (ω t-φ)＜U _StCalculate adjusted mooring line length and whether meet the requirements,, then repeat this step, set up until inequality if inequality is false, in the formula,

$U=\frac{U_0}{\sqrt{{(1-{\mathrm{\Λ}}^2)}^2+{\left(2\mathrm{\ξ\Λ}\right)}^2}},$ $\mathrm{\φ}={\mathrm{tg}}^{-1}\frac{2\mathrm{\ξ\Λ}}{1-{\mathrm{\Λ}}^2}.$

Fig. 3 and Fig. 4 are respectively mooring system Tension Control and calculation flow chart.

Claims (1)

1. a method for monitoring anchoring line of deep-sea terrace comprises the following steps:

(1) installation position displacement sensor on position, platform height of C.G. place, monitoring platform main body moving displacement U in real time ₀, on the mooring line, lay strain transducer, monitor the strain of mooring line in real time, and Monitoring Data is sent to central computer;

(2) according to formula

Whether computational analysis mooring line occurs relaxing-tensioning state, in the formula,

U _StBe the static extention amount of mooring line, Λ is the ratio of wave frequencies and platform heave natural frequency, and ξ is the dimensionless damping ratio,

C _EquBe the ratio of damping of considering mooring line and seawater, M be the deep water platform sole mass with and the added mass of entrained water sum, λ ₀Be platform heave natural frequency,, judge that then lax-tensioning state takes place to be changed if inequality is set up;

(3) according to the computing formula T of dynamic tension _d=EA ε, the analytical calculation dynamic tension, in the formula, E is the mooring linear elastic modulus, and A is a mooring line cross-sectional area, and ε is the strain of any point on the mooring line, and this strain calculates or is obtained by the strain transducer monitoring that is laid on the mooring line;

(4) with the dynamic tension that calculates and the disrumpent feelings warp tension ratio of mooring line, judge whether the mooring line tension is in safe range, and tension force criterion is

Mooring line distortion criterion is: U ₀Sin ω t-Usin (ω t-φ) 〉=U _St, in the formula, T _bBe the disrumpent feelings tension force of mooring line, ω is a wave frequencies, and t is a time parameter, and φ is systematic steady state response phase angle, and one of two formulas more than satisfying are promptly implemented to adjust;

(5) adjust if desired, then the adjusted value with the mooring line sends instruction to each windlass, starts and controls each and play the chain machine, adjusts the length of mooring line, and according to inequality U ₀Sin ω t-U sin (ω t-φ)＜U _StCalculate adjusted mooring line length and whether meet the requirements,, then repeat this step, set up until inequality if inequality is false, in the formula, $U=\frac{U_0}{\sqrt{{(1-{\mathrm{\Λ}}^2)}^2+{\left(2\mathrm{\ξ\Λ}\right)}^2}},$ $\mathrm{\φ}={\mathrm{tg}}^{-1}\frac{2\mathrm{\ξ\Λ}}{{1-\mathrm{\Λ}}^2}.$

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