Research Of The Dynamics Problems Of A Stinger Structure Under The Deep Water Laying Environment

With the depletion of land resource, offshore oil exploitation is becoming a worldwide research hot spot. In recent ten years,60% of the newly discovered gas fields is in the sea, and 50% of the oil and gas fields exploritation are also in the sea, so the marine resources are really abundant. Most of these resources are in the depth of the sea. The exploitation of the oil and gas in deep sea is very difficult, which is a high investment,a high technology and a high risk exploitation mode, and the submarine pipeline laying technology is in urgent need to break through. The core equipment of submarine pipeline laying is the stinger. Only when the quality of the stinger increased can break through the bottleneck of deep water pipeline laying technology. In 2012, our country built pipe laying vessel named’HYSY201’with proprietary intellectual property rights, which makes a great improvement of the deep sea pipeline laying technology of our country. However, as the working environment of the stinger is getting deeper and deeper, the equipment has also revealed some technical shortagesThe purpose of this paper is to put forward the design insufficiency of the stinger which is used for the ultra-deep water and very large diameter pipesFirstly, the author summarizes the movement of hull and expounds the calculation method of hull movement in time domain and frequency domain, then the software ’AQWA’ and the test method are introduced for purpose of getting the hull motion data; Application of hull data for this article are introduced, and get the spectrum estimation function of hull motion computation by spectrum estimation function.Secondly, the dynamic characteristics of the stinger under different working conditions are analyzed. It is found the pipeline’s stiffness matrix and mass matrix will affect the natural frequencies of the stinger. In shallow water this effect is not very obvious, but the impacts on the natural frequencies will become more obvious when the working stage gets deeper, which may be even close to the hull’s motion frequency band.Then,the article introduces the calculation principle of the pseudo-excitation method, and establishes the dynamics pseudo equation of vessel-stinger. According to the characteristics of Pseudo-excitation method transforms Pseudo-excitation into harmonic response analysis, which is come true by finite element softwareFinally, the relationship of stinger-laying ship -pipe is mutual coupling. The article decouples the relationship, using mass to simulate the inertial effect of the pipeline. The hull motion data was applied to the stinger as boundary condition, which can simulated the dynamic impact of the hull on the stinger. The pseudo-excitation method was applied on a general finite element software to obtain the power spectral density function of the stinger hotspot. By using the Dirlik method, the probability density function of the hotspot stress is achieved to evaluate the fatigue life of the stinger.At the end of this paper, the research conclusion and some main problems which should be notice in stinger are proposed. This will provide some guidances on the stinger design for the ultra-deep water and large-diameter pipe laying cases...