浅地层剖面仪在大亚湾海底管道检测中的应用

浅地层剖面探测是海洋工程勘察的主要手段之一。阐述了浅地层剖面仪的工作原理,通过浅地层剖面仪在广州华德石化海底输油管道检测中的实际应用情况,分析浅地层剖面仪在工程区域内使用的优缺点,以期为今后该区域内工程勘察及管线检测工作起到一点参考作用。     

高频浅地层剖面技术在海底管道探测中的应用

在海底管道的探测中,为获知海管在海底的真实赋存状态,确定其埋藏深度或悬跨高度,多使用高频浅地层剖面仪等传统声学设备。但在海底斜坡、凹坑、凸起等不平整地层处,由于设备自身原理造成的地层探测界面偏移、图像失真及资料多解性问题仍困扰着工程人员。通过正演模拟的方法探究高频浅地层剖面仪在海底特殊地层处海管检测的波场传播特征,探讨资料的解释陷阱,并提出了解决方案。研究结果表明,利用浅地层剖面仪探测管道在海底的赋存状态,应将探测图像与海底地形、地貌、沉积物运移等因素结合起来综合考虑,把探测图像回归到真实海底环境中,以准确评价海底管道的安全状态。     

SES-2000浅地层剖面仪在福建LNG海底管道检测中的应用

利用声学浅地层剖面仪对海底管道在海底的赋存状态检测是确保海底输油气管道安全运行的重要措施之一。介绍了新型参量阵浅地层剖面仪SES-2000的基本原理及其特点,通过对福建湄洲湾LNG海底管道检测实际应用,有效识别出了埋藏、裸露和悬空等3类海底管道赋存状态,尤其对沙包回填治理后的管道埋深能有效探测识别。检测结果表明,该设备具有高分辨率和强穿透的特点,稳定性好,能获取高品质的管道检测数据,应用效果良好。获取的基础数据为海底管道日常维护提供了科学依据和技术支持。     

研制海底浅地层剖面仪的某些声学问题

近十年来,探测海底几十米至几百米松散沉积层分层结构的“海底浅地层剖面仪”已逐步发展定型,并广泛用于海底工程施工和海洋地质研究方面。这种浅地层剖面仪主要采用以下几种声源装置：电致伸缩器件、磁致伸缩器件、电磁脉冲声源、电火花放电器以及气枪。 浅层剖面仪实际上是一种以地层为探测目标的主动声纳,本文给出了有关的声纳方程式,它将有助于这类仪器的工程设计和性能预报。 从探层声纳方程式出发,采用电磁脉冲声源研制了浅层剖面仪,获得了穿透地层几十米的较高分辨率的记录。对此,本文也作了简单的介绍。     

上覆硬质保护层海底管道检测技术探讨

海底管道在油气工业中发挥着重要作用,为保障其安全运营必须定期进行检测掌握其在海底的状态。有的海底管道在铺设时为其安全考虑,在海底管道上方覆盖了抛石等硬质保护层,这样就导致在海底管道定期检测时一些检测仪器难以探测到硬质保护层下海底管道的位置和埋深,而浅地层剖面仪和磁力仪仍然可以不同程度地实现这种情况下的海底管道检测。文中对浅地层剖面仪和磁力仪的原理进行了介绍并对其在上覆抛石等硬质保护层海底管道检测中的应用进行了分析探讨。分析结果表明浅地层剖面仪和磁力仪组成的综合检测系统对上覆硬质保护层的海底管道探测有一定效果,可查明海硬质保护层下海底管道的位置和埋深,为海底管道的安全管理和维护提供数据支持,也可为其他类似海底管道检测提供参考。     

基于高分辨率浅剖与钻孔信息对比的金州湾海底声速的统计特征

声波在海底沉积物中的传播速度是一个重要参数,弄清海底沉积物中声速的变化规律具有极其重要的意义。以渤海金州湾海域为例,在进行畸变校正的基础上,基于高分辨率浅地层剖面与钻孔数据的对比分析,实现了全新世沉积层和基岩界面以上沉积层声速的准确反演,并采用统计学方法分析讨论了研究区内的声速特征和变化规律,结果表明,全新世沉积层平均声速的95%置信区间为1 449.60～1 655.72 m/s,平均值为1 560.34 m/s;基岩界面以上沉积层平均声速的95%置信区间为1 657.96～1 970.80 m/s,平均值为1 765.63 m/s;研究区内海底地层的声速与埋藏深度之间呈现明显的正线性相关关系,声速梯度为4.18 s⁻¹。     

海底管道测量声学剖面特征分析

海底管道的位置与埋深测量通常采用浅地层剖面仪等声学手段来实现,由于海管与地层之间的声阻抗差异,会以绕射弧的形态出现在声学剖面中。但当海管埋设于管沟中时,管沟中断棱的绕射与海管绕射易于混淆,给声学剖面图的解译和识别带来困难。基于地震勘探原理,结合浅地层剖面仪的性能、挖沟作业对地层的扰动等,分析了管沟绕射弧的类型与特点、挖沟作业扰动的声学特征等,提出了管沟中海管绕射弧的识别方法。结果表明,正确认识不同类型管沟的绕射、施工扰动产生的绕射等声学特征,才能辨识出海管的绕射现象。实际工作中应根据测量海区的水深、土质、海管属性等多种要素,选用适宜的仪器类型及测量参数。     

海底输油管道掩埋状况调查研究

本文用全球卫星接收定位系统（ＧＰＳ）与浅地层剖面系统（ＧｅｏＣｈｉｒｐ Ｓｕｂ－Ｂｏｔｔｏｍ Ｐｒｏｆｉｌｅ Ｓｙｓｔｅｍ）对珠江三角洲的铜鼓、伶汀、九州水 底输油管道掩埋状况进行勘测,全部数据记录在声纳图像增强工作站。经室内回放增强处理得出硬拷贝资料,然后将全部定位资料输入计算机用ＧＩＳ系统进行处理得出测线的ＫＰ点。解释出所测管道掩埋状况,文中列出了管道几种掩埋状况,为海洋工程调查研究提供参考。     

现代长江水下三角洲浅地层地震相特征

利用传统的地震相分析方法,分析总结现代长江水下三角洲浅地层地震剖面反射波的几何形态、内部反射结构、连续性、振幅等特征,形成对长江水下三角洲各典型地震相特征的认识,圈定相应的地震相范围,并结合钻孔资料,解释了长江口范围三角洲前积、浅海沉积、古河道等各沉积相的分布。结果表明,现代长江水下三角洲浅地层各地震相特征明显。典型的三角洲前积地震相主要分布在长江口外东北部,其余大部为典型浅海沉积地震相,且浅海地震相特征向口内逐渐变弱,表现为浅砂或淤泥型地震相,向口外逐渐有晚更新世基底地震相出露,并发育古河道地震相,此外,浅层气地震相嵌入区内各个地震相范围。     

浅地层剖面测量常见干扰因素分析

为了解浅部地层结构,探测地层属性,查明海底障碍物的分布情况、海域灾害地质情况(如浅层气、滑坡等),经济性、高效性、方便性、分辨率高的浅地层剖面测量得到越来越广泛地应用。在浅地层剖面测量野外施工时常会遇到各种各样的干扰,这些干扰严重影响着资料的质量,增加室内处理的难度,影响解释的准确性。以浅地层剖面测量实际资料为基础,介绍了海流、船速、机械、海况等野外施工时常见的干扰因素及声学特征,并对消除或减弱这些干扰的一些方法进行了分析和比较,针对上述几种典型情况提出了测量作业时减少干扰的建议,如:选择较好的天气条件下作业、控制船速在4～5 kn、远离干扰源等。本文的研究结果能够提高对干扰因素的认识和识别,为获得高质量的资料打好基础。     

投弃式温盐深测量仪在海底地形测量中的应用

介绍了投弃式温盐深测量仪(XCTD)的原理和特点,利用它获得的声速剖面数据与声速剖面仪测量的声速剖面数据进行了精度对比,论述了在特殊环境下,利用多波束测深系统进行海底地形测量时,使用XCTD进行声速剖面测量的优势,解决了测量船停车才能进行声速剖面测量的弊端,显著提高了多波束测深系统作业的效率。     

Waveform Shaping of Sonar Transducers for Improving the Vertical Resolution in Sub-bottom Sediments Profiling

Vertical resolution is of fundamental importance in sonar exploration and is directly related to the duration of the acoustic pulse generated by the transducer. The shorter the radiated pulse, the higher the vertical resolution. Many sub-bottom profiling sonar systems use piezoelectric transducers because they are reversible and well understood. Piezoelectric projectors are normally resonant transducers, which are intrinsically narrowband. A piezoelectric transducer is usually driven by a tone-burst. However, it is possible to use Fourier techniques to find a pre-compensated electrical driving function so that the transducer radiates a prescribed wider band acoustic waveform. This technique can be applied to synthesize zero-phase cosine-magnitude, Gaussian, and bionic pulses, with a conventional sandwich transducer. Zero-phase cosine-magnitude waveforms provide minimum length pulses (and therefore maximum resolution) within a prescribed frequency band.The aim of this paper is to illustrate the synthesis of wideband acoustic pulses using an underwater piezoelectric projector. The conventional acoustic waveform radiated when a Tonpiltz transducer is transiently excited using a “click” and allows its frequency response function to be measured. This function is used to design the electrical signal which then drives the transducer so that it radiates the shortest pulse compatible with its mechanical response. The significant resolution enhancement of the waveform shaping process is illustrated by its application to a sediment wedge model.     

Geoacoustic Uncertainties From Viscoelastic Inversion of Seabed Reflection Data

This paper applies nonlinear Bayesian inversion to seabed reflection data to estimate viscoelastic parameters of the upper sediments. The inversion provides maximum a posteriori probability (MAP) parameter estimates with uncertainties quantified in terms of marginal probability distributions, variances, and credibility intervals; interparameter relationships are quantified by correlations and joint marginal distributions. The inversion is applied to high-resolution reflectivity data from two sites in the Strait of Sicily. One site is characterized by low-speed sediments, resulting in data with a well-defined angle of intromission; the second is characterized by high-speed sediments, resulting in a critical angle. Data uncertainties are quantified using several approaches, including maximum-likelihood (ML) estimation, treating uncertainties as nuisance parameters in the inversion, and analysis of experimental errors. Statistical tests are applied to the data residuals to validate the assumed uncertainty distributions. Excellent results (i.e., small uncertainties) are obtained for sediment compressional-wave speed, compressional attenuation, and density; shear parameters are less well determined although low shear-wave speeds are indicated. The Bayesian analysis provides a quantitative comparison of inversion results for the two sites in terms of the resolution of specific geoacoustic parameters, and indicates that the geoacoustic information content is significantly higher for intromission data     

Expulsion of Shallow Gas in the Skagerrak—Evidence from Sub-bottom Profiling, Seismic, Hydroacoustical and Geochemical Data

A combined high resolution seismic, sub-bottom profiling, and multi-beam echo-sounding survey in the Skagerrak (Danish sector of the North Sea) together with gas analyses at a station along the profile exhibit the expulsion of gas (mainly methane) and the presence of gas-charged sediments at shallow depth. The echo-soundings yield detailed insight into the distribution and shape of typical sea-floor features associated with gas seepage, such as pockmarks. The pockmarks reach dimensions of 800 m in length, 300 m in width, and 15 m in depth, with the long axis running parallel to the slope of the Norwegian Trench. Processing of the multi-channel high resolution seismic data and the digitally recorded sub-bottom profiler signals indicate an internal compressional velocity of about 1050 m s^-1 within the gas-charged sediments reaching from the sea-floor to a sub-bottom depth of about 23 m. Using the lateral distribution and thickness of the gas-charged sediments in conjunction with a mean concentration of gas of 3000 ppb, the present amount of trapped gas is estimated to be 6·45 × 10¹¹ g CH₄. The flux of methane through the sea-bed into the water column appears to be 7·2 × 10¹⁰ g CH₄ per year. To explain the small difference in size between the methane pool in near-surface sediments and the annual flux through the sea-bed, a constantly high supply of methane from leaking hydrocarbon reservoirs at greater depths has to be active.     

海底沉积物烃类气体地球化学异常识别与成因解释

烃类气体是海底渗漏烃的重要组分之一。它们在海底沉积物中主要以游离态和束缚态形式存在。测量海底沉积物烃类气体组成的方法有顶空气法、酸解烃法和热释烃法等。顶空气测量的是在海底沉积物中以游离态存在的烃类气体,酸解烃测定的是吸附在颗粒表面或存在内部包裹体中的束缚烃类气体,热释烃测定的是海底沉积物中被硅铝酸盐所吸附的束缚烃类气体。海底沉积物地球化学异常识别方法包括图解法和计算法等多种方法。海底沉积物地球化学异常成因主要包括有生物成因、热成因和混合成因等。利用烃类气体含量、组合及比值,结合同位素组成特征可以解释地球化学异常成因。     

海底土的电阻率特征及其腐蚀性评价

海底土的电阻率对于海底土的腐蚀性评价具有重要意义．综述了海底土电阻率的特征及洲定方法,介绍和分析了国内外利用土壤电阻率进行土壤腐蚀性评价的方法,并结合我国海底土特征提出了根据海底土电阻率进行腐蚀性评价的分级标准。     

淤泥质海床相邻的岬湾沙滩剖面特征研究

通过对浙江沿海岬角海湾沙滩多处典型剖面的调查,结果表明沙滩与淤泥质海床存在较明显的沙泥分界线,滩面物质自北至南,粒径差别不大,中值粒径在0.15~0.25mm之间,滩面基本呈现单一坡度,坡度为1∶15~1∶30,沙滩坡度与波浪动力相关,沙滩前沿波浪动力强,滩面较缓,反之滩面较陡。沙滩退化表现为滩面的截断、粗化和泥化,滩面截断导致沙滩面积减少,中、细沙供给不足;细沙采挖或局部工程导致的沿岸输沙动力条件的改变会使滩面物质变粗;岬湾的水动力条件减弱,易使沙泥分界线抬升,局部泥化;过度挖沙会导致沙滩消失成为泥滩。     

Chirp技术及其在海底浅层勘探中的应用

Ch irp子波因其宽的频带、长的脉冲延续时间和似白噪音的频率扫描特点,经过子波振幅包络和相关等处理后,具有很高的地层分辨率和资料信噪比,因而在海底浅地层调查中被广泛的采用。文中从Ch irp子波的波形生成开始,逐次讨论它的子波振幅包络和相关处理技术,以及它的分辨率的问题,最后以工程勘查中的实际例子证明Ch irp技术的优越性,同时还讨论了其技术的局限性,以便能对Ch irp技术有个深刻的了解。     

“数字海底”--海底数据集成管理与可视化研究

针对目前"数字海底"建设中存在海底调查数据集成管理与三维可视化表达不足等问题,本文采用GIS技术,以黄河水下三角洲埕北海域为研究对象,利用地理空间数据集成理论与三维建模方法,建立了埕北海域三维海底空间数据库,实现了研究区域地形数据、地层数据、钻孔数据、表层沉积物数据的有效组织管理与可视化,并在此基础上,采用ArcGIS Engine 10.0,结合.NET平台,在Visual Studio 2010开发环境下,利用C#语言进行了二次开发,实现了基于C/S (Client/Server)架构的三维海底虚拟仿真系统的开发,设计了一套面向埕北海域的三维海底虚拟仿真原型系统。     

Physical and Mechanical Characteristics of Seabed Sediment Microstructure in the Northern Shelf of the South China Sea

In the present work, the scanning electron-microscopic observations, electronprobing (energy spectrum) analyses and the analyses of physico-mechanical parmeters have been made for the sediments from two areas of the South China Sea Shelf (i.e., the sea area off the Pearl River mouth and the sea area to the south of Hainan Island); the relaion between the microstructures and the geotechnical (engineering) properties of the shelf seabed sediments has been investigated. Results of analyses reveal the diversity of the micro-structures of sediment and lead to a preliminary micro-structures classification. According to the packing and interconnecting (mutual cotacting) styles of sediment grains, the structure of pores and based on the physical and mechanical parameters, it is possible to comprehensively assess the engineering property of the microenvironments of marine sediments.