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《地球物理学进展》2020,(3)
海底渗漏的羽状流是沉积层赋存天然气水合物的重要证据之一,基于非线性水声学原理的参量阵浅地层剖面仪作为海洋探测的重要设备,对于获得羽状流在水体中的物性特征和渗漏点的浅地层信息有着重大意义.本文根据ATLAS P70浅地层剖面仪在马克兰海域调查中得到的浅地层剖面数据,结合多道地震数据、多波束数据以及地质样品等资料,刻画了研究区内羽状流形态特征,分析了羽状流区海底地层流体运移的通道以及近海底微地形地貌特征.通过研究发现在羽状流区伴随泥火山喷发,自生碳酸盐岩发育,剥蚀海底松散沉积物形成大小不一的麻坑,滋生生物群落等特征.反映在浅剖初始高频(20 kHz)数据界面上羽状流表现为柱状浑浊反射异常,形态呈火焰状,高度由80 m到1500 m不等;对应在次级低频(4 kHz)信号界面可以清晰显示流体渗漏的浅地层结构特征,从中不仅可以识别出流体的运移通道,如泥火山和管状通道等,而且揭示了流体逸散的残留地貌,如麻坑构造和海底滑坡等.本文依托参量阵浅地层剖面数据,对巴基斯坦马克兰海域羽状流有了较全面的认识,为天然气水合物的研究垫定了基础. 相似文献
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声学探测技术在天津隐伏断层探测中的应用 总被引：4，自引：0，他引：4
利用单道地震等水上声学探测技术,对天津海河断裂的浅部构造和地层错断信息进行了探测。探测结果表明,在水深较深,相对宽阔的河道内该方法可以获得较好的结果。在天津塘沽地区,海河断裂的上断点深度位于河底面以下30m左右,对应的最新活动时代为Q_p~3—Q_h~1,这与前期的钻孔勘探结果基本吻合。在渤海近海海域,海河断裂呈一组NWW-NEE向分布的断裂带,其上断点距离海底的深度小于30m,断层断错和影响的地层年代为全新世早中期,断层活动特征与塘沽地区的基本一致。 相似文献
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随着浅剖采集技术的提高,浅剖在深海调查中的应用越来越广泛.与早期仅仅分析实时监控剖面或者纸质剖面不同,人们期望通过对浅剖数据的波形进行处理来获得更多的信息.浅剖数据易受到海底底质、海底地形、海况及采集参数等因素的影响.对原始数据的特征进行分析是后续精细处理和解释的基础,但这方面的工作还较少.本文利用不同海域,不同条件下采集的深水浅剖数据,系统地分析参量阵浅剖原始数据的特征.结果表明:(1)在沉积物比较松软且较为丰富的海域,浅剖数据的穿透深度可超过80 m,而在海底底质比较坚硬的海域,穿透仅为3～20 m;(2)海底地形的较大变化导致浅剖数据上出现大量的绕射波,可能需要更复杂精细的处理来消除它对数据解释的影响;(3)在海况差的海域,涌浪不仅会引起较大的噪声,还导致海底及海底以下地层反射同相轴发生错动,整个剖面呈毛刺状;(4)高低频信号有着不同的特点,包含的信息也不一样,在解释时候需要综合使用.本文的分析结果对精细处理的研究以及浅剖剖面的解释具有指导意义. 相似文献
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本文利用矢量有限元法模拟了一种新型的随钻双感应测井仪器在三维非均匀地层中的响应,分析了井眼、泥浆、侵入带、围岩和仪器偏心对仪器信号的影响,并对仪器刻度时的最佳刻度环参数和刻度系数进行了研究。研究表明:这种新型的随钻双感应测井仪器探测深度优于现有随钻电磁波测井仪器,并具有一定的方位探测能力。深感应和中感应具有不同的最佳刻度环参数和刻度系数,通过刻度和标定响应信号均可达到与地层电导率一致的线性关系。由于探测深度和分辨率不同,深感应和中感应受井眼等地层模型参数和仪器偏心的影响程度不一样,校正系数也不相同。文中结果对随钻双感应测井仪器的研发和资料的应用具有参考意义。 相似文献
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在现有侧向测井仪器基础上,提出了一种新型贴井壁式阵列方位侧向测井电极系,该仪器能提供径向和周向方位电阻率测量.该电极系采用贴井壁测量方式,提供5种径向探测深度.利用三维有限元方法模拟了阵列方位侧向测井电极系的井眼影响特性、径向探测特性、纵向分层能力、方位分辨能力,并模拟其对井周地层、水平井非对称泥浆侵入和倾斜地层的响应.在导电泥浆中最大探测深度为1.23m,纵向分辨率为0.3m,可以识别出0.1m薄层,方位分辨率为20°.贴井壁测量时,纵向分辨率不受泥浆和围岩电阻率的影响,能够准确测量井周方位电阻率,较不贴井壁测量具有很大优势,同时利用12条方位电阻率曲线能够反映出水平井泥浆非对称侵入特性,倾斜地层倾角和倾斜方向. 相似文献
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用面波联合勘探技术探测浅部速度结构 总被引：3，自引：0，他引：3
瑞雷面波勘探技术以其快速经济、受场地条件限制小等优点广泛应用于浅部横波速度结构探测.人工源面波勘探方法对浅部地层的探测精度高,但探测深度较浅;天然源面波勘探方法探测深度较深,但对浅部速度结构的探测精度不高.本文在夏垫和玉溪两地分别开展了人工源和天然源面波联合探测试验,尝试采用不同排列和相同排列两种方法,采集人工源和天然源面波信息,联合处理数据并提取频散曲线,反演得到浅部地层的横波速度结构.探测结果表明:人工源和天然源面波联合勘探,尤其是采用相同排列的方法,可以在几乎不增加常规面波勘探工作量的条件下,既能保证浅部地层的探测精度,又明显拓展探测深度,大大提升了面波勘探能力,有望在工程勘察领域中推广应用. 相似文献
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Th. F. Wever F. Abegg H. M. Fiedler G. Fechner I. H. Stender 《Continental Shelf Research》1998,18(14-15)
The seafloor of central Eckernförde Bay is characterised by soft muddy sediments that contain free methane gas. Bubbles of free gas cause acoustic turbidity which is observed with acoustic remote sensing systems. Repeated surveys with subbottom profiler and side scan sonar revealed an annual period both of depth of the acoustic turbidity and backscatter strength. The effects are delayed by 3–4 months relative to the atmospheric temperature cycle. In addition, prominent pockmarks, partly related to gas seepage, were detected with the acoustic systems. In a direct approach gas concentrations were measured from cores using the gas chromatography technique. From different tests it is concluded that subsampling of a core should start at its base and should be completed as soon as possible, at least within 35 min after core recovery. Comparison of methane concentrations of summer and winter cores revealed no significant seasonal variation. Thus, it is concluded that the temperature and pressure influences upon solubility control the depth variability of acoustic turbidity which is observed with acoustic remote sensing systems. The delay relative to the atmospheric temperature cycle is caused by slow heat transfer through the water column. The atmospheric temperature cycle as ‘exiting function’ for variable gas solubility offers an opportunity for modelling and predicting the depth of the acoustic turbidity. In practice, however, small-scale variations of, e.g., salinity, or gas concentration profile in the sediment impose limits to predictions. In addition, oceanographic influences as mixing in the water column, variable water inflow, etc. are further complications that reduce the reliability of predictions. 相似文献
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分析了石油勘探中采用的薄圆环压电换能器的瞬态响应，研究了它的等效电路并确定了电压激励信号与换能器瞬态振动之间的转换函数。利用留数定理，推导出了在两种类型电压信号激励下，薄圆环压电换能器声源函数的时域及频域的解析式，同时真实地表示了薄圆环压电换能器的实际声源函数。选择合适的压电材料和周围的耦合液体，可以改善发射声波信号的质量．在一定发射功率条件下，保持换能器的几何尺寸不变，降低换能器的共振频率，从而能增加声波测井仪的探测深度和随钻测量（ＭＷＤ）声纳导向系统的测量距离。 相似文献
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浅剖仪在水域活断层调查中的应用研究 总被引：1，自引：0，他引：1
本文利用引进的ChirpⅢ声学剖面系统以及Boomer轰鸣器单道地震系统在不同水域环境下进行了活断层调查研究。通过分别在江河、湖泊以及海域等环境下进行测试,都获得了较好的地层剖面记录,并据此对调查水域的活断层存在情况进行了判断。通过对不同条件下的测试结果进行对比,认为本套探测适合用于查明晚第四系（从数十米到上百米）沉积结构,判断晚第四纪断层存在及其活动性,是了解工程区潜在地质灾害因素的重要途径。另外,本套系统的探测效果与水深以及地层土层性质有较大的关系,在具有一定水深（4m以上）、土层以粘土、粉土居多的地层条件下探测效果较好。 相似文献
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The study of river dynamics requires knowledge of physical parameters, such as porosity, permeability, and wave propagation velocity, of river-bottom sediments. To do so, sediment properties are determined on mechanically sampled specimens and from subbottom profiling. However, mechanical sampling introduces disturbances that affect test results, with the exception of grain-size distribution. In this study, we perform inversion of acoustic data using the grain-size distribution of mechanically sampled specimens and the relation between porosity and permeability from the Kozeny–Carman equation as prior information. The wave reflection coefficient of the water–silt interface is extracted from the raw subbottom profile. Based on the effective density fluid model, we combine the Kozeny–Carman equation and the wave reflection coefficient. We use experimental data from two Yellow River reservoirs to obtain the wave velocity and density of multiple sections and their spatial variations, and find that the inversion and testing results are in good agreement. 相似文献
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The occurrence of gas hydrates in deep-water sections of the continental margins predicted from anomalous acoustic reflectors on seismic profiles has been confirmed by recent deep-sea drilling results. On the Pacific continental slope off Guatemala gas hydrates were brought up for the first time from two holes (497, 498A) drilled during Leg 67 of the DSDP in water depths of 2360 and 5500 m, respectively. The hydrates occur in organic matter-rich Pleistocene to Miocene terrigenous sediments. In the hydrate-bearing zone a marked decrease in interstitial water chlorinities was observed starting at about 10–20 m subbottom depth. Pore waters at the bottom of the holes (near 400 m subbottom) have as little as half the chlorinity of seawater (i.e. 9‰). Similar, but less pronounced, trends were observed during previous legs of the DSDP in other hydrate-prone segments of the continental margins where recharge of fresh water from the continent can be excluded (e.g. Leg 11). The crystallization of hydrates, like ice, excludes salt ions from the crystal structure. During burial the dissolved salts are separated from the solids. Subsidence results in a downward motion of the solids (including hydrates) relative to the pore fluids. Thawing of hydrates during recovery releases fresh water which is remixed with the pore fluid not involved in hydrate formation. The volume of the latter decreases downhole thus causing downward decreasing salinity (chlorinity). Hydrate formation is responsible for oxygen isotope fractionation with18O-enrichment in the hydrate explaining increasingly more positive δ18O values in the pore fluids recovered (after hydrate dissociation) with depth. 相似文献
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V6多功能系统及其在CSAMT勘查应用中的效果 总被引：4，自引：12，他引：4
地球物理多功能探测系统V6是中国科学院地质与地球物理所2000年底从加拿大凤凰公司引进的新仪器，它具有频点多（62频点系列），抗干扰能力强，发射功率大，A/D转换16位置及发射与接收信号GPS（Globe Position System)时钟同步等特点，能有效地提高纵向分辩率和测量信号的信噪比，为浅层精细勘探提供了保障。V6系统在牛栏山水源八厂标准剖面的试验，山东莱芜业庄矿突水勘查工作等充分证明，V6系统能较准确地确定目标的层深度，结合地质资料，可以提供含水性的判断。 相似文献
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Zhao Genmo 《中国地震研究》2004,18(1):27-35
The depth of upper fault point is the key data for ascertaining the active age of a buried fault on a plain. The difference of depth obtained from same fault may be dozens to several hundred meters when using different geophysical methods. It can result in the absolutely opposite conclusions when judging fault activity. Because of a lack of an artificial earthquake source with wide band and high central-frequency, many kinds of methods have to be used together. The higher the frequency of the artificial earthquake wave, electromagnetic wave and sonic wave, the higher the resolution. However the attenuation is also very fast and the exploration depth is very shallow. The reverse is also true. The frequency of artificial seismic waves is in the tens of Hz. Its exploration depth is big and the resolution is poor. The frequency of radar electromagnetic waves is about a million Hz, indicating that the resolving power is better, but the exploration depth is very shallow. However, the acoustic frequency is thousands of Hz, its resolving power is better than that of the artificial earthquake method and the exploration depth is larger than that of the radar method. So it is suitable for extra-shallow exploration in the thick deposit strata of the Quaternary. The preliminary results detected using the high frequency acoustic method in extra-shallow layers indicates that previous inferences about some fault activity in the eastern part of the North China plain may need to be greatly corrected. 相似文献
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Long-term temperature monitoring was carried out in a borehole drilled for investigation of the Nojima fault, an active fault in SW Japan, using the distributed optical fiber temperature sensing (DTS) technique. Temperatures in the borehole had been measured every 1 m along an optical fiber cable with a resolution of about 0.1 K over a period of 6 years. Water injection experiments were conducted in this borehole in 1997, 2000 and 2003. Monitoring of the temperature profile was started after the first injection experiment, and the temperature profile remained very stable until the start of the second injection experiment. During the second and third experiments, the temperatures in the borehole dropped due to cooling by the injected water but no appreciable temperature change was observed below about 580 m. It clearly shows that the water leaked out of the hole around this point and the leaking depth is estimated to be about 540 m based on the shape of the temperature profile. After the injection was stopped, the recovery of the temperature to the undisturbed profile was exceptionally slow around the leaking point, resulting in a local temperature anomaly, probably because the water leaking out of the hole had cooled the surrounding formations extensively. A very similar temperature anomaly was observed at the beginning of temperature monitoring, which suggests that water leaked out at the same depth in the first injection experiment as well. Between the second and third injection experiments, the top of the borehole was kept open to allow groundwater discharge for about 1 month in 2000 and 2003. In both periods, groundwater flowed out continuously and the shapes of the observed temperature profiles indicate that the groundwater entered in the hole at the same depth as the leaking point during the injection experiments. The temperature records also show that the rate of discharge had been nearly constant through the two test periods. The water discharge appears to have been little affected by the water injection. These results demonstrate that the optical fiber temperature monitoring system is a very effective tool for hydrological experiments. 相似文献
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声学深拖作为一个声学设备搭载平台,主要功能是获取高分辨率的声学数据,精细刻画海底地形地貌特征以及浅层剖面结构,对于研究海底浅表层流体活动系统的类型、形成机制和演化模式有着重要作用.本文介绍的合成孔径声学深拖（Synthetic Aperture Sonar Deep-tow）搭载了合成孔径声呐、浅地层剖面仪以及多波束系统等声学设备,相比于传统的侧扫声呐,合成孔径声呐采用小物理孔径基阵通过信号处理虚拟合成大孔径基阵来获得方位向高分辨率,大大提高了测绘速率,同时结合高分辨率的浅地层剖面和多波束背散射数据,可实现海底浅表层特征的三维立体显示.为查明调查区海底浅层流体活动的声学特征,分析天然气水合物相关的流体渗漏活动性与浅层构造之间的关系,我们利用声学深拖对研究区进行了全覆盖的扫测,获得了高分辨率的合成孔径声呐图像、浅地层剖面资料以及多波束背散射数据,平面上识别出多个呈条带状的海底丘状体,火焰状的流体渗漏,新月形的麻坑构造等流体活动地质构造;浅层剖面上可见气体聚集的声学空白段落,凸起的活跃喷口,以及反射杂乱的柱状浑浊带.通过识别流体活动的特征,我们总结了浅层流体活动演化模式具有周期性：游离气体通过高渗透运移通道上升至海底,首先扩散聚集造成局部沉积物体积膨胀形成丘状体;然后受其各种外界因素影响丘状体崩塌而引起气体渗漏;最后流体逸散剥蚀海底松散沉积物而形成麻坑构造;随着流体排出,喷口重新闭合,流体在地层中再次聚集,聚集的气体又将沉积地层上拱,在麻坑底部又可能生成含气丘状体.海底浅表层蕴藏着丰富的地质信息,这对于研究海底复杂的流体活动有着重要意义. 相似文献
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To understand the origin of the methane distributions in sediments of Eckernförde Bay, three sites were sampled in May 1994 for determination of methane, sulfate and chloride concentrations in the sediment porewaters. In much of the Bay, bubbles of biogenic methane gas within the sediments lead to widespread ‘acoustic turbidity’ seen in acoustic surveys, masking the sedimentary structure below the gassy horizon. Acoustic windows, where the gas does not appear to be present, occur in several locations in the Bay, often surrounded by acoustically turbid sediments. Pockmarks, shallow depressions in the sediment, are also found in Bay sediments and may show acoustic turbidity at even shallower depths below the interface than surrounding sediments. One site of each type was sampled in this study. The site probably representative of much of the bay below 20 m water depth, revealed methane saturated conditions by about 75 cm depth below the interface, confirming inferences from acoustic scattering data that free gas was present in the sediment. Above this, the methane concentration profile was concave-upward, indicative of methane oxidation in the overlying, sulfate-reducing sediments. These porewaters showed a slightly decreasing chlorinity with depth. At an acoustic window site, methane concentrations rose to a maximum at about 125 cm depth, but did not reach saturation. Below this depth they decreased in a concave-down pattern. Chloride concentrations decreased markedly with depth, indicative of vertical freshwater flow from below. The third site was a pockmark exhibiting very shallow acoustic turbidity at about 25 cm depth. Here methane concentrations rose to exceed saturation within 25 cm depth below the interface and the porewaters became almost fresh by 1.5 m depth, indicative of a stronger flow of freshwater from below. These groundwater flows have competing effects on the methane inventory. They help exclude sulfate from the sediment, allowing the earlier/shallower onset of methanogenesis, but they also aid loss of methane through advection. A diagenetic model that couples the biogeochemistry of sulfate and methane is used to explain the presence or absence of methane gas in these sediments in relation to the flow rate of fresh groundwater from below. Model results indicate that acoustic windows within otherwise acoustically turbid sediments of the bay are likely due to relatively higher rates of vertical advection of fresh groundwater. The gassy pockmark, however, with an even higher vertical advection rate, seems to require the input of additional reactive organic carbon to explain its vertical methane distribution. 相似文献