海陆两栖地区地震勘探新型检波器的研制及应用效果

本文分析了海陆两栖地带地震勘探中同时使 用的速度检波器和加速度检波器存在的差异及其对 地震信号的影响;在此基础上,设计研制出了陆用 压电检波器,并对其性能特点进行了分析;通过试 验资料分析,消除了海陆两种不同机理的检波器资 料的相位差的问题,陆用压电检波器和水中压电检 波器记录信号的频带和能量达到一致,提高了地震 资料的分辨率;实现了海陆地区可以同时采用相同 机理的检波器进行地震信号的接收,解决了滩海地 区速度检波器和加速度检波器长期混用的问题。     

陆上高分辨率地震勘探检波器性能及应用效果分析(英文)

地震检波器的性能是高分辨率地震数据采集中的一个重要因素,对资料的品质影响很大。为此,作者在不同类型地区对目前在高分辨率地震勘探中常用的动圈式检波器、涡流检波器和数字检波器的性能进行了对比试验。通过野外工作的实际,总结了动圈式检波器、涡流检波器和数字检波器在不同表层地质条件地区的应用效果,提出了适合该类地区高分辨率地震检波器的性能指标,指出合理选择检波器类型和检波器的联接方式,能提高地震资料的信噪比和分辨率。     

流动地震仪检测钻头振动信号的现场试验

钻井过程中钻头对井底的冲击振动为钻头前方地层的探测提供了震源,可用来消除钻井过程中的地质不确定性和降低钻井风险.本研究在分析井下钻头振动信号特点的基础上,根据现代地震观测技术的新发展,将多道勘探地震仪和流动数字地震仪的性能进行了对比分析,将天然地震的观测设备和分析方法应用到随钻地震检测中,提出了一套新的随钻地震检测方案,利用高灵敏度流动数字地震仪连续检测钻井过程中的钻头振动信号,初步现场试验表明该技术方案可行,获得的信号信噪比高,易于钻井工程师掌握,为随钻地震技术提供了新的技术路线.     

宽线地震技术在辽河盆地西部凹陷八一水库区域勘探的应用

宽线地震技术是一种地震勘探方法，它采用的是一种特殊的三维观测系统，特别适合在一些障碍区内施工。本文介绍的这项技术主要包括：研制出新型的水中钻井平台，解决了水中激发问题；精心试验，掌握了不同类型检波器之间的相位差别；采取一些特殊的处理方法，解决了新老资料在采集方法和资料品质上的差异。综合应用这些技术有效地填补了以往勘探地震剖面上的资料空白。     

光栅Bragg地震检波器的传感特性研究(英文)

针对目前石油地震勘探的瓶颈—检波器性能差的问题,设计了一种新型光纤Bragg光栅（FBG）地震检波器,阐述了其工作原理,并从理论上给出了检波器的响应函数等参数。由于FBG的传感优势,这种新型地震检波器动态范围可达94dB,灵敏度高,重量轻,造价低,是理想的新一代地震勘探信号采集单元。     

Passive Seismic Monitoring of Mine-scale Geothermal Activity: A Trial at Lihir Open Pit Mine

The Lihir open pit mine in Papua New Guinea is located inside an old volcano where geothermal activity is strongly present. Outbursts of hot water and steam into the mining areas were a major safety concern. Passive seismic monitoring was carried out at the mine to investigate whether the geothermal activities could be detected and located using microseismic techniques in a mining environment. In this trial, sixteen triaxial geophones which can withstand temperature up to 200°C were used and installed in four deep boreholes inside the pit. The microseismic events were discriminated using the STA/LTA triggering criterion. During 6 weeks of monitoring, more than 17,000 events were recorded. Approximately 12% of the events showed harmonic vibration characteristics similar to those observed in other geothermal and volcanic areas, suggesting that the geothermal activity inside the pit was captured by the microseismic monitoring system. More than 75% of the events present both P and S waves and they were interpreted to be associated with rock fracturing due to stress release near the bottom of the pit. Many geothermal-type events were located in areas where shear events occurred, implying that the detected geothermal events were not far from the mining area below the pit and they may also be associated with mining. The borehole installation of the geophones significantly reduced the interference of mining noise and achieved good observation of the seismic events. However, equipment installation requires great attention as the geophones may be destroyed due to unexpected rising temperature within the boreholes.     

Multichannel analysis of surface wave method with the autojuggie

The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the ‘autojuggie’) is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys.     

基于共姿态道集的静校正方法

静校正问题是地震勘探的关键问题,直接影响地震勘探精度和准确性.实际地震采集过程中,当在相同接收点位置上不同时间内插拔布设了不同的检波器时,对于目前基于地表一致性理论假设的基准面静校正和剩余静校正,以及非地表一致性剩余静校正都不具备适用条件.为解决这一问题,本文提出了基于共姿态道集的静校正方法,将相同接收点位置上不同时间布设的检波点所接收的地震数据抽成不同的共姿态道集,在共姿态道集内实施地表一致性静校正;当某接收点位置上具有若干个共姿态道集时,该接收点位置上可能会存在多个检波点静校量;炮点静校问题仍然采用地表一致性静校正方法解决.该方法解决了同一接收点位置上不同共姿态道集之间的非地表一致性静校正问题,同时也解决了全区的检波点和炮点的地表一致性静校正问题,在实际数据应用效果明显.     

A COMPARISON BETWEEN KIRCHHOFF AND GRT MIGRATION ON VSP DATA1

A modern approach to migration is to perform wavefield extrapolation, subject to an imaging condition. Correct wavefield extrapolation requires that the boundary conditions at the array of geophones satisfy the wave equation. A sufficient condition is to perform the survey with a single stationary source. Contrary to this condition, many VSPs are conducted in deviated wells, where the source is maintained vertically above the down-hole geophone at each well station. Such a survey fails to provide the boundary conditions theoretically necessary for wave-equation migration. A recently published inversion scheme, referred to as acoustic generalized Radon transform migration (GRT migration), was developed to handle any configuration of sources and geophones, including moving-source deviated-well VSP surveys. GRT migration may be viewed as a weighted version of the generalized Kirchhoff migration, derived in this paper from the exploding-reflector model. When a VSP-survey geometry has been specified, GRT migration can be expressed in terms of array parameters, and compared with the equivalent expression for Kirchhoff (wave-equation) migration. The differences between the two integrals are significant and their effect is demonstrated on VSP data.     

Burying receivers for improved time‐lapse seismic repeatability: CO2CRC Otway field experiment

4D seismic is widely used to remotely monitor fluid movement in subsurface reservoirs. This technique is especially effective offshore where high survey repeatability can be achieved. It comes as no surprise that the first 4D seismic that successfully monitored the CO₂ sequestration process was recorded offshore in the Sleipner field, North Sea. In the case of land projects, poor repeatability of the land seismic data due to low S/N ratio often obscures the time‐lapse seismic signal. Hence for a successful on shore monitoring program improving seismic repeatability is essential. Stage 2 of the CO2CRC Otway project involves an injection of a small amount (around 15,000 tonnes) of CO₂/CH₄ gas mixture into a saline aquifer at a depth of approximately 1.5 km. Previous studies at this site showed that seismic repeatability is relatively low due to variations in weather conditions, near surface geology and farming activities. In order to improve time‐lapse seismic monitoring capabilities, a permanent receiver array can be utilised to improve signal to noise ratio and hence repeatability. A small‐scale trial of such an array was conducted at the Otway site in June 2012. A set of 25 geophones was installed in 3 m deep boreholes in parallel to the same number of surface geophones. In addition, four geophones were placed into boreholes of 1–12 m depth. In order to assess the gain in the signal‐to‐noise ratio and repeatability, both active and passive seismic surveys were carried out. The surveys were conducted in relatively poor weather conditions, with rain, strong wind and thunderstorms. With such an amplified background noise level, we found that the noise level for buried geophones is on average 20 dB lower compared to the surface geophones. The levels of repeatability for borehole geophones estimated around direct wave, reflected wave and ground roll are twice as high as for the surface geophones. Both borehole and surface geophones produce the best repeatability in the 30–90 Hz frequency range. The influence of burying depth on S/N ratio and repeatability shows that significant improvement in repeatability can be reached at a depth of 3 m. The level of repeatability remains relatively constant between 3 and 12 m depths.     

Assessment and compensation of inconsistent coupling conditions in point-receiver land seismic data

We introduce a method to detect and compensate for inconsistent coupling conditions that arise during onshore seismic data acquisitions. The reflected seismic signals, the surface waves, or the ambient-noise records can be used for the evaluation of the different coupling conditions of closely spaced geophones. We derive frequency-dependent correction operators using a parametric approach based upon a simple model of the interaction between geophone and soil. The redundancy of the measurements available permits verification of the assumptions made on the input signals in order to derive the method and to assess the validity of the model used. The method requires point-receiver data in which the signals recorded by the individual geophones are digitized. We have verified the accuracy of the method by applying it to multicomponent ambient-noise records acquired during a field experiment in which the coupling conditions were controlled and modified during different phases of the experiment. We also applied the method to field data, which were acquired without the coupling conditions being controlled, and found that only a few geophones showed an anomalous behaviour. It was also found that the length of the noise records routinely acquired during commercial surveys is too short to provide enough statistics for the application of our method.     

基于稀疏约束和多源激发的地震数据高效采集方法

地震勘探目标日趋复杂化和精细化,"两宽一高"等采集技术获得了广泛应用,从而导致当前地震数据采集周期越来越长、成本越来越高,如何解决日益增长的勘探成本问题成为当前地震采集领域的研究热点之一.针对上述问题,本文首先开展了基于稀疏性的地震数据高效采集方法理论研究,对地震数据稀疏性基本理论、稀疏约束下随机采样及其数据重建方法进行了深入探讨,提出使用改进的分段随机采样方法灵活地进行实际地震采集测网设计;详细阐述了多源地震激发方法,对多源地震数据分离方法开展了深入研究,提出了基于小窗口中值滤波与稀疏约束联合随机去噪的多源数据分离方法,并在数据分离处理中取得了较好的效果;将上述两种地震数据采集方案有机结合,提出了1)规则多源、随机检波点(DmsRg)、2)随机多源、规则检波点(RmsDg)和3)随机多源、随机检波点(RmsRg)等三种高效采集方案及相应的数据重建方案,满足了后续常规化数据处理的要求,并讨论了多源激发对数据成像的影响.基于Marmousi模型数据的数值试验表明,本文构建的基于稀疏约束和多源激发的高效采集方法理论对于提高地震数据采集效率、降低勘探成本具有重要的应用价值,建立的数据重建方法流程可以取得和常规数据接近的成像结果.本文方法虽然在数值试验中取得了较为理想的效果,但还需要得到野外实际数据采集的进一步检验.     

Geophone‐ground coupling with flat bases

Seismic acquisition can be costly and inefficient when using spiked geophones. In most cases, such as the desert, the most practical solution is the use of flat bases, where geophone‐ground coupling is based on an optimal choice of the mass and area of contact between the receiver and the ground. This optimization is necessary since areas covered by sand are loose sediments and poor coupling occurs. Other cases include ground coupling in stiff pavements, for instance urban areas and ocean‐bottom nodes. We consider three different approaches to analyse coupling and model the geophone with a flat base (plate) resting on an elastic half‐space. Two existing models, based on the full‐wave theory, which we refer to as the Wolf and Hoover‐O'Brien models, predict a different behaviour with respect to the novel method introduced in this work. This method is based on the transmission coefficient of upgoing waves impinging in the geophone‐ground contact, where the ground is described as an anelastic half‐space. The boundary conditions at the contact have already been used to model fractures and are shown here to provide the equation of the damped oscillator. This fracture‐contact model depends on the stiffness characteristic of the contact between the geophone base plate and the ground. The transmission coefficient from the ground to the plate increases for increasing weight and decreasing base plate area. The new model predicts that the resonant frequency is independent of the geophone weight and plate radius, while the recorded energy increases with increasing weight and decreasing base plate area (as shown from our own experiments and measurements by Krohn) which is contrary to the theories developed by Wolf and Hoover‐O'Brien. The transient response is obtained by an inverse Fourier transform. Optimal geophone‐ground coupling and energy transmission are required, the first concept meaning that the geophone is following the motion of the ground and the second one that the signal is detectable. As a final example, we simulate seismic acquisition based on the novel theory, showing the differences between optimal and poor ground‐to‐geophone energy transmission.     

中国大陆科学钻探孔区全观式三维地震采集

大陆科学钻探不仅是打一口钻,而是深部钻探同地球物理遥测结合起来的相互反馈系统,这里地球物理遥测主要是指三维深反射地震. 中国大陆科学钻探孔区三维地震调查是大陆科学钻探工程的一项重要内容. 在数据采集中提出了全观式三维地震调查新技术,它是指排列不滚动的三维地震调查,即将地震检波器铺满全部测区的一种地震采集方法,尤其适合于有限面积的三维地震工作. 这种方法的优点是：(1)快速高效; (2)叠加次数高; (3)与常规三维地震相比成本大幅度减少. 在中国大陆科学钻探孔区内进行的全观式三维地震测量,全面实现了预期目标,包括：(1) 配合钻探查明孔区地质构造,将钻探的一孔之见扩展到深6000m、长宽超过3000m的三维岩柱;(2)提供高精度定位的地壳反射体以供标定;(3)发现中、下地壳及地幔内的反射体等.     

Field testing of modular borehole monitoring with simultaneous distributed acoustic sensing and geophone vertical seismic profiles at Citronelle,Alabama

A modular borehole monitoring concept has been implemented to provide a suite of well‐based monitoring tools that can be deployed cost effectively in a flexible and robust package. The initial modular borehole monitoring system was deployed as part of a CO₂ injection test operated by the Southeast Regional Carbon Sequestration Partnership near Citronelle, Alabama. The Citronelle modular monitoring system transmits electrical power and signals, fibre‐optic light pulses, and fluids between the surface and a reservoir. Additionally, a separate multi‐conductor tubing‐encapsulated line was used for borehole geophones, including a specialized clamp for casing clamping with tubing deployment. The deployment of geophones and fibre‐optic cables allowed comparison testing of distributed acoustic sensing. We designed a large source effort (>64 sweeps per source point) to test fibre‐optic vertical seismic profile and acquired data in 2013. The native measurement in the specific distributed acoustic sensing unit used (an iDAS from Silixa Ltd) is described as a localized strain rate. Following a processing flow of adaptive noise reduction and rebalancing the signal to dimensionless strain, improvement from repeated stacking of the source was observed. Conversion of the rebalanced strain signal to equivalent velocity units, via a scaling by local apparent velocity, allows quantitative comparison of distributed acoustic sensing and geophone data in units of velocity. We see a very good match of uncorrelated time series in both amplitude and phase, demonstrating that velocity‐converted distributed acoustic sensing data can be analyzed equivalent to vertical geophones. We show that distributed acoustic sensing data, when averaged over an interval comparable to typical geophone spacing, can obtain signal‐to‐noise ratios of 18 dB to 24 dB below clamped geophones, a result that is variable with noise spectral amplitude because the noise characteristics are not identical. With vertical seismic profile processing, we demonstrate the effectiveness of downgoing deconvolution from the large spatial sampling of distributed acoustic sensing data, along with improved upgoing reflection quality. We conclude that the extra source effort currently needed for tubing‐deployed distributed acoustic sensing vertical seismic profile, as part of a modular monitoring system, is well compensated by the extra spatial sampling and lower deployment cost as compared with conventional borehole geophones.     

海底地震仪的信号传递效果和噪声水平

单球式海底地震仪（以下简称OBS）由于其成本低、操作简便的优点在天然地震研究、人工地震探测中获得了广泛应用.本文首先分析多型进口和国产OBS在台湾海峡西部采集的地震数据,发现同一台OBS上的垂直向速度检波器（Z分量）的信噪比常显著低于压力检波器（H分量）,由于这两种检波器记录的都是海底的垂向振动信号,推测速度检波器的低信噪比更多的与仪器特性有关.然后从信号传递和噪声水平两方面分析影响速度检波器信噪比的因素：为检测速度检波器与OBS壳体的耦合效果,对某型宽频带OBS和陆上地震仪进行了同址同步观测试验,发现OBS的整机灵敏度有较大的差异;为分析速度检波器的水底噪声特征,以H分量记录作为基准,对比分析了同一台仪器不同站位的Z分量噪声水平,发现速度检波器在浅海区受到较大的次生干扰.本文指出OBS的内部耦合和水流次生干扰是至今尚未引起大家重视而又严重影响资料品质和多波探测成效的两个关键问题,这一研究结果对于改进OBS结构设计和制造工艺,以及OBS数据多分量处理方法研究有重要的参考意义.     

地震检波器的横向灵敏度特性

地震检波器受到地面横向运动激励时的输入输出关系定义为检波器的横向灵敏度特性.本文对检波器线圈受到横向激励时产生的轴向振动进行了分析.可以看到,当悬挂线圈的弹簧片悬丝发生动力失稳时,检波器的横向灵敏度突然增大;在线圈横向振幅很小的情况下,失稳频率接近悬丝的横向固有频率.利用谱分析技术可以准确地从检波器噪声中检测出检波器的横向灵敏度和失稳频率,即检波器假频.     

ON THE MINIMIZATION OF THE DISTORTION CAUSED BY THE GEOPHONE-GROUND COUPLING *

It is well known that the application of the “bright spot’ technique has been more successful in marine prospecting than in land prospecting. This is due partly to the problem of distortion of the seismic signal caused by the geophone-ground coupling, especially when carrying out high resolution, shallow seismic surveys in swampy terrain. The effect of geophone-ground coupling on the response of a single geophone to the incident compressional waves has been treated by several authors. However, they have always neglected the influence of mutual interaction between an array of geophones on the response of each geophone forming the array. We show that mutual interaction, which results from the re-radiation of the incident compressional waves by the geophones forming the array, can have considerable effect on the response of each geophone. The effect of the geophone-ground coupling on the response of a seismic channel is considered in the absence and presence of mutual interaction between a group of geophones for the case when the shear wave velocity of the soil varies by a factor of three.     

乌鲁木齐市东北郊碗窑沟断层超浅层地震探测初步研究

碗窑沟断层是乌鲁木齐市主要的晚更新世中期活动断层,在市区与郊区被厚约数十米的第四系所覆盖。本文介绍了在乌鲁木齐市东北郊干扰背景较小地段对碗窑沟断层进行的超浅层纵波反射探测情况。在选取小道间距、适当偏移距、短排列、多次覆盖、高频检波器接收的工作方法和合理数据处理方法基础上,获取了3条典型纵波反射剖面,都可较清楚地分辨出第四系底界和断层位置。表明在探测环境比较好的条件下,采用合适的观测系统,在断层两盘介质存在明显差异的地区可以采用纵波反射方法探测出埋深小于50 m的断层。     

SISMIQUE MINIERE A HAUTE FREQUENCE*

High Frequency Mining Seismics. Reflection profiles in mining galleries have been made with a new type of equipment including appropriate arrays, special geophones and high frequency recording (30–2000 c.p.s.). Reflections at frequencies between 600 and 1200 c.p.s. have been obtained, in favourable cases, from coal beds about 3 feet thick, lying at depths reaching 200 feet below the gallery. Good rock compactness is necessary to obtain fair reflections, and in such cases it may be possible to detect discontinuities in the coal beds.