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1.
Vibroseis is a method that imparts coded seismic energy into the ground. The energy is recorded with geophones and then processed using the known (coded) input signal. The resulting time‐domain representation of vibroseis data is an impulsive wavetrain with wavelet properties consistent with the coded input signal convolved with the earth's reflectivity series. Historically, vibratory seismic surveys collect data from one source location at a time, summing one or more sources at each location. We present a method of designing orthogonal sweeps using the concept of combisweeps. The orthogonal sweeps allow simultaneous recording and later separation of two or more unique source locations. Orthogonality of sweeps permits separation of the data into unique source‐location field records by a conventional correlation procedure. The separation power of the orthogonal sweeps is demonstrated by a comparison between separated data and data acquired with one vibrator. Separation noise was at a negligible level for our demonstration data sets when two vibrators were located 50 m to 200 m apart. Coincident generation and recording of two vibroseis sweeps at different locations would allow almost double the amount of data to be recorded for a given occupation time and requires only half the storage medium. 相似文献
2.
滑动扫描技术是高效、高保真、环保的可控震源勘探技术之一,是下一组震源不必等待上一组震源震动结束即可开始震动的高效采集方法。该技术由于缩短了相邻两炮的等待时间,使得生产效率得到显著提高。但是后一炮的谐波畸变与前一炮的基波信号混叠在一起,不易分离,在相关后的地震记录上形成了严重的谐波干扰,降低了地震资料的质量。本文提出一种反相关方法来压制滑动扫描地震数据中的谐波干扰。该方法首先把地面力信号分解为基波和各阶谐波分量;然后将后一炮的相关前数据分别与各分量相关,只选取正时间轴中对应分量的自相关部分,利用各分量的反相关算子提取各阶谐波信息;最后从前一炮数据中减去提取出的高阶谐波,得到压制谐波后的地震记录。该方法对有效信号影响小,可同时处理相关前和相关后数据,而且算法简单稳定,计算效率高。本文分别对理论模型和实际数据进行处理,验证了该方法消除谐波干扰的有效性。 相似文献
3.
Break through the limits of vibroseis data quality 总被引：1，自引：0，他引：1
The vibroseis method has become the principal data acquisition method in land seismic exploration. It seems that this method has been extended to its limits as the search for energy resources continues. Many practical issues arising from field operations have remained theoretically unexplained, for example, variations in wavelet arrival time, inaccurate wavelet estimation and harmonics in the wavelet itself. The focus of this paper is the proposal of a new model, which is referred to as the vibrator‐coupled ground model, to simulate the filtering effects of a complex coupling system consisting of the coupling between the baseplate and the ground as well as the coupling between the captured ground mass near the vibrator baseplate and the surrounding earth. With this vibrator‐coupled ground model many of the practical issues mentioned above were reasonably addressed. Furthermore, it was demonstrated from experimental tests that both the pilot sweep and the weighted‐sum groundforce, when filtered by the vibrator‐coupled ground model, are proportional to the far‐field particle velocity whereas the unfiltered signals are not. The harmonics on the filtered weighted‐sum groundforce successfully maintain a proportional relationship with the harmonics seen in the far‐field signal. 相似文献
4.
Anton Ziolkowski 《Geophysical Prospecting》2010,58(1):41-54
The goal of vibroseis data acquisition and processing is to produce seismic reflection data with a known spatially-invariant wavelet, preferably zero phase, such that any variations in the data can be attributed to variations in geology. In current practice the vibrator control system is designed to make the estimated groundforce equal to the sweep and the resulting particle velocity data are cross-correlated with the sweep. Since the downgoing far-field particle velocity signal is proportional to the time-derivative of the groundforce, it makes more sense to cross-correlate with the time-derivative of the sweep. It also follows that the ideal amplitude spectrum of the groundforce should be inversely proportional to frequency. Because of non-linearities in the vibrator, bending of the baseplate and variable coupling of the baseplate to the ground, the true groundforce is not equal to the pre-determined sweep and varies not only from vibrator point to vibrator point but also from sweep to sweep at each vibrator point. To achieve the goal of a spatially-invariant wavelet, these variations should be removed by signature deconvolution, converting the wavelet to a much shorter zero-phase wavelet but with the same bandwidth and signal-to-noise ratio as the original data. This can be done only if the true groundforce is known. The principle may be applied to an array of vibrators by employing pulse coding techniques and separating responses to individual vibrators in the frequency domain. Various approaches to improve the estimate of the true groundforce have been proposed or are under development; current methods are at best approximate. 相似文献
5.
Ulrich Polom 《Geophysical Prospecting》1997,45(4):571-591
The most common noise-reduction methods employed in the vibroseis technique (e.g. spike and burst reduction, vertical stacking) are applied in the field to reduce noise at a very early stage. In addition, vibrator phase control systems prevent signal distortions produced by non-linearity of the source itself. However, the success of these automatic correction methods depends on parameter justification by the operator and the actual characteristics of the distorting noise. More specific noise-reduction methods (e.g. Combisweep (Trade mark of Geco-Prakla), elimination of harmonics) increase production costs or need uncorrelated data for the correction process. Because the field data are usually correlated and vertically stacked in the field to minimize logistical and processing costs, it is not possible to make subsequent parameter corrections to optimize the noise reduction after correlation and vertical stacking of a production record. The noise-reduction method described here uses the final recorded, correlated and stacked vibroseis field data. This method eliminates signal artifacts caused e.g. by incorrect vibroseis source signals being used in parameter estimation when a frequency–time analysis is combined with a standard convolution process. Depending on the nature of the distortions, a synthetically generated, nearly recursive noise-separation operator compresses the noise artifact in time using a trace-by-trace filter. After elimination of this compressed noise, re-application of the separation operator leads to a noise-corrected replacement of the input data. The method is applied to a synthetic data set and to a real vibroseis field record from deep seismic sounding, with good results. 相似文献
6.
Modelling and modal analysis of seismic vibrator baseplate 总被引：1，自引：0，他引：1
Zhouhong Wei 《Geophysical Prospecting》2010,58(1):19-32
The vibroseis method must be extended to its limits as the search for oil and gas continues on land. To successfully improve vibroseis data quality, it is crucial to evaluate each element in the vibroseis data acquisition system and ensure that the contribution from each element is successful. Vibroseis systems depend greatly upon the ability of vibrators to generate synchronous, repeatable ground-force sweeps over a broad frequency range. This requires that the reaction mass and the baseplate of the vibrator move as rigid bodies. However, rigid-body motion is not completely true for high- frequency vibrations, especially for the vibrator baseplate. In order to accurately understand the motion of the vibrator baseplate, a finite element analysis model of the vibrator baseplate and the coupled ground has been developed. This model is useful for simulating the vibrator baseplate dynamics, evaluating the impact of the baseplate on the coupled ground and vibrator baseplate design. Model data demonstrate that the vibrator baseplate and its stilt structure are subject to six significant resonant frequencies in the range of 10–80 Hz. Due to the low rigidity of the baseplate, the baseplate stilt structure experiences severe rocking motions at lower frequencies and the baseplate pad experiences severe flexing motions at higher frequencies. Flexing motions cause partial decoupling, which gives rise to increased levels of harmonic distortion and less useable signal energy. In general, the baseplate pad suffers more bending and flexing motions at high frequencies than low frequencies, leading less efficiency in transmitting the useable energy into the ground. 相似文献
7.
Jack Bouska 《Geophysical Prospecting》2010,58(1):123-153
Distance separated simultaneous sweeping DS3 is a new vibroseis technique that produces independent records, uncontaminated by simultaneous source interference, for a range of offsets and depths that span all target zones of interest. Use of DS3 on a recent seismic survey in Oman, resulted in a peak acquisition rate of 1024 records per hour. This survey employed 15 vibrators, with a distance separation of 12 km between simultaneous active sources, recorded by 8000 active channels across 22 live lines in an 18.5 km × 11 km receiver patch. Broad distribution of simultaneous sources, across an adequately sized recording patch, effectively partitions the sensors so that each trace records only one of the simultaneous sources. With proper source separation, on a scale similar to twice the maximum usable source receiver offset, wavefield overlap occurs below the zone of interest. This yields records that are indistinguishable from non-simultaneous source data, within temporal and spatial limits. This DS3 technique may be implemented using a wide variety of acquisition geometries, optimally with spatially large recording patches that enable appropriate source separation distances. DS3 improves acquisition efficiency without data quality degradation, eliminating the requirement for special data processing or noise attenuation. 相似文献
8.
Harmonic or subharmonic noise is often present in vibroseis data as reverberation‐like, laterally coherent bands occurring parallel to and before or after, the main events. Such periodic noise is typically generated during the standard correlation process when the actual source signal travelling through the subsurface is, for whatever reason, different from the desired source signal, i.e., the pilot‐sweep controlling the baseplate and used for correlation. A typical cause can be that harmonic or subharmonic frequency partials are generated in addition to the vibroseis sweep's desired fundamental frequencies. These harmonics produce strong ‘ghost events’ during correlation of the geophone trace with the pilot‐sweep, originating from additional correlations between the fundamental and harmonic frequencies. Especially subharmonic ‘ghosts’ will overlap with ‘good’ fundamental signals, since for typically used up‐sweeps they are folded to later traveltimes, where the signal/noise‐ratio is already lower, thus aggravating or preventing a reliable interpretation of possible later reflections. Here, a method is introduced to remove these unwanted noise trains (with only negligible impact on the fundamental signal) by transforming the seismogram traces into a so‐called ‘(sub)harmonic domain’. In this domain, the respective harmonic noise portions are focused and separated from the fundamental signals, enabling easier detection and appropriate suppression. After back‐transformation to the x‐T domain, the records are free from the corresponding harmonic contamination and can then be processed as usual. The method operates in a data‐driven fashion, i.e., the traces are not uniformly processed but are processed depending upon their actual (sub)harmonic content. The decontamination procedure can be applied universally, i.e., to uncorrelated/correlated and/or vertically unstacked/stacked data either in a manual, semiautomated or fully automated manner. The method works perfectly for synthetic vibroseis traces with or without harmonic/subharmonic portions. The application to real, crustal‐scale vibroseis records that were acquired in 2006 in the Dead Sea region, Israel and that were severely contaminated by subharmonic ground‐roll ghosts covering reflectivity from the basement to the Moho, shows the robustness and success of the presented method. 相似文献
9.
当测区噪声很强,采用组合震源工作仍然不能满足信噪比要求时,为进一步提高地震勘探信噪比,引入能形成定向地震波的相控震源.针对水平层状介质模型,对组合震源、相控震源地震进行了数值模拟,并定量计算了采用4,8,15,20单元的组合与相控震源地震数据的信噪比,同组合地震相比,相控地震使来自不同反射层的反射波信号的信噪比平均提高了154～990 dB.结果表明,相控震源地震得到的反射波信号信噪比高于组合地震,并且随着激震器数目增加,相控震源合成地震记录中的反射波地震数据信噪比明显提高. 相似文献
10.
Geophysical benefits from an improved seismic vibrator 总被引：1，自引：0，他引：1
The seismic vibrator has become a very important source for land data acquisition and there have been dramatic improvements in recent times in the application of the vibroseis technique. These improvements have led to much increased productivity and in many cases much denser source sampling. At the same time, the vibrator itself has seen little improvement over the last couple of decades. There are needs in a few areas where an improvement in the vibrator itself can bring benefits to the quality of the seismic data acquired. This paper describes progress in four such areas, low‐frequency performance, high‐frequency performance, an improved estimate of the vibrator groundforce and source signature consistency over variable ground conditions. Each of these vibrator characteristics will be discussed in turn. Meanwhile, two field test results in which the performance of two different vibrators in these four areas are compared. 相似文献
11.
P. NEWMAN 《Geophysical Prospecting》1985,33(2):224-232
The success of signature deconvolution in optimizing both signal-to-noise ratio and time resolution in the seismic section depends critically upon obtaining an accurate estimate of the far-field source signature. Various deterministic estimation schemes have been proposed in recent years, most of which involve direct monitoring of source output within the water layer. As an alternative to elaborate and error-prone source monitoring schemes during data acquisition, a simple modification to any source array permits subsequent estimation of far-field signatures directly from reflected signal. The new method requires the inclusion within any chosen source array of a simple point source, the “reference” source. Initial experiments employed a water gun as the reference source, characterized by a concise implosive signature with peak-to-peak amplitude of approximately 2 bar·m within the seismic sprectrum. In operation the reference source is fired shortly before the main array (typically 2 s during initial trials) and the usual record length is extended by a similar amount. Each recorded trace then comprises two results: the subsurface response to the reference source signal followed by the response of the same subsurface to the main array. The disparities in source amplitudes and NMO differentials ensure that interference effects are negligible in the main recording. Time- or frequency-domain methods can be employed to extract the main array signature from the dual dataset or to invert this to some preferred wavelet simultaneously. As an additional benefit the reference source yields excellent high-resolution profiles of the shallow geology. 相似文献
12.
Abd El‐Aziz Khairy Abd El‐Aal 《Geophysical Prospecting》2011,59(2):279-294
In this paper, an improved method is presented to reduce vibrator harmonic distortion, one harmonic at a time and the method is illustrated with both simulated and field data. This method improves on the previous method that treated all the harmonics at once. The significant contribution in this procedure is a considerable reduction for the harmonics without any alteration for the weakest signals possibly present in positive and negative times. The core of the proposed technique depends on an accurate simulation for all the harmonics one by one existing in the positive and negative times of the data after cross‐correlation with the fundamental sweep and then subtracting the simulated harmonics from the original data using an optimization procedure. The steps and mathematical equations of the procedure are explained in detail in the body of the article in the section titled ‘harmonic by harmonic attenuation procedure’. Accordingly, a well‐developed procedure for enhancing the vibroseis data quality in both down‐ and up‐sweep data is illustrated. The procedure was tested on both synthetic and field data sets. 相似文献
13.
R.M. Laws D. Halliday J.-F. Hopperstad D. Gerez M. Supawala A. Özbek T. Murray E. Kragh 《Geophysical Prospecting》2019,67(6):1443-1471
Marine seismic vibrators are generally considered to be less intrusive than airguns from an environmental perspective. This is because they emit their energy spread out in time, rather than in a single, high-intensity pulse. There are also significant geophysical benefits associated with marine vibrators, and they stem from the ability to specify in detail the output acoustic waveform. The phase can be specified independently at each frequency. Such detailed control cannot be achieved with conventional airgun sources, where the phase can only be modified using simple overall time delays. The vibrator phase can be employed in several different ways: it can be applied to the overall source phase in a sequence so that it varies from one source point to the next; it can be applied to the individual vibrators within the source array so the source directivity is changed; it can be applied to the overall source phase of each source in a simultaneous source acquisition. Carefully designed phase sequences can attenuate the residual source noise, and this in turn allows extra source points to be interleaved between the conventional ones. For these extra source points, the relative phase of the vibrators within the array can be chosen to create a transverse gradient source, which illuminates the earth predominantly in directions out of the plane of the sail line without left/right ambiguity. If seismic vibrator data are acquired using interleaved conventional and transverse gradient sweeps, more information is collected per kilometre of vessel travel than is the case in conventional acquisition. This richer data acquisition leads to the possibility of acquiring all the necessary seismic data in a shorter time. Three-dimensional reconstruction techniques are used to recover the same image quality that would have been obtained using the conventional, more time-consuming acquisition. For a marine vibrator to be suitable for these techniques it must, in general terms, have ‘high fidelity’. The precise device specifications are defined through realistic end-to-end simulations of the physical systems and the processing. The specifications are somewhat more onerous than for a conventional vibrator, but they are achievable. A prototype vibrator that satisfies these requirements has been built. In a simulated case study of a three-dimensional deep-water ocean bottom node survey, the seismic data could have been acquired using marine vibrators in one third of the time that it would have taken using airguns. 相似文献
14.
15.
U. Polom 《Pure and Applied Geophysics》1999,156(1-2):319-344
—Seismic recording systems without a telemetry system have often been affected by electromagnetic induced spikes or bursts, which lead to strong data distortions combined with the correlation process of the vibroseis method. Partial or total loss of the desired seismic information is possible if no automatic spike and burst reduction is available in the field prior to vertical stacking and correlation of the field record.¶Currently, combined with the use of modern telemetry recording systems, the most common noise reduction methods in vibroseis techniques (e.g., spike and burst reduction, diversity stack) are already applied in the field to reduce noise in a very early state. The success of these automatic correction methods depends on the fundamental principles of the recording situation, the actual characteristic of the distorting noise and the parameter justification by the operator. Since field data are usually correlated and already vertical stacked in the field to minimize logistical and processing costs, no subsequent parameter corrections are possible to optimize the noise reduction after correlation and vertical stacking of a production record.¶The noise reduction method described in this paper uses final recorded and stacked vibroseis field data at the correlated or uncorrelated stage of processing. The method eliminates signal artifacts caused by spikes or bursts combined with a standard convolution process. A modified correlation operator compresses the noise artifact in time using a single trace convolution process. After elimination of this compressed noise, re-application of the convolution process leads to a noise-corrected replacement of the input data. The efficiency of the method is shown with a synthetic data set and a real vibroseis field record. Furthermore, several thousand records from a 2-D deep seismic reflection project could be corrected with good results using this method. 相似文献
16.
多震源地震正演数值模拟技术 总被引：2，自引：0，他引：2
常规地震采集技术因受相邻时间激发炮之间时间间隔的制约而存在采集周期过长,采集成本过高的问题,而多震源同步激发地震采集技术可以克服这方面的缺陷,但存在着波场过于复杂的问题,地震正演模拟技术可以帮助我们提高对这种复杂波场的认识水平,为此采用2D弹性波方程交错网格高阶有限差分格式,开发了多震源同步激发波场正演数值模拟技术,能够模拟任意多个同步激发震源的弹性波波场,震源函数可以是雷克子波,也可以是可控震源扫描信号,且同步激发震源之间可以有随机时差.模型试算结果分析表明,该技术既是一项高精度的多震源正演模拟技术,也是一项高效率的地震正演数值模拟技术. 相似文献
17.
Vibroseis productivity: shake and go 总被引：2，自引：0，他引：2
We use both model and field data to compare three methods for increasing vibroseis productivity and decreasing acquisition costs. The first method, HFVS (high-fidelity vibratory seismic), allows us to separate the responses from individual vibrators when multiple vibrators are operating simultaneously. The data quality of the separated records is superior to that of conventional correlated data because they are processed with measured ground-force signals, but the number of sweeps must be greater than or equal to the number of vibrators. The second method, cascaded sweep, eliminates the listening time between multiple sweeps and partially mitigates harmonic noise observed at later times on near-offset traces. Finally, a combined method, continuous-HFVS (C-HFVS), allows source separation with a single, long, segmented sweep. Separation is as good as with HFVS and interference noise is limited to times near the end of a sweep-segment length. All three methods produce acceptable seismic images for post-stack and prestack amplitude interpretation.
The choice of which option to use depends upon the area being investigated. HFVS has numerous benefits, especially when fine sampling is required to mitigate static problems and elevation changes. Due to the ability to separate individual responses, fine sampling can be achieved without sacrificing productivity. For deeper targets, cascaded sweep can be more efficient but data quality suffers from harmonic noise. C-HFVS, which combines features of HFVS and cascaded sweep, has the potential to result in the highest productivity, without sacrificing either fine sampling or data quality. 相似文献
The choice of which option to use depends upon the area being investigated. HFVS has numerous benefits, especially when fine sampling is required to mitigate static problems and elevation changes. Due to the ability to separate individual responses, fine sampling can be achieved without sacrificing productivity. For deeper targets, cascaded sweep can be more efficient but data quality suffers from harmonic noise. C-HFVS, which combines features of HFVS and cascaded sweep, has the potential to result in the highest productivity, without sacrificing either fine sampling or data quality. 相似文献
18.
应用可控震源地震勘探,当环境噪声很强,采用组合震源工作仍不能满足信噪比要求时,引入能形成定向地震波的相控震源.由相控震源定向照明地震理论分析,主波束方向上3单元相控震源产生的反射地震波信号信噪比比单震源高6.53~9.54 dB,比组合震源高1.76~4.77dB.为研究相控地震实际效果,在同一测区进行了三种震源地震对比实验.由单炮地震记录和水平叠加时间剖面可知,相控震源反射波信号信噪比明显高于单震源情况,略高于组合震源情况.进一步对反射波信号功率谱特性做定量分析,得到如下结果：与单震源情况相比,相控震源使各道反射波信号信噪比提高了0.75~8.15 dB,平均提高3.65 dB;与组合震源情况相比,各道信噪比提高了0.93~3.17 dB,平均提高2.02 dB,实验结果与理论分析吻合.综上所述可知,基于相控震源的定向照明地震技术是可行的,可以有效提高地震信号的信噪比. 相似文献
19.
High Fidelity Vibratory Seismic (HFVS) acquisition and separation can play an important role in today's land acquisition schemes. The method – in which multiple vibrators are swept simultaneously using sweeps with known phase encoding and then the data are inverted and separated into individual records – can improve productivity in the field and at the same time improve signal characteristics in the data. It relies on the measured weighted sum of accelerations (base plate and reaction mass) to invert the acquired data and separate the individual vibrator responses. Separation can be sub-optimal if the measured motions vary from the 'true source' input into the ground. Differences in true source and measured source can arise due to poor coupling between vibrators and ground, soil compaction or other factors. Using both a synthetic model and real data, we show that if the true source changes between sweeps but is not measured, vibrator responses can leak into adjacent vibrator responses upon separation. In a recent survey with HFVS acquisition, we observed a 25–30 dB separation between adjacent vibrators, which could be improved with greater reliability of the source measurement. The vibrator leakage can reduce the data quality considerably. We discuss the results of this survey and show that separation is affected by source measurement error. Further, we conclude that it is necessary either 1) to use source measurements that can capture the variability of the true source between sweeps or 2) to compensate for the source measurement variations in processing or in acquisition. 相似文献
20.
常规的可控震源Chirp扫描信号的地震响应存在着相关信号旁瓣大、分辨率低的缺点;用二元伪随机编码信号作为可控震源的驱动信号,地震响应剖面中存在严重的相关噪声,降低了地震记录的信噪比.本文提出的可控震源匹配扫描方法,利用匹配伪随机序列偶调制正弦载波信号作为可控震源驱动信号进行扫描激发,得到两个匹配的原始地震记录,对两个匹配的原始地震记录分别解码后再进行叠加形成最终的综合解码地震剖面.地震数值模拟的结果表明,该方法基本不存在常规Chirp扫描情形的旁瓣效应,可有效避免m-序列编码扫描情形的相关噪声,其最后形成的综合解码地震剖面可以与脉冲震源的炮集记录相媲美. 相似文献