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基于单枪容量为250 in~3的BHS-2200LL井中气枪,在内径0.2、5.0m不同激发井中开展了气枪震源特征对比分析,研究表明:15.0m井中气枪激发产生的信号优势频率集中在10~40Hz,比在0.2m井中的低,这主要是由于较大水体利于气泡的振荡;2在能量方面,5.0m井中激发信号的能量强于0.2m井中的,相差1个数量级,单次激发的传播距离可达9km;32种激发环境下产生的气枪信号都具有较好的重复性。 相似文献
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气枪震源是一种重复性很高的人工震源.受激发条件改变影响,气枪信号一致性会有所下降.反褶积方法可以去除气枪信号中激发压力、沉放深度、位置移动等的影响,但信号中水位变化的影响难以通过反褶积消除.地震信号波速变化反映了介质应力及物理状态的变化.利用气枪信号计算的波速变化受水位变化影响不能完全反应真正的介质变化,对研究结果及后续分析和应用产生较大干扰.为消除气枪信号波速变化中水位变化的干扰,本文提出了一种消除水位影响的方法:(1)水位以△h =0.2 m为间隔分段,将各个水位区间内激发的所有气枪信号叠加;(2)计算所有水位区间内气枪信号的波速变化,得到波速变化与水位变化的关系;(3)进行最小二乘拟合得到水位变化与波速变化的关系式,并计算水位变化引起的波速变化;(4)初始波速变化减去水位变化引起的波速变化,得到消除水位后的介质波速变化.研究结果表明:大银甸水库水位变化引起的气枪信号波速变化率最大可迭10-2,波速变化与水位变化呈线性正相关,水位影响随震中距的增大而减小,相同震中距气枪信号受水位变化的影响大小与气枪信号穿过水体的多少有关.运用本文提出的去除水位影响的方法可较好地消除波速变化中的水位变化信息. 相似文献
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陆地大容量气枪震源可用于区域尺度地球物理结构及变化的勘测.对气枪震源在有限水体内震源过程的研究，有助于我们深入了解气枪信号机制及气枪信号不同震相产生的成因.然而由于有限水体中大容量气枪激发的复杂物理过程，特别是复杂固液界面的存在，目前却没有较好的理论模型用以描述陆地气枪震源信号的能量传播特征.反投影方法是一种计算震源破裂过程的方法，能在动力学参数有限的情况下得到较优的结果.本文以此提出了一种修改的反投影方法，以用于模拟气枪震源激发过程中的能量分布图像.将气枪的激发分解为五个简化的物理过程，并分别建立数值模型，计算每个模型的理论波场，用作新方法的输入数据.通过对五个数值模型的数据计算发现，该方法可以准确地得到气枪激发后水体中的波场形态的变化，能够分辨出气枪激发过程中的气枪激发、气泡上浮、气泡震荡等过程，刻画能量分布特征，并且发现水听器足够密集与合理布置能达到更好的效果.该方法可以为气枪震源的快速评估及气枪震源的有效应用提供参考. 相似文献
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基于可压缩气泡动力学理论,建立改进的高压气枪震源气泡物理模型,其中考虑气枪气泡系统之间的物质输运效应、气液热传导等多种影响因素.改进模型的计算结果与实验数据吻合良好,且优于传统模型.在此基础上,本文分别探究了特征参数对单枪和双枪气泡动力学特性及流场压力波的影响规律.研究表明气枪开口方式是模拟压力波首脉冲的关键因素,但是对于后续的气泡溃灭脉动压力影响较小;气枪平移运动对气泡的影响可忽略不计;气枪非同步激发可在保证压力波低频段能量不降低的前提下,在一定程度上削弱高频段能量.本研究旨在为深海资源勘探新型气枪的设计提供参考. 相似文献
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2011年云南省地震局、中国地震局地球物理研究所在云南省宾川县大银甸水库开展了大容量气枪激发实验。为了深入研究气枪震源激发波形的特征,本文对不同距离台站记录的波形进行了频谱分析,对气枪激发震源的能量进行了计算,并将彩凤台气枪信号的波形、频谱特征与天然地震进行了对比分析。结果表明,1次激发相当于M_L0.7的天然地震。对相近震级天然地震波形的频谱与气枪激发波形的频谱进行对比后发现,气枪震源激发波形频率小于15Hz,主频多数集中在2~5Hz;气枪震源激发的地震波中低频信号较相当震级的天然地震明显;1次激发释放的能量为8.90×10~6J,相当于2.4kg硝铵炸药的当量。 相似文献
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《地震研究》2017,(4)
应用S变换对比分析云南宾川地震信号发射台单次气枪激发信号与同当量天然地震信号在传播过程中的波形和频率特征,并基于参考台聚类分析结果,对其他接收台站的地震信号进行线性叠加和相位加权叠加,研究结果表明:(1)气枪信号传播过程中主频为3~6 Hz,可以在距离为151 km的台站检测到信号,传播过程中能量衰减较慢。天然地震信号主频较高,在传播7.7 km时的主频为10~20 Hz,传播距离约为60 km,传播过程中能量衰减较快;(2)经过2 000余次的线性叠加和相位加权叠加,可以分别在距离为225 km和350 km的台站检测到气枪信号。与天然地震信号相比,气枪信号数据丰富、衰减慢、传播距离远,利用气枪数据可以研究更大范围的地壳介质结构。 相似文献
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监测地下结构以及介质变化是地震学研究的任务之一,选择合适的信号源对监测结果的优劣有着重要的影响。作为区域性地球物理勘探的理想震源,与传统的人工源相比,气枪震源重复性好、低频丰富并且绿色环保,极大地拓展了我们探索地球的手段。陆地水体气枪激发环境与海洋气枪存在显著不同,陆地气枪激发水体为有限小型水体,水体形状各不相同,陆地气枪信号的激发和传播不可避免地受到固液界面的影响。在利用气枪震源进行一些高精度的介质性质监测时,需要详细掌握气枪震源的源部分的特征,以去除气枪震源本身对测量结果的影响。为了研究气枪激发环境对气枪激发信号的影响,探讨气枪震源的能量传播过程,本文结合陆地气枪主动震源在区域尺度地球物理勘探中的应用,辅助以数值模拟方法,进行了不同水体对气枪激发信号性质影响的研究,分析了水体形状对气枪激发信号影响的机制。结合实际的观测数据和数值模拟方法,对快速评估气枪激发后气枪能量的传播过程提出了简单的计算方法。本文结合马刨泉实验,介绍了云南宾川、新疆呼图壁和甘肃张掖气枪地震信号发射台站的工作和取得的进展,发现大容量气枪震源应用到陆地区域尺度地球物理勘测中具有较好的可操作性和很重要的科研意义。利用数值模拟的方法计算地震波的传播,是地震学研究中的有效手段。在主动源探测领域,对地震波在复杂介质中的传播过程进行准确模拟,可以为主动源相关的数据资料的分析解释和区域介质结构反演提供理论支持和依据,有助于利用主动源开展地下介质性质的研究工作。在气枪主动源实验中,由于实地情况非常复杂,如固液界面上发生的反射、折射等现象,水体水位高低的变化、气枪在水体中放置位置的偏移等等因素,都有可能使波场特征发生改变。要想从实际观测的波形中剥离掉这些影响因素,从而得到震源特性,是十分困难的。因此,对气枪震源进行数值模拟的正演研究,有助于我们得到更为准确的震源本身特性。陆地水体气枪激发环境与传统的海洋气枪存在不同。本文通过分析实际气枪激发实验的数据,结合数值模拟实验,从绝对振幅、相对振幅、频率以及形状参数等几个方面,综合分析了水体形状对陆地大容量气枪激发信号的影响。本文的研究表明,不同水体形状对信号存在一定程度的影响,并且不同水体形状对不同频率的信号具有不同程度的影响。在几十米的水体尺度内,陆地有限水体对高频的脉冲信号影响较强,而对低频的气泡脉冲信号影响较弱。陆地气枪信号形成完整的气泡脉冲需要足够的水体体积,而在水体体积足够大的情况下,水体边界越陡,气枪能量转化为低频能量的效率越高,所激发信号波形越尖锐。而这也是陆地有限水体气枪应用的理想水体激发环境。经典气泡振荡理论是解释海洋气枪激发机制的基础理论,它将气枪信号分为压力脉冲信号和气泡脉冲信号两部分来加以阐述。但是在陆地气枪激发中,固液界面的研究一直缺乏准确的理论探讨。虽然无限半空间水体中气枪的激发信号方程可以由经典气泡震荡理论给出,但是由于陆地激发环境边界条件的复杂性,我们很难或者不能求出陆地有限水体中气枪激发信号的解析解。这使得我们有必要寻找一种方法来研究陆地气枪震源的震源特性。依据反投影方法的基本原理,本文改进了算法使之适用于陆上气枪震源的波场监测。通过五组数值模拟实验,本文发现利用布置在水体中的水听器接收到的信号,该方法可以有效地监测到气枪信号的能量传播过程。该方法布置方便,计算迅速,结果可靠,可以有效及时地对气枪震源的效果做出评估,可以为更充分地利用气枪震源提出有益的指导。应用陆地气枪震源可以监测波速变化,但因为气枪数据多来自于单一震源和单侧接收台站的监测配置,我们很难利用传统方法定位波速变化的位置。我们试图通过正演计算对波速变化位置提供一定的约束。首先利用较详细的速度结构信息,建立不同波速异常的试探模型,然后应用数值方法计算不同模型下接收台站的波形信号,与实际数据相比较选出最优模型,估计波速变化的位置以及波速变化的幅度。 相似文献
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Large volume airgun arrays have been widely used in exploring and monitoring underground structures for nearly a decade. Nowadays, large volume airgun arrays adopt the synchronous excitation mode, and source characteristics are controlled by the source signal of a single airgun, which to some extent limits its application. In order to realize the asynchronous excitation of the airgun array, we developed a new firing system for the airgun array, and carried out a field experiment in the Binchuan Fixed Airgun Signal Transmission station to study the influences of the asynchronous excitation on the source signal. The experimental results show that:the newly developed airgun array firing system can ignite the airguns according to the setting time series with high precision. By designing the excitation time series, the asynchronous excitation can enhance the energy of airgun source signal at 3-5Hz, and reduce the energy of pressure pulse wave at 6-18Hz. The signal detection capability of the asynchronous excitation with time series mode is equivalent to the synchronous excitation. 相似文献
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Characteristics of the Seismic Waves from a New Active Source Based on Methane Gaseous Detonation 总被引：1，自引：0，他引：1
WANG Weitao WANG Xiang MENG Chuanmin DONG Shi WANG Zhigang XIE Junju WANG Baoshan YANG Wei XU Shanhui WANG Tao 《中国地震研究》2019,33(2):354-366
Active seismic sources are critical for obtaining high resolution images of the subsurface. For active imaging in urban areas, environment friendly and green seismic sources are required. In present work, we introduce a new type of green active source based on the gaseous detonation of methane and oxygen. When fired in a closed container, the chemical reaction, i.e. gaseous detonation, will produce high pressure air over 150MPa. Seismic waves are produced when high pressure air is quickly released to impact the surroundings. The first field experiment of this active source was carried out in December, 2017 in Jingdezhen, Jiangxi Province, where a series of active sources were excited to explore their potential in mine exploration. In current work, we analyzed the seismic waves recorded by near-field accelerators and a dense short-period seismic array and compared them with those from a mobile airgun source, another kind of active source by releasing high pressure air into water. The results demonstrate that it can be used for high resolution near surface imaging. Firstly, the gaseous detonation productions are harmless CO2 and water, making it a green explosive source. Secondly, the dominant seismic frequencies are 10-80Hz and a single shot can be recorded up to 15km, making it suitable for local structure investigations. Thirdly, it can be excited in vertical wells, similar to traditional powder explosive sources. It can also act as an additional on-land active source to airgun sources, which requires a suitable water body as intermediate media to generate repeating signals. Moreover, the short duration and high frequency signature of the source signals make it safe with no damage to nearby buildings. These make it convenient to excite in urban areas. As a new explosive source, the excitation equipment and conditions, such as gas ratio, sink depth and air-releasing directions, need further investigation to improve seismic wave generation efficiency. 相似文献
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利用大容量气枪震源在陆上水库进行地震波激发试验,研究陆上水库环境下激发气枪震源所产生的地震波特征及传播距离. 试验结果表明,大容量气枪震源是具有丰富的10 Hz以下低频信号的低频震源,其激发的地震波具有传播距离远,穿透深度深的特点. 在185 km长的测线上均记录到了气枪信号,成功检测到Pg,Pc,P2,PmP和Pn等多组震相,并在此基础上对地下深地壳结构进行了一维速度结构正演,讨论了该区域壳幔过渡带的低速结构. 气枪震源还具有一般炸药震源不具有的特征,如长期定点重复激发和有效转换S波的优点,是陆上进行长炮检距深穿透地下结构研究的一种优良人工震源. 相似文献
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In order to study the seasonal variation of large volume airgun signals in Hutubi, Xinjiang, we analyzed 2,936 signals of airgun source excitations during 2015-2016 received by a seismograph on the bank of the excitation pool. Firstly, the RMS value of the signal amplitude and the daily average temperature were compared after linearly superimposing the signal in days, to analyze the influence of the surface ice cover on the excitation energy release of the airgun source. The result shows that the ice cover will reduce the excitation energy, and the thicker the ice cover is, the more obvious the excitation energy reduces. Secondly, the time-frequency analysis method was used to analyze the influence of the surface ice cover on the signal frequency. It is concluded that the existence of the ice cover has little effect on the signal frequency, but it will affect the intensity of the signal around 4Hz between 1-2s after excitation. The cause of these phenomena is that the ice cover affects the bubble oscillation, which in turn affects the energy conversion. The study shows that when using the cross-correlation delay method to calculate the wave velocity, the signals can be divided into two periods according to the daily average temperature:with or without ice cover on the upper surface of the excitation pool. This can help eliminate the influence of the source variation and improve the accuracy of the monitoring results. 相似文献
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Far-field signatures from an airgun array are usually obtained by carrying out extensive field measurements. In order to decrease the need for such measurements, we have developed a method for computing signatures from linear airgun arrays where the distances between the airguns are such that the non-linear interaction among the airguns is negligible. The signature from a single airgun of a given type is computed from the following airgun parameters: airgun chamber volume, chamber pressure, airgun depth and position of the waveshape plate within the chamber. For calibration purposes, a recorded signature for one set of airgun parameters has to be provided for each type of airgun. The signatures are computed by using empirical relations between signature properties and the airgun parameters, and by treating the primary and bubble pulses separately. The far-field signature from a linear airgun array can now be computed by summation of the delayed signatures from the airguns in the array. Practical results are shown for an array with different PAR (Bolt) 1500 C airguns. 相似文献
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J. J. NOOTEBOOM 《Geophysical Prospecting》1978,26(1):194-201
During the last few years many airgun arrays have been designed with the objective of generating a short signature of high amplitude. For linear arrays of non-interacting airguns two rules have been derived that may help in the design or evaluation of airgun arrays. To achieve a short pressure pulse, the total available air volume has to be distributed over the individual guns in such a way that the tail of the signal, owing to the added bubble signals, becomes as flat as possible. When we think of ordering airguns according to volume, this flat signal tail can be achieved by designing the volumes such that the difference in bubble times of two adjacent guns is proportional to their volume to the power 2/3. The amplitude expected from a linear array of non-interacting airguns is limited by the physical length of the array. A graph of measured values tends to confirm this relation. No relation has been found between the total volume of an array and its amplitude. The graph also detects inefficient use of available array length of existing arrays. 相似文献
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XIANG Y YANG Runhai WANG Bin ZHOU Yunyao LU Yongqing WU Huan QI Junwei PENG Jing 《中国地震研究》2019,33(2):336-353
Because of the different excitation conditions of the airgun source, there will be subtle differences in airgun signals. Travel time variation of airgun signals often mix into source information which can''t fully reflect the evolution of the medium. This article uses the airgun signals from the Binchuan Transmitting Seismic Station to analyze the airgun signal''s characteristics of phase and correlation. We conducted a comparative analysis of the effects of the pair difference method and the deconvolution method on eliminating the influence of the excitation conditions in travel time variation. The results show that:(1) The pressure pulse and its subsequent wave of airgun source wavelet are less affected by excitation conditions that we can use it to obtain high-precision excitation moments. (2) Deconvolution can improve the correlation of the airgun signal. (3) The pair difference method can''t eliminate the influence of excitation conditions in travel time variation. Deconvolution can reduce excitation condition interference and the influence of the excitation condition in the travel time variation after deconvolution of the vertical signal is significantly reduced. 相似文献
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M. H. SAFAR 《Geophysical Prospecting》1983,31(2):343-350
Recently the author developed and demonstrated (Safar 1980) an efficient method for operating the airgun. The method involves the generation of a short seismic pulse from the pressure bubble pulses radiated by an airgun when fired several times at the same optimum depth but with different chamber pressures. The purpose of this paper is to present and discuss the test results obtained when implementing the same method using a two-dimensional airgun array. The array consists of seven 0.65 liter airguns fired simultaneously at the same depth but with different chamber pressures. It is shown that the far-field pressure pulse radiated by the seven 0.65 liter airgun array is similar to that radiated by the Flexichoc seismic source. It is concluded that the proposed airgun array can be used as a subarray to form an extremely powerful super-long array suitable for deep seismic exploration. The author would like to thank the Chairman and Board of Directors of the British Petroleum Co. Ltd for permission to publish this paper. Thanks are also due to Mike Symes and Lovell Cox for carrying out the field tests and Seismograph Service (England) Ltd for providing the airguns. 相似文献
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In the design of linear airgun arrays the interaction between the airguns is usually neglected. We review the different formulae which have been proposed for the minimum separation between airguns at which the interaction is negligible. These formulae can all be approximated by a linear function of a single variable. We have analyzed a large number of measurements in order to establish the amount of interaction between two airguns of various volumes at different pressures and depths. The resulting far-field signature has been measured and compared with the sum of the signatures from the two airguns measured in the same experimental situation. The changes in primary pulse amplitude, bubble period and primary/bubble peak-to-peak amplitude ratio were computed from the measurement data as a function of airgun separation, chamber volume, chamber pressure and airgun depth. The influence of a waveshape kit was investigated, and the effects of interaction and the effects of using a waveshape kit were compared. 相似文献