地震激发井深与品质因数的关系

通过对地震波在近地表附近双源传递机理的研究,论述了品质因数与激发井深的关系,并根据不同地区、不同品质因数,其地震波最大激发能量、最大信噪比与激发井深的关系曲线,给出了相应的激发深度.三维地震实例表明,地震波在近地表附近的双源传递与品质因数是选择地震波激发井深的重要因素,另外激发频率的增大,对激发井深的影响程度随之增大;观测同样频率的地震信号,存在小Q值地震波激发井深较大Q值激发井深相应变小的特点.     

高分辨率地震采集方法的研究

从弹性波动理论出发,结合实际的浅层激发条件,系统的讨论了炸药源激发子波的形成及近地表附近地震波的传播特征,研究了地震激发井深与炸药量的地震激发机制,并对实际试验资料进行了分析,提出了地震激发条件的选择方法。从爆炸动力学的角度出发推导了理论上的最佳激发井深,指出了选择并深应优先考虑信噪比,井深的选择对增加地震信号的反射能量是重要的,在理论研究的基础上进行了实地试验,试验结果与理论研究成果是一致的。     

煤炭宽带高精度地震采集方法的研究

从宽带高信噪比地震勘探理论出发,结合实际的浅层激发接收条件,对炸药源激发子波的形成及近地表附近地震波的传播特征进行了研究,并对实际试验资料进行分析,提出了地震激发条件的选择方法。从传感器的动态范围对增加地震信号的反射能量的研究表明,影响地震采集信号信噪比的关键因素是传感器的动态范围,数字检波器的动态范围优于90db可以增加高频弱信号的有效采集。在理论研究的基础上进行了实地试验,试验结果表明,理论研究成果是正确的。     

塔河油田近地表微测井记录中低频段研究

在塔河油田近地表微测井数据中普遍存在一段频率低、能量强、波形胖的低频段记录,一般出现在高速层顶界附近。那么,这一特殊的低频段是如何产生的,对激发井深的选择又会产生什么样的影响,是该地区地震采集时不得不面临的重要问题。以往认为该低频段是由岩性变化引起,并且在井深设计方面是选择避开低频段。笔者通过实际资料、理论分析、井深试验的结果分析,认为该低频段是由虚反射引起,在低频段中激发并不改变单炮质量;并对低频段的表现特征、产生机理及对激发井深选择的影响进行了详细的分析,在激发井深设计中可以不考虑低频段的影响。     

数字高程校正技术在盆地级近地表建模中的应用

准噶尔盆地是新疆油田公司地震勘探的主战场,其复杂多变的近地表条件给地震勘探带了很大困难。建立精确的近地表模型,掌握近地表结构变化规律,对地震勘探3大环节(采集、处理、解释)的研究至关重要。在分析DEM数字高程数据特征基础上,研发DEM数字高程校正方法,实现与实测地表高程的无缝拼接,填补了没有实测高程区域的空缺,为精确建立近地表结构模型奠定了基础。在此基础上,利用校正后的DEM数字高程建立盆地级高精度近地表结构模型,为后续指导新探区表层调查点的布设、地震采集激发井深的精确设计等发挥了重要作用。     

通-南-巴三维地震采集参数设计方法

针对通-南-巴地区山地工区复杂的地表结构和地质构造造成的地震施工难题,结合表层结构调查进行了激发试验确定了激发岩性、激发井深及炸药量等参数,确保主要目的层的地震波反射主频,拓宽有效波频带,提高纵向分辨率,以获取高信噪比地震资料;同时进行了基于地质模型及地震正演模拟的观测系统参数的设计,最终达到了突出有效反射,得到复杂构造信息的目的。     

深层地震勘探激发井深探讨

深层地震勘探野外资料采集的关键是在保证原始资料一定信噪比的基础上,同时兼顾分辨率,激发井深是决定资料品质的重要因素之一。通过对虚反射滤波作用分析,提出了充分利用虚反射能量设计最佳激发井深,增强下传地震波能量的采集方法。理论分析和试验资料表明,在高速层下4～7m的最佳激发岩性深度是深层勘探的理想井深。     

彭水地区碳酸盐岩山地地表地震激发接收因素优选及效果

彭水地区位于四川盆地东南缘武陵褶皱带,属于典型的喀斯特岩溶山地地貌,具有十分复杂的近地表结构,导致地震采集效果差、信噪比低,严重影响油气勘探效果。对此重点开展了碳酸盐岩裸露山地地表条件下的炸药药型、激发方式、激发井深、激发药量等激发试验以及干扰波调查、检波器类型、组合方式等接收试验与研究,优选了一套具有较好经济性与可操作性的激发与接收参数,建立了针对复杂山地地形的激发点位优选技术;与以往资料相比,新采集单炮记录能量、信噪比及一级品率明显提高,新资料处理剖面显示了较为丰富的信息,反射特征清楚、信噪比较高,在碳酸盐岩地表区显示出明显的地震构造格局。     

垦东地区海陆过渡带地震采集技术应用

分析了垦东地区海陆过渡带勘探的难点,针对地震波激发和接收条件差、干扰波发育等特点,在海陆过渡带地震波的激发、接收以及测量等方面进行研究:优选了气枪震源和炸药震源激发参数;改进了检波器及检波器固定方法,从而提高了检波器与地表的耦合效果;对检波器进行实时定位监测。采用上述措施,提高了地震采集资料的信噪比和分辨率,顺利完成了该区的地震采集任务。     

层析法在黄土塬区近地表结构调查中的应用

我国西部黄土塬区的静校正问题十分突出,精细、准确的近地表结构调查对于解决激发井深的设计和静校正问题尤为重要,但该区的常规小折射解释精度极低,微测井难以追踪到高速层。在充分试验的基础上,提出了一种新的近地表结构调查方法——层析近地表结构调查法,该方法有效解决了上述难点,与常规小折射方法比较,该方法获取的近地表结构信息更丰富,刻画的近地表结构更为精细,能够较好地用于井深设计和静校正处理中初始模型的建立。     

黄土塬区煤田三维采区地震勘探采集技术在王家岭矿区的应用

王家岭矿区属黄土塬地貌,各种干扰波十分发育,地震波吸收、衰减严重,主要煤层埋藏浅、层数多、小构造发育,常规煤田地震采集方法获得的地震资料信噪比和分辨率较低,难以达到采区地震勘探的“三高”要求。针对王家岭矿区实际特点,在精细调查浅表层黄土速度分层结构的基础上,综合采用逐点设计井深、震／检联合组合、低频检波器接收、大偏移距／高覆盖观测系统等关键采集技术,有效提高了地震资料信噪比与分辨率,获得了连续性较好的下组煤层反射波,为精细构造识别与岩性研究奠定了基础。     

Mapping and attenuation of surface waves side scattered by near-surface diffractors

Near-surface diffractors are one of the problems in land seismic exploration. They can scatter the surface wave energy emanating from the seismic source and contaminate the signal received by seismic receivers. The scattered energy from the near-surface diffractors manifests itself on seismic shot gathers as strong hyperbolic events, called diffractions, masking the weakly reflected body waves. Diffractions present complications to most of surface-wave suppression schemes, especially when they have been scattered by scatterers outside the receiver line. Different methods have been used to eliminate diffractions from seismic data, including geophone arrays, filtering, and inverse scattering. Each of those methods has its own limitations. In this study, we present processing algorithms to map and attenuate near-surface diffractors of surface waves in seismic shot gathers. The mapping algorithm is based on semblance measurements and time–offset relations, while the attenuation algorithm is based on the least-square fitting of a source wavelet. The algorithms are applied on synthetic data from two different models. The first model has three near-surface diffractors, while the second model has three clusters of near-surface diffractors. Each cluster consists of three near-surface diffractors with a different geometry for each cluster. The results show that the proposed algorithms are successful in locating and attenuating most near-surface diffractors, except when the separation between individual diffractors is below the wavelength of the diffracted surface wave.     

不耦合装药爆破对硬岩应力场影响的数值分析

爆破地震勘探石油是一种重要的方法,但爆破地震效应与爆破参数、地质条件等密切相关。采用动力有限元软件ANSYS/LS-DYNA,对柱状炸药与药孔壁之间为空气或其他介质以及空隙间距变化时碳酸盐岩岩石中爆炸应力波的传播规律和爆炸地震波能量的衰减特性进行了数值模拟研究,得到了不耦合装药爆炸时岩石应力、振动速度的衰减规律以及与不耦合系数、间隙介质的关系,分析了不耦合效应对爆炸地震波能量的影响。研究表明,不耦合或耦合不好时会使岩体中爆炸应力波的强度大大降低;耦合状态对岩体应力及速度的衰减系数和衰减指数影响较大;在空隙中注水或灌满泥浆会改善它们的耦合关系,增大下传的爆破能量。所得成果可为我国西南地区优选适合碳酸盐地层地震勘探的激发因素提供技术途径和方法。     

The Possibility of Increasing the Efficiency of Powerful Vibroseismic Sources

Doklady Earth Sciences - A numerical parametric study of the scattering features of Rayleigh waves that appear during the operation of a vibroseismic source on near-surface inhomogeneities (seismic...     

Dynamics of magmatic flow and compressional waves in Magma

The dynamics of magmatic melts in the near-surface part of several kilometers depth is determined by gas release processes. Formation of free gas share is an energy source, while decreasing of the density of the melt creates conditions for magma motion to the Earth’s surface. As the water content in the total volume of gas is about 80% for magmatic basaltic melts, gas release of water in the near-surface part of the magmatic column realizes the main share of energy, which leads to volcanic bursts and continuous gas-ash flows throughout the eruption process. Gas release processes create pressure variations in magmatic melts, and these variations are transferred into the solid medium as elastic oscillations forming seismic waves. The principal frequency of seismic signals for active volcanoes is several hertz, and the presence of spectral peaks has been explained by the presence of resonant sources.     

Discontinuity of the Mozumi–Sukenobu fault low-velocity zone, central Japan, inferred from 3-D finite-difference simulation of fault zone waves excited by explosive sources

We delineate shallow structures of the Mozumi–Sukenobu fault, central Japan, using fault zone waves generated by near-surface explosions and detected by a seismometer array. Two explosive sources, S1 and S2, were placed at a distance of about 2 km from the array, and the other two, S3 and S4, were at a distance of about 4 km. Fault zone head waves and fault zone trapped waves following direct P wave arrivals were clearly identified in the seismograms recorded by a linear seismometer array deployed across the fault in a research tunnel at a depth of 300 m. Synthetic waveforms generated by a 3-D finite-difference (3-D FD) method were compared with observed fault zone waves up to 25 Hz. The best fitting model indicates a 200-m-wide low-velocity zone extending at least to shot site S1 located 2 km east of the seismic array with a 20% decrease in the P wave velocity relative to the wall rock. The width of the low-velocity zone is consistent with the fault zone defined by direct geological observation in the research tunnel. However, the low-velocity zone should disappear just to the east of the site S1 to explain the observed fault zone waves for shot S3 and S4 located 4 km east of the seismometer array. Yet the observation and the simulation show notable trapped wave excitation even though shots S3 and S4 are outside the fault zone. These results indicate that (1) the effective waveguide for seismic waves along the fault does not exist east of source site S1 although the surface traces of the fault are observed in this region, and (2) considerable trapped waves can be excited by sources well outside the fault zone. These results highlight the along-strike variability in fault zone structure.     

基于附加层法的非规则剖面的瑞利波频散特性研究

对于某些非规则水平层状地质剖面,采用传递矩阵法获得的瑞利波频散曲线可能会出现截止或截断现象,但采用附加层的方法可避免这些现象的发生。通过采用附加层法前后相速度与激发强度大小的对比,来论证附加层法的正确性。对3个典型的非规则剖面进行模拟计算,利用传递矩阵法算得添加附加层前后瑞利波频散曲线,以及某些特征点处位移分量随深度的变化情况。通过对计算结果的对比分析可知,附加层法不仅可计算出地质剖面的实数导波,还可算出其泄漏模式波;在固定的频率点上,附加层的埋深越大,则添加附加层后算得的激发强度大小与原模型的误差越小;当附加层的埋深固定时,添加附加层后计算出的位移曲线与原位移曲线之间的误差随着对比点频率的增大而减小。可见,今后根据实际工作的精度要求,可用附加层法计算某些非规则剖面的瑞利波频散曲线。     

庐枞铁多金属矿集区龙桥铁矿反射地震初至波层析成像与隐伏矿床预测

为落实安徽庐枞地区北部的龙桥铁矿含矿层位在第二找矿深度的空间分布,本文应用小道距、长排列接收的地震反射初至波走时数据,运用层析成像方法,得到该地区近地表1000m以上的速度结构。研究结果显示,反射地震初至波携带了丰富的上地壳速度结构特征和界面变化的构造信息,精细的速度结构揭露出龙桥铁矿隐伏岩体顶界面深度与起伏形态,发现岩体顶面凸起及陡变化部位与矿体分布存在着明显的对应关系。长排列的深地震反射初至波走时层析成像方法能够为金属矿集区深部隐伏矿床的勘探与研究提供岩体的空间分布信息。