共查询到20条相似文献，搜索用时 46 毫秒
1.
为了利用煤镜质组反射率推断豫北构造应力场，基于构造应力是造成镜质组反射率各向异性（VRA）的主要控制因素，对在豫北焦作、安阳、鹤壁三个矿区井下取的定向煤样品进行了室内显微镜下反射率测试，对测试数据按有关公式进行计算后就得出了由最大反射率值、中间反射率值、最小反射率值为轴组成的镜质组反射率椭球体（VRI）.结果表明，研究区煤样显示二轴晶正光性，它们经过了强烈的构造变形，研究区煤样镜质组反射率各向异性是由构造应力所引起；由镜质组反射率椭球体（VRI）得出的豫北构造应力场与钻探、节理统计、河南省区域构造应力场分析等方法得出的应力场基本上是吻合的，但也有一定的区别，主要体现在应力场到安阳、鹤壁矿区后发生了向左的偏转.总之，利用煤镜质组反射率各向异性推断构造应力场的方法是可行的、是有效的. 相似文献
2.
煤镜质组反射率是评价煤阶、区分煤种的重要参数之一,在煤层气勘探与开发、采煤、化工和冶金中有着重要的应用.以往煤阶的评价单纯通过巷道和钻孔取芯的煤样实验室测试分析获得,受取样点有限限制.本文通过6种不同变质程度煤的挥发分和镜质组最大反射率的测试,配合煤样的超声弹性测量,探讨了镜质组最大反射率与地震属性参数-波速、密度和弹性模量之间的相关性.研究发现:煤镜质组最大反射率与地震属性参数均存在较好的线性正相关,其中以密度与纵波速度的相关程度最高.从而为利用煤田地震预测镜质组最大反射率,进而预测煤阶的三维立体分布提供了试验与物理依据. 相似文献
3.
通过6种不同煤阶煤的弹性测试,分析了煤岩变质程度（以镜质组最大反射率表示）与煤岩品质因子之间的关系;在此基础上,进一步分析了煤岩速度与品质因子之间的关系及纵波与横波品质因子的各向异性特征.研究发现：煤岩镜质组最大反射率与纵波、横波品质因子均存在良好的线性相关性;垂直层理方向的波速与品质因子存在良好的线性关系,好于走向与倾向方向;垂直层理方向的纵波与横波品质因子线性相关,相关系数可达93.5%;煤岩的三方向品质因子存在各向异性,且强于速度的各向异性.通过横波品质因子与纵波品质因子间相互换算的理论公式计算结果与实验室实测结果的对比,证明了该理论公式的可靠性,误差小于10%,为多分量转换波的吸收衰减补偿提供了理论依据. 相似文献
4.
煤弹性是反映煤的物质组分和结构的重要力学特征之一.在钻孔与测井的约束下,运用地震勘探获取煤层的弹性特征以反映其物性等,对于煤炭井工开采和煤层气储层评价及开发具有重要的工程意义,而其中,煤样的超声实验是实现地震反演煤层物性的基础.鉴于此,本文针对中国义马、阜康、淮南、平顶山、鹤壁和焦作6个矿区采集的6种不同变质程度的原煤样30块,在常温常压条件下分别进行了沿煤层走向、倾向及垂直层理三个方向煤样的实验室超声波测量.测试结果显示:煤样纵横波速度在走向、倾向、垂向三个方向上依次减小,存在各向异性,且P波速度的平均各向异性强于S波;品质因子与弹性模量在三个方向上也存在较大差异,且S波的品质因子大于P波的品质因子;弹性模量除泊松比外,均小于一般的沉积岩.通过本实验与分析进一步证明了:Gardener与Castagna公式不适用于中国煤田的煤岩弹性描述,并给出了精度更高的经验公式. 相似文献
5.
Microcosmic analysis of ductile shearing zones of coal seams of brittle deformation domain in superficial lithosphere 总被引：1，自引：0，他引：1
JU Yiwen WANG Guiliang JIANG Bo & HOU Quanlin . Graduate School Chinese Academy of Sciences Beijing China . College of Mineral Resources Geosciences China University of Mining & Technology Xuzhou China 《中国科学D辑(英文版)》2004,47(5)
For many years, the study on ductile shearing zones mainly focuses on the strain analysis and the characteristics of microcosmic structure of felsic duc-tile shearing zones in deep layers (8—10 km). Discus-sions on the process of the development of small-type and mini-size ductile shearing zones have been re-ported in recent years[1,2]. 揇uctile deformations in brittle deformation擺3] and 揵rittle deformations in ductile deformation擺4] are rather a familiar phenome-non in nature. Researchin… 相似文献
6.
Patrick N.J. Rasolofosaon 《Geophysical Prospecting》2010,58(4):637-655
Seismic anisotropy in geological media is now widely accepted. Parametrizations and explicit approximations for the velocities in such media, considered as purely elastic and moderately anisotropic, are now standards and have even been extended to arbitrary types of anisotropy. In the case of attenuating media, some authors have also recently published different parametrizations and velocity and attenuation approximations in viscoelastic anisotropic media of particular symmetry type (e.g., transversely isotropic or orthorhombic). This paper extends such work to media of arbitrary anisotropy type, that is to say to triclinic media. In the case of homogeneous waves and using the so‐called ‘correspondence principle’, it is shown that the viscoelastic equations (for the phase velocities, phase slownesses, moduli, wavenumbers, etc.) are formally identical to the corresponding purely elastic equations available in the literature provided that all the corresponding quantities are complex (except the unit vector in the propagation direction that remains real). In contrast to previous work, the new parametrization uses complex anisotropy parameters and constitutes a simple extension to viscoelastic media of previous work dealing with non‐attenuating elastic media of arbitrary anisotropy type. We make the link between these new complex anisotropy parameters and measurable parameters, as well as with previously published anisotropy parameters, demonstrating the usefulness of the new parametrization. We compute the explicit complete directional dependence of the exact and of the approximate (first and higher‐order perturbation) complex phase velocities of the three body waves (qP, qS1 and qS2). The exact equations are successfully compared with the ultrasonic phase velocities and phase attenuations of the three body waves measured in a strongly attenuating water‐saturated sample of Vosges sandstone exhibiting moderate velocity anisotropy but very strong attenuation anisotropy. The approximate formulas are checked on experimental data. Compared to the exact solutions, the errors observed on the first‐order approximate velocities are small (<1%) for qP‐waves and moderate (<10%) for qS‐waves. The corresponding errors on the quality factor Q are moderate (<6%) for qP‐waves but critically large (up to 160%) for the qS‐waves. The use of higher‐order approximations substantially improves the accuracy, for instance typical maximum relative errors do not exceed 0.06% on all the velocities and 0.6% on all the quality factors Q, for third‐order approximations. All the results obtained on other rock samples confirm the results obtained on this rock. The simplicity of the derivations and the generality of the results are striking and particularly convenient for practical applications. 相似文献
7.
选择４种地壳岩石样品,经干燥或水饱和处理后在不同围压条件下测量了在其中传播的纵、横波的速度及其各向异性．在大气压条件下低孔隙度(＜１％岩样中,水饱和样品中的纵波速度明显地比干燥样品中的高,但横波速度的差别不大．因为在低孔隙度岩样中纵波速度对孔隙流体的反应比横波速度敏感,可以用泊松比的变化来反映随着围压的增加晶粒间流体对弹性波传播特性的影响．根据实验数据,按Ｏ’Ｃｏｎｎｅｌｌ模型分别计算了干燥和水饱和岩样中的裂纹密度,与通过实测体应变曲线得到的裂纹孔隙度十分吻合．利用横波的速度和偏振特性可以推断岩样中定向排列微裂纹的空间取向情况．研究表明,同时测量在岩样中传播的纵、横波的速度,通过Ｖｐ／Ｖｓ比值可以给出有关颗粒边界流体的证据,也可以估计岩样中的裂纹密度． 相似文献
8.
9.
THE VITRINITE REFLECTANCE OF FAULT ROCKS FROM THE WENCHUAN EARTHQUAKE FAULT ZONE: CONSTRAINTS ON FRICTIONAL PROPERTIES OF THE FAULT DURING THE EARTHQUAKE 
下载免费PDF全文
下载免费PDF全文 YAO Lu MA Sheng-li WANG Yu HE Hong-lin CHEN Jian-ye YANG Xiao-song SHIMAMOTO Toshihiko 《地震地质》2016,38(4):817-829
The temperature rise caused by frictional heating during seismic slip is able to indicate dynamic frictional properties of the seismic fault,which provides an approach to understand the dynamic process and energy budget of an earthquake.The residual indicators of frictional heating within the fault zone also can be taken as an evidence for seismic events.The vitrinite reflectance is a commonly-used geothermometer in the coal,oil and gas industries.It also has some potential applications in the studies of fault rock and fault mechanics.We studied vitrinite reflectance (VR) of fault rocks collected from surface outcrops of the Wenchuan earthquake fault zone in this paper.The measured data reveal that the VR of fault rocks are affected by fault motion,and there is a trend that the VR increases towards the fault core,which indicates the effects of frictional heating.The VR of fault rocks from the Bajiaomiao outcrop is much higher than those from the Shenxigou outcrop,which probably suggests the difference in fault activity at the two outcrops.Our study also suggests that systematic measurement of VR across the fault zone is helpful in identifying slip zones and determining their widths.From the VR measurement on an oriented specimen containing the slip surface of the Wenchuan earthquake from the Shenxigou outcrop,we observed anomalous high VR values in two black-colored slip zones of about 2mm in width near the slip surface.The numerical calculation shows that the maximum temperature rise on the fault plane near Shenxigou was probably less than 162℃ during the Wenchuan earthquake,which means the dynamic fault strength was quite low.These estimations are roughly in accord with the results from the high-velocity frictional experiments. 相似文献
10.
Hydraulic fracturing reservoir reconstruction technology is crucial in the development of shale gas exploitation techniques.Large quantities of high-pressure fluids injected into shale reservoirs significantly alter compressional(P)and shear(S)wave velocities,rock mechanical parameters,and anisotropic characteristics.In this study,differentiated hydraulic fracturing petrophysical experiments were carried out on Longmaxi Formation shale under pseudo-triaxial stress loading conditions.The effects of stress loading methods,and water-rock physical and chemical reactions on P-and S-wave velocities and rock mechanical parameters were compared.The experimental results showed that isotropic stress loading may increase the P-and Swave velocities and Young’s modulus of dry shale kldnsample.Furthermore,it may lead to a weakening of the corresponding anisotropy.In contrast,differential stress loading was able to improve the anisotropy of Young’s modulus and accelerate the decrease in the compressive strength of shale in the vertical bedding direction.The water-rock physical and chemical reactions prompted by hydraulic fracturing was found to"soften"shale samples and reduce Young’s modulus.The influence of this"soften"effect on the compressional and shear wave velocities of shale was negligible,whilst there was a significant decrease in the anisotropy characteristics of Thomsen parameters,Young’s modulus,and Poisson’s ratio.The negative linear relationship between the Poisson’s ratios of the shale samples was also observed to lose sensitivity to stress loading,as a result of the"soften"effect of fracturing fluid on shale.The results of this study provide a reliable reference point and data support for future research on the mechanical properties of Longmaxi shale rocks. 相似文献
11.
Quantifying Damage, Saturation and Anisotropy in Cracked Rocks by Inverting Elastic Wave Velocities 总被引：1，自引：0，他引：1
Alexandre Schubnel Philip M. Benson Ben D. Thompson Jim F. Hazzard R. Paul Young 《Pure and Applied Geophysics》2006,163(5-6):947-973
Crack damage results in a decrease of elastic wave velocities and in the development of anisotropy. Using non-interactive
crack effective medium theory as a fundamental tool, we calculate dry and wet elastic properties of cracked rocks in terms
of a crack density tensor, average crack aspect ratio and mean crack fabric orientation from the solid grains and fluid elastic
properties. Using this same tool, we show that both the anisotropy and shear-wave splitting of elastic waves can be derived.
Two simple crack distributions are considered for which the predicted anisotropy depends strongly on the saturation, reaching
up to 60% in the dry case. Comparison with experimental data on two granites, a basalt and a marble, shows that the range
of validity of the non-interactive effective medium theory model extends to a total crack density of approximately 0.5, considering
symmetries up to orthorhombic. In the isotropic case, Kachanov's (1994) non-interactive effective medium model was used in
order to invert elastic wave velocities and infer both crack density and aspect ratio evolutions. Inversions are stable and
give coherent results in terms of crack density and aperture evolution. Crack density variations can be interpreted in terms
of crack growth and/or changes of the crack surface contact areas as cracks are being closed or opened respectively. More
importantly, the recovered evolution of aspect ratio shows an exponentially decreasing aspect ratio (and therefore aperture)
with pressure, which has broader geophysical implications, in particular on fluid flow. The recovered evolution of aspect
ratio is also consistent with current mechanical theories of crack closure. In the anisotropic cases—both transverse isotropic
and orthorhombic symmetries were considered—anisotropy and saturation patterns were well reproduced by the modelling, and
mean crack fabric orientations we recovered are consistent with in situ geophysical imaging.
Our results point out that: (1) It is possible to predict damage, anisotropy and saturation in terms of a crack density tensor
and mean crack aspect ratio and orientation; (2) using well constrained wave velocity data, it is possible to extrapolate
the contemporaneous evolution of crack density, anisotropy and saturation using wave velocity inversion as a tool; 3) using
such an inversion tool opens the door in linking elastic properties, variations to permeability. 相似文献
12.
ANISOTROPIC TRAVELTIME TOMOGRAPHY 总被引：1，自引：0，他引：1
Velocity estimation technique using seismic data is often based on time/distance equations which are independent of direction, and even though we now know that many rocks are quite anisotropic, useful results have been obtained over the years from these isotropic estimates. Nevertheless, if velocities are significantly direction-dependent, then the isotropic assumption may lead to serious structural interpretation errors. Additionally, information on angle-dependence may lead to a better understanding of the lithology of the rocks under measurement. VSP and cross-well data may each lack the necessary aperture to estimate more than two velocity parameters for each wave type, and if the data straddle a symmetry axis, then these may be usefully chosen to be the direct velocities (from time-and-distance measurements along the axis) and NMO velocities (from differential time-offset measurements). These sets of two parameters define ellipses, and provide intermediate models for the variation of velocity with angle which can later be assembled and translated into estimates of the elastic moduli of the rocks under scrutiny. If the aperture of the measurements is large enough e.g. we have access to both VSP and cross-well data, we divide the procedure into two independent steps, first fitting best ellipses around one symmetry axis and then fitting another set around the orthogonal axis. These sets of four elliptical parameters are then combined into a new, double elliptical approximation. This approximation keeps the useful properties of elliptical anisotropy, in particular the simple relation between group and phase velocities which simplifies the route from the traveltimes measurements to the elastic constants of the medium. The inversion proposed in this paper is a simple extension of well-known isotropic schemes and it is conceptually identical for all wave types. Examples are shown to illustrate the application of the technique to cross-well synthetic and field P-wave data. The examples demonstrate three important points: (a) When velocity anisotropy is estimated by iterative techniques such as conjugate gradients, early termination of the iterations may produce artificial anisotropy. (b) Different components of the velocity are subject to different type of artifacts because of differences in ray coverage, (c) Even though most rocks do not have elliptical dispersion relations, our elliptical schemes represent a useful intermediate step in the full characterization of the elastic properties. 相似文献
13.
气煤裂隙丰富,具有弹性各向异性,确定气煤弹性各向异性类型与大小,对煤田各向异性研究具有重要意义. 本文在对气煤煤样孔隙率测试的基础上,测量了顺煤层面、垂直于煤层面、与煤层面成45°三个方向上纵波速度（VP）和横波速度（VSH、VSV）,计算弹性常数. 对于具有垂向对称轴横向各向同性模型,各向异性系数平均值|ε|≤0.2、|δ|≤0.2和|γ|≤0.2,表明气煤是弱各向异性介质;对于横向对称轴横向各向异性模型,各向异性系数平均值ε(V)≈δ(V),按照Thomsen观点气煤各向异性是由椭圆裂隙引起弹性各向异性.本文还讨论了各向异性系数与孔隙率的关系,表明各向异性的大小与孔隙率之间有一定的关系. 因此当煤层厚度与其顶底板岩性不变或变化很小,可以认为气煤各向异性主要由裂隙引起的,气煤各向异性大小和方向能够反映煤的裂缝密度和方位. 相似文献
14.
由弹性波纵横波速比计算得到的泊松比,在利用地震波反演地下结构和物质组成时,可以提供比单纯地利用纵波或者横波波速更强的约束. 为了研究不同岩石中泊松比及其各向异性随围压的变化,选取19块典型的岩石样品,在不同围压下沿相互正交的3个方向同时测量纵、横波速度,并通过计算得到了泊松比及其各向异性. 结果表明,在大部分样品中泊松比各向异性与纵波速度各向异性有一定的相关性,但在有的样品中泊松比各向异性与纵波速度各向异性没有明显的关系,甚至表现出完全相反的变化规律. 由于泊松比也表现出很强的各向异性,在排除微裂隙的影响后有的仍可以达到30髎以上,在利用实际地震波传播数据通过泊松比反演地下物质结构时必须考虑其各向异性的影响. 相似文献
15.
The characteristics of coal pores and the interaction relationship between hydrocarbons and pores in coal are analysed based
on the typical example of oil from coal in Tuha Basin, pointing out that the interaction between hydrocarbon molecules and
coal pore surface particles is a major controlling factor of expulsion of oil from coal. Distribution characteristics of coal
pores and the ability of hydrocarbon generation are inner factors of the expulsion of the oil from coal; tectonic compressive
shear stress is an external force of the expulsion of oil from coal; expulsion of the oil from coal has greater geochromatographic
effect than that from mudstone, the low mature stage (or vitrinite reflectance Ro is less than 0.9%) is advantageous to the coal-formed oil expulsion and migration; hydrocarbons in the hydrocarbon network
are linked with carrier beds (such as fault), through the pore network and fissure which are connected with each other, which
constitutes the main pathway of expulsion and migration. 相似文献
16.
Alireza Malehmir Magnus Andersson Maxim Lebedev Milovan Urosevic Vassili Mikhaltsevitch 《Geophysical Prospecting》2013,61(1):153-167
To provide a guide for future deep (<1.5 km) seismic mineral exploration and to better understand the nature of reflections imaged by surface reflection seismic data in two mining camps and a carbonatite complex of Sweden, more than 50 rock and ore samples were collected and measured for their seismic velocities. The samples are geographically from the northern and central parts of Sweden, ranging from metallic ore deposits, meta‐volcanic and meta‐intrusive rocks to deformed and metamorphosed rocks. First, ultrasonic measurements of P‐ and S‐wave velocities at both atmospheric and elevated pressures, using 0.5 MHz P‐ and S‐wave transducers were conducted. The ultrasonic measurements suggest that most of the measured velocities show positive correlation with the density of the samples with an exception of a massive sulphide ore sample that shows significant low P‐ and S‐wave velocities. The low P‐ and S‐wave velocities are attributed to the mineral texture of the sample and partly lower pyrite content in comparison with a similar type sample obtained from Norway, which shows significantly higher P‐ and S‐wave velocities. Later, an iron ore sample from the central part of Sweden was measured using a low‐frequency (0.1–50 Hz) apparatus to provide comparison with the ultrasonic velocity measurements. The low‐frequency measurements indicate that the iron ore sample has minimal dispersion and attenuation. The iron ore sample shows the highest acoustic impedance among our samples suggesting that these deposits are favourable targets for seismic methods. This is further demonstrated by a real seismic section acquired over an iron ore mine in the central part of Sweden. Finally, a laser‐interferometer device was used to analyse elastic anisotropy of five rock samples taken from a major deformation zone in order to provide insights into the nature of reflections observed from the deformation zone. Up to 10% velocity‐anisotropy is estimated and demonstrated to be present for the samples taken from the deformation zone using the laser‐interferometery measurements. However, the origin of the reflections from the major deformation zone is attributed to a combination of anisotropy and amphibolite lenses within the deformation zone. 相似文献
17.
Ismael Himar Falcon-Suarez Kelvin Amalokwu Jordi Delgado-Martin Ben Callow Katleen Robert Laurence North Sourav K. Sahoo Angus I. Best 《Geophysical Prospecting》2019,67(4):784-803
Synthetic rock samples can offer advantages over natural rock samples when used for laboratory rock physical properties studies, provided their success as natural analogues is well understood. The ability of synthetic rocks to mimic the natural stress dependency of elastic wave, electrical and fluid transport properties is of primary interest. Hence, we compare a consistent set of laboratory multi-physics measurements obtained on four quartz sandstone samples (porosity range 20–25%) comprising two synthetic and two natural (Berea and Corvio) samples, the latter used extensively as standards in rock physics research. We measured simultaneously ultrasonic (P- and S-wave) velocity and attenuation, electrical resistivity, permeability and axial and radial strains over a wide range of differential pressure (confining stress 15–50 MPa; pore pressure 5–10 MPa) on the four brine saturated samples. Despite some obvious physical discrepancies caused by the synthetic manufacturing process, such as silica cementation and anisotropy, the results show only small differences in stress dependency between the synthetic and natural sandstones for all measured parameters. Stress dependency analysis of the dry samples using an isotropic effective medium model of spheroidal pores and penny-shaped cracks, together with a granular cohesion model, provide evidence of crack closure mechanisms in the natural sandstones, seen to a much lesser extent in the synthetic sandstones. The smaller grain size, greater cement content, and cementation under oedometric conditions particularly affect the fluid transport properties of the synthetic sandstones, resulting in lower permeability and higher electrical resistivity for a similar porosity. The effective stress coefficients, determined for each parameter, are in agreement with data reported in the literature. Our results for the particular synthetic materials that were tested suggest that synthetic sandstones can serve as good proxies for natural sandstones for studies of elastic and mechanical properties, but should be used with care for transport properties studies. 相似文献
18.
Ultrahigh-pressure (UHP) eclogites often show strong plastic deformation and anisotropy of seismic properties. We report in this paper the seismic velocity and anisotropy of eclogite calculated from the crystallographic preferred orientations (CPOs) of constituent minerals (garnet, omphacite, quartz and rutile) and single crystal elastic properties. We also compared the calculated results with the measured results in similar eclogites. Our results suggest that (1) Except that garnet is a seismically quasi-isotropic mineral, omphacite, quartz, coesite and rutile all have strong seismic anisotropies (AVp = 23.0%―40.9%, Max. AVs = 18.5%―47.1%). They are the major sources for anisotropy in eclogite. The average seismic velocities are fast in garnet and rutile, moderate in omphacite and coesite, and slow in quartz. (2) The deformed eclogites have the maximum Vp (8.33―8.75 km/s) approximately parallel to foliation and lineation, the minimum Vp (8.25―8.62 km/s) approximately normal to foliation and lineation and the Vp anisotropies of 1.0―1.7%. Their Vs are 4.93―4.97 km/s. The corresponding maximum anisotropies (0.73%―1.78%) of Vs are at 45° to both foliation and lineation and the minimum anisotropies at positions normal to lineation on the foliation plane. The Vs1 polarization planes are approximately parallel to foliation. The mean Vp and Vs of eclogite under UHP peak metamorphism conditions (P = 3―5 GPa, T = 900―1100℃) are estimated to be 3.4%―7.2% and 6.3%―12.1% higher than those at ambient pressure and temperature conditions, respectively. (3) Omphacite component dominates the anisotropy of eclogite while garnet component reduces the anisotropy and increases the seismic velocities. Quartz component has a small effect on the anisotropy but reduces the seismic velocities of eclogite. The effect of rutile component is negligible on seismic properties of eclogite due to its trivial volume fraction. (4) The increase of volume fraction of omphacite in eclogite will reduce the seismic velocities and increase the anisotropy. Omphacitite has seismic velocities reduced by 6%―8% and anisotropies increased to 3%―4% compared to those of garnetite. Our results suggest that the seismic properties calculated with single crystal elastic properties and CPOs are equivalent to those measured in laboratory. Moreover, it provides insights into the mineral physical interpretations of eclogite seismic properties. 相似文献
19.
CAI YiDong LIU DaMeng PAN ZheJun YAO YanBin LI JunQian QIU YongKai 《中国科学:地球科学(英文版)》2014,57(7):1567-1582
Pore structure of Chinese coals with heating and pressurization treatments was studied using small angle X-ray scattering(SAXS),N2adsorption/desorption isotherms and scanning electron microscope(SEM).SAXS was performed for some samples after heat treatment at seven elevated temperatures from 25 to 250°C at 0 MPa and for other samples with hydrostatic pressure treatment at 0,5,10,15 and 20 MPa at the room temperature.The results show that N2adsorption isotherm together with SAXS could be a comprehensive method to evaluate the pore shape and the pore size distribution:the pore shapes are generally spherical for low rank coal and they are mainly ellipsoidal for high rank coal.All these measurements were then interpreted using the fractal theory to reveal relationship between surface fractals and coal rank,and the evolution of surface fractals under heating and pressurization treatments.The results show that surface fractal dimension(Ds)changes with different treating temperature and pressure and maximum vitrinite reflectance(Ro,m).Especially in the bituminous stage,Ds shows an increasing trend with Ro,m under varied temperatures.Moreover,Ds shows an increasing trend with increasing temperature before 200°C,and a decreasing trend after 200°C.Furthermore,the results show that Ds has a more complex relationship with Ro,m under varied treating temperature than that under varied treating pressure. 相似文献
20.
We have pursued two-dimensional (2D) finite-difference (FD) modelling of seismic scattering from free-surface topography. Exact free-surface boundary conditions for the particle velocities have been derived for arbitrary 2D topographies. The boundary conditions are combined with a velocity–stress formulation of the full viscoelastic wave equations. A curved grid represents the physical medium and its upper boundary represents the free-surface topography. The wave equations are numerically discretized by an eighth-order FD method on a staggered grid in space, and a leap-frog technique and the Crank–Nicholson method in time.
In order to demonstrate the capabilities of the surface topography modelling technique, we simulate incident point sources with a sinusoidal topography in seismic media of increasing complexities. We present results using parameters typical of exploration surveys with topography and heterogeneous media. Topography on homogeneous media is shown to generate significant scattering. We show additional effects of layering in the medium, with and without randomization, using a von Kármán realization of apparent anisotropy. Synthetic snapshots and seismograms indicate that prominent surface topography can cause back-scattering, wave conversions and complex wave patterns which are usually discussed in terms of inter-crust heterogeneities. 相似文献
In order to demonstrate the capabilities of the surface topography modelling technique, we simulate incident point sources with a sinusoidal topography in seismic media of increasing complexities. We present results using parameters typical of exploration surveys with topography and heterogeneous media. Topography on homogeneous media is shown to generate significant scattering. We show additional effects of layering in the medium, with and without randomization, using a von Kármán realization of apparent anisotropy. Synthetic snapshots and seismograms indicate that prominent surface topography can cause back-scattering, wave conversions and complex wave patterns which are usually discussed in terms of inter-crust heterogeneities. 相似文献