OVT域处理技术在沁水盆地深部煤层气勘探中的应用

沁水盆地中东部煤层埋深大（大于1 000 m）、煤储层薄且煤层各向异性强,构造褶皱强烈、小构造及裂隙发育,煤体结构破碎等,为提高本区薄煤储层、小断裂、裂缝成像精度及满足岩性解释的需求,开展了宽方位三维地震勘探。为了充分发挥宽方位地震数据的优势,在处理中引入先进的OVT域处理技术,通过道集分选、OVT域五维插值、OVT域叠前时间偏移、方位各向异性校正等关键技术,获得了高分辨率、高保真度的地震数据;在解释中充分利用OVT处理形成的全方位和分方位地震数据。实现了深部含煤地层及其断层、陷落柱、挠曲等微小构造的精细刻画,提高了构造解释的精度及准确性,同时为叠前反演和各向异性研究提供了基础资料,为后期煤层气勘探开发部署提供了技术保障。      

Different modes of the Late Cretaceous–Early Tertiary inversion in the North German and Polish basins

Several selected seismic lines are used to show and compare the modes of Late-Cretaceous–Early Tertiary inversion within the North German and Polish basins. These seismic data illustrate an important difference in the allocation of major zones of basement (thick-skinned) deformation and maximum uplift within both basins. The most important inversion-related uplift of the Polish Basin was localised in its axial part, the Mid-Polish Trough, whereas the basement in the axial part of the North German Basin remained virtually flat. The latter was uplifted along the SW and to a smaller degree the NE margins of the North German Basin, presently defined by the Elbe Fault System and the Grimmen High, respectively. The different location of the basement inversion and uplift within the North German and Polish basins is interpreted to reflect the position of major zones of crustal weakness represented by the WNW-ESE trending Elbe Fault System and by the NW-SE striking Teisseyre-Tornquist Zone, the latter underlying the Mid-Polish Trough. Therefore, the inversion of the Polish and North German basins demonstrates the significance of an inherited basement structure regardless of its relationship to the position of the basin axis. The inversion of the Mid-Polish Trough was connected with the reactivation of normal basement fault zones responsible for its Permo-Mesozoic subsidence. These faults zones, inverted as reverse faults, facilitated the uplift of the Mid-Polish Trough in the order of 1–3 km. In contrast, inversion of the North German Basin rarely re-used structures active during its subsidence. Basement inversion and uplift, in the range of 3–4 km, was focused at the Elbe Fault System which has remained quiescent in the Triassic and Jurassic but reproduced the direction of an earlier Variscan structural grain. In contrast, N-S oriented Mesozoic grabens and troughs in the central part of the North German Basin avoided significant inversion as they were oriented parallel to the direction of the inferred Late Cretaceous–Early Tertiary compression. The comparison of the North German and Polish basins shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress field. A thick Zechstein salt layer in the central parts of the North German Basin and the Mid-Polish Trough caused mechanical decoupling between the sub-salt basement and the supra-salt sedimentary cover. Resultant thin-skinned inversion was manifested by the formation of various structures developed entirely in the supra-salt Mesozoic–Cenozoic succession. The Zechstein salt provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation and redistribution. Only in parts of the NGB and MPT characterised by either thin or missing Zechstein evaporites, thick-skinned inversion directly controlled inversion-related deformations of the sedimentary cover. Inversion of the Permo-Mesozoic fill within the Mid-Polish Trough was achieved by a regional elevation above uplifted basement blocks. Conversely, in the North German Basin, horizontal stress must have been transferred into the salt cover across the basin from its SW margin towards the basins centre. This must be the case since compressional deformations are concentrated mostly above the salt and no significant inversion-related basement faults are seismically detected apart from the basin margins. This strain decoupling in the interior of the North German Basin was enhanced by the presence of the Elbe Fault System which allowed strain localization in the basin floor due to its orientation perpendicular to the inferred Late Cretaceous–Early Tertiary far-field compression.     

基于环形扫面测量的三维直流电阻率法任意各向异性模型响应特征

高精度地下任意各向异性介质电性分布特征识别是当前的热门研究课题。本文以国内外前人工作为基础,基于非结构化网格,利用基于梯度恢复的后验误差估计指导网格自适应细化过程,实现了直流电阻率法三维有限元数值模拟。通过与一维模型半解析解的对比,验证了本文算法的有效性。考虑到电各向异性介质在观测中存在视电阻率反常现象,本文采用了环形扫面测量方法。通过对几种典型各向异性模型的模拟分析,得到了相应的各向异性影响规律和识别特征,各向异性主轴电阻率之间的比值大小决定了椭圆型视电阻率极性曲线长轴与短轴的比值大小,主轴电阻率的旋转方向会改变视电阻率极性曲线的形状。本文的算法研究及数值模拟技术可为直流电法数据精细处理和解释提供技术支撑。     

Inversion of GDS data of northwest Himalaya using EM2INV

This paper reviews the validity of earlier models obtained after quantitative interpretation of GDS data and presents a fresh model using the inversion scheme EM2INV. The 2-D inversion of data is more objective than the earlier interpretation performed by using trial and error method. The inversion results indicate that the present model differs from the earlier ones. The reason could be that available GDS data are sufficient only for deriving the horizontal variation of subsurface resistivity. In order to study the vertical resistivity variation additional MT sounding data would be required. It would therefore be desirable to carry out MT survey in the specified area. A more comprehensive/appropriate model could be derived from joint inversion of GDS and MT data.     

Structural evolution of a normal fault array in the Gambier Embayment,offshore Otway Basin,South Australia: insights from 3D seismic data

This study was undertaken to determine the structural evolution of a normal fault array using detailed kinematic analysis of normal fault tip propagation and linkage, adding to the growing pool of research on normal fault growth. In addition, we aim to provide further insight into the evolution of the offshore Otway Basin, Australia. We use three-dimensional (3D) seismic reflection data to analyse the temporal and spatial evolution of a Late Cretaceous–Cenozoic age normal fault array located in the Gambier Embayment of the offshore Otway Basin, South Australia. The seismic reflection data cover a NW–SE-oriented normal fault array consisting of six faults, which have grown from the linkage of numerous, smaller segments. This fault array overlies and has partial dip-linkage to E–W-striking, basement-involved faults that formed during the initial Tithonian–Barremian rifting event in the Otway Basin. Fault displacement analysis suggests four key stages in the post-Cenomanian growth history of the upper array: (1) nucleation of the majority of faults resulting from resumed crustal extension during the early Late Cretaceous; (2) an intra-Late Cretaceous period of general fault dormancy, with the nucleation of only one newly formed fault; (3) latest Cretaceous nucleation of another newly formed fault and further growth of all other faults; and (4) continued growth of all faults, leading to the formation of the Cenozoic Gambier Sub-basin in the Otway Basin. Our analysis also demonstrates that Late Cretaceous faults, which are located above and dip-link to basement-involved faults, display earlier nucleation and greater overall throw and length, compared with those which do not link to basement-involved faults. This is likely attributed to increased rift-related stress concentrations in cover sediments above the upper tips of basement faults. This study improves our understanding of the geological evolution of the presently under-explored Gambier Embayment, offshore Otway Basin, South Australia by documenting the segmented growth style of a Late Cretaceous normal fault array that is located over, and interacts with, a reactivated basement framework.     

井地联合提取VTI介质各向异性参数

在新疆塔里木盆地某地区的宽方位三维地震数据中,VTI介质火成岩的各向异性和垂向速度变化引起非双曲线时差。通过对实际资料的系统分析,我们不能利用DMO反演法,移动震源VSP反演法和多偏移距VSP初至旅行时反演法提取Thomsen参数用于各向异性地震资料的处理。因此本文提出一个新的方法:运用地震资料和零偏移距VSP井求取火成岩的各向异性参数δ;在比较精确确定火成岩地层深度和厚度的情况下,利用偏移距VSP井,求取了各向异性参数ε,从而获得火成岩的瞬时各向异性参数η;充分考虑VTI介质垂向速度变化对时差曲线的影响,获得了各向异性参数ηeff。最后,利用所提取的各向异性参数,进行VTI介质各向异性速度分析和成像,成像质量得到明显改善。     

利用一维正则化反演进行大地电磁测深数据拟二维反演解释

大地电磁测深的反演问题是不适定的,其反演结果不稳定,且具有非唯一性。通过在目标函数中采用正则化方法,可以使得不适定反演问题具有稳定的反演结果,并改善解的稳定性和非唯一性问题。为了提高野外大地电磁测深数据的处理效率和初步解释的精度,提出了大地电磁测深数据的一维正则化反演进行拟二维反演解释方法。这里所述的大地电磁测深一维反演解释,与以往的解释方法不同,其思路首先用Bostick反演的深度来控制层参数,使反演计算的模型参数仅存在电阻率;最后采用阻尼高斯-牛顿算法进行反演计算,并将Bostick反演结果作为反演计算的初始模型。通过模型试算,结果表明其处理速度快、解释直观,对野外大地电磁测深数据进行初步反演解释是可行的。     

Integrated geophysical interpretation for the area located at the eastern part of Ismailia Canal, Greater Cairo, Egypt

The integrated geophysical interpretation for the different geophysical tools such as resistivity and gravity is usually used to define the structural elements, stratigraphic units, groundwater potentiality, and depth to the basement rocks. In the present work, gravity and resistivity data were utilized for detecting the groundwater aquifer and structural elements, as well as the upper and lower surfaces of the subsurface basaltic sheet in an area located at the eastern side of Ismailia Canal, northeastern Greater Cairo, Egypt. Two hundred and ten gravity stations were measured using an Autograv instrument through a grid pattern of 50?×?50 m. The different required corrections were carried out, such as drift, elevation, tide, and latitude corrections. The final corrected data represented by the Bouguer anomaly map were filtered using high- and low-pass filters into regional and residual gravity anomaly maps. The resulting residual gravity anomaly map was used for gravity modeling to calculate the depths to the upper and lower surfaces of the basaltic sheet. The resulting gravity models indicated that the depths to the upper surface of the basaltic sheet are ranged between 26 and 314 m, where the shallower depths were found around the southern and eastern parts. The depths to the lower surface of the basaltic sheet are varied from 86 to 338 m, and the thickness of the basaltic sheet is ranged from 24 to 127 m, where the biggest thicknesses were found around the southern and northern parts of the study area. Forty-two vertical electrical soundings (VES) were carried out using Schlumberger configuration with AB/2 spacings ranged from 1.5 to 500 m. 1D quantitative interpretation was carried out through manual and analytical interpretations. The VES data were also inverted assuming a 3D resistivity distribution. The results from the 3D resistivity inversion indicated that the subsurface section consists of sand, sandstone, and sandy–clays of Miocene deposits overlying the basalts. Such basaltic features (of Oligocene age) are underlain by Gabal Ahmar Formation of Oligocene deposits, which are composed of sand and sandstone. Therefore, two aquifers were deduced in the area. The first is the Miocene aquifer (shallower) and the other is the Oligocene aquifer (deeper).     

Proterozoic tectonothermal processes imaged with magnetotellurics and seismic reflection in southern Australia

Over the last two decades,co-located seismic and magnetotelluric(MT) profiles provided fundamental geophysical data sets to image the Australian crust.Despite their complimentary nature,the data are processed and often interpreted separately without common processes in mind.We here qualitatively compare 2 D resistivity inversion models derived from MT and seismic reflection profiles across a region of Archean-Proterozoic Australia to address the causes of variations in seismic response and anomalous conductivity in the crust.We find that there exists a spatial association between regions of low reflectivity in seismic sections and low resistivity in co-located2 D MT modelled sections.These relationships elucidate possible signatures of past magmatic and fluid-related events.Depending on their diffuse or discrete character,we hypothesize these signatures signify fossil melting of the crust due to mafic underplating,magma movement or hydrothermal fluid flow through the crust.The approach discussed herein is a process-oriented approach to interpretation of geophysical images and a significant extension to traditional geophysical methods which are primarily sensitive to a singular bulk rock property or state.     

太康隆起东段地热资源远景区调查评价与研究

应用大地电磁测深法(MT)对太康隆起东段深部地层结构及隐伏断裂进行探测研究,共布设了4条MT剖面,获得了97个测深点,并对所获得的MT数据的二维偏离度、构造走向等进行计算和分析,采用非线性共轭梯度(NLCG)二维反演方法对TE和TM模式的数据进行联合反演,得到了可靠的地下介质二维地电模型。研究结果表明,商丘凸起电性结构纵向上具有典型的分层特征,从上到下可分为三层,即低阻层-中高阻层-高阻层。根据该电性结构模型,结合研究区域重力、航磁、地震及区域地质资料,绘制了商丘凸起基岩地质图,同时根据深部基底隆起形成的高阻异常与区域地温场高值区具有较好的对应关系,据此圈定了2处地热异常远景区。     

Seismic anisotropy of the lithosphere around the Trans-European Suture Zone (TESZ) based on teleseismic body-wave data of the TOR experiment

A passive teleseismic experiment (TOR), traversing the northern part of the Trans-European Suture Zone (TESZ) in Germany, Denmark and Sweden, recorded data for tomography of the upper mantle with a lateral resolution of few tens of kilometers as well as for a detailed study of seismic anisotropy. A joint inversion of teleseismic P-residual spheres and shear-wave splitting parameters allows us to retrieve the 3D orientation of dipping anisotropic structures in different domains of the sub-crustal lithosphere. We distinguish three major domains of different large-scale fabric divided by first-order sutures cutting the whole lithosphere thickness. The Baltic Shield north of the Sorgenfrei–Tornquist Zone (STZ) is characterised by lithosphere thickness around 175 km and the anisotropy is modelled by olivine aggregate of hexagonal symmetry with the high-velocity (ac) foliation plane striking NW–SE and dipping to NE. Southward of the STZ, beneath the Norwegian–Danish Basin, the lithosphere thins abruptly to about 75 km. In this domain, between the STZ and the so-called Caledonian Deformation Front (CDF), the anisotropic structures strike NE–SW and the high-velocity (ac) foliation dips to NW. To the south of the CDF, beneath northern Germany, we observe a heterogeneous lithosphere with variable thickness and anisotropic structures with high velocity dipping predominantly to SW. Most of the anisotropy observed at TOR stations can be explained by a preferred olivine orientation frozen in the sub-crustal lithosphere. Beneath northern Germany, a part of the shear-wave splitting is probably caused by a present-day flow in the asthenosphere.     

Joint inversion of 2D resistivity and seismic travel time data to image saltwater intrusion over karstic areas

The simultaneous inversion of multiple geophysical data types has been proven to be a powerful tool to both improve subsurface imaging and help in the interpretation process. The main goal of this paper was to develop joint inversion strategies to provide improved resistivity and seismic velocity images for delineating saline water zones in karstic geological formations. The cross-gradient constraint approach was adopted to jointly invert resistivity and seismic first arrival data. The basic idea of this approach is to quantitatively estimate the structural similarity between resistivity and seismic velocity models, using the cross product of their gradients and to achieve a unified geological model which satisfies both data sets. Initially, synthetic data were employed to help develop a joint inversion strategy to be used over such complex geological structures. The proposed strategy uses a weighting factor for the cross-gradient constraints and separate damping factors for the resistivity and seismic data. This strategy was applied successfully on field data from the karstic region of Stilos, Crete, Greece.     

The Langeland Fault System unravelled: Quaternary fault reactivation along an elevated basement block between the North German and Norwegian–Danish basins

The reactivation of faults and possible impact on barrier integrity marks a critical aspect for investigations on subsurface usage capabilities. Glacial isostatic adjustments, originating from repeated Quaternary glaciations of northern Europe, cause tectonic stresses on pre-existing fault systems and structural elements of the North German and Norwegian–Danish basins. Notably, our current understanding of the dynamics and scales of glacially induced fault reactivation is rather limited. A high-resolution 2D seismic data set recently acquired offshore northeastern Langeland Island allows the investigation of a fault and graben system termed the Langeland Fault System. Seismo-stratigraphic interpretation of reflection seismic data in combination with diffraction imaging unravels the spatial character of the Langeland Fault System along an elevated basement block of the Ringkøbing–Fyn High. In combination with sediment echosounder data, the data set helps to visualize the continuation of deep-rooted faults up to the sea floor. Initial Mesozoic faulting occurred during the Triassic. Late Cretaceous inversion reactivated a basement fault flanking the southern border of the elevated basement block of the Ringkøbing–Fyn High while inversion is absent in the Langeland Fault System. Here, normal faulting occurred in the Maastrichtian–Danian. We show that a glacial or postglacial fault reactivation occurred within the Langeland Fault System, as evident by the propagation of the faults from the deeper subsurface up to the sea floor, dissecting glacial and postglacial successions. Our findings suggest that the Langeland Fault System was reactivated over a length scale of a minimum of 8.5 km. We discuss the causes for this Quaternary fault reactivations in the context of glacially induced faulting and the present-day stress field. The combination of imaging techniques with different penetration depths and vertical resolution used in this study is rarely realized in the hinterland. It can therefore be speculated that many more inherited, deep-rooted faults were reactivated in Pleistocene glaciated regions.     

祁连山北缘深部弧形褶皱—逆冲带及其油气勘探前景

祁连山北缘-河西走廊西段位于青藏高原东北缘,是新生代陆内构造活动最强烈地区。基于野外构造观测、横跨山前及前陆盆地区的三维地震构造分析与解释,结合地震地质属性提取分析,识别出祁连山北缘-酒泉盆地西段窟窿山-柳沟庄带隐伏的弧形褶皱-逆冲带,该弧形构造是造山带基底逆冲构造楔体垂向差异抬升与向前陆方向差异运动的产物;该弧形结构控制本区下白垩统地层裂缝发育、分布与破裂强度,并与本区先期断裂、裂缝带产生构造叠加效应,形成弧形构造“中央强裂缝发育带”,是形成构造裂缝型油气藏的有利区域。     

电磁资料在柴达木盆地东部地区石炭系勘探中的应用

以柴达木盆地东部新采集的电磁资料为基础,同时以钻井、地震资料为约束,结合其他勘探资料、重力资料进行柴东地区石炭系综合研究、联合解释。研究过程中,首先对电磁资料进行了前期的预处理和反演,主要采用了一维Bostick反演、一维连续介质反演、二维共轭梯度反演、二维连续介质反演及最优化电性分层等反演技术;而后通过对电磁资料进行联合解释和综合研究,得出了柴达木盆地东部石炭系厚度图、石炭系埋深图等柴东地区综合研究成果;最后利用上述研究成果预测了柴达木盆地东部石炭系含油气有利区带,并且进一步针对柴达木盆地东部石炭系勘探提出了有意义的结论和建议。     

Influence of shallow infiltration on time-lapse ERT: Experience of advanced interpretation

Previous time-lapse Electrical Resistivity Tomography (ERT) studies have experienced difficulties in reconstructing reliable calculated resistivity changes in the subsurface. Increases or decreases of resistivity appear in the calculated ERT image where no changes were noted in the subsurface, leading to erroneous hydrological interpretations of the geophysical results. In this article, we investigate how a variation of actual resistivity with time and at shallow depth can influence time-lapse ERT results and produce resistivity artefacts at depth. We use 1 and 2-D numerical modelling to simulate infiltration scenarios. Using a standard time-lapse inversion, we demonstrate the resistivity artefact production according to the electrode spacing parameter. We used an advanced inversion methodology with a decoupling line at shallow depth to attenuate or remove resistivity artefacts. We also applied this methodology to a field data set obtained in a semi-arid environment in Burkina Faso, West Africa. Here, time-lapse ERT shows several resistivity artefacts of calculated resistivity if a standard inversion is used. We demonstrate the importance of a dense sampling of shallow resistivity variations at shallow depth. Advanced interpretation allows us to significantly attenuate or remove the resistivity artefact production at intermediate depth and produce reliable interpretation of hydrological processes.     

Regional gravity analysis of the crustal structure of Tunisia

Gravity data were integrated with seismic refraction/reflection data, well data and geological investigations to determine a general crustal structure of Tunisia. The gravity data analysis included the construction of a complete Bouguer gravity anomaly map, residual gravity anomaly maps, horizontal gravity gradient maps and a 2.5-D gravity model. Residual gravity anomaly maps illustrate crustal anomalies associated with various structural domains within Tunisia including the Sahel Block, Saharian Flexure, Erg Oriental Basin, Algerian Anticlinorium, Gafsa Trough, Tunisian Trough, Kasserine Platform and the Tell Mountains. Gravity anomalies associated with these features are interpreted to be caused either by thickening or thinning of Palæozoic and younger sediments or by crustal thinning. Analysis of the residual gravity anomaly and horizontal gravity gradient maps also determined a number of anomalies that may be associated with previously unknown structures. A north-south trending gravity model in general indicated similar subsurface bodies as a coincident seismic model. However, thinner Mesozoic sediments within the Tunisian Trough, thinner Palæozoic sediments in the Gafsa Trough, and a greater offset on the Saharian Flexure were required by the gravity data. Additionally, basement uplifts under the Kasserine Platform and Gafsa Trough, not imaged by seismic data, were required by the gravity data. The gravity model revealed two previously unknown basins north and south of the Algerian Anticlinorium (5 km), while the Erg Oriental Basin is composed of at least two sub-basins, each with a depth of 5 km.     

基于模拟退火粒子群优化算法的裂缝型储层各向异性参数地震反演

发育垂直定向排列裂缝的地下岩石可等效为具有水平对称轴的横向各向同性（horizontal transverse isotropic,HTI）介质。针对HTI介质模型,本文研究了裂缝型储层的各向异性参数地震振幅随方位角变化（amplitude variations with azimuth,AVAZ）的反演方法。首先,在地震AVAZ反演流程中,提出采用模拟退火粒子群优化算法实现裂缝型储层各向异性参数反演。之后,通过理论模型测试,验证了基于模拟退火粒子群优化算法的地震AVAZ反演的有效性。最后,将反演方法应用于四川盆地龙马溪组页岩气储层实际方位地震数据;在反演之前先利用傅里叶级数方法估计裂缝方位并对实际数据进行方位校正,以提供更准确的输入数据;通过计算得到的P波、S波各向异性参数可用于评价裂缝发育程度。反演结果表明,研究区域构造顶部裂缝较发育,与地质基本理论一致,验证了反演方法的合理性。     

三维大地电磁测深在库车坳陷库车组岩性判别中的应用

三维大地电磁测深(MT)资料用于沉积相分布的研究中,弥补了野外露头、测井和地震等传统识别和研究方法的不足.通过对三维MT资料进行去噪、编辑与平滑和静态位移校正等预处理和三维反演处理,使三维MT数据更加准确地反映研究地区岩石的电阻率.在野外露头观察和测井解释成果的基础上,利用岩芯或岩屑对电阻率进行标定,界定出库车组不同岩性的电阻率值范围,然后将三维MT剖面与相对应的地震剖面叠合,进行电震同平台解释,建立构造样式,最终在建立的地层格架内对沉积相分布特征进行精细的识别和研究,该方法在库车坳陷库车组沉积相识别及分布研究中取得了良好的应用效果,解决了井间相带变化和地震相特征不明显带来的研究困难,对研究沉积相带分布和沉积相演化等基础石油地质研究具有重大的意义.     

纵波VTI介质各向异性参数的求取

在新疆塔里木盆地某地区的宽方位三维地震数据中,通过速度分析和不同炮检距范围数据的叠加剖面的比较,发现了各向同性基于双曲线时差曲线的NMO动校正时,远炮检距数据存在比较大的剩余动校正量。分析表明,是由于VTI介质火成岩的各向异性和垂向速度变化引起非双曲线时差。应用纵波短排列地震数据求取的均方根动校正速度,分别以扫描法和旅行时法得到了各自相互验证的各向异性参数。最后,利用所提取的各向异性参数,进行VTI介质各向异性速度分析、动校正和成像,剩余动校正得到消除,成像质量得到明显改善。