【作者】 侯贺晟；

【导师】 高锐；

【作者基本信息】 中国地质科学院 ， 地球探测与信息技术， 2009， 博士

【摘要】 中国西部发育着闻名世界的第三极-青藏高原,亚洲巨大的沙漠盆地-塔里木盆地,中亚造山带的典型代表-天山造山带,等等。这些构成了中国西部雄伟壮观的构造地貌景观,也为人们研究高原形成、陆内变形与造山成盆等大陆动力学前沿科学提供了天然实验室。特别是这些地质过程仍在进行,可以用深部探测方法观测其正在进行的行为,理解其深部的动力背景,为预测和减轻地质灾害。创新发展大陆动力学理论提供基础依据。深地震反射剖面是全球公认的探测地球内部结构的先锋技术。自上个世纪70年代以来,全球运用深地震反射剖面技术,探测造山带与盆地的深部结构,取得许多重大发现,极大地促进了地球科学发展。我国学者也自1992年以来,在中国西部造山带开始进行深地震反射剖面探测试验。中国西部造山带及其前陆地区也是油气富集地区和天然地震灾害多发地区。位于青藏高原腹地的羌塘盆地,处于全球巨型油气聚集带-特提斯构造域的东段,是青藏高原内部海相地层保存最完整、最具油气远景的盆地。南天山造山带与塔里木盆地接合部位,是地震活动区,新近发现了克拉2和迪那2等油气田。近年来,在这些造山带内进行的深地震反射剖面以其独特的技术优势,正逐渐给我们展现出深藏于地球深处的矿藏构造与灾害的发生的深部背景。然而,在青藏高原及其周缘造山带地区进行深地震反射剖面探测是挑战全球的技术难题。主要有两方面的问题制约着深层地震勘探。一是复杂的地表条件,地表起伏落差大,新老地层交替出露,近地表结构复杂,低、降速层横向变化大;二是复杂的地下地质构造,上地壳隐伏断裂与逆冲构造发育,下地壳流体作用明显。由于这些地区地表条件和地下构造的复杂性,使地震波高频信息吸收衰减严重,低频干扰发育,获得深层反射的信息非常困难。在这类地区进行地震勘探,不但勘探成本比常规地区高,并且往往有得不到资料的风险性。并且,由于地表低降速带厚度和速度的变化,引起地震波旅行时的不均匀延迟,带来了复杂的静校正问题。众所周知,静校正问题是山区地震资料处理的门槛,只有在有效解决静校正基础上才能使地震数据处理结果成像。地震波在地层中有一定的振幅、频率传播特性,通过对地震有效波和干扰波传播的特性分析,分析实际采集过程的难点,针对性地改进采集参数可以减少这种得不到资料的风险性。通过对复杂近地表结构的精细建立,在此基础上进行静校正计算是目前解决复杂山区静校正问题的有效途径。本文通过野外实践和室内理论分析,研究了深地震反射剖面技术在中国西部造山带应用时存在的问题,针对特定地质条件试验改善采集效果的技术方法,根据已有的和新采集的羌塘地震勘探资料以及最新采集的天山与塔里木盆地结合部位的深地震反射探测剖面(TT2007)数据为基础,进行实际资料数据处理的关键技术之一静校正应用研究。论文结合这两个地区的关键问题分两大部分内容展开研究。论文的第一部分,在野外采集实践基础上,对以往高原腹地羌塘盆地石油地震与新完成的深地震反射采集资料进行了干扰因素分析及相应的采集、处理对策研究。在对羌塘地区地震波场进行地表一致性自相关分析、吸收和衰减分析等理论分析的基础上,总结了采集资料的总体特征及干扰因素。在此基础上,进行压制规则干扰波的方法测试及应用。实践表明,羌塘盆地复杂的近地表结构是影响地震采集和处理的关键干扰因素。对近地表结构的认知程度有助于山区地震数据的野外采集与室内去噪、静校正等处理工作,因而,近地表速度模型的反演建立是本文主要研究内容之一。利用两条衔接并横过羌塘中央隆起的深地震反射剖面探测数据,进行了初至波层析成像试验,揭示了羌塘中央隆起的表层结构特征。并在反演的近地表速度结构的基础上进行了正演数值模拟,分析了勘探中的实际问题,如冻土层对地震波传播的影响。进行了提高深地震反射资料信噪比方面的激发和接收参数的优化研究,在激发方面,分析了地震激发的一致性差异,正演分析了激发井深与频率的关系,接收方面,探讨了接收道距与规则干扰的压制关系。研究结果表明,通过采集技术改进与处理参数优化的剖面,成像质量较之以前有较大的改善。论文的第二部分,在野外采集实践基础上,针对西南天山与塔里木盆地结合地带地震数据处理的静校正问题,进行了地表速度建模应用研究。在盆山结合的部位复杂的近地表地层中,地震射线并非垂直,当地形起伏落差较大,尤其是存在较大的横向速度变化时,会引起长、中、短波长的静校正问题。本文首先分析了影响静校正的主客观因素及常规静校正方法在造山带地震资料处理的适用性,在对盆山结合部探测数据进行分段层析静校正处理、对比、分析的基础上,针对TT2007线地形起伏落差大,横向速度变化大的特点,提出了利用层析反演速度结构精确求得的浮动面静校量和高程静校正量相结合的静校正处理技术流程。为使层析校正量更符合盆地巨厚的低速体、山地出露的基岩高速体以及结合部位横向变化的速度结构特征,采用了分线闭合处理,应用于常规速度分析与动校正,之后对CMP道集施加高程校正量。通过以上对两个地区采集方法技术与数据处理应用上的研究,得到深地震反射剖面技术在这些地区应用的多方面新认识:(一)深地震反射剖面数据近地表速度结构的建立及应用方面的研究结果(1)深地震反射数据的层析反演试验结果表明,羌塘中央隆起区二维地震测线层析射线密度随地下复杂构造的程度而变化,反演得到的速度结构与地表结构存在着良好的对应关系,高速层的厚度与地表出露岩性的年代呈负相关。(2)天山与塔里木盆地的速度结构在结合部存在明显的差别,对盆山结合带的静校正量计算采取分段层析反演建模,闭合处理,综合层析与高程方法的静校正流程,能够较好的解决天山与塔里木盆山结合带的静校正问题。(3)综合应用小折射调查结果和大炮记录数据层析反演的近地表结构,正演模拟野外放炮的研究,在逼近实际地表条件下进行采集模拟和理论分析,能够有效指导实际生产工作。这应是复杂山地改善地震采集难度的有效技术。(二)羌塘地区采集方面的研究结果与采集对策(1)理论分析与正演模拟表明,在冻土层中、或其下激发的深层有效波的波能量强于冻土层上激发,能减少由于冻土层对地震波传播的高速而导致地震波能量难以有效下传的影响。冻土层中的“冰”经钻化成水与土混为泥浆,可能会糊死钻头,可考虑在该区域使用大功率特型钻机成井以提高钻井效率。(2)正演模拟结果表明,激发井越深,地震记录频带则越宽,干扰波越弱,实际资料也验证浅井激发炮集受声波、面波干扰严重。以往激发井深单井未能超过12m,多数为双井组或多井组合,根据近年来试验结果,对于上地壳,单井激发井深＞18m,能够取得比较好的资料。(3)羌塘地区规则干扰的频率低,一般在10Hz左右,当炮集上这些规则干扰的时间倾角大于50ms时,就会出现规则干扰的空间假频,对于这种野外记录,单纯通过f-k域滤波是难以压制,这种低频干扰严重时会影响深层反射成像,导致错误的构造解释。目前在羌塘地区试验的最小20m道距接收的炮集记录中,也出现空间假频。因此,在勘探成本允许的情况下,野外施工时仍尽量缩小道距,在采集阶段减少产生空间假频的可能性。更多还原

【Abstract】 In west China, there lies the world famous No.3 pole - Qinghai-Tibetan plateau, the widest desert basin -Tarim Basin in Asia, and the typical orogenic belt - Tianshan orogen in central Asia, et al. These units not only make of majesty and grand tectonic physiognomy scenery for west China, also offer us a natural laboratory to research on the leading science of continental dynamics, such as the formation of Qinghai-Tibetan plateau and intra-continental deformed orogeny and basin-forming. Especially these geology process is still on-going, for that we can use deep probe method to observe the being behavior, to understand the deep dynamic background for the purpose of forecasts and alleviates the geology calamity, to supply basic gist for the developing of continental dynamics theory.Deep seismic reflection profiling is recognized globally as an avant-courier technology to probe the deep earth. The deep seismic reflection profiling has been applied in many range and basin area to detect the deep structure and has obtain many important discovery since the 1970’s. It greatly promote the development of the earth science. Our scholars have deployed the deep seismic reflection profiling experimentation in orgoenic in west China since 1992.It is both hydrocarbon enrichment areas and earthquakes disaster zones in western China orogens. Qiangtang basin situated in the hinterland of the thickened Qinghai-Tibetan orogenic belt where is located in the east of Tethys domain. It is a region of the most hydrocarbon potential and the most intact marine strata within the Qinghai-Tibetan plateau. There are new discovery of Kela-2 and Dina-2 oil & gas fields and also Jiashi strong earthquake swarm along the junction of Tianshan orogen and Tarim basin. Recently some deep seismic reflection profiles take its high resolution advantage have been deployed in these orogenic belts are gradually open out the inside information of resource and disaster hides in deep earth.However, it is also very hard to probe the Qinghai-Tibetan plateau and its surrounding orgoenic belts. As is known to us, there are two main issues that restrict the deep seismic prospecting in the orogenic zones. One is the complicated earth’s surface condition, typically as undulating landform, alternating new information and old outcrop, lateral variation of LVZ. The other is the complicated subsurface structures, i.e., concealed faults or over-thrusts are developed in upper crustal, and channel flow are obvious in lower crustal.Due to these complicated surface and subsurface conductions, the absorption of high frequency of seismic wave field is serious, and shallow low-frequency interference wave disturb the deep reflection events. So it is hard to obtain the deep structure information and some time takes a risk of no gains with high pains in these orognenic areas. And the lateral variation of LVZ brings the asymmetry travel-time delay to the seismic wave lead to complex statics correction problem. As is well known, the statics problem is the threshold to the seismic data processing in mountain area. Only if the best methods for the mountain area statics problem have been resolved, the profile can be stack naturally.As we know that seismic wave has definite amplitude and frequency characteristic when travelling throw the stratum. We may reduce the risk by the analysis of the characteristic of seismic wave, finding the main issues that hinder the seismic acquisition process, and then promote corresponding methods to improve the profile quality. It is also an efficient approach to calculate the statics based on the accurate velocity building for complex near surface to solve the statics correction issues in the complicated area.Through field practice and room theory analysis, the author has studied the key problem when applied the deep seismic reflection profile in orgonenic belts in west China. The paper has tested the technology and method to improve the acquisition quality under the complicated geology condition, and about twelve seismic survey lines obtained in the last decade and four new seismic acquisition lines recently deployed in Qiantang basin and one deep seismic reflection profile in the junction belt of Tianshan and Tarim (TT2007) are analyzed in this paper for the application of statics correction which is the key process during the seismic data process in complex areas.The paper divides into two main parts, accordingly.Part one is based on the experience of field acquisition and back to the room study of the interference factors analysis and corresponding countermeasures for data acquisition and process to improve the S/N ratio of the oil seismic data and the new finished deep seismic reflection profiling. Through the analysis of attenuation by earth absorption, surface-consistence statistical autocorrelation of seismic data, the author summed up the general characters of the data and the factors of interference the wave spreading, furthermore, carried out the test of coherent noise attenuation. Practices show that the complicated near-surface velocity structure is the key factor that influence the seismic field acquisition and data process. For the more knowledge of the near-surface structures the better for the job of seismic field acquisition, noise attenuation, and statics correction. So the establishment of near-surface velocity structures is the main research content of this paper. Two reflection seismic profiles that linking up and crossing the central uplift of the Qiangtang basin were tested for the first arrival tomographic method and the results reveal the central uplift the undulate character of the high velocity structure both vertical and horizontal. Based on the near-surface structure created by these inversion methods the author did forward simulation to analyze the actually problem during this area exploration, such as the blocking effect of the permafrost and the relationship between the well depth and seismic wave frequency. As for the optimize study of shooting the author researched the inconsistent of the survey line and adjacent shots assembles ,and in recording aspect, discussed the relationships between the receiver arrange and coherent noise attenuation, group interval and the spatial aliasing. The research results indicate that after acquisition technology improvement and data process parameters optimization, the quality of seismic profile are much more improved than before.The second part of this paper is based on the experience of field acquisition and focus on the statics correction problems of the junction belts between the southwest Tianshan and Tarim basin, the author carried out the application of near-surface velocity. Where there the complicated near-surface made the seismic rays are no-perpendicularity to the surface especially when the undulating landform and lateral variation of the LVL are all sharp, it will lead to long, medium and short wavelength statics problems. The author first analyzed the major factors to the statics problems that come from objectivity and subjectivity, and then discussed the applicability of the common statics correction methods, such as, elevation statics, model statics, refraction statics, and tomography statics during seismic data processing in the basin and range junction with complex structure character. Based on the subsection of the basin, range and its junction seismic data using tomographic statics correction method to process, compare and analyze the results, to deal with the big fall of the altitude and sharp variety of the LVL especially under the junction part, the author bought forward the statics correction technology work flow, i.e., combination of the tomographic method to create the velocity model and calculate the floating statics values for the shot and receiver station with elevation method to calculate the final datum statics values. In order to make the statics value accord with the huge low velocity of Tarim basin, and the shallow high velocity of Tianshan range, and the sharp changed velocity of the junction zone, the author used multi-line tying process, after the matching process the statics were applied during the velocity analysis and NMO, at last add the elevation statics to CMP ensembles.Upon the research of the two parts contents in acquisition technology and data process application in the two areas, this paper arrives at some new understandings of the deep seismic reflection profiling in these areas as follows:(1)The research results of the near-surface velocity model using deep seismic reflection profiling data1) The tomographic travel-rays assemble where the structure is complex underground. The tomographic image reveals the undulate character of the high velocity structure both vertical and horizontal. And its thickness has negative correlation with the age of the outcrop in the central uplift of Qiangtang.2) There is a distinct velocity variety in the junction of the Tianshan and Tarim basin. The method of adopting subsection tomograhpic and use multi-line tying process to combine with elevation method can solve the statics problem in TT2007 deep seismic reflection profile and improve the quality of the profile.3) The research course of creating the forward model based on the inversion method using the interpretation results of shallow refraction survey and the first arrivals data, to simulate the field shots and to do the theoretic research in approximately the real-surface condition, can be the guideline to supervise the field work. This will be an efficient way to improve the seismic acquisition quality.(2) Research results and countermeasures for the deep seismic acquisition in Qiangtang area.1) Theory analysis and results of seismic records simulation indicates that explode in or under the frozen layer can have better energy than above the high-velocity frozen layer and can reduce the effect of the wave-front spreading in this layer. The ’ice’ may be melt with the soil to form mud and may stuff the aiguille when drilling in the permafrost. In case of that, it will be better to use special drilling equipment to get rid of the mud and make the aiguille clear.2) Model forward simulation shows that the deeper the drill hole the broader the record frequency and the less the interference wave. The real field shots also validate the fact that the shallower the record the serious the air blast and surface wave. Concluded from the experiment and comparison with the field shots in this area, it is recommended that the single well depth be more than 18m for the exploration of upper crustal.3) The frequency of coherent noise are low, about around 10Hz. When these wave in the record with the time dip angle great than 50ms, it will produce spatial aliasing in the F-K domain. So it is difficult to get rid of this kind of noise and it may influence the interpretation of the deep refection event. Even the ever test of 20mgroup interval record has spatial aliasing. So it is recommended to reduce the group interval considering the costallowable during the field work to decrease the possibility of spatial aliasing.更多还原