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高分辨地震勘探仪器设计研究

Study on High Resolution Seismic Exploration System Design

【作者】 王兵

【导师】 王砚方;

【作者基本信息】 中国科学技术大学 , 物理电子学, 2008, 博士

【摘要】 石油是战略资源,目前我国石油对外依存度超过50%,已经威胁到了国家安全。我国地质条件复杂,石油、天然气勘探程度低,石油的储采比为14:1,远低于世界平均水平40:1。目前,东部地区油气田面临持续稳产的迫切需要,西部地区勘探条件复杂需要突破,海上更面临开辟前新生代海相残留盆地油气勘探新领域的挑战。如何提高深层(3500m或更深)地震勘探的分辨率成为勘探攻关的难点。地震勘探仪器是油气勘探的关键设备,其勘探能力直接决定了国家对油气资源的掌握。在地震仪器研制方面,我国长期处于落后状态,目前所使用的地震仪器设备全部依赖进口,核心技术受发达国家严格限制无法引进,严重制约了我国物探事业和石油工业的发展。计算机技术、网络通信技术、电路工艺技术、电源技术、微机械加工技术、材料科学技术等领域的技术进步,给我们提供了跨越式发展地震勘探仪器的机遇。然而在地震勘探仪器的设计中,如果单纯从电子信息技术角度去提高地震仪的性能指标,很难做出“好的仪器”,不仅会造成研制成本的增加和难度的加大,往往还很难达到理想的勘探结果。因此本文一方面着重从理论上研究了我国深层地质条件对地震仪器性能指标的要求,另一方面研究了不断改进的资料数据处理的方法、手段和能力对地震仪器结构和获取数据的要求,从而从勘探活动的全过程来探讨未来我国高分辨地震仪器的发展。物理原理是地震勘探的基础,地震勘探仪器设计也必须从充分了解物理背景出发。本文第2章首先从地震分辨率的概念、地震子波与分辨率的关系等出发,研究地震波的传播特点与规律;在调研我国地球物理研究成果的基础上,选取了我国华北地区的典型地层数据,通过建模仿真研究了地层衰减吸收的规律,认真分析了影响地震分辨率的地质因素,搞清楚了高分辨勘探需要捕获信号的范围和特点。对设计一个高分辨地震勘探仪器来说,最重要的指标包括:道间距、排列长度、总道数、采样间隔、瞬时动态范围、谐波失真、功耗等。这些指标与勘探目标的深度及需要采集信号的频率有着密切关系:需要分辨的地层越薄,则需要记录的信号频率越高;而勘探目标地层越深,则反射波信号中低频部分与高频部分的振幅差异就越大。好的地震仪器必须将信号的低频和高频部分同时记录下来。本文第3章里利用已经建立的地层吸收衰减模型,以DFS-V地震仪和SN388地震仪为例,选择Ricker子波为震源,仿真计算了仪器对各目标深度地层反射波信号的记录能力及分辨能力;分析了为达到高分辨效果仪器所需要的瞬时动态范围以及噪声对仪器的影响;明确阐述了高分辨地震仪器用于深层勘探必须具有大瞬时动态范围、小道间距、多道数、超低的谐波失真以及相应的采样间隔。这些指标确定以后,又决定了仪器的拓扑结构和数据传输能力,他们之间符合一定的定量和定性关系。上述两章内容反映了地震仪器与勘探目标的物理关系,是本文重点研究的内容之一。作为地震仪接收记录地震信号的第一步,其最前端的地震检波器应有理想频带和足够大的动态范围。高分辨地震勘探对检波器的精度要求也更高。检波器设计不是本文的研究方向,但检波器的特性和使用方式,对仪器整机的设计有较大的影响,因此本文接下来第4章阐述几种主要检波器,讨论了检波器组合使用的效果,对比了动圈检波器和MEMS数字检波器的各自优势。其中,MEMS数字检波器动态范围和瞬时动态范围都远高于传统检波器;幅频特性和相位一致性都好于传统检波器;谐波失真较低。就高分辨和信号保真而言,采用MEMS数字检波器改善检波器的技术特性要比提高采集站的瞬时动态显得更为迫切和重要。同时采用高质量数字检波器将会使整个地震仪的设计思想发生重要变化,不但使野外采集方式发生了改变,也使后期资料处理更灵活更丰富。然而动圈式检波器通过增加反馈电路等措施尚有不少可挖掘的潜力。如果能在此基础上改进成动圈式数字检波器,将会使现有的地震资料采集质量得到很大的提高。地震仪器设计是整个勘探活动全过程中的一个环节,要达到最终高分辨勘探的良好效果,数据采集是基础,数据处理是关键。论文在第5章描述地震资料后期处理的方法和手段,并反过来研究它们对仪器结构和获取数据的要求。论文从整体系统观的角度来研究地震仪器设计如何与后期资料处理的方法相适应,最大限度地发挥作用,来提高勘探的分辨率。噪声滤波、叠加处理、偏移处理等方法和能力的改进,对数据的抽取、覆盖的次数等提出了相应的要求,决定了仪器要提供的道间距、排列长度、采样间隔、总道数等主要参数。一些新兴的高分辨勘探技术的出现,如:高密度勘探技术、宽方位角三维地震技术、AVO技术、多波多分量地震技术等,实际上也是后期资料处理手段和能力不断发展的反映,它们对仪器结构、特征和性能提出了新的要求,决定了仪器的发展方向,对将来仪器的设计有着很大的影响。因此本文在第6章介绍了这些新兴技术的发展历程和应用状况,探讨了其主要原理和特点,分析了他们对仪器主要指标的要求。这两章讨论构成了本文的另一重要研究内容。论文第7章介绍了本人参加的中石油十一五重大专项“陆上大型地震数据采集记录系统”中关键的部分“基于LRE-PHY的地震勘探数传采集系统”项目。项目的目标是研制出总体功能和指标达到国际同类仪器水平的陆上石油地震勘探系统。我们承担的任务包括:电源站、采集站、交叉站接口部分的全套软硬件及相关的纵缆传输部分研制。经过约一年时间艰苦的开发工作,一个构成最小验证系统的原理样机已经开发完成,开发中采用了电子学领域的一些新技术,具有高水平的系统指标,样机已经于通过中石油专家组的验收并受到高度评价。本文利用前述各章的研究结果,对完成的样机的性能特点和整机能力进行了讨论和分析。在此基础上,论文最后针对我国华北地区深层高分辨勘探需要,具体分析了所需仪器的物理参数,讨论了仪器的结构和主要的系统指标,给出了一个面向未来的新一代大型地震勘探仪器的概念设计。通过本文的研究取得了以下主要成果:1)从物理原理出发,围绕高分辨勘探仪器设计对地震勘探相关领域的理论知识进行了融会贯通,结合电子信息技术的实现方法进行了交叉集成,进而得到指导设计石油地震勘探仪器的原则。在地层吸收模型进行仿真的基础上,仔细探讨了地震仪器对深层高频信号的记录能力,通过分析影响分辨率的主要因素,提出了适合我国高分辨地震采集勘探仪器的改进策略和方向;2)提出地震仪器设计要用系统、整体和发展的理念来进行,即把地震仪器的设计看成是整个油气勘探全过程中的一个局部环节,这一环节的实现要服从于整体目标以达到最佳。在深入了解地震资料处理的主要流程和方法的基础上,尝试利用已有理论、方法、资料,制定出适合未来高分辨地震仪的结构和参数设计要求,充分体现集成创新的成效。3)中石油十一五重大专项“基于LRE-PHY的地震勘探数据采集系统”项目的研制成功本身是一大创新成果,本人参加了部分开发工作;在此基础上结合上述集成创新的理念对项目进行了分析总结,最后用发展的眼光针对具体勘探需要给出一个下一代仪器的概念设计。

【Abstract】 Petroleum is the important strategic resource. The degree of China depending on overseas oil is already more than 50%. It has been a threat to our national security. Because of the complex geological conditions, the level of our oil and gas exploration is low, and our petroleum reserve-production ratio is 14:1 well below the world average of 40:1. At present, we face to the urgent need that the oil and gas fields continued to produce stably in the eastern regions, and the breakthrough need for the complex exploration conditions in the western regions, and the challenge to open a new oil and gas exploration field for pre-Cenozoic marine residual basins. It is difficult and hot focus to improve the seismic exploration resolution in deep stratum (below 3500m).The seismic exploration system is the kernel equipment for the oil and gas exploration and its exploring ability directly determines the level to control the state’s oil and gas resources. In the development of exploration equipments, China has been in a backward state for a long time. Our seismic exploration equipments are all rely on imports, the core technology couldn’t be introduced for the stringent restrictions by the developed countries. This seriously hampers the development of our oil exploration and the petroleum industry.The technological progress in the fields of computer, network communication, circuit, power, micro-machining, material science and such areas has provided us an opportunity to great-leap-forward develop seismic exploration equipments. However, if the instrument performance is improved in the seismic instrument design just from the electronic information technology, it is difficult to make a "good instrument". It will bring not only an increasing costs and difficulty to develop, but also difficult to achieve the desired results of the exploration. Therefore, on the one hand this dissertation focuses on the seismic equipment performance requirements for the deep stratum geological conditions, on the other hand studies the improving data processing methods, means and capacity to the seismic instrument’s requirements on its structure and data acquisition, and thus discusses the development the high resolution seismic equipment from the entire process on exploration activities.Physical principle is the basis of seismic exploration, seismic equipment design also must comprehend the physical background enough. At first, Chapter 2 studies on the seismic wave propagation characteristics and laws from the concept of the seismic resolution, and the relationships between the seismic wavelets and the resolution; By the research of geophysics, this dissertation selects the typical data of North China Cenozoic basin, studies on the attenuation laws of the stratum absorption by computer simulating, analyses of the geological influencing factors to the seismic resolution, and finds out the scope and characteristics of the seismic wavelet signal need to be captured in the high resolution seismic exploration.To design a high resolution seismic exploration instrument, the most important parameters include the group interval, the spread length, the sampling interval, the gross trace number, the instantaneous dynamic range, harmonic distortion, power, and so on. These parameters have close relationships to the depth of the exploration target stratum and the seismic signal frequency need be collected:the thinner the stratum need to distinguish, the higher the seismic signal frequency need to collect; the deeper the exploration target stratum, the higher the seismic signal frequency, and the greater amplitude attenuation on the high-frequency components of the reflected waves to its low-frequency components. A good seismic instrument can record the signal including the high-frequency components and low-frequency components at the same time. Chapter 3 makes use of the stratum absorbtion model, and chooses Ricker wavelet and the DFS-V and SN388 seismic instruments to simulate the instrument’s record capability and resolution to the reflected wave signal from the different depth stratum; and analyzes the requirements of the instantaneous dynamic range for the high resolution effect and the influence of noise on the instrument; explains that a high resolution seismic equipment for in-depth exploration must have high indexes of the large transient dynamic range, the small group interval, the multi-channel, the ultra-low harmonic distortion, and the suitable sampling interval. When these indexes to be determined, then the equipment topology and data transmission capacity are determined, they must comply with the qualitative and quantitative relations.These two chapters focus on the physical relationships between the seismic equipment and the exploration targets, and they are important content of the dissertation.As the infront-end of a seismic instrument received seismic signals, the geophones should have ideal band and sufficiently large dynamic range. The high resolution seismic exploration needs the high accuracy of seismic detectors. The designing of the detector is not this dissertation’s research direction, but the detector features and usages have a greater influence on the whole instrument design. So Chapter 4 describes some of the main detectors, discusses the usages of detector group, and then compares the respective advantages between the geophone and MEMS digital detector. Hereinto, the MEMS digital detector has wider dynamic range and instantaneous dynamic range than the traditional detector, and its amplitude and phase consistency are better than the traditional detector, and its harmonic distortion is lower. On the high resolution and signal fidelity, the use of MEMS digital detector to improve the instrument technical characteristics is more urgent and important than to improve instantaneous dynamic of the collection station. At the same time, the use of high quality digital detector will make the whole design of the seismic exploration equipment significant changes, not only the wild collection methods, but also the latter data processing --more flexible, more abundance. However, by increasing the feedback circuit, the geophone has more potential. If you can improve it to the digital geophone that will make the seismic data quality greatly improved in the existed equipments.However the seismic exploration instrument design just is a link of the chain of the entire exploration activities process, the data collection is the basis and the data processing is the key for achieving the good ultimate results of the high resolution exploration. Chapter 5 of the dissertation describes the seismic data latter processing methods and means, and then studies on the requirements for the instrument structure and data acquisition, and how the seismic instrument design to suit the latter data processing method to maximize the improvement of the seismic resolution from the view of the overall system. The improvement to the noise filtering, stack, migration and other methods provides the corresponding requirements to the data extraction and stacking fold, determines the instrument main parameters, such as the group interval, the spread length, the sampling interval, the gross trace number, and so on.The continued improving for the data processing means and capacity results in the emergence of high resolution exploration new technologies, such as the high-density space exploration, the wide azimuth angle 3-D seismic exploration, the AVO technique and the multi-wave and multi-component seismic exploration. These new techniques provide the new requirements to seismic instrument structure, characteristics and capacity, and have great impact on the seismic instrument design, and determine the direction of the instrument development. Therefore, Chapter 6 introduces the situation of the development and the application of these new technologies, and discusses their essential elements and features, and analyzes their equipment on the instrument main parameters. These discussions are another important research of the dissertation.Chapter 7 introduces the research and development of the Seismic Data Acquiring and Transferring System (SDARS) based on the LRE-PHY, one of the important and key projects of the 11th Five Year Development Program of the China National Petroleum Corporation (CNPC). Objective of this project is to develop a land large scale seismic exploration system with the high level of the overall function and key indexes. The author participated in the project, our lab is responsible for development of the Power Management Unit, the Data Acquisition Unit, the Interface to the Line Management Unit, and the Vertical Transmission Cable related to the full hardware and software. After about a year of hard work, a small prototype verification system had been implemented with high performance electronics for using some electronics new techniques in the development, the prototype had been passed inspection and acceptance by the CNPC expert group and got a high evaluation. This dissertation gives a discussion and an analysis on the prototype machine’s performance characteristics and its capability.On this basis, the dissertation analyzes the physical parameters of the instrument, discusses the structure of the instrument and the main electronics indexes met with the deep stratum high resolution exploration in North China, and gives a conceptual design of the new generation of large-scale seismic instrument for the future.This dissertation presents the following major achievements:1) From the physical principles, this dissertation integrates seismic exploration theoretical knowledge with the electronic technology around the high resolution exploration to guide the instrument design, discusses in detail on the instrument capability to record the high-frequency components of the deep stratum reflected waves with the stratum absorption simulation model, suggests the development improving strategy and direction to suit for China’s high resolution seismic exploration instrument through analyzing the influencing factors of the seismic resolution.2) This dissertation suggests that the seismic instrument design should comply with the principle of systematic view, whole view, development view, and comply with the overall goal to be achieved best, because the seismic instrument design is just a link of the chain of the oil and gas exploration entire process. Based on the understanding of the seismic data processing method and the primary process, this dissertation tries to give the seismic instrument structure and design parameters suitable for future high resolution exploration with the extracted theories, methods, means, reflects the effect of integrated innovation.3) It is an important innovation that we have successfully achieved the key project of "the research and development of the seismic data acquiring and transferring system based on the LRE-PHY". Base on the experiences in this project, the dissertation summarizes the prototype verification system. On this basis, the thesis finally gives a conceptual design of the new generation of large-scale seismic instrument for the future.

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