Study On High Resolution Seismic Exploration System Design

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.