【摘要】：核磁共振測(cè)井是目前最先進(jìn)的井下油氣勘探方法之一。核磁共振測(cè)井原理是通過測(cè)井儀探頭永磁體對(duì)地層施加靜磁場(chǎng)，使地層中氫原子核磁化，再利用探頭中射頻線圈產(chǎn)生射頻信號(hào)使氫原子核發(fā)生共振，最后采集接收共振信號(hào)進(jìn)行成像。國外的核磁共振測(cè)井技術(shù)研究相對(duì)發(fā)達(dá)，但實(shí)施技術(shù)保密；國內(nèi)對(duì)核磁共振測(cè)井技術(shù)研究主要集中在諸如測(cè)井解釋模型的建立和對(duì)巖心地質(zhì)特性的核磁共振分析等計(jì)算機(jī)科學(xué)及地質(zhì)學(xué)方面。本文重點(diǎn)研究了一種改進(jìn)型核磁共振測(cè)井儀探頭磁體系統(tǒng)的設(shè)計(jì)問題。主要工作如下： 首先，基于MAGNET軟件分析了國外兩種典型核磁共振測(cè)井儀探頭磁體的靜磁場(chǎng)分布，討論了其產(chǎn)生的探測(cè)區(qū)域及探測(cè)深度兩項(xiàng)主要技術(shù)指標(biāo)。在此基礎(chǔ)上，提出了一種改進(jìn)型的探頭永磁體設(shè)計(jì)方案，，結(jié)構(gòu)方案采用了居中式梯度磁場(chǎng)測(cè)井方式，磁體結(jié)構(gòu)除了包括還有產(chǎn)生靜磁場(chǎng)的主磁體外，還引入了調(diào)整磁體，以實(shí)現(xiàn)對(duì)靜磁場(chǎng)的微調(diào)。 其次，采用表面響應(yīng)模型與遺傳算法相結(jié)合的優(yōu)化策略完成了探頭磁體結(jié)構(gòu)的優(yōu)化設(shè)計(jì)。依次選取主磁體和調(diào)整磁體的幾何參數(shù)作為優(yōu)化變量，以提高井眼外探測(cè)深度為優(yōu)化目標(biāo)，結(jié)合拉丁超立方采樣策略和多二次徑向基函數(shù)建立了近似目標(biāo)函數(shù)的表面響應(yīng)模型，并采用遺傳算法對(duì)建立的表面響應(yīng)模型進(jìn)行尋優(yōu)，最終實(shí)現(xiàn)了探頭磁體的最優(yōu)設(shè)計(jì)。 然后，基于MAGNET軟件對(duì)優(yōu)化后的探頭磁體產(chǎn)生的靜磁場(chǎng)進(jìn)行了仿真分析，討論了在井眼四周可能存在的探測(cè)區(qū)域，以及探測(cè)深度和磁場(chǎng)強(qiáng)度的大小，分析了所提出的磁體結(jié)構(gòu)對(duì)探測(cè)深度的改進(jìn)效果。 最后，在確定好探頭磁體結(jié)構(gòu)的基礎(chǔ)上，根據(jù)測(cè)井要求完成了與磁體匹配的射頻線圈的設(shè)計(jì)，分析了射頻磁場(chǎng)與靜磁場(chǎng)的正交性，確定了所提出的探頭磁體在井眼外探測(cè)區(qū)域的位置和體積。
[Abstract]:Nuclear magnetic resonance logging is one of the most advanced downhole oil and gas exploration methods. The principle of nuclear magnetic resonance logging is that the magnetostatic magnetic field is applied to the formation through the permanent magnet of the probe of the logging tool to magnetize the hydrogen nucleus in the formation, and then the radio frequency signal of the radio frequency coil in the probe is used to cause the resonance of the hydrogen nucleus. Finally, the received resonance signal is collected for imaging. The research of nuclear magnetic resonance logging technology abroad is relatively developed, but the implementation of technology confidentiality; The research of nuclear magnetic resonance logging technology in our country mainly focuses on computer science and geology, such as the establishment of logging interpretation model and the nuclear magnetic resonance analysis of core geological characteristics. This paper focuses on the design of an improved magnetic resonance logging probe magnet system. The main work is as follows: firstly, based on MAGNET software, the static magnetic field distribution of the probe magnet of two kinds of typical nuclear magnetic resonance logging instruments abroad is analyzed, and the detection area and the detection depth of the magnetostatic magnetic field produced by the magnetostatic magnetic field are discussed. On the basis of this, an improved design scheme of probe permanent magnet is presented. The structure of the probe permanent magnet adopts the central gradient magnetic field logging method. The magnet structure not only includes the main magnet which produces static magnetic field, but also introduces the adjusting magnet. In order to achieve the fine-tuning of the static magnetic field. Secondly, the optimization strategy of surface response model and genetic algorithm is used to optimize the structure of probe magnet. The geometry parameters of the main magnet and the adjusted magnet are selected as the optimization variables, and the surface response model of the approximate objective function is established by combining the Latin hypercube sampling strategy and the multi-quadratic radial basis function, in order to improve the detection depth outside the hole. Finally, the optimal design of probe magnet is realized by using genetic algorithm to optimize the established surface response model. Then, the static magnetic field generated by the optimized probe magnet is simulated and analyzed based on MAGNET software, and the possible detection area around the well hole, as well as the detection depth and the magnetic field intensity are discussed, and the static magnetic field generated by the optimized probe magnet is simulated and analyzed. The improvement effect of the proposed magnet structure on the detection depth is analyzed. Finally, on the basis of determining the structure of the probe magnet, the RF coil matching with the magnet is designed according to the logging requirements, and the orthogonality between the RF magnetic field and the static magnetic field is analyzed. The position and volume of the probe magnet outside the well are determined.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P631.83

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