声电瞬变电磁测井方法研究-控制科学与工程专业毕业论文.docxVIP

万方数据 万方数据 摘 要 用于激发振动的压电管或压电片在高电压的冲击性下产生振动时还伴随有瞬 变电磁场。该瞬变电磁信号在井中传播，接收探头得到的瞬变电磁信号携带地 层的电导率信息。该瞬变电磁信号过去被当成干扰信号屏蔽掉，本文对该信号中 所包含的地层电阻率信息进行了研究。首先分析了压电换能器的瞬态响应 波形， 归纳出了阶跃函数和高斯函数两种激发波形；其次详细推导了裸眼井中压电管激 发的瞬变电磁响应计算公式——实轴积分法，并实现了相应的算法，获得了两种 激发波形的响应；最后分析了 Ez、H 和 Er 的响应波形，结果发现 Ez 的 幅度与 地层电导率关系密切，随地层电导率变化很大，从其波形幅度中可识别出地层的 电导率。在近源距 Ez 波形的最大值与地层电阻率呈近似的线性关系；地层电阻 率之差与对应的 Ez 响应之差的最大值也呈近似的线性关系。随着源距的增加， 以上的线性关系不再成立。通过 Ez 的测量可以直接获得地层电阻率。 设计了阵列声波测井信号采集系统、发射系统和深度采集系统。信号采集系 统实现了对接收探头感应信号的滤波放大、A/D 转换、数据传输、数据处理和保 存以及对采集到的波形实时显示等功能，可对毫伏级信号实现采集。深度采集系 统实现了对光电编码器正反转的判断以及转动圈数计数。信号发射系统由深度采 集系统给出的两个 I/O 口控制场效应管 IFR460 的导通与关断，从而实现发射信号 的发射与停止。为进一步验证声电组合测井仪器提供了理论和实验基础。 关键词： 声波 瞬变电磁场 实轴积分法 地层电阻率 ABSTRACT When the piezoelectric crystal used in acoustic logging is motivated by high voltage, a transient electromagnetic field will be generated. This transient electromagnetic field propagates in the well and its response carries the message of formation conductivity. This transient electromagnetic field response used to be regard as interference signal, while the message of formation conductivity it carries is studied in this paper. First, after analysing the transient response waveform of piezoelectric transducer, two kinds of exciting wave is chosen: jump function and Gaussian function. Second, computational formula of transient response of piezoelectric tube in open hole, real axis integration method, is derived in detail. And relevant algorithm is implemented, two kinds of response waves is gained. Last, the waveform of Ez, H and Er is analysed. It can be found that the amplitude of Ez varies considerably while the formation conductivity varies. So the formation conductivity can be read off from the amplitude of Ez. The maximum value of Ez is nearly linear with formation conductivity under the condition of short spacing and different formation conductivity. The maximum value of difference of Ez is nearly linear with the difference of formation conductivity under the same condition. The relationship