宽频带大功率纵-弯式随钻测井声学发射器研究

Logging while drilling sonic measurement is the key technology for oil and gas reservoir exploration in deep earth and sea. Transmitter, the core part, has bottleneck problems, including working frequency band (such as 5-20 kHz) transmitting power (greater than 1kPa@1m), and high temperature (above 200 ℃), that need to be urgently conquered. In order to solve the above problems, we propose a new type of longitudinal-flexural transmitter, utilizing the wide frequency band theory of multi-mode coupling between longitudinal and flexural vibration modes, and high energy density of longitudinal piezoelectric stacks, combining piezoelectric characteristics of relaxor ferroelectric single crystal at high temperature. This study has a certain academic value and strong application background..Based on the pre research, this project will establish the physical model of the longitudinal-flexural transmitter consisting of composite rods and a bending beam. Effective coupling theory of multiple longitudinal modes and flexural modes will be analyzed theoretically and numerically. Influences of materials and structural parameters on the frequency bandwidth, maximum sound source level, and directivity will be numerically simulated. Optimization design with wider frequency bandwidth, higher emitting power and controllable beam width will be obtained. Moreover, we will study the growth process and high temperature characteristics of relaxor ferroelectric single crystal. The sample transmitter will be prepared and tested. Results will be compared between numerical simulation and measurement. This project lays a solid theoretical foundation and provides a strong experimental basis for the next generation of azimuthal acoustic logging while drilling transmitters.

随钻声学测量是深地与深海油气资源勘探的关键技术，其核心部件发射器存在工作频带(如5-20kHz)、发射功率(大于1kPa@1m）和耐高温(200℃以上)等方面的瓶颈问题，亟需攻克。为解决这些问题，基于纵振与弯振多模式耦合的宽频原理和压电晶堆纵振的高能量密度，结合弛豫铁电单晶的高温压电特性，本项目提出一种新型的纵-弯发射器。该研究具有一定的学术价值和较强的应用背景。. 基于前期预研，本项目拟建立基于纵振复合棒和弯曲梁的纵-弯式发射器物理模型，理论分析和数值仿真多阶纵振与弯振模式的有效耦合，分析材料和结构参数对频带、最大声源级和指向性的影响，以拓宽频带、提高辐射声压和控制波束宽度，探索弛豫铁电单晶生长方法与高温特性，试制换能器样件，对比数值仿真与实测结果，为新一代随钻方位声波测井发射器性能突破，奠定坚实的理论基础和提供强有力的实验依据。

随钻声学测量是深地与深海油气资源勘探的关键技术，其核心部件发射器存在工作频带(如5-20kHz)、发射功率(大于1kPa@1m）和耐高温(200℃以上)等方面的瓶颈问题，亟需攻克。为解决这些问题，基于纵振与弯振多模式耦合的宽频原理和压电晶堆纵振的高能量密度，结合弛豫铁电单晶的高温压电特性，本项目提出一种新型的纵-弯发射器设计方案，建立了基于压电复合棒和弯曲梁的U型发射器物理模型，绘制了换能器的等效电路图，数值仿真了压电复合棒与弯曲梁的弯曲振动的模式耦合，计算了换能器远场发射电压响应和指向性，探讨了压电复合棒部分和弯曲梁部分的材料参数和结构尺寸对发射电压响应级曲线的影响，研究了换能器黏结与封装工艺，成功制作了换能器样件，并测量了电声性能。实测发射电压响应级最高144dB，16.5kHz对应的辐射主瓣波束角为25.5°。本项目还探索了PIN-PT和PYN-PMN-PT弛豫铁电单晶生长方法，通过优化交流极化方法，将PYN-PMN-PT单晶的压电常数和机电耦合系数分别提至2490pC/N和91%，并提高了在200℃以下的温度稳定性，为新一代随钻方位声波测井高温高性能的偏极子发射器设计提供了坚实的理论基础和可靠的实验依据。