基于反褶积最优化设计的双源反激过套管声波测井理论和方法研究

Through casing logging is very important in dealing with valuating remaining oil, potentiality exploration and development of old fields and the loss of open hole logging well-log data. Up to now, the problem in the through casing acoustic logging technology that the casing waves would disturb formation waves in the bad cementation condition between the casing and formation has never been resolved. The cased-hole acoustic logging technique using the dual source of opposite polarity is proposed to suppress casing waves before data acquisition. However, this technology is influenced by many factors (such as the transformer consistencies). To thoroughly improve the casing wave suppress efficiency, the key influence factors must be found out and accurately compensated. This program would build the acoustic logging model using the dual sources with opposite polarity and considering above factors. The key casing wave influence mechanisms are concentrating researched. Considering the main influence factors, the convolution filter relationships between the signal source, propagation medium and receipt signal are performed. the optimize transmitter exciting function is built to realize the best casing wave suppressing effect, and then, it is realized by the high voltage random waveform realization technology. Thereafter, the key influence factors are made up, and through casing acoustic logging data with high noise-signal ratio are obtained. Lastly, the casing wave suppressing effect and the signal to noise ratio are certified by experiments in many module wells.

过套管测井在剩余油评价、老油田挖潜改造和裸眼井测井资料缺失等方面具有重要意义。对过套管声波测井来讲，现有技术一直没有解决套管或地层界面固井质量不好时，地层信号受套管波强烈干扰而难以测量的问题。新兴的双源反激测井技术在数据采集前压制套管波，有望突破这一重大难题，然而该技术受声源一致性等多种因素影响较大，为进一步提升套管波压制效果，需确定套管波压制的关键影响因素并进行精确补偿。基于此，本项目拟建立考虑上述因素的双源反激套管井声波测井模型，重点研究和明确各种因素影响套管波压制效果的作用机理；在考虑主控影响因素条件下，建立声源、传播路径和接收波形间的褶积滤波关系；构建达到最佳套管波压制效果的最优化声源激励函数，并通过任意波形高压激励技术实现，从而补偿关键因素影响，获得高信噪比过套管声波测井数据，最终套管波压制效果及地层波信噪比通过模型井中的实验进行验证。

老油田的勘探工程开发和挖潜改造过程中需要透过套管进行测井，套管的导电、传声特性给测井带来了巨大的难题。现有的声波过套管测井技术在地层与套管胶结不好时，地层波受套管波干扰十分严重。双源反激测井技术在数据采集前压制套管波，对该问题的解决提供了一个有力的途径。然而，该技术的套管波压制效果影响因素众多。基于此，本项目开展双声源反相位延迟激励的过套管声波测井技术声场理论与数值模拟研究，基于有限元数值模拟的方法构建双源反激套管井声波测井模型，分析了发射换能器、声信号传播距离和套管变形等因素对接收波形中套管波成分的影响，总结出了影响套管波的主控因素，提炼出简化的双源声波测井解析理论，详细考察了这些因素的影响机理。基于声信号的激励源、传播路径和接收波形之间的褶积滤波关系，建立了反演方程并最优化反褶积因子，理论计算出所需的两个不同声源信号最优化理论波形。设计实现了自反馈双通道任意波形高压激励技术进行实现，分析了实际波形与理论波形的差异并进行持续改进，在实验室标准套管模型井中开展了电激励实验和声场实验，验证主要影响因素影响套管波压制的作用效果和机理，并对接收波形进行综合处理和对比分析，实验结果表明该理论和方法对套管波压制效果由巨大提升。该技术的实现有助于提升过套管声波测井仪器的套管波压制效果，对随钻声波测井仪器压制钻铤波有重要的指导意义。