快速识别页岩气“甜点”目标的时频电磁勘探技术及应用

The TEEM technology for quick identification of 'sweet spot' of shale gas and its applications

通过研究南方碳酸盐岩海相地层发育区岩石标本电磁物性特征,得出页岩层系在地层剖面中为典型的低阻目标,具备利用电磁法勘探的基础,同时,基于岩石样品和井中岩芯的测定结果证实富有机质页岩层系的高极化响应和高TOC含量有很好的对应关系,具备利用极化异常圈定页岩气"甜点"区的有利条件。时频电磁法将时间域电性勘探和频率域极化性勘探结合在一起,通过大功率发射有效激发页岩层系的响应,配合地震勘探等技术,发挥了综合勘探的技术经济优势,实现了快速识别页岩气"甜点"目标的目的。笔者从页岩气目标的物性基础研究入手,总结了针对页岩气目标的电性和极化性异常提取和综合分析技术,为页岩气勘探提高成功率提供了一种快速识别"甜点"目标的新思路和有效手段。

Based on a study of the electromagnetic characteristics of marine carbonate samples collected in southern China, the authors have reached the conclusion that shale beds typically show low resistivity on sections in marine carbonate areas, and this means that the shale beds can be identified with electromagnetic technique. In addition, measurement data of rock samples and core samples show that organic-rich shale beds have high polarization, which is closely related to high TOC, and this implies that we can identify＇sweet spot＇area of shale gas by using polarization anomaly. TFEM （ Time and Frequency Electromagnetic） combines both time-domain sounding and frequency-domain sounding into a joint system, which induces target shale beds with a high-power transmitter. The method can help seismic technique to quickly identify target＇sweet spot＇of shale beds. The authors firstly analyze the physical properties of target shale beds, and then demonstrate the method for extracting electric and polarization anomalies aiming at the target beds. The combination of TFEM and seismic method makes the shale beds exploration more economical. This paper introduces this new and effective approach for quick identification of ＇sweet spot＇and improving the success rate of shale gas exploration.