时域电磁法在我国南方富有机质页岩勘探中的可行性分析

The feasibility of TDEM in the exploration for rich organic shale reservoir in Southern China

我国南方地表与地质构造复杂,地震方法在页岩气勘探中面临着巨大挑战。时域电磁勘探方法因其具有勘探深度大、工作效率高、成本低廉和方法灵活等特点,可作为页岩气地震勘探的有效补充。基于我国南方页岩储层岩石露头及井中岩心,经过岩石复电阻率测试与分析,认为我国南方富有机质页岩储层具有低阻、高极化特征,表明在该地区利用时域电磁法进行富有机质页岩勘探具有较好的物性基础。分析了滇黔渝地区页岩层地质与地球物理特征,并结合富有机质页岩复电阻率测试结果,建立了该地区富有机质页岩储层地电与激电融合模型。基于该融合模型,实现了基于极化介质条件下时域视电阻率正演模拟。模拟结果表明,在研究区地质条件下,富有机质页岩存在时,视电阻率变化明显,表明时域电磁勘探方法能有效识别富有机质页岩储层,具有较广阔的应用前景。

Seismic method plays an important role in the shale gas exploration.But at the same time it faces huge challenges because of the rugged topography and complex geological conditions in Southern China.The time domain electromagnetic（TDEM）exploration method could be used as an effective supplement way in the exploration for rich organic shale reservoir because it features deeper exploration depth,high efficiency,low cost and flexible layouts.Complex resistivity measurement and analysis have been carried out based on the samples of shale reservoir which were collected from the outcrops and the cores in Southern China.The results show that the rich organic shale reservoirs in Southern China are characterized by low resistivity and high polarization,and which is the physical basis for the application of TDEM method in rich organic shale exploration.By the research of geological and geophysical characteristics of rich organic shale stratums distributed in Yunnan,Chongqing and Guizhou,combined with the laboratory measurements of complex resistivity,the fusion model of geo-electric and induced polarization of rich organic shale was built.Based on this model,forward modeling of TDEM method under the condition of polarized medium was realized.The result reveals that the apparent resistivity has changed distinctly when there is rich organic shale stratum.This proves that the TDEM method could identify the rich organic shale reservoir more effectivly.