Complex Resistivity Measurement And Research Of Induced Polarization Mechanism Based On Rich Organic Shale From Southern China

In recent years, with the constant improvement of the exploration and development of technology, shale gas and other unconventional energy resources gradually go into people’s horizons. Shale gas is both a potential alternative energy for conventional natural gas and pure green energy. Shale gas stays in the gas source rock. The commercial development countries of shale gas are the United States and Canada, especially outstanding achievements in the United States. Geological study has showed that the rich shale in southern China has good quality for exploitation. Due to the unique storage condition and continuous complicated accumulation pattern of shale gas, it is difficult to use conventional geophysical method to predict sweet spots. The shale has a good quality of total organic content and thickness, which indicate the huge potential reserves of unconventional gas. In order to exploit the shale gas effectively, mapping the distribution of shale gas sweet spots and identifying their thermal maturity, organic carbon content (TOC) and natural fracture network using geophysical methods are of critical importance. Surely, seismic method is the first choice to be taken to do this job, but unfortunately, it has run into difficulties in southern China because of rugged tomography and complicated geology.At room temperature and atmospheric pressure, we do the sweep measurement experiment of complex resistivity on saturated cores by the instrument SI 1260 impedance analyzer and the joint inversion of complex resistivity amplitude and phase using single Cole-Cole, double Cole-Cole, Cole-Cole multiply Brown and Dias model respectively. Inversion results indicate that the double Cole-Cole model can describe shale cores’complex resistivity and phase curves with smallest fitting error than other models. We can also get accurate spectral parameters from the inversion.Total Organic Content (TOC) is one of the key and important parameter to evaluate shale gas formation effectively. According to geological deposition theory, the TOC is the basic key element that controls the form of pyrite in the marine sediment under deep water deposition environment. There is a close relationship between the TOC and pyrite in such deep water deposition environment. In this paper we have found that pyrite plays an important role in the prediction for TOC, Testing and analysis of the results showed that high TOC shale cores’broadband complex resistivity parameter was high polarizability abnormality.Research and analysis the mechanism of IP combined with the TOC content, mineral analysis results. Finally, we conclude that high TOC shale reservoirs are the abnormal characteristics of low resistivity, high polarizability. An IP model based on lots of complex resistivity measurements and composition analyses for cores and samples collected from southern China was proposed. The model features that the rich organic shale itself is a strong IP body with low resistivity.Spectral induced polarization (SIP) is very effective to explore the induced polarization target and the deep mineral in geophysical prospecting. With that IP model SIP data can be interpreted effectively in the exploration for shale gas.Finally, I think that it’s fully useful to find high quality shale reservoir by Spectral induced polarization (SIP) or time-frequency electromagnetic method (TFEM) which has been considered as an effective supplementary method for seismic.