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Summary Shale gas is becoming increasingly important exploration and production targets. 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. Complex resistivity (CR) method has been used to detect hydrocarbon for more than ten years, because laboratory studies of measureable induced polarization(IP) effects associated with non-metallic minerals(such as oil and gas), and two IP models were proposed for conventional oil and gas exploration, but this is not the case for shale gas prospecting with CR. In this paper we have found that pyrite plays an important role in the prediction for total organic content (TOC) of shale, and 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. With this model CR data can be interpreted effectively in the exploration for shale gas. Application showed that chargeability and resistivity anomalies inverted by CR were in good agreement with the seismic prediction for sweet spots.
- Asia > China > Sanshui Basin (0.99)
- Asia > China > Qinghai > Qaidam Basin (0.99)
- Africa > South Africa > Western Cape Province > Indian Ocean > Bredasdorp Basin > Block 9 > EM Field (0.99)
Complex Resistivity Characteristics of High TOC Marine Shale Core Samples and its Applications
Yu, Gang (BGP Inc.) | Hu, Wenbao (Yangtze University) | He, Zhenxiang (BGP Inc.) | Xiang, Kui (Yangtze University) | Hu, Hua (Yangtze University) | He, Lanfang (BGP Inc.) | Wang, Tianping (BGP Inc.) | Li, Pengfei (Yangtze University)
Summary Total Organic Content (TOC) is one of the key and important parameters to effectively evaluate the shale gas formation production potential. 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 strong reducing deposition environment. There is a close relationship between the TOC and pyrite in such deep water reducing deposition environment. Through the laboratory measurement and analysis of the complex resistivity on marine shale formation core samples from South China, the high TOC shale reservoir core samples contain more pyrite, and they show clearly low resistivity and high polarization anomaly. In comparison with well log data, the laboratory measurements of TOC and pyrite are closely related to the results from the log data analysis. We concluded that high TOC marine shale formation has the characterization of low resistivity and high induced polarization (IP) anomaly. Based on the research results, the application of the induced polarization or complex resistivity method to measure the subsurface resistivity and polarization anomaly is a new approach to effectively evaluate the TOC content within the shale gas formation, and it has high potential value for future shale gas reservoir evaluation and characterization.
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Electromagnetic Surveying (0.94)