Predicting the characteristic parameters of shale sweet-spot with complex resistivity

  • Author(s): Feng-Jiao Xu, Liang-Jun Yan, Kui Xiang, Xiao-Long Tong, and Xing-Bing Xie
  • DOI: 10.3319/TAO.2020.03.22.01
  • Keywords: Complex resistivity Sweet spots Chargeability TOC Brittleness
  • Citation: Xu, F.-J., L.-J. Yan, K. Xiang, X.-L. Tong, and X.-B. Xie, 2020: Predicting the characteristic parameters of shale sweet-spot with complex resistivity. Terr. Atmos. Ocean. Sci., 31, 497-505, doi: 10.3319/TAO.2020.03.22.01
  • Organic-rich shale was characterized by low resistivity and high chargeability
  • The content of pyrite in organic-rich shale is higher than that of the surrounding rocks
  • TOC and brittleness can be predicted based on the true IP parameters

It is important to predict the capacity related parameters of reservoir such as brittleness, total organic carbon (TOC), in-situ stress, maturity of organic carbon (Ro), and buried depth in shale gas exploration and exploitation. Among these parameters, brittleness and TOC are especially important for shale gas exploitation. The complex resistivity measurement and analysis show that the rich organic shale in southern China features low resistivity and high chargeability. These characteristics are a geophysical prerequisite for predicting the sweet spot characteristic parameters of shale, such as TOC and brittleness, with rapid developing of high resolution controlled source electromagnetic (CSEM) method prospecting which can give resistivity and chargeability distribution of underground. Based on the rich organic shale composition analysis and complex resistivity measurements in southern China, this paper analysed the presence of pyrite as an associated mineral in organic-rich shale, and examined its relationship to resistivity, chargeability, TOC content and brittleness, and the quantitative relationship between the models has been established. Therefore, this study provides a firm experimental foundation for predicting parameters of shale sweet spots with CSEM prospecting.

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