Multimineral Modeling and Brittleness Index Estimation Using Core and Geophysical Well Log Data in the East Bokaro Coalfield of India

Abstract

Abstract —Accurate assessment of mineral content and the brittleness index (BI) is crucial for designing effective hydraulic fracturing treatments in coal seams, a parameter required in the East Bokaro Coalfield in India. This study combines sidewall-core and well log data, focusing on well A-1, where X-ray diffraction analysis of sidewall cores was conducted to identify mineral content. The obtained mineralogical data were extrapolated to well A-2 through a synthesis of well log parameters, X-ray diffraction analysis, and prior research results. Linear regression equations incorporating known minerals and well log data as input parameters were employed to calculate volumetric mineral content in the formations. The reliability of the model was validated by assessing the minimal difference between predicted and observed log curves. Furthermore, the brittleness index was determined using both geomechanical methods based on compressional wave velocity and mineralogical methods incorporating quartz, feldspar, and dolomite content. Comparative analysis of BI values demonstrated a consistent trend, while variations in the mineralogic BI were observed in relation to mineral content. This study not only establishes a continuous multimineral model for cases with unavailable core data but also contributes to advancing the understanding of mineral content variations. Additionally, the correlation between BI variations and mineral contents enhances our knowledge of the geomechanical properties essential for design of hydraulic fracturing in coal formations. The results presented herein offer valuable insights for optimizing hydraulic fracturing strategies in the East Bokaro Coalfield and provide a foundation for further research in similar geologic settings.