APPLICATION OF FULLBORE FORMATION MICRO IMAGER (FMI) LOG FOR CHARACTERIZATION OF CAMBAY SHALE, GUJARAT, INDIA

Fullbore Formation Micro Imager (FMI) is an advanced logging tool for geological and reservoir characterization in a cost and time saving manner through resistivity-based borehole imaging to provide detailed information about the reservoir rocks. The present study focuses on the interpretation of FMI log recorded to cover the entire Cambay Shale section in a well drilled to evaluate Cambay Shale for hydrocarbon prospect, in Jambusar-Broach block of Cambay basin, India. Processed FMI data were used to produce resistivity- contrast image log. For visualization of the image log, two different types of colour normalization, namely static and dynamic, were done on the data. In static normalization a preferred spectrum of colours is distributed over the entire data interval. In dynamic normalization, higher resolution normalization is achieved, where the spectrum of colours is distributed over a 1m-window length, with sliding window method. Interpretation of the FMI log was done jointly with other logs, for identification and classification of different sedimentary features. Lithology in majority interval is found to comprise of shale or very fine-grained siltstone. Different types of shale facies are observed for the logged section of the Cambay Shale, like laminated shale, massive shale, bioturbated shale, shale with occurrences of conductive minerals and resistive shale respectively.

FMI data were also used for geomechanical characterization of Cambay Shale. From image log analysis, fractures are observed at several intervals. FMI image analysis also provides information on drilling-induced features like borehole breakouts and drilling-induced fractures (DIFs). Breakout and DIF are observed at some intervals. Breakout and DIF are important indicators of horizontal stress orientation and FMI data provides key information for controlling wellbore stability problems with improved design of the drilling program. The observations through FMI log interpretation can be integrated with core studies along with the analysis of other logs, to get better geological and reservoir characterization of Cambay Shale.

Acknowledgement

The authors would like to thank Oil and Natural Gas Corporation Limited, India for providing the requisite data and samples for the present study.