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Semi-automatical Sedimentary Analysis From a New High Resolution Oil-based Mud Borehole Resistivity Image

Abstract

Detail sedimentology interpretation is often conducted from core or borehole image data manually. Different interpreters may produce significantly different descriptions and interpretations for the same borehole image. To improve at the same time the efficiency and the consistency of the sedimentary structure interpretation, a new semi-automatic sedimentary structure analysis from borehole image dips is proposed in this paper. First, the sedimentary structure boundaries dip and internal laminations are picked from borehole image and classified and processed to remove the structural dip component. Then, they are processed to remove their structural dip component. The dip trend of each sedimentary structure is automatically compared with different pre-defined geometrical types. These pre-defined geometrical types are editable to better match the characteristics of the depositional environment. Finally, an interpretation of the sedimentary structures is automatically proposed. We present a case based on a new oil-based imager acquisition, logged in the Devonian sand of Catoosa, Oklahoma. This image tool provides a high resolution of sedimentary features with its nominal resolution of 0.2 in from 192 buttons and 98% borehole coverage in an 8 in hole. The resulting discrete sedimentary structure interpretation log allowed to distinguish five micro-facies that we validated by the comparison with standard water based borehole image data and outcrop descriptions.