INTEGRATED RESISTIVITY INTERPRETATION OF ARRAY INDUCTION, MULTI-COMPONENT INDUCTION AND BOREHOLE RESISTIVITY IMAGING MEASUREMENTS IN THINLY BEDDED SAND-SHALE SEQUENCES

摘要

In many exploration wells operators utilize a combination of advanced openhole logging tools such as array induction, multi-component induction, and borehole resistivity imaging for computing accurate water saturation in thinly bedded sand-shale sequences. A consistent resistivity interpretation of such combinations may become an issue due to different inherent vertical resolution and different sensitivity of these tools with respect to various formation parameters. This paper discusses how to integrate those measurements into one consistent earth model while utilizing the advantages of each logging technology. In thinly bedded anisotropic sand-shale sequences, traditional array induction measurements are dominated by the conductive shale response and as such are insensitive to the resistivity of the hydrocarbon-bearing sands. The vertical resolution of the array induction in favorable conditions may approach 1 ft, but the resolution is usually insufficient to resolve individual layers in thin beds. Concurrently, the sounding capabilities of array induction tools can be extremely useful in detecting the presence and properties of formation mud invasion that can significantly affect other measurements. In contrast to the resolution of traditional array induction tools, the vertical resolution of a multi-component induction tool is much more coarse. However, its measurements are affected by highly resistive sand fraction of the formation and therefore provide an accurate estimate of the hydrocarbon saturation in thin beds. The borehole resistivity image tool allows for the delineation of inch-thick individual layers in sand-shale sequences and visualization of the scale dependant, micro-anisotropy that may provide for integration of petrophysical and geological data. We will present a field example to illustrate how advanced processing techniques allow the operator to utilize strengths of each logging service and combine those for a consistent and accurate resistivity interpretation of thinly bedded sand-shale sequences.