Petrophysical evaluation in horizontal wells using standard logging while drilling (LWD) data is challenging, especially in thin reservoirs (~ 4 ft) bounded by dense resistive formation. These challenges are predominately associated with the propagation deeper depth of investigation (DOI) resistivity measurements and limitation in recording azimuthal data around the borehole.
In thin reservoirs the currently used electromagnetic (EM) resistivity tools with deeper DOI are usually affected by proximal beds which results in inaccurate saturation estimation for the target zone. Add to that, the traditional way of computing saturation using average porosity and resistivity measurements neglecting the variation around the borehole; this may result over/underestimating the water saturation which is an important factor in the STOOIP calculation.
This paper will discuss a "3D Petrophysical" approach utilizing a new technology that provides shallow azimuthal resistivity measurements around the borehole. The approach is used in integration with the available methodology of utilizing azimuthal density data to capture the variation in water saturation (Sw) around the borehole in thin heterogeneous carbonate reservoirs.