Far Field Petrophysics Utilizing Deep Resistivity High Definition and Ultra-Deep Resistivity 3D Inversion in Thin Laminated Reservoirs

Resistivity measurement is a fundamental tool for evaluating reservoir fluid and rock properties. This technology has evolved over the past few decades to address different challenges. It has been utilized widely as the primary geo-steering measurement given its large depth of investigation compared to other logging measurements. Near wellbore resistivity measurements are used for evaluating the saturation and identifying the borehole fluid while deep and ultra-deep resistivity tools are used for well placement. Conventional deep azimuthal resistivity tools can map resistivity at a distance with limited depth of investigation and a limited number of contrasting layers. In contrast, ultra-deep resistivity technologies see deeper but don't generally detect thin layers. Recent development of new deep resistivity high-definition technologies, with associated inversions, has resulted in higher depth of detection with better definition of the thin layers. This is due to improved antenna design, better signal-to-noise ratio, and multi-frequency transmission. 3D inversion of ultra-deep resistivity has enabled reduction of near wellbore cell size for mapping thin zones. This helps define more formation detail while reducing the uncertainty in the resistivity values mapped for these layers. An innovative workflow for far field saturation has been developed based on acquired resistivity data, combining multiple sources from near wellbore measurements, offset logs and inverted resistivity data. The workflow has been tested on conventional deep resistivity data, and while this provides a good indication of the saturation away from the wellbore it doesn't provide a detailed definition of the thin layers further away from the well trajectory. Deep resistivity high-definition inversion and 3D inversion of ultra-deep resistivity with reduced near wellbore cell size has been tested in multiple wells and clearly provides improvement in the detection of multiple layers away from the wellbore, including with thin layers. It has been used as an input to generate far field saturation maps and has provided analysts with a better definition of the reservoir properties at a distance, which is key to current and future development plans. This paper demonstrates the improvement in far field saturation mapping utilizing the high-definition deep resistivity inversion and 3D inversion of ultra-deep resistivity with reduced near wellbore cell size. This represents a step change in far field petrophysics.