Abstract
Ultra-deep ElectroMagnetic (EM) inversion is used to resolve multiple layers at a distance from the wellbore. Since it primarily responds to resistivity variations, it has been used for mapping formation boundaries and fluid away from the wellbore, such information has been key for improved well placement decisions and mapping the reservoir boundaries and areal extent. Enhancements in LWD Ultra-deep technologies and processing techniques including reservoir visualization in three dimensions, and inversion for anisotropy provide new applications for these technologies. As more advanced uses are developed it is important to shed some light on the integration of some of these unique cases.
Real-time transmission of nine ultra-deep resistivity components allows 3D inversion for both resistivity and anisotropy far away from the wellbore. Inversion for resistivity and anisotropy in three dimensions provides a solution for multiple reservoir challenges such as azimuthal well placement as well as lithology identification at a distance, differentiating different lithologies that have similar resistivity responses. Faults showing resistivity contrasts can also be mapped at distance from the wellbore. Inverting for the 3D volume using a smaller scale cell size has enabled resolving thin layers in real time. Finally, the integration of near and far field resistivity and 3D has improved far field petrophysical understanding in carbonates and clastic reservoirs.
Ultra-Deep Resistivity has been used in real-time to identify fluid and lithology at distance, this is critical to understand the proximity to fluid contacts or the presence of fluid barriers, such information is key for well placement decisions and completion design. Enhanced processing techniques has enabled resolving thin beds down to 1-2 ft thickness using Ultra-deep Resistivity 3D Inversion which compliments the visualization away from the wellbore and improves real-time decisions. Faults mapped at a distance provided an understanding to water encroachment behavior in carbonate reservoirs. It has also provided key information along with 1D and 3D for far field petrophysics, utilizing offset data and the information provided by the Ultra-deep resistivity inversion. This Paper covers all the challenges that deep and Ultra-deep Resistivity can cover from optimizing the well placement to formation evaluation in the far field.
