Multiscale Logging While Drilling Data Integration Unveiled Complex Geological Scenario While Geosteering

Abstract

The first Eni geosteering operation in Mexico was executed during the global COVID-19 crisis. The complex geology and the uncertainty related to this undrilled portion of the reservoir determined the employment of advanced Logging While Drilling (LWD) technology for real-time geosteering and a comprehensive geological interpretation. The target is an oil bearing sandstone reservoir, represented by deltaic front sands bars within an anticline structure on a salt core with faults and lateral heterogeneity. A sedimentological conceptual model was used to feed the 3D geological model, supporting a development strategy based on the geosteering of a horizontal well. The trajectory was designed within the best petrophysical properties interval to maximize production. The pre-drill risk analysis determined the need for a pilot hole to confirm structural setting, reservoir properties and fluid contacts to mitigate the associated uncertainties. The landing data acquisition strategy included standard LWD measurements and density images to optimize the wellbore inclination. The drain section was going to be geosteered with an Ultra-Deep Azimuthal Electromagnetic tool, dual-physics imager for oil-based mud systems and sourceless Density/Neutron technology. The pilot hole confirmed the pre-drill expected scenario but the LWD images and data interpreted while landing, revealed a more complex than expected target reservoir architecture. The detailed geological picture was completed while drilling the drain section. The multi-scale data (Reservoir Mapping information, Resistivity images, Logs, Seismic Interpretation and Pressure points) were integrated and exchanged 24/7 by experts through a commercial hub for team collaboration. A communication and information sharing protocol was customized to overcome the restrictions dictated by COVID-19 health emergency. The combination of acquired information and knowledge, unveiled a reservoir made of stacked clinoforms with internal geometries non-conformable with the general structural trend. Real-time geosteering with advanced technologies information, mitigated the impact of the unexpected complex subsurface setting. A total of 270 m were drilled inside the target, maximizing the drilled Net-to-Gross compared with the planned trajectory. Furthermore, the geological scenario reconstructed with multiscale LWD data, was exploited for a detailed 3D reservoir model update.