This paper presents a method for integrating information obtained from ultradeep azimuthal electromagnetic (EM) technology, and processed during geosteering activity, to update a 3D reservoir model. The latest developments in logging-while-drilling (LWD) technology, unimaginable until a few years ago, dramatically improve understanding reservoir structure far away from the wellbore. Ultradeep azimuthal EM technology provided a step change in remote detection capabilities by mapping resistivity contrasts up to tens of meters away from the wellbore. This innovation helps identify unexpected pay zones while drilling, improves subsurface understanding, and leads to well placement optimization in real time. In addition, the multiboundary reservoir mapping, provided by inversion of the ultradeep azimuthal EM measurements, allows for improvement in 3D reservoir model updates when addressing field development optimization. The method presented integrates field geological knowledge, wellbore-centric LWD data (logs and images), EM reservoir mapping information, and interpreted seismic data to refine a 3D reservoir model in the neighborhood of the well. The ultimate goal is to include the data acquired in horizontal wells in a live reservoir model update across the entire cycle of the well placement workflow. The process includes a feasibility study for technology and strategy selection, real-time geosteering execution and data integration to update the 3D reservoir model in near real time. Collaborative cross-disciplinary teams, composed of both operator and service company specialists, are focusing more and more of their attention on integrating this information into optimal field development strategy. Nowadays, it is possible for operators to handle multiboundary reservoir mapping data directly within dedicated geological modeling platforms. Advanced software solutions, designed to improve data accessibility, are the base for new integrated workflows for accurate 3D reservoir models using a multiscale dataset.

Structural estimation capability ahead of the bit is evolving with innovative combination while drilling of borehole and surface data in real time. A pioneering workflow has been developed to recalibrate the reservoir structure via integration of surface seismic with synthetic seismic, derived from logging-while-drilling (LWD) measurements. Modern LWD services have nowadays reached a significant depth of investigation capability, expanding the horizons of geosteering applications. The most recent ultradeep azimuthal electromagnetic (EM) technology provides real time information on a cylinder of rock around the wellbore, up to 200 feet of diameter. This technology enables a new opportunity to update the pre-drill 3D geo-model with the measured local volume of information. Synthetic seismic, derived from EM measurements, is compared with real seismic data, using non-rigid matching to quantify the depth mismatch. The estimated displacement is then applied to the real seismic and to the pre-drill 3D geo-model repository (i.e. identified reservoir horizons, faults, and geobodies) to predict the structural setting of the reservoir ahead of the bit. It is possible to iterate through these steps using an automated process while geosteering. The workflow was tested on post-drill data acquired on an Eni well, recently geosteered within an oil reservoir consisting of fluvial and deltaic deposits of Triassic age. The automated interpretation tools, integrated on the seismic interpretation software, allowed building a pre-drill model in two-week time. The model provided a base for the creation of the geosteering roadmap considering the structural features potentially present along the planned trajectory. The real time simulation lasted two days in a play back mode, focusing on the assessment and validation of the workflow. Each process iteration took few minutes to provide results, validated in parallel with LWD available data. The calibration provided a robust dip and structure estimation and additionally the confirmation of fluid contact position, as identified in the pre-drill model. The workflow unlocked extra look ahead possibilities for optimal geosteering, and proved to be able to provide robust information 150m, on average, ahead of the bit. The presence of structural discontinuities was successfully validated within 30 m measured depth from the predicted position. This novel approach is a step further toward the possibility of providing accurate reservoir updates ahead of the bit, and so forth to improve well placement operations while updating 3D geo-models in real time.

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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.

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