AAPG Latin America and Caribbean Region Geoscience Technology Workshop

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Extra-Deep Azimuthal Resistivity Reduce Geological Uncertainty and Enhance Reservoir Navigation in Highly Complex Carbonate Reservoir in Polvo Field, Offshore Brazil


Strategic reservoir mapping and real-time wellbore placement techniques have become crucial for achievingthe targeted footage in the challenging Albian carbonate reservoir such as the Quissamã Formation, Campos Basin, Offshore Brazil. These reservoirs are dominated by oolitic and oncolytic calcarenites that are confined to the crest of paleo rollovers and are heterogeneous as well. During a well drilling campaign for the Revitalization Plan of the Polvo Oil Field, the application of the extra deep azimuthal resistivity (EDAR) technology combined with advanced inversion while-drilling techniques and real-time 3D visualization was the key to reduce uncertainty in the geological model (based on seismic & basic offset well logs). The advanced inversion allows multiple optimum earth models derived from smart inversion workflows. The earth models are divided into two groups, one using a geological priori-knowledge and the other using defined strategies.The new workflow proposed compared the geo-navigation model and bedding position information derived from the rig-site inversion of extra-deep resistivity measurements with the seismic model using a 3D visualization tool. This resulted in an updated seismic interpretation in real-time, enabling early re-planning of a new optimum well trajectory based on mapping the reservoir architecture. A pilot sidetrack well confirmed the presence of oil in the well’s main target, the Quissamã Formation carbonate reservoirs, Macaé Group. The reservoir has a net pay of 59 meters TVD and is highly interstratified with cemented or low permeability carbonates. The reservoir has an average porosity of 15%, API gravity of 21.5 degrees, with similar features to the rest of the Polvo Field. Following a period of stabilization, the measured initial production rate was around 2600 barrels of oil per day. This represents a 35% increase in the field’s total production. The additional reserves are estimated to exceed 1.5 million barrels of recoverable oil. The synergy and integration between the operator and the service company has proven to be fundamental for achieving these results in this producer well. The expertise of both operator and service company experts provided several, both for navigating within the reservoir and for its characterization. During the original Field Development Project, wells were drilled through a geometric well plan. Geocorrelation and confirmation were performed while drilling but no real-time decisions were made using the information gathered during the drilling process. This paper presents a multidisciplinary collaborative concept combining the advanced inversion on EDAR data that provided a better overview of the geologic structure and layering; especially in the section with a high degree of uncertainty in the Seismic interpretation which warranted using proactive geonavigation techniques on these carbonate reservoirs.