Delineating Thin Heterogenous Reservoir Layer While Enhancing Geosteering Performance with Advanced Deep Resistivity Measurements and a High-Resolution Multi-Layer Inversion for Reservoir Characterization in Real Time. A Case Study of New Advanced Technology from the Middle East
Authors: Goraya Yassar , Alabed Sundos , Biyanni Hanifan , Al Silwadi Basil , Almarzooqi Khulood , Buhindi Hani Ahmed , Bourgeois Daniel , Siddiqui Wamiq Nasr , Aubakirov Ruslan , Wang Hui 
Published: November 2024

Objective / Scope: A horizontal production well targeting the C Reservoir layer in the offshore field was recently drilled. The well was initially planned to be drilling using ultradeep resistivity boundary mapping to geosteer the well in the target formation. However, modeling suggested that the resistivity contrast was to low to allow for definitive mapping of the upper boundary of the target layer. The layer being target was expected to be 5 – 10 ft thick with structural uncertainty and the possibility of faulting. In order to geosteer the horizontal well in the targeted layer, a precise solution would be required.

Methods, Procedures, Process: Although deep and ultradeep propagation resistivity measurements from various tool configurations have been used for geosteering and reservoir boundary mapping for several years, the resistivity inversion is challenged as reservoir complexity increases. Recently newly introduced technology with deep, calibrated resistivity measurement from a tilted antenna at farther spacing than typical resistivity measurements and a high-definition, multi-layer deterministic inversion. Modeling for the ADNOC Offshore suggested that this latest generation of technology could map the complex layering expected in the targeted reservoir layer. This technology was deployed to drill the horizontal section while mapping and entering into conductive low resistive layers in the subject well while drilling.

Results, Observations, Conclusions: Using the latest generation of deep resistivity boundary tools, the well was successfully geosteered entirely in the target formation. The 1D high-definition inversion was able to map higher a conductive layer above the well bore and a more resistive dense layer below the well bore. Using the multi-layer high-definition inversion, two sub-seismic faults were identified. In WI these mapped faults were covered with blank pipe to avoid any water break through in other layers.

Based on the successful first deployment of this technology, a second trial was conducted with encouraging results while geosteer well in thin target layer preciously Figure A. Based on real time inversion results it was decided not to penetrate into second layer. Decision not to penetrate into deeper layer resulted in successful delivery of oil well with good rate, where as offset wells are unable to flow due to high water cut. Future wells in the field that target thin reservoir layers are currently being planned with this deeper resistivity distance to boundary tool.

Novel / Additive Information: Previously, there were two options for geosteering using resistivity mapping, deep or ultradeep LWD tools. The common deep distance to boundary tool would not have enough depth of investigation to identify the reservoir layer boundaries in this case. While ultradeep resistivity tools would have this depth of investigation, the resolution of the inversion would not allow for identification of the thin beds required to remain in the targeted layer. The depth of investigation and high definition inversion with the latest generation of distance to boundary tool overcame these limitations and allowed for successful geosteering of horizontal wells in this field.