Optimized BHA Length and Enhanced Real-Time Decision Making Using Near-Bit 3D Ultra-Deep Azimuthal Resistivity Solution in MRC Well, Offshore Abu Dhabi

Abstract In Offshore Abu Dhabi, horizontal wells have been essential for improving hydrocarbon recovery and enhancing reservoir drainage. Maximizing reservoir contact in carbonate reservoirs is critical to reducing the number of wells, minimizing operational costs, and lowering environmental impacts. However, precise well placement and accurate reservoir mapping in these complex formations remain a challenge. This paper highlights the innovative application of Near-Bit Ultra-Deep Azimuthal Resistivity (UDAR) logging-while-drilling (LWD) technology, which optimized Bottom Hole Assembly (BHA) length and facilitated proactive real-time decisions to achieve successful Geosteering and reservoir mapping objectives. The project involved drilling an 8.5″ horizontal section with 11,000 ft of lateral length in a carbonate reservoir. The primary challenge was maintaining the trajectory within the optimal zone while accurately identifying conductive boundaries and providing enhanced reservoir mapping. A 6-3/4″ LWD BHA was deployed, incorporating a triple combo assembly and a Near-Bit UDAR tool with the transmitter strategically positioned 9 ft from the bit. The optimized BHA length ensured precise near-bit resistivity measurements for better oil saturation estimations while enabling efficient Geosteering control. The Near-Bit UDAR technology delivered shallow, medium, and deep resistivity measurements, which improved water saturation calculations and oil-in-place estimations. A transmitter-receiver configuration with 40 ft spacing, selected based on pre-well modeling, enabled detailed mapping of conductive zones above and below the wellbore. Real-time near-bit resistivity data ensured proactive decision-making, allowing the wellbore to be safely landed in the high-porosity reservoir zone while avoiding conductive layers below. The tool's advanced real-time 1D/3D inversion mapping capabilities enhanced reservoir characterization by identifying boundary layers and confirming no lateral fluid movement around the wellbore. This timely information enabled the completion team to proactively design pump systems and isolate sections prone to water breakthrough ahead of reaching Total Depth (TD). By combining optimized BHA design, near-bit resistivity measurements, and real-time Geosteering, the project successfully maximized reservoir contact and delivered precise well placement. The integration of these advanced LWD technologies resulted in reduced drilling time, operational costs, and risks while maintaining strict adherence to safety standards. This achievement sets a new standard for horizontal drilling in carbonate reservoirs, demonstrating how advanced near-bit resistivity tools, real-time reservoir mapping, and proactive decision-making can overcome operational challenges and improve reservoir understanding. The success of this project offers a valuable reference for future offshore developments in complex carbonate reservoirs.