High-Definition Well Placement: Navigating a Mature Carbonate Reservoir with Next-Generation Boundary Mapping LWD Technologies

Abstract

Mature reservoirs often have significant uncertainties in the position of oil–water contacts (OWC) due to decades of hydrocarbon production, water injection, uneven depletion, and complex reservoir architecture. Horizontal well placement in thin producing zones is highly challenging when a nonproductive upper roof lies close above the target and an OWC boundary lies below. Logging-while-drilling (LWD) technologies address such challenges by mapping resistivity boundaries far from the wellbore. This paper presents a successful case study using a next-generation LWD deep resistivity inversion to maintain an 18-ft standoff from the OWC while maximizing reservoir exposure and sustaining long-term production. Conventional LWD tools often lack the depth of investigation to map boundaries far from the wellbore. Electromagnetic signals from deep and ultra-deep resistivity tools were used to construct high-resolution geological maps, continuously defining the upper and lower boundaries of the horizontal well. The real-time visualization enabled multidisciplinary teams to make rapid trajectory adjustments, guided by resistivity data, offset well information, structural models, and cuttings analysis. Continuous 24-hour geosteering monitoring and proactive trajectory adjustments ensured the wellbore consistently tracked the most productive zone, avoiding exits into nonproductive rock or encroachment into the underlying water column. The advanced geosteering workflow enabled precise mapping of both the tight upper roof and the OWC, approximately 18 ft below the wellbore. Continuous real-time updates supported proactive steering decisions, resulting in the wellbore remaining entirely within the targeted reservoir interval. The operation achieved a 100% net-to-gross ratio, preserving long-term production potential. This case illustrates how deep boundary mapping, combined with rapid multidisciplinary decision-making, directly translates into improved reservoir drainage and consistent well placement within thin producing zones bounded by restrictive layers. This case demonstrates a fully executed example using next-generation LWD technology in a mature reservoir. The combination of high-resolution deep resistivity measurements, real-time inversion, and integrated team decision-making provides a proven, replicable workflow for precise well placement. It highlights how advanced LWD enables successful navigation of thin producing zones bounded by closely spaced restrictive boundaries, offering practical guidance for optimizing reservoir development and maximizing hydrocarbon recovery.