This paper presents field applications of a new slim pulsed neutron logging tool (PNL) in the Sultanate of Oman. In the spectroscopy mode, the tool provides high-resolution capture and inelastic spectroscopy measurements with significantly improved accuracy and precision over the previous-generation tools. In the gas, sigma, and hydrogen index (GSH) mode, the tool provides self-compensated sigma and neutron porosity measurements for a wide range of environmental conditions, including gas-filled boreholes. This mode also introduces the fast neutron cross section (FNXS) measurement, which is sensitive to variations in gas-filled porosity and is insensitive to variations in liquid- filled porosity. The answers from this tool are valuable for formation evaluation and reservoir monitoring in conditions where existing technologies are limited.

Five case studies of various field applications demonstrate the benefits from the tool's elevated specifications in comparison with existing technology. The first case study addressed three fluid phases in a carbonate oil reservoir undergoing water and gas cap expansion. The second case study evaluated the gas-bearing potential of the Gharif formation. Evaluation of the Middle Gharif formation is particularly challenging due to its complex mineralogy and the co-existence of bitumen and gas. The third case study targeted the tight gas reservoirs in the Barik and Miqrat formations. The challenging environment posed by the combination of low permeability and a gas-filled borehole made this well a very good candidate to explore the new tool's capability for providing accurate self-compensated sigma and hydrogen index logs with the required precision. The fourth case study was conducted in an observation well that is completed with plastic-based casing to monitor an enhanced oil recovery pilot. Achieving optimal saturation accuracy was the primary objective. The fifth case study targeted organic-rich carbonate mudstone in the Natih formation. The primary objective was the determination of total organic carbon (TOC) behind casing. Openhole logs, production data, and core analysis were used to verify the results of the new slim PNL tool.

The traditional applications of PNL spectroscopy tools, such as reservoir monitoring and analysis behind casing, benefit greatly from the tool's elevated precision, accuracy, and detailed mineralogy description. In addition to this, integrating carbon-oxygen and the FNXS measurements enables the evaluation of multiple phases, such as those typical in thermal or gas-injection-based developments.