Alaska North Slope Extended-Duration Gas Hydrate Production Test Site Logging-While-Drilling Data Acquisition

One of the critical goals of the Collaborative Gas Hydrate R&D Project in Alaska, as being led by the Japan Organization for Metals and Energy Security (JOGMEC – MH21-S), the U.S. Department of Energy, and the U.S. Geological Survey (USGS), was to implement a production test at the Alaska North Slope (ANS) within the Prudhoe Bay Unit. Included in this effort were the drilling of four test site wells and the acquisition of downhole logging-while-drilling data from all four test site wells. With the confirmation of the viability of the test site for future testing provided by the HYDRATE 01 Stratigraphic Test Well (STW) completed in 2019, the project moved ahead with drilling and data acquisition in the HYDRATE 02 Geo Data Well (GDW) completed in 2022, and the HYDRATE Production Test Well P1 (PTW-1) and HYDRATE Production Test Well P2 (PTW-2), both completed in 2023. As in the STW, SLB logging-while-drilling (LWD) tools were utilized to acquire wellbore data in the GDW, PTW-1, and PTW-2. The primary acquired well log data consisted of neutron porosity, density, caliper, compressional slowness and shear slowness velocities, natural γ ray, nuclear magnetic resonance porosity, and phase shift and attenuation resistivities. This paper presents a quality check of the acquired LWD logs and a “quick-look” preliminary interpretation of the acquired data that was used in support of the design of the PTW-1 completion and production testing plan. A quick-look interpretation based on Archie’s analysis of resistivity logs indicates hydrate saturation ranging from 50–90% for B1 sand (unit B) and 45–85% for D1 sand (unit D). In general, the acquisition parameters for the LWD data yielded relatively high-quality logs, with the exception of the NMR data in the PTW-1. NMR and core data analysis results from STW and GDW were used to calibrate the NMR porosity and permeability log data from the PTW-1. Using measurement-after-drilling data (MAD), well-log-derived gas indicators, including changes in MAD Delta Transit-time Compressional Slowness (DTCO) and Nuclear Magnetic Resonance Porosity (NMR MRP) log values with time in the STW, were considered to be the product of drilling-induced gas hydrate dissociation.