Overview of the Monitoring Program in the Alaska North Slope Extended-Duration Gas Production Test from Gas Hydrate

Abstract

Abstract As a part of an extended-duration gas production test conducted under the JOGMEC-DOE-USGS Collaborative Gas Hydrate R&D Project in Alaska, one of the main objectives was to understand the behavior of gas hydrate formation and the production system during long-term depressurization. To achieve this, the wells completed for the production test were equipped with a wide variety of sensors to monitor changes in both reservoir and wellbore conditions. The primary monitoring tools for monitoring the condition around the wells included pressure–temperature (PT) sensors and distributed temperature sensing (DTS) systems, which had been recognized to yield critical data on formation responses in previous gas hydrate field experiments. Furthermore, the program also included the use of distributed strain sensing (DSS) and distributed acoustic sensing (DAS). Sensors were installed by strapping them to the exterior of the well casings. The only damage was to the DSS in the HYDRATE P2 production well (PTW-2), in which one of the fibers was broken during the installation. The remaining sensors successfully acquired measurements over the duration of the 10-month-long production test. After the end of the production testing operation, an additional three months of post-test monitoring were conducted to understand the PT recovery process of the formation. This report reviews the types and specifications of the sensors, installation, and the acquired data, along with a discussion of measurement-related issues. The information provided here provides the foundation for a detailed analysis of project-acquired monitoring data as reported in other papers within the “Recent Advances on Gas Hydrates Scientific Drilling in Alaska – An update from Production Testing Operations during 2023/2024 (Part I) Special Issue” (SI).