Operational Overview of the JOGMEC-DOE-USGS Gas Production Test from Gas Hydrate on the Alaska North Slope

Abstract To understand the long-term production behavior of gas hydrate, an extended-duration gas production test was conducted under the JOGMEC-DOE-USGS Collaborative Gas Hydrate R&D Project in Alaska. The production test began in September 2023 using an electric submersible pump (ESP). During ESP operation, stepwise depressurization was followed by an extended period of continuous operation under constant bottom-hole pressure (BHP). Pressure reduction below a level of ∼850 psi (∼400 psi of drawdown) was not possible due to strong surges in gas production rate, which caused the ESP to cease functioning (“gas lock”). To prevent gas lock, continuous operation under constant BHP was implemented at 850 psi and maintained for two months, with only one short-term disturbance for the safety shutdown valve (SSV) function test. No significant variation in either gas or water production rate was detected, and production continued at a stable rate of 70 mcf/d of gas and ∼10 bbl/d of water for 60 days. Although the continuous production under constant BHP provided insights into long-term production behavior, no upward or downward trend in the production volume associated was observed, indicating that further investigation is required to understand the nature of long-term production. Following the ESP operation, the ESP was replaced with a jet pump (JP) to mitigate gas lock. During JP operation, BHP was depressurized to very low levels (∼200 psi); however, this depressurization had only a limited effect on the formation pressure, which was assumed to be due to the presence of skin (buildup of a low-permeability fine-grained layer) associated with the sand control system. Injection of chemicals was attempted to remove this skin effect, but it was unsuccessful, resulting in higher differential pressure and low productivity. The test facility was successfully operated for ten months from September 2023 to July 2024. Within this period, there were 315 days of operation, including 64 days of nonproduction time due to various mechanical failures, issues relating to sand production, and replacement of the ESP with a JP. Post-test operations to retrieve the completion confirmed the ultimate failure of the aggressive sand control system installed. The operational finding with respect to sand control and artificial lift will inform future gas hydrate production test designs.