Simulations and Experimental Results for a High-Power Laser Tool to Dissociate Hydrate on Oil and Gas Production Equipment in Deep Water

Abstract

Abstract The formation of gas hydrates on oil and gas production equipment in deep water can hinder subsea operations, often requiring removal by using expensive and time-consuming methods that can damage the equipment. This paper discusses simulations and experimental tests to evaluate a lower-cost, safer, and more efficient tool under development to remove the hydrates by dissociation through radiation from a high-power laser installed on a Remotely Operated Vehicle (ROV). The laser source used in the first phase was a blue (445 nm) diode laser of 730 W, while an 1800 W source is currently used for the second phase. Depending on the scenario and material, the laser beam can either irradiate the hydrate formation to heat it and achieve the necessary temperature for dissociation, or it can be aimed at equipment adjacent to the formation, with laser beam spot size and power enough to transmit the necessary heat to the hydrate, without damaging the equipment. Simulations and experimental tests to optimize the parameters were performed to ensure that the required temperatures are reached. Metal samples and materials similar to hydrates were used in simulations and lab tests in air and in water, and under various laser parameters, demonstrating that heating from deep ocean water temperatures found near subsea equipment (4°C or slightly higher, depending on the depth) up to hydrate dissociation temperatures (17°C–26°C) can be attained with the proposed tool. Additionally, the comparison between the simulations and the experimental results showed good agreement. This paper focuses on the experimental and simulated results obtained with a steel disk and on experimental results for a metal tube, discussing how the ability to reach the temperatures required for dissociation is affected by the water temperature and flow, how far the radiation propagates in water before reaching the target, the temperature distribution on the target, and the irradiation time. Simulations and experimental results obtained with a high-power-laser tool for deep-water dissociation of hydrates are discussed. The lab tests provided reliability and adjustments for the simulations, in addition to performance estimates for the prototype. The tool is a safer and lower-cost method to dissociate hydrates interfering with the operation of oil and gas production equipment in deep water.