Perspectives on Gas Hydrates Cold Flow Technology

Abstract

Gas hydrates cold flow can be defined as flow of non-adhesive and non-cohesive hydrate particles dispersed in the production fluids flowlines. Implementation of cold flow related hydrate management strategies might significantly reduce the costs of oil and gas field development and production by removing or reducing the need for injection of chemicals, insulation, and heating. Several research groups have performed experiments focusing on different methods of producing hydrate dispersion. Hydrate particles can be seeded into the production fluids at hydrate stable conditions to initiate controlled growth of hydrates as the dispersion is cooled to temperature conditions in production systems. Alternatively, the water droplet size in water in oil dispersions can be reduced by utilizing static mixers, high velocity, or small concentrations of chemicals, which might facilitate readily conversion of the small water droplets into hydrate particles. One researcher has proposed separating liquid phases from gas and supercooling of liquid phases before mixing the phases for hydrate formation. Use of antiagglomerants combined with reducing viscosity by increasing water content has been proposed by other researchers. Cold flow as a component of a natural gas dehydration process is described in a patent application but has not been experimentally tested. Laboratory-scale flow loop experiments indicate that cold flow works well for low to medium gas/oil ratios and up to 20% water cut for both oil and condensate dominated systems. Experiments with crude oils containing wax show that cold flow could significantly reduce or eliminate wax deposition on pipeline walls. A field trial of the cold flow method in a once-through flowline focused on reducing droplet size, resulting in hydrate deposition. This review discusses utilized methods and published results on cold flow from various research groups in light of known mechanisms for hydrate formation. Some suggestions are also given with focus for future research in order to develop, validate, and implement cold flow as a reliable technology for hydrate management method in the production of hydrocarbon fluids.

Investigation on Hydrate Growth at the Oil–Water Interface: In the Presence of Wax and Kinetic Hydrate Inhibitor

“…Natural gas hydrates (NGHs) are crystalline compounds composed of water and hydrocarbon gas molecules . NGHs are readily formed under the low-temperature and high-pressure conditions in oil and gas industry and could therefore pose a great threat to subsea flow assurance by agglomerating, jamming, bedding, and depositing in the transmission pipelines. − So far, NGHs in subsea flow assurance have been extensively investigated, and several hydrate prevention/management strategies have been proposed. − Except for NGHs, another big concern in subsea flow assurance is about wax. When the pipeline operating temperature falls below the wax appearance temperature (WAT), wax molecules dissolved in the crude oil will gradually precipitate and may deposit on the pipe wall, which may further lead to pipeline plugging.…”

Lattice Boltzmann phase field simulations of droplet slicing

“…The equilibrium distributions must satisfy conditions (8) and is advected by fluid, which can be given by the follow equation:…”

“…Applications of slicing (or cutting) droplets are mainly found in microfluidics [7] and also-on a larger scale-in static mixers. [8] Forte et al [9] investigated the fundamental mechanisms of oil droplet breakup in static mixers. They found that the drop size decreased to a critical point when the continuous phase (water) flow rate is increasing.…”

Modeling Heat and Mass Transfer Limitation Processes of Gas Hydrate Formation Under Slug Flow

“…Although 100% conversion of water does not influence the particle size noticeably (which grows at a ratio of 1.09 wh   for methane hydrates), agglomeration can drastically change the number and average size of particles. Agglomeration is neglected for the sake of simplification (cold flow assumption; Straume et al, 2019), but coupling with proper population balance models (Balakin et al, 2010;Herri et al, 1999;Sampaio et al, 2017) will be done in a near future.…”