Antiagglomerants Affect Gas Hydrate Growth

Abstract

In gas clathrate hydrates, inclusion gas molecules stabilize crystalline water structures. In addition to being fundamentally interesting, gas hydrates attract significant practical attention because of their possible application in various high-tech technologies. However, gas hydrates pose health, safety, and environmental risks when they form within oil and gas pipelines, as well as within hydrocarbon-producing and treatment facilities. Among available strategies to control and sometimes prevent hydrate plug formation is the use of surface-active low-molecular-weight compounds, known as antiagglomerants (AAs). AAs prevent the agglomeration of small hydrate particles into large plugs. It is not clear whether AAs promote or frustrate hydrate growth. We present two molecular mechanisms by which AAs promote and frustrate, respectively, hydrate growth. Our results could lead to innovative methodologies for managing hydrates in high-tech applications, as well as for securing the safety of oil and gas operations.

Synergistic and Antagonistic Effects of Aromatics on the Agglomeration of Gas Hydrates

“…This could be because polycyclic aromatics yield better packing than monocyclic ones at the interface. The lower concentration of methane at the interface in the presence of aromatic compounds could reduce the hydrate growth rate 9 , which is consistent with the experimental data obtained in the presence of asphaltenes and resins 48 . When AAs are present at low surface density, fewer methane molecules are present at the interfaces compared to results obtained when no AAs are present.…”

Molecular properties of interfaces relevant for clathrate hydrate agglomeration

“…This approach could be used to quantify how chemical additives/guests, e.g., tetrahydrofuran [5], affect hydrate growth rate and stability. Bui et al [40], e.g., simulated hydrate growth in the presence of AAs (see Figure 1). Those simulations combined brute force MD with metadynamics.…”

“…In panel (A) the simulated system is shown, where are highlighted the crystal hydrate seed, the film of liquid water, the anti-agglomerants adsorbed at the water-hydrocarbon interface, and the hydrocarbon phase, composed of dodecane and methane. In panel (B) the schematic representation of the anti-agglomerants considered by Bui et al [40] is provided. In panel (C) a schematic is provided for the growth of the hydrate in the presence of AAs: the simulations start with the system shown on the left and are concluded when all the free water has been converted in hydrate (right).…”

“…For these AAs, small tail length variations yield large changes in performance. For example, when the linear chain identified as R2 in Figure 1 contains 4 carbon atoms, the experimental performance is reported as 'good' when R1 is a linear chain of 12 carbon atoms, but 'poor' when R1 contains 8 carbons [40]. The molecular mechanisms responsible for these changes in experimental performance are not fully understood, but simulations could help.…”

Thermodynamic study on gas hydrates: experimental determination of equilibrium data by high-pressure microcalorimetry and modeling up to 100 MPa.

“…Besides, kinetic inhibitors are often applied in order to delay the hydrate growth and plugging processes while fluid goes within the pipeline (KELLAND et al, 2006;. It is still possible to add anti-agglomerants agents along the flow path to prevent the adhesion between the hydrate particles formed (BUI et al, 2018;SLOAN;.…”