Insights into kinetic inhibition effects of MEG, PVP, and L-tyrosine aqueous solutions on natural gas hydrate formation

Abstract

It is necessary to understand all the prerequisites, which result in gas hydrate formation for safe design and control of a variety of processes in petroleum industry. Thermodynamic hydrate inhibitors (THIs) are normally used to preclude gas hydrate formation by shifting hydrate stability region to lower temperatures and higher pressures. Sometimes, it is difficult to avoid hydrate formation and hydrates will form anyway. In this situation, kinetic hydrate inhibitors (KHIs) can be used to postpone formation of gas hydrates by retarding hydrate nucleation and growth rate. In this study, two kinetic parameters including natural gas hydrate formation induction time and the rate of gas consumption were experimentally investigated in the presence of monoethylene glycol (MEG), L-tyrosine, and polyvinylpyrrolidone (PVP) at various concentrations in aqueous solutions. Since hydrate formation is a stochastic phenomenon, the repeatability of each kinetic parameter was evaluated several times and the average values for the hydrate formation induction times and the rates of gas consumption are reported. The results indicate that from the view point of hydrate formation induction time, 2 wt% PVP and 20 wt% MEG aqueous solutions have the highest values and are the best choices. It is also interpreted from the results that from the view point of the rate of gas consumption, 20 wt% MEG aqueous solution yields the lowest value and is the best choice. Finally, it is concluded that the combination of PVP and MEG in an aqueous solution has a simultaneous synergistic impact on natural gas hydrate formation induction time and the rate of gas consumption. Furthermore, a semi-empirical model based on chemical kinetic theory is applied to evaluate the hydrate formation induction time data. A good agreement between the experimental and calculated hydrate formation induction time data is observed.

Gas Hydrate in Oil-Dominant Systems: A Review

“…The comparison made in terms of inhibition strength (°C) when compared in terms of systems with brine water gave a higher inhibition strength for all inhibitors, which is around 0.4 °C; however, in terms of inhibitors, mSA-RmAFP1 gave the highest inhibition strength of around 5.5 °C. After that come PVP at 4 °C and then glycine at 3 °C, and Saberi 90 studied the impact of PVP on the induction time with two different concentrations, 1 and 2 wt % of l -tyrosine, 1 wt % of MEG, and 10 wt % and a mix of MEG and PVP on different concentrations and 2 wt % of PVP + 10 wt % of MEG and 2 wt % of PVP + 20 wt % of MEG using Stainless Steel (SS-316) on CH 4 hydrate with mineral oil with 40% water cut under 8 MPa pressure and 4.7 °C temperature. It has been reported that PVP gave the highest induction time around 85 min compared to MEG at 51 min, but after mixing PVP and MEG the induction time was increased.…”

Review of Kinetic Hydrate Inhibitors Based on Cyclic Amides and Effect of Various Synergists

“…However, because of the excess amount requirements (35–50% of the water flow rate) and the toxic elements associated with THIs, researchers are working on low-dosage kinetic hydrate inhibitors (KHIs) that could be economical and environmentally responsible, as only 0.5% of the water flow rate or less is required to inhibit hydrates . Note that low-dosage KHIs slow down the hydrate formation process but do not change the thermodynamic state of the system, as opposed to the THIs …”

“…39 Note that low-dosage KHIs slow down the hydrate formation process but do not change the thermodynamic state of the system, as opposed to the THIs. 40 For a deepwater pipeline in the Gulf of Mexico, KHIs were considered for hydrate prevention. For cost savings, two scenarios were considered: (1) using a THI (e.g., methanol) and (2) using a KHI alone.…”

Effect of the Ethylene Vinyl Acetate Copolymer on the Induction of Cyclopentane Hydrate in a Water-in-Waxy Oil Emulsion System

“…Gas hydrate, a type of cage-like crystal structure constructed by water and gas molecules, is generally formed in a low-temperature and high-pressure environment. − The gas molecules, such as methane, ethane, carbon dioxide, and so forth, − are able to be enveloped by the cages of water molecules, forming structure I, II, and H hydrate. − The formation of hydrate becomes a challenge in the development of deep-water fields, where the oil or gas is exposed to the environment of high pressure, low temperature, and water cuts. , Therefore, hydrate forms more easily in the deep water environment and increases the risk of plugging pipelines. − Webb et al studied the effect of water fraction in a water-in-dodecane emulsion on the rheological behavior of a hydrate slurry via a high-pressure rheology apparatus. The results show that the viscosity of the hydrate slurry increases apparently with the increase of water fraction from 5 to 30%.…”