Degradation and hydrate phase equilibria measurement methods of monoethylene glycol

Monoethylene glycol (MEG), a common chemical used for the inhibition of gas hydrate formation may undergo degradation in the regeneration/reclamation process. Limited research exists on the effect of degradation of MEG on hydrate formation, production facilities and equipment especially in the presence of other chemical additives. The proposed method allows for streamlining the process of preparing, degrading and analysis of MEG solutions for hydrate testing and degradation products. • Procedure to prepare accurate MEG solutions avoiding oxidative degradation of MEG (i.e., controlling oxygen ingress).• Two methods are suggested to mimic field-like degradation of MEG solutions (i.e., degradation by reclamation and autoclave).• Adoption of the isochoric hydrate testing method while using a high pressure cell with the aid of a computer script to accurately evaluate hydrate phase equilibria conditions

Economic material for large-scale H2 storage and H2-CO2 separation

Hydrogen is a clean fuel that can potentially completely decarbonize the energy supply chain and mitigate global warming. Hydrogen – a highly volatile gas – however, needs to be separated from CO2 during H2 production, and also from cushion gas in H2 geo-storage projects; in addition, large-scale H2 storage is a key obstacle. We thus tested and chemically upgraded common sub-bituminous coal as a material for H2-CO2 separation and H2 storage. The coal adsorbed significant amounts of H2 and CO2 and demonstrated an excellent H2-CO2 separation efficiency if chemically modified. The work presented here thus provides fundamental data required for the economic production and storage of H2, so that an industrial-scale clean and sustainable energy supply can be established

Application of a novel green nano polymer for chemical EOR purposes in sandstone reservoirs: Synergetic effects of different fluid/fluid and rock/fluid interacting mechanisms

In this research, a novel natural-based polymer, the Aloe Vera biopolymer, is used to improve the mobility of the injected water. Unlike most synthetic chemical polymers used for chemical-enhanced oil recovery, the Aloe Vera biopolymer is environmentally friendly, thermally stable in reservoir conditions, and compatible with reservoir rock and fluids. In addition, the efficiency of the Aloe Vera biopolymer was investigated in the presence of a new synthetic nanocomposite composed of KCl-SiO2-xanthan. This chemically enhanced oil recovery method was applied on a sandstone reservoir in Southwest Iran with crude oil with an API gravity of 22°. The Aloe Vera biopolymer’s physicochemical characteristics were initially examined using different analytical instruments. The results showed that the Aloe Vera biopolymer is thermally stable under reservoir conditions. In addition, no precipitation occurred with the formation brine at the salinity of 80,000 ppm. The experimental results showed that adding ethanol with a 10% volume percentage reduced interfacial tension to 15.3 mN/m and contact angle to 108°, which was 52.33 and 55.56% of these values, respectively. On the other hand, adding nanocomposite lowered interfacial tension and contact angle values to 4 mN/m and 48°, corresponding to reducing these values by 87.53 and 71.42%, respectively. The rheology results showed that the solutions prepared by Aloe Vera biopolymer, ethanol, and nanocomposite were Newtonian and fitted to the Herschel-Bulkley model. Finally, core flooding results showed that the application of a solution prepared by Aloe Vera biopolymer, ethanol, and nanocomposite was effective in increasing the oil recovery factor, where the maximum oil recovery factor of 73.35% was achieved, which could be attributed to the IFT reduction, wettability alteration, and mobility improvement mechanisms

The impact of tides on the capillary transition zone

The capillary transition zone, also known as the capillary fringe, is a zone where water saturations decrease with height above the water table/oil–water contact as a result of capillary action. In some oil reservoirs, this zone may contain a significant proportion of the oil in place. In groundwater assessments, the capillary fringe can profoundly affect contaminant transport. In this study, we investigated the influence of a tidally induced, semi-diurnal, change in water table depth on the water saturation distribution in the capillary fringe/transition zone. The investigation used a mixture of laboratory experiments, in which the change in saturation with depth was monitored over a period of 90 days, and numerical simulation. We show that tidal changes in water table depth can significantly alter the vertical water saturation profile from what would be predicted using capillary–gravity equilibrium and the drainage or imbibition capillary pressure curves

Protein–like fully reversible tetramerisation and super-association of an aminocellulose

Unusual protein-like, partially reversible associative behaviour has recently been observed in solutions of the water soluble carbohydrates known as 6-deoxy-6-(v-aminoalkyl)aminocelluloses, which produce controllable self-assembling films for enzyme immobilisation and other biotechnological applications. Now, for the first time, we have found a fully reversible self-association (tetramerisation) within this family of polysaccharides. Remarkably these carbohydrate tetramers are then seen to associate further in a regular way into supra-molecular complexes. Fully reversible oligomerisation has been hitherto completely unknown for carbohydrates and instead resembles in some respects the assembly of polypeptides and proteins like haemoglobin and its sickle cell mutation. Our traditional perceptions as to what might be considered ‘‘protein-like’’ and what might be considered as ‘‘carbohydrate-like’’ behaviour may need to be rendered more flexible, at least as far as interaction phenomena are concerned

Evaluation of different hydrate prediction software and impact of different MEG products on gas hydrate formation and inhibition

© 2016, Offshore Technology Conference New hydrate profile correlations for methane gas hydrates were obtained computationally (using three different hydrate prediction software packages) and experimentally (with three different MEG products from different suppliers). Methane gas with pure distilled water was the benchmark case used for the software comparison at pressures of 50 to 300 bar. In order to compare the hydrate inhibition performance of the MEG products, aqueous 10 wt% MEG solutions were tested using the isobaric method at a pressure range of 50 to 200 bar. Furthermore, the kinetics of MEG hydrate inhibition were studied experimentally for methane gas using a stirred cryogenic sapphire cell. Hydrate formation start, hydrate dissociation initiation and hydrate dissociation end points were identified and analysed. The results were correlated with the hydrate formation start points predicted by three well known selected hydrate prediction software packages (which all use the Peng-Robinson equation of state). Moreover, the hydrate inhibition performance of the three MEG products was evaluated to determine the superior MEG product that provides the best hydrate inhibition performance. Our analysis shows that the hydrate formation points predicted computationally are not identical to the hydrate formation start points measured in this work. Software A and software B predicted results matching with the average curve of the experimental hydrate formation start and hydrate dissociation start points, and with a deviation value of 0.06 °C for software A and a deviation value of 0.03 °C for software B. However, software C predicted results almost identical with the experimental dissociation start points, and with an average deviation value of 0.54 °C. The methane gas hydrate profiles for the three different MEG products (X-MEG, Y-MEG and Z-MEG) indicated that X-MEG was the most efficient inhibitor as it shifted the hydrate curve most to the left; X-MEG shifted the hydrate formation curve by an average temperature of 2.07 °C when compared to the benchmark curve (100% water); while Z-MEG shifted the curve by an average temperature of 1.81 °C and Y-MEG shifted the curve by an average temperature of 1.71 °C. We conclude that not all software packages predict the same results although they are all based on the same equation of state. Furthermore not all MEG products supplied have the same hydrate inhibition efficiency. Importantly, choosing the best MEG supplier will reduce the OPEX by reducing the amount of MEG used, and it will accommodate more relaxed operating conditions of lower temperatures and higher pressures

Hydrate Phase Equilibria for Methyldiethanolamine and Empirical Modeling for Prediction

© 2018 American Chemical Society. The issue of gas hydrates in gas pipelines is commonly addressed by injecting hydrate inhibitors at the well heads. Alongside these inhibitors, other chemical additives are also injected to address various concerns such as to reduce the risk of corrosion and scaling. However, it is not clear how the combined chemical cocktail affects gas hydrate formation over a wide pressure range. Monoethylene glycol (MEG) and methyldiethanolamine (MDEA) are common chemicals that are usually used as part of hydrate inhibition and corrosion control programs respectively. Thus, in this study, the methane hydrate inhibition performance of MDEA in the presence and absence of MEG was assessed. The study produced new hydrate phase equilibria data at a high pressure range, suggesting MDEA performs as a thermodynamic hydrate inhibitor and thus enhances the hydrate inhibitory performance of MEG. Furthermore, because there does not appear to be any flow assurance prediction software that has the capability to simulate the effect of MDEA on hydrate formation, an algorithm that can accurately predict the equilibrium temperature of aqueous MDEA solutions with and without MEG was developed. The algorithm is based on the empirical modeling of the experimental data obtained in this study. This work will thus aid in the industrial application of hydrate inhibitors and improve gas hydrate prevention in production pipelines

Evaluation of MEG reclamation and natural gas hydrate inhibition during corrosion control switchover

© 2018 Elsevier B.V. The breakthrough of formation water increases the risk not only of gas hydrate formation but also of corrosion. Switching between corrosion strategies may be necessary as formation water increases the risk of scale formation in the presence of methyl diethanolamine (MDEA), acetic acid, and cations. The switchover from pH stabilization with MDEA to a film-forming corrosion inhibitor (FFCI) was investigated when studying the effect of pH changes on the removal of MDEA, FFCI, acetic acid, and salts in the reclamation unit. The natural gas hydrate inhibitory performance (35 wt%) of the reclaimed monoethylene glycol (MEG) samples were also assessed. The study found that an optimum operating pH for the whole system was not achievable because of the contrasting pH requirements in the pretreatment and reclamation units. The study recommends operating the pretreatment unit at pH > 8 to precipitate out the divalent salts, and injecting acid before the regeneration unit, which allows for the volatile acetic acid to be removed via the reflux drum. We found that FFCI and MDEA accumulation in the reclamation unit resulted in a highly viscous residue (1430.53 mPa-s) and a discoloration (from brown to very dark brown). Further, new natural gas hydrate equilibria data for reclaimed MEG have been reported. The performance of reclaimed MEG varied compared with that of pure MEG, and was lower at the end of the experiment, whereas MDEA showed a hydrate-inhibiting effect

Compressional wave velocity of hydrate-bearing bentheimer sediments with varying pore fillings

© 2018 Hydrogen Energy Publications LLC A potential alternative energy resource to meet energy demands is the vast amount of gas stored in hydrate reserves. However, major challenges in terms of exploration and production surround profitable and effective exploitation of these reserves. The measurement of acoustic velocity is a useful method for exploration of gas hydrate reserves and can be an efficient method to characterize the hydrate-bearing sediments. In this study, the compressional wave velocity (P-wave velocity) of consolidated sediments (Bentheimer) with and without tetrahydrofuran hydrate-bearing pore fillings were measured using the pulse transmission method. The study has found that the P-wave velocity of consolidated sediments increase with increasing hydrate formation and confining pressure. Of the two samples tested, the increase in wave velocity of the dry and hydrate-bearing samples amounted to 27.6% and 31.9%, respectively. Interestingly, at the initial stage of hydrate formation, there was no change in P-wave velocity, which was followed by a steady increase as the hydrate crystals began to agglomerate and then it increased rapidly to a constant value, suggesting that the test solution had converted to a hydrate solid