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This study is a continuation of our previous work, which focused on a near-wellbore water blockage alleviation by applying a thermally cured silane-functionalized benzoxazine to modify rock wettability. In this new analysis, we have demonstrated that the resin can be applied in low-permeability sandstones (approximately 15 mD as opposed to 100 to 200 mD in the previous study) to change the rock surface wettability from water-wet to intermediate gas-wet. We have also demonstrated that curing temperatures as low as 125 °C (as opposed to 180 °C in our previous study) can significantly change wettability, indicating surface functionalization through the silane moiety and ring-opening polymerization of the benzoxazine moiety. In drainage core flooding experiments at 2.5 wt.% resin loading, compared to untreated samples, brine recovery increments of 6.3 to 6.9% were obtained for curing temperatures of 125 to 180 °C, respectively. A maximum 20% increment in the end-point relative gas permeability was achieved at a curing temperature of 180 °C. A coupled experimental and numerical study, conducted at core and wellbore scales, demonstrates the potential effectiveness of our chemical treatment in improving gas productivity at the field scale. Reservoir simulations indicate a 2.9 to 10.6% improvement in gas deliverability for a treatment radius of 4 to 16 m, respectively.

A novel superhydrophobic/superoleophilic surface has been developed by direct surface condensation of dichloroxylene that results in a controlled coating of hyper-cross-linked polymers. Specifically, the coating was successfully applied to a melamine formaldehyde sponge and optimized by fine-tuning the reaction variables. The resulting hierarchical porous sorbents stabilized by polydimethylsiloxane exhibited an increased surface area, good physiochemical stability, high selectivity, and adsorption capacities for a variety of oils and solvents. The composite can separate oil in water emulsions with ultrahigh separation efficiency >99% over 10 cycles in liter-scale experiments, wherein the highest separation efficiency was as low as 2 ppm even with a short period of filtration, suggesting strong potential for oil/water separation and recovery.

Wax precipitation has become a serious problem for the petroleum industry. The problem occurs when there is equilibrium disturbance on the pressure and temperature as well as crude oil composition. Wax deposits will eventually result in restriction of the fluid flow inside the pipeline, and severe deposition will cause blockage. The chemical additives currently being implemented in the industry have various limitations including the high cost and the irreversible impact it has on the environment. Therefore, the use of cheaper organic wax inhibitor obtained from crude palm oil (CPO) and crude palm kernel oil (CPKO) on the rheology and deposition of wax was investigated by using Chenor waxy crude oil from the Penyu basin, Pahang, Malaysia. To compare the efficiency of palm oil additives in inhibiting wax deposition, currently utilized chemical additives such as triethanolamine (TEA) and ethylene vinyl acetate (EVA) were also examined. The pour point of the crude oil was determined using SETA cloud & cryostat, while the rheological behavior of the crude was determined using a rotational Fann viscometer. The results obtained from this study reveal that CPO and CPKO could be used to improve the flow of crude oil, especially when 1 wt.% CPO or when 0.5 wt. % CPKO is used. It was also noted that the palm-based additives were much more effective at reducing the viscosity of the Chenor crude oil than the commercial wax inhibitor tested (TEA and EVA).

We have previously used surface chemistry analysis techniques to optimize the functionalization of carbonate rocks with a silylated polyacrylamide-based relative permeability modifier (RPM). The RPM is expected to selectively reduce the permeability to water in a hydrocarbon reservoir setting, resulting in a reduction in the amount of produced water while maintaining the production of oil/gas. This study will focus on using core flooding techniques with brine/crude oil under reservoir conditions (i.e., 1500 psi pore pressure and 60 °C temperature) to understand the impact of a silylated polyacrylamide-based RPM on the fluid transport properties in carbonate rocks. The effects of RPM concentration, brine salinity, rock permeability, and pore structure on permeability characteristics were studied. Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDX) provided visual images of the polymer adsorbed onto the rock surfaces and confirmed the attachment of the polymer on the surface of the rock pore space after treatment. The relative percentage of Si increased from 1.65 to 13.55%, and the relative percentage of N increased to 4.54%. Core flooding showed that increasing the PAM-co-AA (poly acrylamide-co-acrylic acid partial sodium salt) concentration resulted in residual resistance factors for oil (RRFoil) and brine (RRFbrine) that were greater than 1. However, there was a modest decrease in the disproportionate permeability reduction (DRP) ratio (RRFbrine/RRFoil) from 1.75 to 1.60 when the polymer concentration was increased from 0.05 to 0.1 wt %. Furthermore, the RRFbrine values decreased slightly from 120 to 62 with increasing salinity (i.e., 1-10% NaCl) because of electrostatic shielding caused by charged ions in brine and the RPM. The cross-over points of relative permeability in these four samples shifted to the right because of the larger decrease in relative water permeability compared with relative oil permeability. End-point relative permeability to water in sample C-5 decreased by 80%, showing a reduction greater than that in the sample C-2 (i.e., 74%). Kr curves indicated a stronger formation damage in sample C-1, C-2, and C-4 than in sample C-5. Rock samples with a higher initial permeability exhibited a higher RRFbrine to RRFoil ratio (i.e., 3.05) under similar test conditions. This can be attributed to a larger pore radius, which was verified by nuclear magnetic resonance (NMR) measurements. Furthermore, a detailed mechanism has been proposed to understand the effects of the RPM on fluid transport in porous carbonate cores. In this study, SEM-EDX and NMR measurements combined with core flooding tests provide insights into the performance of silylated polyacrylamide-based RPMs and benefit its future implementation in carbonate reservoirs.

Excessive water production is a significant challenge during hydrocarbon production from oil and gas reservoirs, and it is typically controlled by polymer gel placement. However, the fundamental pr...

Relative permeability modifiers (RPMs) are chemicals that can be injected into a reservoir to change its fluid/gas transport characteristics. For example, RPMs can reduce the relative permeability ...

We have developed a cross-linked polyethyleneimine non-porous material (PEI "snow") for direct air capture (DAC) of CO2. This new hydrogel is green, inexpensive, readily scalable and can be fabricated through simple crosslinking of PEI with triglycidyl trimethylolpropane ether (TTE) in 10 minutes. It demonstrates outstanding DAC performance (overall CO2 uptake efficiency of approximately 50 mg g-1 of sorbent) at lab scale (sorbent weight roughly 60 g, air flow rate 2000 ml min-1) and the CO2 can be desorbed using low-grade waste steam.

The ever-increasing demand for the finite source of oil has led oil production companies to produce and transport the produced crude oil as efficiently and economically as possible. One of the major concerns especially in waters like the South China Sea is the deposition of wax on the walls of the pipeline or wellbore, constricting and hindering the hydrocarbon flow. This is due to the low seabed temperatures, which can be below the wax appearance temperature (WAT), leading to the deposition of wax out of waxy crude oil through the molecular dispersion mechanism. Currently, many prevention and remedy methods are in place to overcome the problem, but most of the additives possess environmental threat, as most of the chemical solutions used are toxic, nonorganic, and costly. Hence, this paper aims to provide some insights into the effect of palm oil derivatives such as crude palm oil (CPO) and crude palm kernel oil (CPKO) on wax inhibition. The effect of aging time (i.e., immersion time) was also evaluated. A comparison was made between paraffin inhibition efficiency results (PIE %) obtained by CPO, CPKO, poly(ethylene-co-vinyl acetate) (EVA), and triethanolamine (TEA). It was observed that the average efficiency of 81.67% was obtained when 1% CPO was added to heavy crude oil. The wax inhibition performance reached a plateau after 1.5 h of aging time for all of the investigated samples.

The application of polymer-based relative permeability modifiers (RPM) in low-permeability sandstone reservoirs has long intrigued production engineers. We hypothesize that lowering salinity may ex...

Conformance control in fractured tight formations remains a challenge because of large permeability contrasts between fractures and the matrix. Therefore, there is an emerging interest in particle ...

This study explores hyper-cross-linking of the cores of block copolymer micelles as a means to generate star polymers with a hyper-cross-linked core surrounded by linear corona arms. A solution of poly(methyl methacrylate)-b-polystyrene (MS) was prepared in acetonitrile to form micelles which were reacted with α,α′-dichloro-p-xylene in the presence of FeCl3 to produce core hyper-cross-linked star (CHS) polymers by selective cross-linking of the PS core. A kinetic investigation showed formation of high-molar mass species (>104 kg mol−1) within 1 h of reaction, which supported conversion of individual MS micelles into CHS polymers. We synthesized several CHS polymers by varying the PS core fractions from 20 to 53%. All the polymers possessed discrete spherical cores that were 19–60 nm in diameter and all were highly soluble in organic solvents retaining the CHS architecture. While permanent microporosity was not detected by gas sorption measurements, increased dye uptake of CHS polymer in solution suggests utility of CHS polymers as stable and solution-processible nanocontainers with accessible free volume in the core.

Multiphase fluid flow characteristics of a reservoir rock, such as capillary pressure, displacement efficiency, relative permeability, and saturation distribution are substantially influenced by th...

SummaryRecent reports have demonstrated that carbon dioxide (CO2) injection can further raise the oil recovery of fractured tight reservoirs after natural depletion, with major projects in progress worldwide. There is, however, a lack of understanding of the mass-exchange process between the matrix and fracture at pore scale. In this study, a matrix (0.8 md)/fracture model was designed to experimentally simulate a CO2-cyclic-injection process at 80°C and 35 MPa (Lucaogou tight formation). The oil (dead-oil) concentration in the matrix and fracture was continuously monitored online using a low-field nuclear-magnetic-resonance (NMR) technique aiming to quantify the oil recovery in situ and clarify the mass-exchange behaviors. The results showed that CO2 cyclic injection was promising in improving the oil recovery of fractured tight reservoirs. Nevertheless, the oil-recovery rates rapidly declined with the cycle of CO2 injection and the incremental oil was primarily produced by large pores with 100 ms > T2 > 3.0 ms. The NMR T2 profiles of the model evidenced the drainage of the matrix oil by CO2 toward the fracture. Because of the light-hydrocarbon extraction, the produced oils became lighter than the original oil. We noted that the main driving forces of the incremental oil recovery were CO2 displacement, CO2/oil interactions (mainly extraction and solubility), and pressure gradient (depressurization). In the first cycle, the CO2/oil interactions driven by CO2 diffusion during soaking enhanced the mass exchange between the matrix and the fracture. However, from the second cycle, CO2/oil interactions and CO2 displacement became insignificant. The results of this study supplement earlier findings and can provide insights into the CO2-enhanced-oil- recovery (EOR) mechanisms in fractured tight reservoirs.NOTE: Supporting information available.

Escalating global temperatures have spurred the development of various CO2 sorbents. Liquid amines are the most widely employed sorbent but they exhibit multiples drawbacks including low absorption capacity, high regeneration energy and degradation of the amine. This work presents the performance of an entirely new CO2 absorbent that is prepared by simply adding commercial or synthesized hydrogels into a solution of a standard liquid amine, diethanolamine (DEA) solution with a low concentration (5.0 wt. %, 10.0 wt. % and 20.0 wt. %) to generate DEA-infused hydrogels. This new material can rapidly capture CO2 even with relatively low amounts of DEA Higher overall uptake has been achieved compared to the commonly used DEA solutions. Moreover, hydrogels with various crosslinking degrees were prepared and employed for preparing the DEA infused hydrogels. It was found that the overall CO2 absorption was largely independent of the crosslinking degree, but the absorption kinetics generally improved with a higher crosslinking degree. In addition, breakthrough experiments demonstrate the outstanding performance of this proposed material for CO2 removal from flue gas. The absorption capacity of the DEA-infused hydrogels is well maintained after multiple regeneration cycles especially with the addition of polyethylenimine (PEI) so the hydrogels can easily be recovered and reused. This new material shows promise as a new CO2 absorbent in the CO2 capture industry.

Foam stability is a crucial consideration in the view of its numerous applications. Herein, a series of nanocellulose fibrils containing lignin segment (L-NCF) was designed and then utilized for interfacial stabilization of liquid foams for eco-friendly oil recovery applications. The ability to form foams and their stability at bulk scale and bubble scale were thoroughly investigated using a foam scanner. Liquid drainage rate, bubble rupture, interfacial dilational viscoelasticity, and bubble transport in porous media were studied as a function of lignin content. We observed that in a vertical column the addition of L-NCF significantly mitigated the drainage of the liquid foams. The foam volume stability (FVS) index indicated that the stability of the foams in the presence of L-NCF was up to five times higher than that of surfactant-only foam. The hydrophobic interaction between the surfactant (mixture of alkyl polyglycoside (APG) and anion surfactant alpha olefin sulfonate (AOS)) and L-NCF (lignin segmen...

Recent reports have demonstrated that gas injection can improve oil recovery of tight reservoirs after natural depletion, with major projects in progress worldwide. There is however a lack of understanding of the gas displacement behaviors at pore-scale especially under reservoir conditions. Herein we conducted an experimental investigation of CO2 and N2 flooding in the Lucaogou tight formation at 35.0 MPa and 80 °C. The flooding dynamics were continuously monitored by use of low-field nuclear magnetic resonance (NMR) to map the displacement processes at pore-scale and quantify the reduction of oil saturation in-situ. We observed that the overall oil recoveries of CO2 and N2 flooding were 38.4% and 35.1%, respectively. Due to the interactions between the oil phase and CO2, a uniform displacement along the core plug was yielded by CO2 flushing, indicated by the 1D spatial distribution of local oil saturation and 2D transverse images. Interestingly, during CO2 flooding, the major reduction of NMR T2 signals occurred in the large pores (4.2 ms

Water production is one of the common problems that is faced in mature gas reservoirs. A number of methods exist to tackle this problem, including injecting polymer that can selectively reduce wate...

One of the major concerns during the production of crude oil especially in tropical waters is the deposition of wax on to the walls of the pipeline. This is due to the low seabed temperatures which can be below the wax appearance temperature (WAT) which leads to wax depositing out through molecular diffusion. Currently, there are many methods to prevent and remedy wax deposition but most of these solutions pose a serious environmental threat and are expensive to produce. Hence, this research investigated the use of an organic and cheaper alternative by utilizing synthetic fatty acid esters such as oleic acid which has shown promising results in reducing the pour point of waxy crude oils. The solution that was used was of palm oil origin, crude palm oil (CPO) and crude palm kernel oil (CPKO) and was subsequently compared with the pour point depressant and wax inhibition efficiency of the current industry used inhibitors utilizing the SETA Pour Point and Cloud Point as well as the cold finger apparatus. It was observed that the palm oil inhibitors were highly effective at 1 wt.% due to the high composition of oleic acid present portraying a similar result to Triethanolamine (TEA) while Ethylene Vinyl Acetate (EVA) performed best at low concentration of 0.1 wt.% but deteriorates significantly as the concentration increases due to the polar end agglomerating among itself.

Amino acid salt (AAS) is a promising class of green material for CO2 capture due to its extremely low toxicity, negligible volatility and decent absorption capacity. However, the slow absorption kinetics and significant regeneration energy requirements hinder its widespread application. Here, for the first time, we present the encapsulation of AAS into solid polymer matrices to simply prepare a scalable material, namely liquid AAS hydrogel particles (LAHPs), for carbon capture. Owing to the enlarged contact area and more intense interaction between CO2 and the AAS, the absorption rate was significantly increased. Meanwhile, CO2 uptakes of LAHPs were improved, on average, by 40% compared to their stirred aqueous AAS solutions counterparts for a wide spectrum of AASs. Moreover, breakthrough experiments demonstrated that LAHPs had sufficient kinetics and capacity characteristics to be used across many fields such as post-combustion capture (15.0 vol% CO2), CO2 removal from enclosed systems (e.g., submarines at 0.5 to 1.0 vol% CO2) and direct air capture of CO2, with CO2 uptake values of 62.8, 53.1, and 42.4 mg g-1 absorbent, respectively. For regeneration, low-grade steam proved to be an effective heating source for LAHPs regeneration, which could significantly decrease overall energy costs if the waste industrial steam was readily available. We have also explored replacing water with a higher boiling point polar solvent (i.e. ethylene glycol). A 30 wt% solution of potassium sarcosinate in ethylene glycol can be infused into a cross-linked poly(N-hydroxyethyl acrylamide) hydrogel. Furthermore, with the use of a higher boiling point solvent (i.e. ethylene glycol), the sorbent can be regenerated with minimal loss of solvent at 60 °C in a vacuum for 60 minutes. CO2 uptake capacities of 36.5 mg g-1 absorbent (average of 11 sorption-regeneration cycles) and 18.7 mg g-1 absorbent with pure CO2 and air, respectively, were obtained. Although the CO2 uptake of LAHPs is not among the highest reported, the simplicity of this approach may provoke ideas on the design of AAS-based CO2 absorbents that are green, versatile, readily scalable and economically regenerable.

Summary Excessive water production is becoming common in many petroleum reservoirs. Relative permeability modifiers (RPM) have been used to disproportionately reduce water permeability (DPR) with minimum effect on the gas/oil phases. This manuscript reports the results of an experimental study where we examined the effect of prolonged successive water-gas injection on RPM’s performance in gas/water system. The results show that the volume of water coming in contact with the polymer-treated porous medium has a direct impact on the extent of polymer swelling and thus the water permeability of the medium. It was also shown that over a large volume of gas injection, treated porous medium presents a better permability for gas at later times compared to the early times of injection. The reason could be the dehydration of the polymer layer adsorbed to the pore surfaces of the medium. It was found that successive water-gas injection could lead to stronger performance of polymer towards reducing water permeability, but it comes with the cost of a further reduction in gas relative permeability.

Among the various flow assurance problems that the petroleum industry faces, the deposition of paraffin waxes on to the wall of the pipeline is the most challenging. The challenge arises when the crude oil temperature decreases below the wax appearance temperature (WAT) which leads to the wax crystal in the crude oil to crystallize. An efficient method in remedying paraffin wax deposition is the utilization of chemical inhibitors. However, currently used chemical inhibitors are costly and environmentally harmful if a spillage occurs. Therefore, the use of biodegradable or environmently friendly inhibitors as potential chemical inhibitors are being studied by various researchers. This study investigated oleic acid, poly (ethylene-co-vinyl acetate) (EVA) and triethanolamine (TEA) as inhibitors that perform based on the van der Waals intermolecular interaction between the main wax component molecule eicosane C20H42 using the molecular dynamics simulation (MD) procedure via Material Studio 8.0 software package. In order to analyse the desired structural property which is the Radial Distribution Function (RDF), COMPASS force field was used. The RDF and g(r) function portrayed the functional atoms which aid in inhibiting the agglomeration and crystallization of the wax crystal formation. The presence of a carbonyl oxygen in oleic acid plays a vital role to inhibit the wax formation through the van der Waals interaction between active hydrogen atoms in eicosane molecule. Therefore, the chances of wax inhibition in eicosane is higher by introducing oleic acid as an inhibitor as compared to EVA and TEA. The results were then validated experimentally utilizing a cold finger technique under static condition.

We have developed a cross-linked polyethyleneimine non-porous material (PEI "snow") for direct air capture (DAC) of CO

This proof-of-concept study demonstrates a facile and scalable 'dry water' method for producing micrometer-sized microgel particles by use of 'water-in-air' droplets as micro-reactors. Solid microgel particles could be easily produced by this method with no further purification. The microgel particles comprise of porous hydrophobic shells and hydrophilic cores and could absorb both oil and water. The swelling of the particles could be triggered by a surfactant under a wide range of conditions.

As the oil and gas industry produces hydrocarbons from deeper waters and colder regions the issue of hydrate formation becomes more serious. As a result, hydrate inhibition has focused on kinetic hydrate inhibitors (KHI) and anti-agglomerants (AA) as an alternative to the existing approaches which involves injecting vast quantities of thermodynamic inhibitors. In this research, we evaluated the effect of different architectures (linear and branched) of poly(N-isopropylacrylamide) (PNIPAM) polymers synthesized using reversible addition−fragmentation chain-transfer (RAFT) polymerization. Unlike non-reversible deactivation radical polymerisation (RDRP) synthetic routes this generates accurately controlled KHI candidates with target molecular weight, narrow molecular weight distributions and controlled architecture, so that the effect on hydrate inhibition can be more accurately assessed. The RAFT-based polymers (linear and branched) were compared to a commercially available linear PNIPAM synthesized via non-RDRP radical polymerization and control groups (pure water, PVP, and Luvicap). The hydrate experiments were performed in a high pressure autoclave with continuous cooling under different cooling rates (0.25 K/min, 0.033 K/min, and 0.017 K/min). In addition, a cold restart was simulated using constant subcooling. The results regarding subcooling temperature, onset time, and hydrate fraction with resistance-to-flow were compared to known KHIs. These revealed that a linear PNIPAM-MacroRAFT polymer delayed the hydrate nucleation with similar performance to known KHIs (eg., PVP and Luvicap). However, a branched polymer showed the best performance in terms of hydrate fraction and resistance-to-flow among all of the systems tested in this study. These data provide valuable information regarding linear and branched PNIPAM-MacroRAFT polymers by demonstrating their ability to delay hydrate formation but also in preventing hydrate agglomeration. These findings confirm that polymer architecture can effect hydrate inhibition.

Nanocellulose was surface-functionalized toward the applications in enhanced oil recovery (EOR) as a green alternative. The focus of this paper is on the effect of this material based nanofluid (NF) on foam lamella stabilization through studying its bubble breakup dynamics and flow behaviors in constricted mircofluidic devices. The NF stabilized foam produced an improved flow resistance across the capillary largely due to the capillary trapped bubbles at the contraction. The “snap-off” caused the NF stabilized foam to produce finer textured bubbles, which can migrate readily forward to the deep porous media, as revealed by the pressure profiles.

The geochemistry of a reservoir is of great significance for CO2 Enhanced Oil Recovery (CO2-EOR) and CO2 geosequestration operations. However, due to the massive diversity in mineralogy and physicochemistry of different reservoirs, the current data base is not yet sufficient to conclusively determine the alterations of geochemical prosperities when CO2 is injected especially for tight reservoirs. The attention of this work was given to a tight sandstone reservoir in Lucaogou formation of Jimsar sag (China). The interactions of reservoir rocks, formation brine and supercritical CO2 were extensively investigated under reservoir conditions (75 °C and 32 MPa) aiming to reveal possible mechanisms behind. The results showed that the dissolution of supercritical CO2 in the brine created an acidic environment (solubility = 0.94 mol/Kg), which induced the dissolution of minerals into the brine and their subsequent precipitation. The primary precipitants in this work were found to be iron minerals and kaolinite, as evidenced by Scanning Electron Microscopy and Energy Dispersion Spectrum (SEM-EDS) analyses. Moreover, the SEM-EDS observations have shown clear signs of mineralogical changes of the rocks with the preferred dissolution of K-feldspar, albite and ankerite. Kaolinitation due to the corrosion of K-feldspar and albite occurred during the CO2-exposure experiments. The mineral surface after exposure to CO2 was altered to be more water-wet as a result of mineral dissolution, kaolinite formation and surface corrosion.

Direct gas thickening is a conventional mobility control method to improve volumetric sweep efficiency for miscible gas injection (MGI) projects. However, the viability of this approach with technically feasible thickeners has not been verified at the field-scale due to a combination of high costs and/or environmental issues. One approach to make this technique economically more attractive is the implementation of an alternating injection scheme (similar to water-alternating-gas (WAG)) that would require less of the thickened gas compared with a continuous injection scheme. In this study, the effectiveness of this approach where a miscible alternating injection of thickened associated gas (TAG) or thickened CO2 (TCO2) with unthickened AG is explored in both nonfractured and fractured composite carbonate cores. Twelve core-flooding experiments were conducted using different injection schemes (i.e., continuous unthickened, continuous thickened, and alternating thickened–unthickened). These tests demonstrate...

A diverse range of alkali/amine infused hydrogels (AIHs) were generated by incorporating the liquids into a hydrogel particle for carbon capture application. As a consequence, the CO2 uptake was significantly enhanced owing to the increased contact area. This AIHs technique was highly tunable as it could be applicable to varying species of alkali chemicals and it was found that their molecular structure and architectures could impact the CO2 uptake. Compared to stirred bulk alkali/amine solutions, the CO2 absorption capacity of AIHs was increased by 400% within 30 min with a low hydrogel loading (10 w/w%). In addition, the recyclability of various AIHs was assessed and was found to be extremely encouraging. The effect of salinity on the performance of AIHs was also investigated and high salinity was found to have a minimal effect on CO2 absorption. Most importantly, the preparation of AIHs is fast and straightforward with few wastes and byproducts formed in the preparation process. In all, extensive inves...

A High Pressure Differential Scanning Calorimeter (HP-µDSC) was used to characterize the kinetic inhibition performance of several kinetic hydrate inhibitors (KHIs) up to 390 bar (39 MPa) of model natural gas. A novel protocol was devised to increase the spread between effective KHIs to obtain their performance ranking. The natural gas used in the study was a mixture of 90 mol% methane and 10 mol% propane. Linear cooling ramps at a constant cooling rate of 0.5 K/min were used under isobaric conditions. Both the formation temperature of natural gas hydrate during a linear cooling ramp and the amount of hydrate formed were used for comprehensive analysis. The second method was based on the growth inhibition of natural gas hydrates and opened a new possibility that only several repeat measurements may be sufficient for fast screening of good KHIs. The results showed that HP-µDSC is a promising tool for the evaluation of kinetic inhibition performance of KHIs that can only be obtained in minute quantities.

Supercritical carbon dioxide (scCO2) is considered to be an excellent candidate for miscible gas injection (MGI) because it can reduce oil viscosity, induce in situ swelling of the oil, and reduce the IFT of the in situ fluid system. However, the unfavorable mobility associated with scCO2 flooding poses a major challenge due to the large viscosity contrast between the crude oil and scCO2, resulting in viscous fingering. An effective approach to overcome this challenge is to increase the viscosity of scCO2 (scCO2 thickening) to effectively control gas mobility and improve the sweep efficiency. The primary focus of this study was on an oilfield (Field A) that is located in the Harweel cluster in southern Oman. In this work, we present results in which the suitability of a library of commercially available polymers capable of thickening scCO2 at a high temperature (377 K). Previous studies have focused on the use of polymers as viscosifiers at much lower temperatures. Out of 26 potential polymers, 4 polymers...

Carbon dioxide (CO2) hydrate-based cold thermal energy storage (CTES) is a promising method for load shifting and demand management of cooling systems and for CO2 utilisation. A challenge of CO2 hydrate-based CTES is to find a compatible CO2 gas storage, the CO2 regeneration and absorption conditions of which can be coupled with the charging and discharging conditions of the CTES, respectively. Amine diethanolamine infused hydrogels (DEAIHs) can be an effective CO2 absorber as the gas–DEA surface contact area is greatly enlarged by infusing the solution into a hydrogel. However, the influencing factors of the CO2 absorption and regeneration performance of DEAIHs are unknown. This paper investigates the performance of DEAIHs and explores the possibility of applying them in cyclic CO2 gas storage for CTES. The effects of pressure, temperature, DEAIH sample mass and amine diethanolamine (DEA) mass fraction on CO2 absorption and absorption rate are investigated. It was found that a higher pressure prompted CO2 absorption while a temperature of 12℃ resulted in the highest CO2 absorption rate. The average CO2 absorption rates in the first 100 min were 0.250, 0.228, 0.155 and 0.033 mmol min–1 for 20-g DEAIH sample with 30-wt% DEA and 60-g DEAIH sample with 30, 47 and 89-wt% DEA, respectively. CO2 regeneration from DEAIH under zero and non-zero gauge pressures are studied. Under non-zero gauge pressures, a pressure rise followed by a pressure drop caused by CO2 re-absorption appeared in the CO2 regeneration from DEAIH. It was found for the first time that the system passed through a meta-equilibrium state before it reached an equilibrium pressure. Cyclic absorption and regeneration at 110℃ under zero gauge pressure showed that the CO2 absorption decreased dramatically after the third cycle due to the volatility of amine. Operating a coupled CO2 hydrate-based CTES and CO2 gas storage system demonstrated the possibility of DEAIH material for CO2 gas storage in CTES systems.

In situ combustion (ISC) is advantageous for (ultra)heavy reserves due to its high heating efficiency and small surface footprint compared to steam injection. Herein, the focus of this work was given to the key factor in sustaining the continuity of the combustion front, the asphaltene fraction. Structure–property alterations of Tahe asphaltenes caused by low temperature oxidation (LTO) were thoroughly examined. Particular attention was placed on its combustion and pyrolysis kinetics. The results showed that after LTO 10.35 wt % coke was formed. Scanning electron microscopic observations indicated that the surfaces of the oxidative products were fairly rough as a result of air attack and the caused reactions on site, and these alterations promoted the subsequent combustion. The textures of the products were observed to be further compacted and condensed after LTO. As anticipated, distinguished reaction regions were clearly identified on the thermogravimetric (TG)/differential scanning calorimetric curves ...

A new class of CO2 sorbents, namely polyethylenimine hydrogel beads (PEI HBs), has been developed via a simple one-step crosslinking reaction of PEI using epichlorohydrin (EPC). The beads have an increased surface area which increases the CO2 uptake compared to the liquid PEI. Moreover, they possess exceptional thermal stability so the issues with solvent loss encountered with conventional amines are avoided. In contrast to the majority of other reported PEI-functionalized CO2 sorbents, PEI HBs perform well under humid conditions. More importantly, PEI HBs can be quickly and easily regenerated via microwave heating. This new material extends the application of hydrogels and may shed light on the development of other functional materials apart from CO2 sorbents.

We report a proof-of-concept study on an entirely new class of CO2 absorbent which is prepared by simply adding commercially available hydrogels into organic amine solutions to generate amine infused hydrogels (AIHs). The hydrogel ensures that the CO2–amine reactions are maintained in AIHs but the interfacial area/kinetics for these interactions is significantly increased. As a result, this new material rapidly captures CO2 with higher overall uptake compared to the commonly used aqueous amine solutions under similar experimental conditions. It reaches exceptional CO2 uptake without the need for stirring. In terms of recycling, the absorption capacity of AIHs is well maintained after multiple regeneration cycles if high molecular weight amines and a suitable hydrogel are applied. Moreover, the hydrogel can easily be recovered and reused, noticeably reducing material costs. In all, this proof-of-concept study demonstrates that by using an inexpensive and readily available material (hydrogel), AIHs show promise as a CO2 absorbent.

The low salinity effect (LSE) in enhanced oil recovery (EOR) is widely accepted. However, its underlying mechanisms remain unclear due in part to the complex interactions at the oil/brine/rock interface. The chemistry of brine largely depends on the ionic composition. Thus, in this work, attention was placed on the roles of individual ions and salinity in LSE through direct measurements of oil/brine/rock interfacial behaviors, oil displacement efficiencies, and oil–water relative permeability in sandstone porous media. The results showed that the oil/water interfacial tensions (IFTs) were weakly dependent on ion and the lowest IFTs were generated at the salinities of 0.2–0.5 wt %. In contrast, the interfacial dilational modulus varied significantly with ion types and salinities due to the adsorption of polar components at the oil/water interface. Moreover, wettability alteration of the sandstone surface was found to be associated with the divalent ions in our work. As a result of the viscoelastic interfac...

Multi-functional polymers were designed and synthesized that contain both kinetic hydrate inhibitor and corrosion inhibitor groups. This was achieved by modifying a co-polymer of vinyl caprolactam and acrylic acid (PVCap-co-AA) where the acid groups were converted to known corrosion inhibitor groups including imidazole (APIM) and quaternary ammonium (ATCH) moieties. Therefore, all of the resulting polymers had the same molecular weight, end groups and overall composition which allowed for accurate determination of the performance of these inhibitors. Their performance as kinetic hydrate inhibitors were evaluated by determining the hydrate onset time, growth rate, and resistance to flow using a high pressure autoclave. The experimental results show that both PVCap-co-APIM and PVCap-co-ATCH were able to delay hydrate nucleation, however PVCap-co-APIM was better than PVCap-co-ATCH. The performance of new KHICIs were evaluated and compared with a commercial KHI, Luvicap, with three different cooling rates: fo...

Corrosion and unwanted gas hydrate formation in subsea flowlines are two of the major issues that the global gas industry faces when transporting natural gas. Gas hydrates can cause severe blockages due to the formation of hydrate plugs that block the flow. Corrosion issues lead to significant economic loss in terms of prevention and repair. To manage these issues, hydrate and corrosion inhibitors are injected separately to subsea flowlines. However, there are often compatibility issues that negatively impact their performance as a result of surface and molecular interactions. The aim of this study is to tackle this compatibility problem by developing single polymer molecules that simultaneously prevent hydrate formation and inhibit corrosion. The resulting materials are termed as kinetic hydrate and corrosion inhibitors (KHCIs). The molecules are designed and assembled using key structural motifs that are known kinetic hydrate inhibitors (KHIs) and corrosion inhibitors. Specifically a KHI base polymer is...

Hydrate shell growth on hydrogel particles incorporating monoethylene glycol (MEG) was investigated using Raman spectroscopy and a high pressure autoclave apparatus. Surface images of hydrogel particles covered by a hydrate shell are presented and the obtained Raman spectra indicate MEG molecules were excluded from the formation of the hydrate shell. The Raman spectra and surface imaging of the particles demonstrate that the particles remain intact after the dissociation of the shell. In subsequent hydrate formation cycles, the hydrate fraction in the liquid phase was determined from gas consumption measurements in a high pressure autoclave. The hydrate fraction reached only 0.11 for hydrogels containing MEG while a high hydrate fraction of 0.41 was observed for a control system consisting of bulk water and decane mixture. The growth rate in the presence of hydrogel particles was suppressed in the early stages of hydrate formation, suggesting that the increasing MEG concentration inside the hydrogel core may limit the further inward hydrate growth. After hydrate formation the hydrogel particles were analyzed by thermogravimetric analysis (TGA), suggesting the possibility of recovering hydrogel polymer through conventional heating methodologies. These results demonstrate that injecting hydrogel particles containing high concentration of MEG may be feasible to manage the risk of hydrate plug formation as they will absorb the free water resulting in the dispersed hydrogel particles among the hydrocarbon liquid phase.

Hydrocarbon-miscible gas flooding typically involves injection of an associated gas (AG) mixture containing mainly methane (CH4) enriched with light hydrocarbon fractions and possibly acid gases. The AG mixture has been recognized as an excellent candidate for miscible gas injection (MGI). However, in general, the viscosity of the AG at reservoir conditions is significantly lower than that of crude oil leading to an unfavorable mobility ratio and low volumetric sweep efficiency during flooding. This study assesses the suitability of a library of commercially available polymers to thicken AG as a means of mobility control. The focus of the study is on the Field A located in the Harweel cluster in southern Oman. First, soluble polymeric thickeners for an AG mixture (CH4 60%, C2H6 9%, C3H8 6%, and CO2 25%) were identified using a parallel gravimetric extraction technique combined with cloud point measurements. Then, the viscosity of the identified soluble polymeric candidates in AG mixture was measured in a ...