Viscous Oil Recovery Research Articles

Non-thermal recovery of a viscous oil with a surfactant-polymer process

The goal of this work is to improve recovery of a viscous oil reservoir at 70 °C using a non-thermal process. Polymer floods can improve sweep efficiency, but leave behind a residual oil saturation. A surfactant-polymer flood has the potential to improve both the sweep as well as the displacement efficiency. Phase behavior experiments with the viscous oil, water and surfactants were conducted to identify surfactants. 1D and 2D sandpack displacements were conducted to evaluate the efficacy of the process. Phase behavior experiments showed Winsor type I behavior with a low interfacial tension using a single surfactant, but not ultralow tension. Water flood recovered about 50% OOIP and reduced the oil saturation to about 45% in 1D floods. The subsequent SP flood increased the cumulative oil recovery to 99% in sandpacks when the viscosity of chemical slugs exceeded the oil viscosity. When the permeability decreased (as in a Bentheimer core), the oil recovery decreased to about 86%. Secondary SP floods also recovered most of the oil and faster than tertiary floods. Reduction of polymer concentration (and viscosity to about 1/4th of the oil viscosity) reduced the oil recovery, especially in 2D sandpack floods. Decrease in interfacial tension increased the requirement of polymer concentration to maintain flood front stability. This flood demonstrates the effectiveness of Winsor type I SP formulation for viscous oil, high permeability reservoirs. Such a SP process would reduce the carbon footprint of viscous oil recovery compared to that of thermal processes.

Alkali Polymer Flooding of a Romanian Field Containing Viscous Reactive Oil.

The study demonstrates the significant enhancement in oil production from a Romanian oil field using alkali-polymer (AP) flooding for reactive viscous oil. We conducted comprehensive interfacial tension (IFT) measurements across various alkali and AP concentrations, along with phase behavior assessments. Micromodel flooding experiments were used to examine pore-scale effects and select appropriate chemical concentrations. We tested displacement efficiency at the core level and experimented with different sequences and concentrations of alkali and polymers to minimize costs while maximizing the additional recovery of reactive viscous oil. The IFT analysis revealed that saponification at the oil-alkali interface significantly lowers IFT, but IFT gradually increases as soap diffuses away from the interface. Micromodels indicated that polymer or alkali injection alone achieve only minimal incremental recovery beyond waterflooding. However, AP flooding significantly enhanced incremental oil recovery by efficiently moving the mobilized oil with the viscous fluid and increasing exposure of more oil to the alkali solution. Coreflood experiments corroborated these findings. We also explored how divalent cations influence polymer concentration selection, finding that softening the injection brine significantly increased the viscosity of the AP slug.

Superhydrophobic Co-MOF-based sponge for efficient oil-water separation utilizing photothermal effect

Effectively addressing crude oil spills remains a global challenge due to its high viscosity and limited flow characteristics. In this study, we successfully prepared a modified sponge (PCP@MS) by embedding the photothermal material of Co-HHTP and coating the melamine sponge (MS) with low-surface-energy polydimethylsiloxane (PDMS). The PCP@MS exhibited outstanding hydrophobicity with WCA of 160.2° and high oil absorption capacity of 59–107 g/g. The PCP@MS showed high separation efficiency of 99.2% for various oil-water mixtures, along with notable self-cleaning properties and mechanical stability. The internal micro-nano hierarchical structure on the sponge surface significantly enhanced light absorption, synergizing with the photo-thermal conversion properties of Co-HHTP, enabled PCP@MS to achieve a surface temperature of 109.2 °C under 1.0 solar light within 300 s. With the aid of solar radiation, PCP@MS is able to heat up quickly and successfully lowering the viscosity of the surrounding crude oil, resulting in an oil recovery rate of 8.76 g/min. Density functional theory (DFT) calculation results revealed that Co-HHTP featured a zero-gap band structure, rendering advantageous electronic properties for full-wavelength light absorption. This in situ solar-heated absorbent design is poised to advance the practical application of viscous oil spill cleanup and recovery.

Solar-heated melamine sponge decorated with Fe3O4 for continuous recovery of viscous crude oil

Solar-heated melamine sponge decorated with Fe3O4 for continuous recovery of viscous crude oil

Simple fabrication of superhydrophobic carbon felt with outstanding Joule heating and photothermal effects for all-weather recovery of viscous crude oil

The development of materials with simple preparation methods and exhibiting excellent photothermal and Joule heating effects, especially at low safety voltage inputs for reaching desired temperatures, is of great significance for realizing all-weather rapid recovery of high viscosity crude oil, but some challenges currently exist. Herein, carbon felt (CF), known for its excellent electrical properties, was used as a substrate and coated with molybdenum disulfide (MoS2) with excellent electrical properties and light absorption ability through a one-step hydrothermal method. Subsequently, the surface energy of the felt was reduced by further surface modification using polydimethylsiloxane (PDMS) to prepare superhydrophobic and superoleophilic CF (PDMS@MoS2@CF). It exhibited significant photothermal effects and exceptional Joule heating capabilities at safe low voltages, benefiting from the excellent electrical properties of CF and the exceptional photothermal and electrical properties of MoS2. Under 1 sun irradiation or a 2 V voltage, the surface temperature of PDMS@MoS2@CF could reach up to ∼78.5 °C or 93.0 °C, respectively. In addition to achieving low viscosity oil recovery, this material rapidly generated heat due to photothermal and Joule heating effects, significantly reducing the viscosity of crude oil and effectively achieving crude oil recovery. Further, the continuous recovery of crude oil from water surface could be realized using a peristaltic pump. Furthermore, the two effects complemented each other, enabling the all-weather rapid recovery of high viscosity crude oil while maximizing resource conservation and thus showing practicability. This material shows application prospects in addressing oil spills, particularly in scenarios involving high viscosity crude oil.

Superhydrophobic and photothermal sponge for effective oil/water separation and solar‐assisted recovery of viscous oil

AbstractWith the occurrence of offshore oil spills, the recovery of viscous oil continues to be a significant issue. The multi‐functional sponge with superhydrophobic, absorption of high viscosity oil is an effective approach to settle this problem. In this work, the melamine‐formaldehyde (MF) sponge was the backbone and doped with polydopamine (PDA) to mimic mussels. Subsequently, candle soot nanoparticles (CS) and polydimethylsiloxane (PDMS) were applied to modify the MF sponge into a superhydrophobic sponge (P‐CS‐PDA@MF) (WCA = 153.56°). The P‐CS‐PDA@MF sponge showed good absorption properties for many oils and organic solvents (33.87–78.90 times of its own weight). In addition, the P‐CS‐PDA@MF sponge also showed outstanding chemical stability, low density (0.013 g/cm3), emulsion‐breaking ability and flame retardancy. More interestingly, the P‐CS‐PDA@MF sponge showed superior photothermal conversion capability, the temperature of it increased to approximately 91°C within 100 s under simulated sunlight from room temperature (about 25°C), and the sorption capacity of viscous oils was significantly increased. Moreover, the P‐CS‐PDA@MF sponge exhibited a high efficiency (over 97%) for separating viscous oils/water mixtures with the aid of sunlight. This versatile and efficient multifunctional P‐CS‐PDA@MF sponge via a simple and low‐cost way shows promising prospect in oily wastewater treatment and water ecosystem remediation.

Engineered MoSe2-rGO composite for efficient recovery of viscous crude oil spills

High-performance photothermal materials capable of harnessing the entire solar spectrum have garnered significant interest in developing solar-heating sorbents for the effective recovery of viscous oil. Herein, we developed narrow-bandgap MoSe2-loaded reduced graphene oxide (MoSe2-rGO) nanocomposite with efficient solar utilization. MoSe2-rGO with synergistically-enhanced light absorption and photothermal conversion, was first employed for fabricating melamine sponge (MS)-based sorbent (PMGP/MS sorbent) via a facile dip-coating method. The sorbent showed excellent solar-heating capability, reaching a surface temperature of 78 °C in 100 s under 1.0 sun. The sorbent proved effective in recovering highly viscous oil via solar-motivated viscosity-reduction of oil. The sorption rate for viscous crude oil increased 10.6 times under 1.0 sun compared with no sunlight illumination, and the sorption saturation reached around 55.6 g/g within 750 s. Moreover, continuous sorption was achieved under a self-priming pump based on the reduced viscosity and increased fluidity, with capacity of 1.1 g/cm2 at 650 s under 1.0 sun.

INFLUENCE OF TEMPERATURE ON THE RECOVERY OF OILS SPILLED IN SEAWATER USING HYDROPHOBIZED POST-CONSUMER POLYURETHANE FOAMS

Although economically vital, whether in cold Scandinavian or warm Caribbean waters, offshore oil exploration accounts for oil spills at sea. One of the mechanisms used for recovering spilled oil consists of using porous materials with high sorption capacity in the cleanup process. Post-consumer polyurethane foams (PC-PUFs) are highly porous polymers typically disposed by consumers in Brazilian cities. In this work, PC-PUFs obtained from discarded mattresses were modified superficially to promote hydrophobization and increase their selectivity for oils over water. The characterization showed foams with well-defined macro pores. Surfaces of MoS2-modified foams (MoS2-PC) showed an increase in seawater penetration rejection and oil attraction when compared to unmodified foams (Un-PC). Sorption tests simulating oil spillage at 1 °C, 12 °C, and 23 °C were conducted to verify the influence of temperature on oil recovery by PC-PUFs. Tests on the seawater-diesel system showed that diesel, a low-viscosity oil with slight viscosity variation with temperature reduction, penetrated both Un-PC and MoS2-PC foams easily, making the modifications on MoS2-PC irrelevant. In the seawater-S46 lubricant system, which had a more viscous oil and presented a substantial variation in viscosity with temperature reduction, there was greater difficulty in penetrating the Un-PC foam when compared to MoS2-PC, showing that the modifications were responsible for the increase in the recovery of more viscous oils spilled in seawater at different temperatures.

Melt-blown fiber felt for efficient all-weather recovery of viscous oil spills by Joule heating and photothermal effect

Adsorbents play a vital role in responding to marine oil spills, yet effectively cleaning up viscous oil spills remains a technical challenge. Herein, we present a superhydrophobic oil-adsorbing felt prepared using melt-blown technology and functionally enhanced with a photoelectric composite CNT/PANI coating for effectively cleaning up high-viscosity oil spills. By virtue of its superior solar/Joule heating ability and thermally conductive fiber network, p-CNT/PANI@PP notably reduced crude oil viscosity and enhanced the oil diffusion coefficient within pores. Leveraging primarily solar heating and supplemented by Joule heating, p-CNT/PANI@PP demonstrates an impressive in-situ adsorption rate of up to 560 g/h for ultra-high-viscosity crude oil (c.a. 138000 mPa·s), alongside an adsorption capacity of 15.57 g/g. This measure enables efficient viscosity reduction and continuous day-and-night recovery of viscous crude oil, addressing the challenges posed by seasonal fluctuations in seawater temperature and adverse weather conditions. Moreover, a conveyorized collector integrated with an oil-adsorbing felt realizes continuous recovery of viscous oil spills with speed control to tackle varying thicknesses of oil film. Given the top-down material design, superior functionality, and applicability to applications, this work provides a comprehensive and feasible solution to catastrophic large-area viscous oil spills.

Energy-Optimized Oil Spill Cleanup: Joule-/Solar-Heating Copper Foam for Efficient All-Weather Recovery of Viscous Crude Oil

Energy-Optimized Oil Spill Cleanup: Joule-/Solar-Heating Copper Foam for Efficient All-Weather Recovery of Viscous Crude Oil

Immiscible Viscous Fingering at the Field Scale: Numerical Simulation of the Captain Polymer Flood

Summary Immiscible fingering in reservoirs results from the displacement of a resident high-viscosity oil by a significantly less viscous immiscible fluid, usually water. During oil recovery processes, where water is often injected for sweep improvement and pressure support, the viscosity ratio between oil and water (μo/μw) can lead to poor oil recovery due to the formation of immiscible viscous fingers resulting in oil bypassing. Polymer flooding, where the injection water is viscosified by the addition of high-molecular-weight polymers, is designed to reduce the impact of viscous fingering by reducing the μ0/μw ratio. A considerable effort has been made in the past decade to improve the mechanistic understanding of polymer flooding as well as in developing the numerical simulation methodologies required to model it reliably. Two key developments have been (i) the understanding of the viscous crossflow mechanism by which polymer flooding operates in the displacement of viscous oil and (ii) the simulation methodology put forward by Sorbie et al. (2020), whereby immiscible fingering and viscous crossflow can be simply matched in conventional reservoir simulators. This publication extends the work of Beteta et al. (2022b) to conceptual models of a field case currently undergoing polymer flooding—the Captain field in the North Sea. The simulation methodology is essentially “upscaled” in a straightforward manner using some simple scaling assumptions. The effects of polymer viscosity and slug size are considered in a range of both 2D and 3D models designed to elucidate the role of polymer in systems both with and without “water slumping.” Slumping is governed by the density contrast between oil and water, the vertical communication of the reservoir and the fluid velocity, and, when it occurs, the injection of water channels along the bottom of the reservoir directly to the production well(s). It is shown that polymer flooding is very applicable to a wide range of reservoirs, with only modest injection viscosities and bank sizes returning significant volumes of incremental oil. Indeed, oil incremental recoveries (IRs) of between 29% and 89% are predicted in the simulations of the various 2D and 3D cases, depending on the slug design for both nonslumping and slumping cases. When strong water slumping is present, the performance of the polymer flood is significantly more sensitive to slug design, as alongside the viscous crossflow mechanism of recovery, a further role of the polymer is introduced—sweep of the “attic” oil by the viscous polymer flood, which is able to overcome the gravity-driven slumping, and we also identify this mechanism as a slightly different form of viscous crossflow. In slumping systems, it is critical to avoid disrupting the polymer bank before sweeping of the attic oil has been performed. However, as with the nonslumping system, modest injection viscosities and bank sizes still have a very significant impact on recovery. The conceptual models used here have been found to be qualitatively very similar to real field results. Our simulations indicate that there are few cases of viscous oil recovery where polymer flooding would not be of benefit.

A laboratory investigation of CO2 influence on solvent-assisted polymer flooding for improving viscous oil recovery on Alaska North Slope

In this study, the CO2 influence on enhancing Alaska North Slope (ANS) viscous oil recovery for polymer flooding with assistance of solvents is investigated. Seven coreflooding tests were conducted at reservoir conditions to evaluate ANS viscous oil recovery performance of five solvent-assisted EOR methods including LHS (light hydrocarbon solvent)-alternating-LSW (low salinity water) flooding, CO2-enriched LHS-alternating-LSW flooding, LHS-alternating-LSP (low salinity polymer) flooding, CO2-enriched LHS-alternating-LSP flooding, and CO2-enriched LHS-LSW-LSP flooding. Besides, the CO2 influence on the performance of solvent-assisted EOR methods is investigated. In addition, Constant Composition Expansion (CCE) tests were performed at reservoir temperatue of 85 °F to explore mechanisms of oil recovery improvement with solvent injection in EOR methods of this study. Moreover, water ion analyses of DI-water/natural-sand and DI-water/natural-sand/CO2 systems were carried out to discover the complex reaction between CO2, sand, and LSP solution for better understanding underlying mechanisms of solvent-assisted EOR methods. Coreflooding experiment results demonstrate that five proposed EOR methods all present remarkable production performance with recovery factor ranging from 79.73% to 92.23%. The main EOR mechanisms can be attributed to oil swelling and viscosity reduction effects resulting in the enhancement of microscopic displacement efficiency during solvent flooding and the improvement of macroscopic sweep efficiency of subsequent LSW/LSP flooding resulting from obtaining better mobility control. Considering the recovery factor from the 1st solvent flooding, no obvious improvement was observed with solvent containing CO2. However, higher oil recovery improvement was obtained from the subsequent LSW/LSP flooding of tests using solvent with CO2 than that without CO2, mainly resulting from better mobility control due to the greater viscosity reduction effect by CO2-enriched LHS. Nevertheless, a severe blockage occurred at the production end in the CO2-enriched LHS-alternating-LSP flooding test, which was likely due to the polymer precipitation. CCE test results present that more solvent could be dissolved into the ANS viscous oil by increasing the pressure of the system, which causes greater oil swelling and viscosity reduction effects. The saturation pressure was affected little by adding CO2 in LHS, while the presence of CO2 had a negative impact on oil swelling effect but a positive influence on oil viscosity reduction effect. In addition, water ion analyses results show that, after introducing CO2 to the DI-water/natural-sand system, a great amount of multivalent cations were generated probably due to the dissolution of minerals in the natural sand, which may explain the polymer precipitation. Therefore, the blockage issue at the production end could be solved by injecting LSW as a spacer between CO2-enriched LHS flooding and LSP flooding to reduce the concentration of generated cations.

Highly efficient recovery of viscous oil through nondispersive solvent extraction using polydopamine modified PVDF Janus membrane

Viscous oil separation and its highly efficient recovery is a great challenge in oil/water separation applications. Membrane separation was considered as a prospective strategy for oil/water separation, but membrane contamination caused by the oil droplets restricted its applications significantly. We here propose a nondispersive solvent extraction strategy to efficiently recover viscous lubricant oil from emulsions via a polydopamine modified PVDF Janus membrane. The incorporated thin polydopamine layer facilitates the adsorption and diffusion of surfactant stabilized oil droplets through the membrane. We studied the influence of polydopamine coating time, the flow rate on both feed and extraction sides, the weight content of lubricant oil on the recovery of oil. The optimized membrane exhibited a 10 h accumulative flux (1595 g·m−2) for viscous lubricant oil in water emulsion, which was 70 % higher than the contrast PVDF membrane. The current study might significantly advance application of this novel method for highly efficient separation and recovery of viscous oils from oil/water mixtures.

A Visualization Study of Low-Tension Polymer Flooding for Viscous Oil Reservoirs

Summary Polymer flooding improves the sweep efficiency of viscous oil recovery over waterflooding. The low-tension polymer (LTP) flooding has the potential to improve the displacement efficiency due to low interfacial tension (IFT) without sacrificing sweep efficiency. Compared with ultralow tension (<0.001 mN/m) alkaline-surfactant-polymer (ASP) floods, LTP flooding uses a low concentration surfactant to moderately reduce the IFT (>0.01 mN/m). The objective of this research is to evaluate the performance of LTP floods as a function of IFT for a viscous oil in a 2D sandpack. Over 20 nonionic surfactants/cosolvents were tested. A series of sandpack flooding experiments were conducted in a custom-designed 2D visualization cell. The results show that short-hydrophobic surfactants 2EH-xPO-yEO can reduce the IFT to as low as 0.05 dyne/cm. Flooding experiments were performed in sandpacks with and without connate water saturation. The sandpack was water-wet for the experiments with connate water. For the experiments without connate water, the sandpack was oil-wet. A base-case secondary polymer flood (without any surfactant) with a viscosity ratio (µo/µp) of 10 showed a stable displacement and an oil recovery of 82% at the first pore volume injected (PVI). An LTP flood with an IFT of 0.1 dyne/cm also had a stable displacement front, but a higher oil recovery at 1 PVI [90% original oil in place (OOIP)]. Further reduction in IFT to 0.05 dyne/cm resulted in an unstable displacement and a lower recovery of 65% OOIP. For the experiments without connate water saturation, sandpack was oil-wet; the base-case polymer flood at a viscosity ratio of 10 showed severe fingering and a low oil recovery at 1 PVI (58% OOIP). Adding surfactants did not improve the oil recovery in oil-wet sandpacks.

Superhydrophobic polyurethane sponge for efficient water-oil emulsion separation and rapid solar-assisted highly viscous crude oil adsorption and recovery

Rapid and efficient cleaning of oily wastewater and high viscosity crude oil spills is still a global challenge. Conventional three-dimensional porous adsorbents are ineffective for oil-water separation in harsh environment and are restricted to the low fluidity of high viscosity crude oil at room temperature. Increasing temperature can enormously improve the fluidity of viscous crude oil. Herein, the polydimethylsiloxane (PDMS) /carbon black (CB) -modified polyurethane sponge (PU) were prepared by a simple one-step dip-coating method. PDMS/CB@PU (PCPU) exhibits high adsorption capacity to various oils and organic liquid (28.5–68.7 g/g), strong mechanical properties (500 cycles at 50%), outstanding reusability (100 cycles of adsorption and desorption) and excellent environmental stability due to the special PDMS/CB coating. The maximum surface temperature of PCPU sponge can reach 84.7 ℃ under 1 sunlight irradiation. Therefore, the PCPU sponge can rapidly heat and enhance the fluidity of viscous crude oil, significantly speeding up the viscous oil recovery process with the maximum adsorption capacity of 44.7 g/g. In addition, the PCPU sponge can also combine with the vacuum pump to realize the continuous and rapid repair of viscous oil spills from the seawater surface. In consideration of its simple preparation, cost-effectiveness and high oil absorption ability, this solar-assisted self-heating adsorbent provides a new direction for large-scale cleanup and recycling of viscous crude oil spill on the seawater surface.

Solar-heating superhydrophobic modified melamine sponge for efficient recovery of viscous crude oil

Developing self-heating sorbents for rapid clean-up of viscous oil spills by using clean solar energy is attracting attention. Still, simple and scalable fabrication approaches of solar-heating sorbents remain challenging. Herein, a facile and practical modification strategy was presented to develop a solar-heating modified melamine sponge (rGO/CNT/MS) by dip-coating layer-by-layer (LBL) electrostatic assembly of GO and CNT with opposite charges onto MS skeleton followed by thermal reduction, without any complicated microfabrication and hydrophobic modification processes. Based on the intercalation of CNT into rGO layers and strong conjugation/hyperconjugation synergy of rGO and CNT, the light sorption ability, photothermal conversion, hydrophobicity and mechanical properties of the rGO/CNT/MS sorbent were further improved compared to rGO/MS and CNT/MS. The surface temperature could reach 75 ℃ in 100 s under 1 sun radiation (1 kW m−2), which would effectively absorb crude oil by in-situ sunlight-heating to reduce its viscosity. The sorption speed increased by about 30 times compared with no sunlight irradiation, and the continuous sorption capacity was up to 1.71 g/cm2 at 610 s driven by pump force. The easily-prepared solar-assisted rGO/CNT/MS with high photothermal performance, corrosion resistance, mechanical compressibility, coating firmness and oil sorption ability showed huge potential application in oil spill recovery.

The Performance of Engineered Water Flooding to Enhance High Viscous Oil Recovery

Low salinity/engineered water injection is an effective enhanced oil recovery method, confirmed by many laboratory investigations. The success of this approach depends on different criteria such as oil, formation brine, injected fluid, and rock properties. The performance of this method in heavy oil formations has not been addressed yet. In this paper, data on heavy oil displacement by low salinity water were collected from the literature and the experiments conducted by our team. In our experiments, core flooding was conducted on an extra heavy oil sample to measure the incremental oil recovery due to the injected brine dilution and ions composition. Our experimental results showed that wettability alteration occurred during the core flooding as the main proposed mechanism of low salinity water. Still, this mechanism is not strong enough to overcome capillary forces in heavy oil reservoirs. Hence, weak microscopic sweep efficiency and high mobility ratio resulted in a small change in residual oil saturation. This point was also observed in other oil displacement tests reported in the literature. By analyzing our experiments and available data, it is concluded that the application of standalone low salinity/engineered water flooding is not effective for heavy oil formations where the oil viscosity is higher than 150 cp and high oil recovery is not expected. Hence, combining this EOR method with thermal approaches is recommended to reduce the oil viscosity and control the mobility ratio and viscous to capillary forces.

The Role of Immiscible Fingering on the Mechanism of Secondary and Tertiary Polymer Flooding of Viscous Oil

Immiscible viscous fingering in porous media occurs when a low viscosity fluid displaces a significantly more viscous, immiscible resident fluid; for example, the displacement of a higher viscosity oil with water (where μo > > μw). Classically, this is a significant issue during oil recovery processes, where water is injected into the reservoir to provide pressure support and to drive the oil production. In moderate/heavy oil, this leads to the formation of strong water fingers, bypassed oil and high/early water production. Polymer flooding, where the injected water is viscosified through addition of high molecular weight polymers, has often been applied to reduce the viscosity contrast between the two immiscible fluids. In recent years, there has been significant development in the understanding of both the mechanism by which polymer flooding improves viscous oil recovery, as well as in the methodologies available to directly simulate such processes. One key advance in modelling the correct mechanism of polymer oil recovery in viscous oils has been the development of a method to accurately model the “simple” two-phase immiscible fingering (Sorbie in Transp Porous Media 135:331–359, 2020). This was achieved by first choosing the correct fractional flow and then deriving the maximum mobility relative permeability functions from this. It has been proposed that central to the polymer oil recovery is a fingering/viscous crossflow mechanism, and a summary of this is given in this paper. This work seeks to validate the proposed immiscible fingering/viscous crossflow mechanism experimentally for a moderately viscous oil (μo = 84 mPa.s at 31 °C; μw = 0.81 mPa.s; thus, (μo/μw) ~ 104) by performing a series of carefully monitored core floods. The results from these experiments are simulated directly to establish the potential of our modified simulation approach to capture the process (Sorbie, et al., 2020). Both secondary and tertiary polymer flooding experiments are presented and compared with the waterflood baselines, which have been established for each core system. The oil production, water cut and differential pressure are then matched directly using a commercial numerical reservoir simulator, but using our new “fractional flow” derived relative permeabilities. The use of polymer flooding, even when applied at a high water cut (80% after 0.5 PV of water injection), showed a significant impact on recovery; bringing the recovery significantly forward in time for both tertiary and secondary polymer injection modes—a further 13–16% OOIP. Each flood was then directly matched in the simulator with excellent agreement in all experimental cases. The simulations allowed a quantitative visualisation of the immiscible finger propagation from both water injection and the banking of connate water during polymer flooding. Evidence of a strong oil bank forming in front of the tertiary polymer slug was also observed, in line with the proposed viscous crossflow mechanism. This work provides validation of both polymer flooding’s viscous crossflow mechanism and the direct simulation methodology proposed by Sorbie et al. (Transp Porous Media 135:331–359, 2020). The experimental results show the significant potential for both secondary and tertiary polymer flooding in moderate/heavy oil reservoirs.

Water flooding of sandstone oil reservoirs: Underlying mechanisms in imbibition vs. drainage displacement

In this work the effect of wettability in waterfloods of viscous oil is investigated in a combination of experiments in sandpacks and microfluidic chips. Thirty-nine sand-pack flooding experiments were conducted to investigate the effect of core wettability, oil viscosity, and injection velocity on oil recovery to water flooding. An in-line densitometer, installed downstream of the core, was used to record the instantaneous fluid production and help understanding the mechanism of oil displacement in porous media. Additional microfluidic experiments were conducted to understand the mechanism of viscous oil displacement in imbibition vs. drainage.The effect of injection velocity on oil recovery is a strong function of core wettability and oil viscosity. In water-wet systems, below a critical viscosity (∼60 mPa s), increasing injection velocity enhances oil displacement. In more viscous oil systems, injection velocity reduction improves imbibition. This is confirmed through visualization in microfluidic tests. Post breakthrough bypassed oil is produced in the form of low viscosity oil in water emulsion. In oil-wet waterflooding, oil imbibition into the preformed water channels pinches off (snaps-off) some continuous fingers, diverting water to un-swept regions. This temporary channel closure can explain the cyclic pressure build-ups observed oil-wet core flooding experiments. casein oil-wet systems, oil is produced as a series of viscous oil slugs rather than an emulsion.A new dynamic dimensionless time is presented to quantify imbibition time to which imbibition data are well correlated. This number along with the previously presented “viscous drainage number” can quantify different mechanisms responsible for oil displacement in systems of different viscosity ratio, injection velocity, and core wettability. The proposed dimensionless numbers can be used to determine expected viscous oil recovery efficiency in different wettability systems.

SmartWater based synergistic technologies for enhanced oil recovery

Enhanced oil recovery (EOR) technologies based on chemicals and solvents require significant volume of source injection materials, and have limited applicability in difficult environments and harsh reservoir conditions. Synergizing injection water compositions in terms of salinity and ionic content (SmartWater) with existing recovery methods can become a game changer to overcome these limitations.The main objective is to explore the synergistic effects of SmartWater as a potential optimization avenue for achieving more efficient and economic EOR applications. To achieve this objective, a range of multiscale experimental data from macro- to core-scale were analyzed to demonstrate and quantify the benefits of water chemistry synergies with different recovery methods. The multiscale experimental data analyzed comprised of polymer rheology, contact angles, core floods, foam stability and rheology, besides evaluating the zeta potential results obtained from surface complexation modeling (SCM).The dilute concentrations of polymer ranging from 250 to 500 ppm in SmartWater increased the injection water viscosities by 2 to 4 times to provide better mobility control for light oil recovery. The tailored water chemistry reduced the polymer consumption requirements by one-third (from 3000 ppm to 2000 ppm) and increased the oil recovery by 5–7% in polymer flooding processes used for viscous oil recovery. Synergizing water chemistry with surfactant-polymer flooding resulted in an incremental oil recovery of about 4% besides lowering the surfactant and polymer concentrations by 50% (from 2000 ppm to 1000 ppm). SmartWater has also been found to synergistically combine with carbonated waterflooding to increase the CO2 dissolved volumes by 25–30% for effectively lowering the pH and develop favorable wettability alterations towards water-wet conditions. The tailored water chemistry increased the foam stabilities by resulting in 2–3 times higher foam half-lifes in addition to raising the foam apparent viscosities by 1.5 times. SmartWater foams also increased the pressure drops in porous media by 50% to confirm higher foam apparent viscosities and more resistance to gas flow.The benefits of different SmartWater based synergistic EOR technologies demonstrated in this study can be significant. They can deliver higher oil recoveries in addition to lowering the volume requirements of different EOR agents such as chemicals and gas. These findings will have a practical impact to result in more practical, efficient and economical EOR projects in the field.