Full Characterization of CO2âOil Properties On-Chip: Solubility

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Full Characterization of CO2–Oil Properties On-Chip: Solubility, Diffusivity, Extraction Pressure, Miscibility, and Contact Angle Atena Sharbatian, Ali Abedini, ZhenBang Qi, and David Sinton Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.7b05358 • Publication Date (Web): 24 Jan 2018 Downloaded from http://pubs.acs.org on January 25, 2018

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Analytical Chemistry

Full Characterization of CO2–Oil Properties On-Chip: Solubility, Diffusivity, Extraction Pressure, Miscibility, and Contact Angle Atena Sharbatian†§, Ali Abedini†§, ZhenBang Qi†, David Sinton†* †

Department of Mechanical and Industrial Engineering and Institute for Sustainable Energy, University of Toronto, 5 King’s College Road, Toronto, ON M5S 3G8, Canada

ABSTRACT: Carbon capture, storage, and utilization technologies target a reduction in net CO2 emissions to mitigate greenhouse gas effects. The largest such projects worldwide involve storing CO2 through enhanced oil recovery - a technologically and economically feasible approach which combines both storage and oil recovery. Successful implementation relies on detailed measurements of CO2–oil properties at relevant reservoir conditions (P = 2.0–13.0 MPa, and T = 23 and 50 ºC). In this paper, we demonstrate a microfluidic method to quantify the comprehensive suite of mutual properties of a CO2 and crude oil mixture including solubility, diffusivity, extraction pressure, minimum miscibility pressure (MMP), and contact angle. The time-lapse oil swelling/extraction in response to CO2 exposure under step-wise increasing pressure was quantified via fluorescence microscopy, using the inherent fluorescence property of the oil. The CO2 solubilities and diffusion coefficients were determined from the swelling process with measurements in strong agreement with previous results. The CO2–oil MMP was determined from the subsequent oil extraction process with measurements within 5% of previous values. In addition, the oil–CO2–silicon contact angle was measured throughout the process, with contact angle increasing with pressure. In contrast with conventional methods which require days and ~500 mL fluid sample, the approach here provides a comprehensive suite of measurements, 100-fold faster with less than 1 µL of sample, and an opportunity to better inform large scale CO2 projects. CO2 is the prominent anthropogenic greenhouse gas (GHG) and rising emissions present a major global environmental stressor. Over the past decades, CO2 emissions from fossil fuelled power plants and industrial processes has accelerated. The atmospheric concentration of CO2 increased from preindustrial level of 280 ppm to 380 ppm in 2005, and is predicated to reach 550 ppm by 2050 with a progressively faster rate.1,2 Carbon capture, utilization, and storage technologies at commercial scale is an important approach in the global grand challenge presented by current CO2 emissions.3–5 CO2 can be stored through injecting into geological formations mainly oil reservoirs, abandoned gas fields, and deep saline aquifers.6–8 CO2 injection into the depleted oil reservoirs (i.e., CO2 enhanced oil recovery) is the more common approach which combines both CO2 storage and oil recovery.9–12 Currently the majority of CO2 storage/oil recovery projects - also the largest CO2 projects worldwide - are in United States and Canada, allowing ~370 billion tonnes of CO2 storage potential and additional ~1300 billion barrels of oil recovery.9 CO2 can be injected into the formation via various processes, depending on reservoir conditions and operational constraints, including continuous CO2 injection (CO2 flooding),13,14 CO2 huff-npuff,15–17 carbonated water injection,18,19 and wateralternating-CO2 injection.20–23 In all of these cases, CO2 interacts with the reservoir fluids and geology, with implications for storage, oil recovery and associated environmental and economic performance. A range of mechanisms contribute to CO2 enhanced oil recovery

including oil swelling, component extraction, interfacial tension reduction, and viscosity reduction.24–26 CO2–oil phase behavior analysis - the study of CO2 and oil interactions at relevant conditions - is essential to the design, implementation, and optimization of projects.27,28 A variety of experimental methods have been applied to study the CO2–oil systems and quantify the phase properties as a function of conditions. High-pressure high-temperature PVT cells are the traditional standard for the measurement of CO2–oil mutual properties such as solubility, diffusivity, oil swelling, and component extraction.26,29–35 For a typical PVT cell test, the cell is filled with a definite volume of crude oil sample and CO2 is injected into the cell and the pressure is kept constant. The volume of each phase is recorded over time to determine the phase properties. Alternatively, the pressure decay may be used to determine the CO2 concentration and diffusivity in the oil, whereby the volume is kept constant in the PVT cell and the pressure is monitored over time.32,36 Asphaltene precipitation during CO2 injection was also investigated using a PVT apparatus combined with a high-pressure core flooding system.37 The pendant drop method has also been used to measure the interfacial tension, oil swelling, and extraction pressure of CO2–oil mixtures.33,38 The minimum miscibility pressure (MMP) of CO2–oil (i.e., the lowest pressure at which a gas becomes miscible with oil through a multiple contact process at given temperature) is commonly measured separate from PVT testing, via the slim tube apparatus, rising bubble system, or vanishing

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interfacial tension method.39–41 Moreover, a high pressure cell combined with an X-ray source has been used to measure the oil swelling and minimum miscibility pressure for a CO2/n-decane system.42 MMP of a CO2–oil system was also determined using a high pressure acoustically monitored separator.27 While the aforementioned conventional methods provide details of CO2–oil phase behavior, they suffer from long technician times - from days to weeks, and generally involve large volumes of fluid samples required for tests. For example, a typical isobaricisothermal oil volume expansion technique in a conventional PVT cell requires ~10 days and ~500 mL fluid sample to provide a single measurand at a single pressure.29 While oil samples are not inherently valuable, the cost to operators to obtain and process samples can be very high – motivating methods that can do more tests, quicker, with less sample. A rapid comprehensive test would also enable testing of different oil samples in the reservoir (e.g. as a function of depth), testing at different temperatures, as well as continuous monitoring of properties over time during operation – a resolution that is not practical with current methods.

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reservoir fluids requires many measurements. Specifically, in the case of CO2 utilization and storage in enhanced oil recovery, the critical parameters are: solubility, diffusivity, extraction pressure, minimum miscibility pressure, and contact angle. In this paper, we present a microfluidic platform to measure the comprehensive suite of mutual properties of a CO2 and crude oil mixture at relevant reservoir conditions (P = 2.0–13.0 MPa, and T = 23 and 50 ºC). Leveraging the inherent fluorescence property of crude oil sample, the mass transfer and interfacial interactions between CO2 and oil are observed within a silicon-glass chip containing multiple separate micro-PVT channels, with pressure increasing stepwise. CO2 solubility and the diffusion coefficient are determined at different pressures and temperatures using 1-D oil swelling models and the results are compared against published data. The extraction pressure and minimum miscibility pressure of CO2 and oil are quantified from the subsequent oil extraction. Additionally, the equilibrium contact angle between the oil and CO2 on the silicon surface is measured continuously throughout the test, and recorded as a function of pressure. All the aforementioned parameters are determined through full-range pressure swelling/extraction tests combined with automated image analysis.

Microfluidic technologies have a growing track record in life sciences and recently have gained traction in industrial chemical applications.43–47 Specifically for phase behavior measurements, microfluidic tools have been developed to measure the bubble point, dew point, and phase envelope – all much faster than conventional tests.48– 52 Gas diffusivity and miscibility in liquid systems have also determined through static and dynamic measurements in microfluidics.53–56 Extra heavy oils present many instrumentation challenges and a microfluidic chip was designed to determine solubility and diffusivity of light hydrocarbon solvents in these highly viscous samples.57 This approach to swelling-derived measurements with bitumen was effective but not applicable to oil with lower viscosity because it is not possible to ensure the oil volume in the cell. In addition, a microfluidic approach was developed to determine the solution gas-oil ratio for live oil samples.58 The combination of microfluidics and optical absorption were applied to comprehensively quantify asphaltene precipitation and deposition.59,60 Moreover, microfluidic networks as physical models of microporous media – or micromodels – have been widely employed to visualize the complex pore-scale dynamics of various displacement and enhanced oil recovery processes.61–69 Microfluidic platforms can provide unprecedented control over operating conditions (e.g., pressure, temperature, pore geometry, and saturation) together with direct observation of the process. They also offer rapid transport, with potential for fast quantification and ease of operation; all stemming from the small test volume. While individual microfluidic tests demonstrated to date make a strong case for microfluidics-based measurements of thermodynamic fluid properties, they have been limited, in general, to one measurand. That is, one chip provides one measurement. In contrast, fully characterizing the complex interactions of

EXPERIMENTAL SECTION

Figure 1 shows the schematic diagram of the microfluidic platform used for CO2-oil phase behavior experiments. A microfluidic chip was designed and fabricated using deep reactive ion etching (DRIE) of silicon followed by anodic bonding to glass. The oil-wettability of both silicon and glass surfaces was also verified at atmospheric condition, showing that both surfaces are strongly oil-wet with similar wetting properties - reflecting the oil-wet properties found in many reservoir rocks70 (details are in Supporting Information). In addition, the DRIE does not have a notable impact on the surface chemistry of the silicon. The process does generate a surface roughness in a range of ±1 µm, however, this is less than 1% of the channel depth. The chip had a main channel (100 µm width × 120 µm depth) and four close-ended side channels (60 µm width × 120 µm depth) serving effectively as micro-PVT channels. The depth of the micro-PVT channel was twice of its width, to aid the measurement of the CO2–oil contact angle on the silicon surfaces (i.e., the sides of the micro-PVT channel). Employing multiple micro-PVT channels on the same chip allowed multiple tests to be performed under the same conditions, simultaneously. While the chip geometry could allow for many more such tests in parallel, four was found to be convenient in this study. A new chip was used for each run to ensure that the chip condition is the same in all tests. Eight separate microfluidic chips were designed and fit on a single 2″ × 2″ silicon wafer which significantly reduced both fabrication time and cost per chip. Teledyne-Isco


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260D pump was used to store and supply the CO2 at the desired pressure.

was imaged at a constant pressure. Moreover, all experiments were conducted under static condition, so that there was no net CO2 flow inside the chip. Thus, the oil volume variation observed inside the micro-PVT channels was only due to the CO2–oil interactions. The operating CO2 pressure range was selected so that the CO2–oil phase behavior was determined over a wide range of immiscible to miscible conditions. An Olympus BXFM fluorescent microscope (peak excitation wavelength λex ~451 nm) with X-CITE 120 LED light source connected to the Leica MC 170 HD camera was used, and the images were stored for analysis. The images were imported to an image processing software (ImageJ) to quantify the oil swelling over time. The limit of detection with respect to swelling length was one pixel, or ±1 µm. This variation corresponds to ~0.5% variation in oil swelling factor, which was equivalent to ~0.6 kg/m3 variation in CO2 concentration (~0.8% variation) at the most extreme conditions (i.e., highest pressures).

RESULTS AND DISCUSSION

Extraction pressure and minimum miscibility pressure. Figure 2a and 2b show the dynamic oil swelling factor defined as the ratio of the oil volume to the initial oil volume (i.e., SF = v/vi) - vs. time as a result of the CO2 exposure at different pressures for tests conducted at 23 and 50 ºC. It is noted that the measured pressures are reported as gauge pressure. The profile is typical of that observed in larger cells. At both temperatures, the oil swelling factor exhibits three distinct regions, namely the swelling region, the major extraction region, and the minor extraction region. Both the low and high temperature cases show similar behavior with the higher temperature generally requiring higher pressure to initiate extraction, as observed elsewhere.33,72 In the swelling region (P = 2.0–4.0 MPa at 23 ºC), the mass transfer from CO2 phase to the oil phase occurs through molecular diffusion at the CO2–oil interface, resulting in oil expansion inside the micro-PVT channel. As the pressure was increased further, the oil swelling factor increased faster due to larger CO2 solubility and diffusivity at higher pressure. In the second region (P = 5.0–7.3 MPa at 23 ºC) the oil volume markedly shrank with increased CO2 pressure over time indicating major extraction. In this region, CO2 extracted the crude oil components, preferentially removing the lighter components of the oil. While the crude oil sample is dead, and contains negligible traditional light fractions, it contains significant intermediate fractions (typically up to C9s) that can be extracted by CO2 at high pressure with the remaining oil containing heavier fractions - in keeping with previous studies.24,25,30,72 In the minor extraction region (P = 8.0–10.0 MPa at 23 ºC), further reduction in the oil volume in the PVT channel with increasing pressure was minimal with majority of extractable components already removed. A similar trend was also observed for swelling/extraction experiments carried out at 50 ºC, with

Figure 1. Microfluidic platform for CO2-oil phase behavior; a) Schematic of microfluidic setup combined with fluorescence microscopy, and b) typical oil swelling and extraction inside the micro-PVT channel. In each experiment, the chip was embedded in a stainless-steel manifold with Viton ring seals, enabling high pressure. For high temperature experiments, an ultrathin heat sheet (1″ × 3″,115 VAC, McMaster-Carr, 35475K334) connected to a temperature controller (Omega CNi3222) was mounted on the manifold (i.e., underneath the chip) to control the temperature. Low pressure CO2 (P < 5 bar) was first injected into the chip to displace the air. The dead West Texas crude oil sample with no dissolved gas (ρ = 0.830 g/cm3 and µ = 4.9 mPa.s) was then continuously injected from inlet toward the outlet to fill the entire chip. Compositional analysis of representative West Texas crude oil71 is presented in Supporting Information. The oil in the main channel was then displaced by low pressure CO2, leaving individual oil plugs within the microPVT channels with no trapped air. Continuous flow in the main channel removes oil in the side channels, albeit slowly, via corner-flow. Given the length of the micro-PVT channel is 500 µm, the initial oil plug length for each test was adjusted to be 150–200 µm, providing sufficient space for oil expansion during the test. Once the CO2 pressure reached atmospheric pressure, the outlet of the chip was closed via a high pressure two-way valve, and the test was initiated. Experiments were conducted under constantpressure mode. At each temperature, the CO2 was incrementally pressurized, changing from gas phase to liquid phase (up to supercritical phase at 50 ºC). Following each incremental pressure step, the oil volume variation



the results shown in Figure 2b. The oil swelling factor initially increased in the swelling region (P = 2.0–5.7 MPa) and then noticeably declined in the major extraction region (P = 6.5–10.0 MPa) followed by a minimal oil swelling factor reduction in the minor extraction region (P = 11.0– 13.0 MPa). The system was closed during the step-wise pressure increasing process. Therefore, with no net flow, the observed oil shrinkage in the micro-PVT channel at high pressures was only due to the component extraction mechanism.

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uniform CO2 and oil phase (i.e., multi-contact MMP). This significant mass transfer corresponds to the major extraction process in which large amount of CO2 diffuses into the oil phase (i.e., condensation mechanism) as well as noticeable amount of intermediate oil components are extracted by high pressure CO2 phase (i.e., vaporization mechanism). It has been shown that the CO2–oil MMP can be estimated from the oil swelling/extraction data and the point where major component extraction gives way to minor.33,72,73 Here, the transition point was estimated by fitting a straight line in the minor extraction zone, and determining the intercept with the extraction trend line as shown in Figure 2c. The quality of the linear fit (R2) was used to determine which pressures to include in the minor zone linearization (with the equations of the linear fits as presented in Figure 2c). Using this analysis, 7.4 MPa and 10.6 MPa are the MMP values of this crude oil and CO2 system at temperatures of 23 and 50 ºC, respectively, which is in close agreement with the results reported by other experimental and theoretical studies used the same crude oil sample.53,74 It is noted that the interface imaged at pressures near and above the multi-contact MMP is the interface between hydrocarbon-rich CO2 phase and nonextractable oil components. While in cases of CO2–pure hydrocarbon systems (e.g., CO2–C10), the interface ultimately vanishes as the pressure approaches the MMP.42This is not the case for crude oil. Similar results were also obtained in previous static-based CO2–oil experiments using high pressure PVT cells and pendant drop apparatus.38,72 While the method can be extended to live reservoir fluids, in our tests, and comparison cases from the literature,33,38,72 the MMP values were measured from dead crude oil samples. Light components expected in a reservoir fluid would generally increase the MMP values.

Figure 2c shows the final oil swelling factor as a function of applied pressure at two temperatures of 23 and 50 ºC. For both temperatures, the swelling factor increased gradually and then sharply as it approached the peak, corresponding to the extraction pressure (the pressure at which the volume fraction of components in the oil phase being extracted into the CO2 phase exceeds the volume fraction of CO2 entering the oil phase). Here the extraction pressure is Pext = 4.4 and 5.8 MPa at T = 23 and 50 ºC, respectively. Thereafter, the swelling factor rapidly decreased followed by a gradual decline, corresponding to major and minor extraction regions, respectively. These trends in swelling and extraction as a function of pressure and temperature reflect those observed using traditional methods.30,33,34,72 CO2–oil minimum miscibility pressure (MMP) is also a key parameter in CO2-enhanced oil recovery processes, particularly as it determines whether the injected CO2 phase will largely merge with the oil phase (miscible injection) or remain a separate phase with associated capillary effects (immiscible injection).27,33,53 At the MMP, CO2 becomes miscible with oil when a significant mass transfer occurs at the interface, resulting in formation of a

Figure 2. Swelling/extraction test results at temperatures of 23 and 50 ºC: a) dynamic oil swelling factor vs. time indicating three distinct regions for CO2–oil interactions: swelling region, major extraction, and minor extraction (T = 23 ºC); b)


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dynamic oil swelling factor vs. time indicating three distinct regions for CO2–oil interactions: swelling region, major extraction, and minor extraction (T = 50 ºC); c) final oil swelling factor at different pressures estimating the extraction pressure and CO2–oil MMP (Pext = 4.4 MPa and MMP ~ 7.4 MPa at T = 23 ºC; Pext = 5.8 MPa and MMP ~ 10.6 MPa at T = 50 ºC); d) variation of fluorescence intensity of the oil inside the PVT channel. 81.1 and 79.9 kg/m3 at 23 and 50 ºC, respectively, which is in agreement with the observations reported in the literature.28

Fluorescence intensity of the oil phase provides an additional indicator of the transition from immiscibility to miscibility condition. Figure 2c shows the variation of fluorescence intensity of the oil sample in the micro-PVT channel as a function of pressure at temperatures of 23 and 50 ºC. Data highlighted with green circles correspond to the images inset. While fluorescence is used here only to indicate the extent of the liquid oil phase, it is notable that the fluorescence intensity continuously decreased with increasing CO2 pressure and reached a minimum value (at 7.4 and 10.6 MPa) corresponding to the MMP values at 23 and 50 ºC calculated separately above. Beyond this pressure, there was no significant change in the fluorescence intensity, we expect because the CO2–oil mutual phase interaction is minimal. While the fluorescence intensity variation can provide a qualitative indication of compositional change, making it a quantitative measurement would require detailed compositional and component-quenching dynamics to be established for a given sample, due to the inherent complexity of fluorescence in multicomponent crude oil.75

The finite length diffusion model (details are presented in the Supporting Information) - with the final equation given in Eq. 229 - was used to determine the CO2 diffusion coefficient in the oil with results plotted in Figure 3c.

1 1

= ln ()

, 1 − − ,

− , + , 1 − ,

, =

%$(2)

Where Csi is the CO2 interfacial concentration (i.e., CO2 solubility), a is a fitting parameter, t is the time (s), and D is the diffusion coefficient (m2/s). As with the solubility data, the CO2 diffusion coefficient increased with increasing pressure, as expected. Table S1 in Supporting Information provides the input parameters and calculated solubility and diffusivity values of CO2–oil system under all experimental conditions. The range of interest for both solubility and diffusivity data is at the lower, pre-extraction pressures. At pressures above the extraction pressure, the assumptions in the 1-D swelling model are no longer valid (i.e., constant oil composition). Above the extraction pressure, the crude oil composition changes due to the extraction of intermediate components of the crude oil into the CO2 phase. Figure 3c compares the diffusion coefficient data (at 23 and 50 ºC) determined using the microfluidic method developed in this study with the data reported elsewhere obtained by pressure decay and pendant drop experiments.80–83 The literature reported values are all from light oil. While there is no exact match between the fluid samples, test conditions, and experimental methods, the results obtained here were in good agreement with the literature data.

CO2 Solubility and Diffusivity. Gas-liquid swelling data can also be used to determine gas solubility and diffusivity in the liquid phase. Established models for 1-D oil swelling29,57,76 were applied here to the micro-PVT test system to determine the time-lapse average CO2 concentration in the oil phase, CO2 solubility in the oil, and the corresponding CO2–oil diffusion coefficient (details are presented in the Supporting Information). Figure 3a plots the average CO2 concentration in the oil vs. time at different pressures and temperatures of 23 and 50 ºC calculated by Eq. 129, with a trend similar to that of the base swelling curve. , =

!"#

(1)

where Cs,av is the average concentration of the CO2 in the oil sample (kg/m3), vs is the specific volume of CO2 at the experimental pressure and temperature (m3/kg), xo and xt are the initial oil length and oil length at time equal to t, respectively, and SF is the oil swelling factor. The point of maximum CO2 concentration is taken as the CO2 solubility for a given pressure, with results here plotted in Figure 3b. The CO2 solubility data determined by the microfluidic method were also compared with the literature in Figure 3b, showing there is a strong agreement.24,77–79 At both experimental temperature, the CO2 solubility increased with increased pressure. It has been reported that a definite volume of CO2 should be dissolved in the oil phase to initiate the extraction mechanism at any operating temperature. Here, the CO2 solubility at extraction pressures were determined to be



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improve the oil mobility by lowering the oil wettability trapping in pores.

Figure 4. Contact angle between the oil and CO2 on the silicon at different pressures and 23 ºC. Inset images show the CO2–oil interface at two pressures indicated (the brightness of the images was increased to resolve the interface shape and for presentation). The contact angle measurement schematic is also shown inset. Figure 3. Solubility and diffusivity results at temperatures of 23 and 50 ºC: a) average CO2 concentration in the oil; b) CO2 solubility data obtained in this study compared with literature data; c) CO2 diffusion coefficient data obtained in this study compared with literature data.

The oil swelling/extraction analysis here is userindependent and requires under 15 min to achieve the equilibrium condition (i.e., final oil swelling in the microPVT channel) at each pressure. The speed and fast quantification stems from the low sample volume, ~100 nL, which is in stark contrast to typical PVT experiments that require ~500 mL fluid sample.29. Specifically, a full range pressure analysis combined with automated image processing enables high resolution mutual CO2–oil property data in less than ~2–3 hr, which is notably faster than days to weeks required for conducting conventional methods. In addition, employing multiple micro-PVT channels on the same chip here allows multiple tests to be conducted under the same conditions simultaneously. Lastly, this approach is readily applicable to live oil samples, with some modification. Most notably, the initial loading step could not employ low pressure CO2 to clear the channel and compartmentalize the oil in the test channels. Rather, a pressurized intermediate inert fluid, such as N2, could be used to clear the channel at elevated pressure (using a back-pressure regulator), prior to the application of CO2. The resulting method provides a powerful tool to inform emerging strategies for CO2 storage and enhanced oil recovery operations. The resulting method provides a powerful tool to inform emerging strategies for CO2 storage and enhanced oil recovery operations.

Contact angle. The contact angle between the oil and CO2 on the silicon surface was determined with results shown in Figure 4. The angle measured through imaging from top of the chip, is most reflective of the contact angle of CO2– oil interface with silicon surfaces on the side of the microPVT channel. While the top glass surface could have some influence on the observed contact angle, the effect is expected to be negligible, particularly as both silicon and glass surfaces exhibited a similar oil-wet condition (details in the Supporting Information). Inset images show the CO2–oil interface at two selected pressures of 2.0 and 6.5 MPa. The contact angle was calculated by measuring the distance between the silicon-oil-water contact line and the y-axis of the PVT channel, as shown inset in Figure 4. The contact angle increased with the CO2 pressure in the three distinct regions, in agreement with results reported elsewhere.42 In the low pressure range (P < 2.0 MPa), the contact angle slightly increased with pressure. In the pressure range P = 2.0–7.3 MPa, the contact angle significantly increased due to strong oil swelling/extraction mechanisms, and approached a maximum value at a pressure near the minimum miscibility pressure (i.e., MMP ~7.4 MPa). At pressures greater than 7.3 MPa, the contact angle increased marginally with increasing pressure. In general, the oil-wet nature of the surface reduced with increasing CO2 pressure, which under reservoir conditions serves to

CONCLUSION

In summary, we demonstrate a microfluidic-based approach to quantify mutual CO2–oil phase behavior properties. Critical properties including CO2 solubility and diffusivity, extraction pressure, minimum miscibility


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pressure, and contact angle were measured concurrently. The results obtained here are in close agreement with published data and the microfluidic method offers significant advantages over conventional PVT methods. With a small fluid sample volume (~100 nL), this method uniquely provides rapid measurement and high-resolution quantification (over 100-fold faster) compared with conventional PVT cell apparatus. A rapid comprehensive test enables testing of different oil samples in the reservoir (e.g. as a function of depth), testing at different temperatures, as well as continuous monitoring of properties over time during operation – a resolution that is not practical with current methods. The silicon-glass system is also suited to the full range of reservoir-relevant operating conditions and can readily be made compatible with hazardous solvents and live reservoir fluids.

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ASSOCIATED CONTENT Supporting Information Oil-wet condition of glass and silicon surfaces at atmospheric condition; Graphical determination of minimum miscibility pressure (MMP) of CO2–oil system using oil swelling/extraction data; Mathematical modeling of 1-D oil swelling use to determine the CO2 solubility and diffusivity in the crude oil at different pressures and temperatures; Compositional analysis of the West Texas crude oil.

AUTHOR INFORMATION Corresponding Author * E-mail: [email protected]. Author Contributions §

A.S. and A.A. contributed equally to this work.

Notes The authors declare no competing financial interest.

ACKNOWLEDGEMENTS The authors would also like to thank Natural Sciences and Engineering Research Council of Canada (NSERC) for their funding support through the Collaborative Research and Development Program, the Discovery Grant Program, the Discovery Accelerator Program, an E.W.R. Steacie Memorial Fellowship (D.S.), and a Postdoctoral Fellowship (A.A.). Support through Alberta Innovates Energy and Environmental Solutions and the Canada Research Chair Program is also gratefully acknowledged, as is infrastructure provided by the Canada Foundation for Innovation and the Ontario Research Fund.

REFERENCES

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Graphical abstract (for TOC only)


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Full Characterization of CO2âOil Properties On-Chip: Solubility

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