Imbibition Measurements Research Articles

Efficacy Comparison of Three Atmospheric Pressure Plasma Sources for Soybean Seed Treatment: Plasma Characteristics, Seed Properties, Germination

Plasma seed treatment has proven to be a useful technique for improving germination, growth dynamics, as well as plant resistance. In this paper, we studied the efficacy of soybean seeds treatment using various sources of cold atmospheric pressure plasma generated in air. We compared three types of plasma treatments: direct treatment with plasma generated by a diffuse coplanar surface barrier discharge (DCSBD), direct treatment with plasma generated by a multi-hollow surface dielectric barrier discharge, and indirect treatment using the gaseous products of plasma generated by an air plasma jet. The composition of plasma generated by each of the sources was analysed using optical emission spectroscopy and Fourier Transform Infrared spectroscopy (FTIR). Parameters of the plasma treatments have been optimized to improve soybean germination. Plasma-treated seeds were examined by the means of water contact angle, surface free energy and imbibition measurements, attenuated total reflectance FTIR (ATR-FTIR), x-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) analyses. Surface analysis by ATR-FTIR and XPS showed changes in the chemical bonds on the surface of the plasma-treated seeds, which led to an increase in wettability and imbibition. SEM analysis confirmed that the plasma treatment is non-invasive and does not cause changes in seed surface morphology. Among the studied sources, DCSBD proved to be the best suited for soybean seed treatment in terms of germination improvement as well as treatment time and energy efficiency.

Wettability Alteration with Weak Acid-Assisted Surfactant Flood

Summary Oil-wetness and heterogeneity are two key reasons for low oil recovery by waterflooding in carbonate reservoirs. Surfactants have been effective in altering the oil-wet matrix to a more water-wet condition and initiating spontaneous imbibition. Because it takes time for the surfactant to alter wettability, oil recovery from the tight matrix is slow and sometimes not economically feasible. Acids have the potential of dissolving minerals, which may alter wettability. In this study, the enhanced oil recovery (EOR) performance of an acid-assisted surfactant solution, a novel technique, was evaluated for low-temperature applications. A set of acids and their acetates were tested. Bulk rock-acid reaction, wettability alteration (WA) tests, and spontaneous imbibition measurements were conducted at reservoir temperature (35°C) to identify effective candidates. Coreflood tests were then performed to evaluate the selected acid-surfactant formulations. Before and after a coreflood test, the core was scanned using micro-computed tomography (CT) to investigate pore structure alteration. Bulk reaction measurements showed that weak acids, especially acetic acid (AA), have the desired low reaction rates at 35°C. WA tests showed that AA can remove the crude oil off the rock surface and alter wettability through mineral dissolution. The surfactant can reduce contact angles from 160° to 58°; adding acid into the surfactant can further reduce it to 52°. Spontaneous imbibition experiments showed the synergy between the acid and the surfactant; the AA-surfactant solution had the highest oil recovery (62.6%) among acid-surfactant formulations. The acid improves the WA efficiency by the surfactant through surface mineral dissolution and lower ζ-potential. The imbibition transports the acid-surfactant solutions into the matrix, which minimizes face dissolution. Coreflood tests show that the AA-surfactant flood can increase the oil recovery rate and recover about 8% more oil compared to the surfactant flood. Micro-CT showed that a few mineral particles were transported along the core and partially plugged pore throats, which reduced permeability and diverted flow leading to improved oil recovery. The transport of the acid in reservoirs and the potential plugging issues have to be carefully evaluated in future studies.

Wettability Evaluation by Spontaneous Imbibition Measurement

The propensity of one fluid in a fluid pair to coat the surface voluntarily is known as wettability. Fluid distribution and flow behavior in porous rocks mainly controlled by wettability. Oil recovery by water flooding depend mainly on the wettability of the reservoir rock. Many methods used for wettability measurement. These methods are qualitative and quantitative. Spontaneous imbibition is one of widely used methods for quantitative wettability measurement. Direct measurement and weighing technique are two known methods for spontaneous imbibition measurement. This work presents comparison between the two aforementioned methods. Experimental measurement of spontaneous imbibition achieved on core samples from the same source. Results approved that the samples are water wet but having different tendencies, the imbibition rate related to time have variable trend in addition, ultimate water saturation in weighing method experiment are higher than that in volume measurement method. The weighing method is better than the volume measurement method.

Water Imbibition and Oil Recovery in Shale: Dynamics and Mechanisms Using Integrated Centimeter-to-Nanometer-Scale Imaging

Summary Water imbibition, and the associated oil displacement, is an important process in shale oil reservoirs after hydraulic fracturing and in water-based enhanced oil recovery (EOR). Current techniques for water imbibition measurement are mostly “black-box”-type methods. A more explicit understanding of the water imbibition/oil recovery dynamics and geological controls is in demand. In this paper, a multiscale imaging technique that covers centimeter to nanometer scale (i.e., core to pore scale), integrating neutron radiography, microcomputed tomography (micro-CT), and scanning electron microscope (SEM) is applied to investigate the water imbibition depth and rate and the cause of heterogeneity of imbibition in shale samples. The dynamic processes of water imbibition in the 1-in. (25.4-mm) core sample were explicitly demonstrated, and the imbibition along the matrix and imbibition through microfractures are distinguished through neutron radiography image analysis. The causes of observed imbibition heterogeneity were further investigated through micro-CT and SEM image analysis for 1.5-mm diameter miniplug samples from different laminas of the 1-in. core samples. Imbibition depth and rate were calculated on the basis of image analysis as well. Estimation of oil recovery through water imbibition in shale matrix was performed for an example shale field. This innovative and integrated multiscale imaging technique provides a “white/gray-box” method to understand water imbibition and water-oil displacement in shale. The wide span of the length scale (from centimeter to nanometer) of this technique enables a more comprehensive, accurate, and specific understanding of both the core-scale dynamics and pore-scale mechanisms of water imbibition, oil recovery, and matrix-fracture interaction.

Wettability alteration to maintain wellbore stability of shale formation using hydrophobic nanoparticles

Wellbore stability is a complex issue to achieve safe and efficient drilling operations, especially in shale formations using water-based drilling fluids. The objective of this paper is to maintain wellbore stability by wetting reversal of shale with synthesized hydrophobic nanoparticles (HN). The molecular structure and microstructure of HN were studied by Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM), respectively. Experiments were conducted to analyze the particle size, dispersion stability, and thermal stability of HN. The effects of HN on the wettability of the shale surface were investigated by a series of contact angle measurements. The changes of shale microstructure were observed by scanning electron microscopy (SEM). To evaluate the wellbore strengthening performances of HN, spontaneous imbibition measurements and uniaxial compression strength tests were performed. The effect of HN on the base fluid was also evaluated. The results showed that the HN with an average particle size of 217.4 nm was successfully prepared. High temperature slightly promoted the dispersion of HN in water. HN was still relatively stable at 240 ℃. HN was strongly adsorbed on the shale surface to form a hydrophobic layer, which transformed the shale surface from hydrophilic to hydrophobic. Moreover, the ability of HN to cause a wetting reversal of shale was not susceptible to temperature and could be maintained even at ultra-high temperatures. After the HN treatment, the water absorption of shale decreased obviously, and the uniaxial compressive strength increased significantly. In addition, the addition of HN had no significant effect on the rheology and filtration properties of drilling fluids. The HN presents a high application potential as a nano-structured wetting alteration agent to ensure the stability of the wellbore.

Water Uptake Behavior and Influence Factors of Longmaxi Shale: Implications from Water Physisorption and Imbibition Measurements

Water Uptake Behavior and Influence Factors of Longmaxi Shale: Implications from Water Physisorption and Imbibition Measurements

Wettability alteration using benzoxazine resin: A remedy for water blockage in sandstone gas reservoirs

As a low carbon fuel, natural gas is leading the transition to a cleaner energy system. However, water blockage is seen to reduce gas deliverability significantly in many gas producing wells. We have developed an environmentally friendly and cost-effective non-fluorinated chemical treatment using a new benzoxazine monomer as a wettability modifier to combat water blockage. This chemical would adhere to silicate surfaces through a silane moiety followed by the application of a thermally accelerated ring-opening polymerization of the benzoxazine moiety. The performance of the treatment has been evaluated using contact angle measurements, spontaneous imbibition tests, and core-flooding experiments at 60 °C and 10.35 MPa. After chemical treatment, the contact angle shifts from almost 0° to 90°, implying that the treatment alters the wettability from strongly water-wet to an intermediate gas-wetting state. Spontaneous imbibition measurements show about 65% reduction in the volume of water imbibed into the rock sample after chemical treatment, suggesting a substantial increase in hydrophobicity of rock pore surfaces. Core-flooding experiments indicate that the chemical treatment increases gas relative permeability (by up to 22%) whilst decreasing residual water saturation (by up to 10%). Taken together, we demonstrate that this novel non-fluorinated benzoxazine monomer can successfully shift wettability of sandstone rocks from a strongly water-wet to an intermediate-wet state and thus aid to mitigate water blockage at relatively low cost and in an environmentally friendly manner. Furthermore, this chemical can withstand extra high temperatures encountered in many deep low permeability gas reservoirs where water blockage may be highly pronounced.

Effects of swelling-clay and surface roughness on the wettability of transitional shale

Wettability in unconventional reservoirs is poorly understood. However, it plays a fundamental role in fluid-rock interactions, and an understanding of wetting behavior is essential for capillary seal assessments and hydrocarbon reserve estimation and recovery in clay-rich reservoirs. In this study, the wetting behavior of transitional Shanxi-Taiyuan shale from the southern North China basin was examined via the contact angle (CA) and spontaneous imbibition (SI) measurement methods. Under water-air-shale conditions, water-wet and neutral-wet behaviors were observed, whereas neutral-wet and oil-wet behaviors were observed under water-oil-shale conditions (Young's equation was used to convert the water-air-shale system to the water-oil-shale system). When the CA method was used, the shale was shown to be hydrophobic, whereas when the SI test was used, the shale was observed to be hydrophilic. The water-air CAs are negatively correlated with the total organic content (TOC), carbonate and clay mineral contents (excluding those of illite). Furthermore, iron-containing compounds, such as pyrite and siderite, were shown to decrease the water wetness. A linear negative correlation was found between the surface roughness and the CA value. The relationship between these parameters can be used to predict the CAs at different surface roughness values for a given sample. The contradictory wetting behaviors between the results of SI and CA methods can be explained by: (i) differences between the CAs formed under water-air-shale conditions and those formed under hydrocarbon-brine-shale conditions; (ii) differences in the surface roughness, which is dependent on the texture and mineralogy of the shale sample; and (iii) clay swelling after water sorption and the formation of microfractures due to water–rock interactions.

Measurement and Modeling of Spontaneous Capillary Imbibition in Coal.

Coal is a typical dual-porosity medium. The implementation process of water invasion technology in coal is actually a process of spontaneous imbibition of external water. To obtain a model of spontaneous capillary imbibition in coal, the spontaneous imbibition of water in coal samples with different production loads is conducted experimentally. Due to the coal particle deformation and the cohesive forces, the porosity and maximum diameter decrease gradually with increasing pressing loads. Due to the filling effects and occupying effects, the proper particle grading can reduce the porosity and tortuosity. The Comiti model can be used to describe the tortuosity. The tortuosity increases with decreasing porosity. The smaller the porosity, the smoother the surface of the coal sample. The contact angle is negatively correlated with the surface roughness. The fractal dimension decreases with increasing pressing load. The difference in the pore characteristics between particles is the main reason for the difference in the fractal dimension. The proposed model of spontaneous capillary imbibition in coal is consistent with the experimental data. The implications of this study are important for understanding the law of spontaneous imbibition in coal and the displacement of gas by spontaneous capillary imbibition in coal, which is important for optimizing the parameters of coal seam water injection.

Mechanism of Synergistically Changing Wettability of an Oil-Wet Sandstone Surface by a Novel Nanoactive Fluid

Various methods, including ζ potential, infrared (IR), quartz crystal microbalance (QCM), contact angle, and spontaneous imbibition measurements, were used to investigate the micromechanism of syne...

Simplified Green‐Ampt Model, Imbibition‐Based Estimates of Permeability, and Implications for Leak‐off in Hydraulic Fracturing

AbstractPredicting water imbibition into porous materials is important in a wide variety of fields, and hydraulic fracturing of low permeability hydrocarbon reservoirs has emerged as an application that is imposing a large water footprint. Reliable predictions of imbibition are needed to better manage water use, yet are challenging because of uncertainties in both the permeability and capillary pressure driving force. Here, this uncertainty is reduced through evaluating correlations between the permeability and the effective capillary pressure associated with the wetting front, Pc,f. These correlations allow elimination of Pc,f from the Green and Ampt equation and concentrate all uncertainties in fluxes on the effective permeability k. Over a wide range of k and porosities n, imbibition scales approximately with k1/3. Although Leverett k1/4 scaling for predicting Pc,f is shown to be inferior when tested with data spanning a wide range of n, it nevertheless predicted imbibition fairly well. From simple imbibition measurements, both the empirical and Leverett scaling approaches allow estimates of k that have root‐mean‐square deviations of about one order of magnitude relative to measurements that ranged over 10 orders of magnitude in k.

Brine composition effect on the oil recovery in carbonate oil reservoirs: A comprehensive experimental and CFD simulation study

In order to understand the potential role of divalent ions involved in smart water, fluid-fluid and rock-fluid interactions are studied through contact angle and interfacial tension (IFT) measurements. Then, the suitable brines in changing contact angle and IFT are brought into measurement with spontaneous imbibition experiments to evaluate the co-impact of fluid-fluid and rock-fluid interactions. The results show the importance of SO42− ions during smart water injection as removing them from the injection water leads to a sharp drop in ultimate oil recovery. Accordingly, when the concentration of SO42− within the injection water increases four times, 10% ultimate oil recovery is recovered. Furthermore, the spontaneous imbibition measurements exhibit the higher ultimate oil recovery from the neutrally-wet core plugs more rather than the strong water-wet plugs. Further elaborating about the effect of wettability on the pore-scale displacement of oil by injection water is conducted through Computational Fluid Dynamics (CFD) modelling. The results confirm that the lowest residual oil saturation is achieved in the model with neutral wettability state as well as the highest oil recovery which is in line with the piston-like displacement in the neutral wet rock medium.

Estimation of the Bubble Influence on the Imbibed Liquid Measurement During Tight Rock Continuous Imbibition

Abstract Bubble influence makes the measured liquid content in rock become less during continuous imbibition because it attaches to the surface of the tight sand increasing the buoyancy of rock in liquid. The imbibition experiment was performed to research this influence. The experiment has two parts. One is the repeated measurement of imbibition with the same sample to investigate the repeatability of the imbibition experiment under the bubble influence. The other part includes the measurement with bubble influence and without bubble influence of the same sample. The results are listed as follows. The repeated measurement of the same rock imbibition reflects a similar characteristic with the bubble influence. The water content is very close with the corresponding imbibition time. This characteristic presents that tight sand imbibition has the characteristic of repeatability, which was the basis for the other experiment. Some different characteristics appear during the measurement of the liquid content with and without bubble influence in the same sample. The liquid content without bubble influence is apparently larger than the liquid content with bubble influence. The difference between the liquid content in these two conditions is small at the end of imbibition time. It becomes larger in the middle imbibition time. The error can reach 50%. It severely influences the accurate evaluation of the imbibition capacity of tight sand. Our research contributes to the acquaintance of liquid imbibition in the formation during hydraulic fracturing and is also conducive to better measure the liquid content through the laboratory experiment.

Effect of salinity, Mg2+ and SO42− on “smart water”-induced carbonate wettability alteration in a model oil system

HypothesisWe present a systematic study of the “smart water” induced wettability alteration. This process is believed to be greatly affected by the brine salinity and the presence of Mg2+ and SO42− in the brine. Experiments and modellingTo characterize the wettability alteration, we perform spontaneous imbibition measurement using Indiana limestone cores and a model oil with added naphthenic acid. Both single-electrolyte-based and seawater-based “smart water” are tested to investigate the effect of Mg2+, SO42− and salinity on wettability alteration. Rock/brine and oil/brine zeta potentials are measured, and the electrostatic component of disjoining pressure is calculated to understand the role of electrostatics in the wettability alteration. The surface concentration of charged species on the limestone surface is analyzed based on a natural carbonate surface complexation model (SCM). FindingsBoth the reduction of Na+ and addition of SO42− are found to contribute to wettability alteration. Mg2+ is found to be unfavorable for wettability alteration. Ca2+ is believed to facilitate SO42− with wettability alteration based on the comparison between the single-electrolyte-based and seawater-based brines. The reduction of the Na+ surface complexation (>CaOH⋯Na+0.25) in low salinity brines is believed to be a critical mechanism responsible for wettability alteration based on the SCM calculations.

Measurement of Spontaneous Imbibition Capillary Pressure, Saturation and Resistivity Index by Counter Current Technique at Net Reservoir Stress and Elevated Temperature

Capillary pressure and resistivity index spontaneous imbibition experiments by the porous plate method, in a core holder at elevated temperature and net reservoir stress, are both difficult and time consuming special core analysis measurements to perform. In this type of experiment, low capillary forces act against a low permeable porous plate and only one face of the cylindrical core sample is in capillary contact with the fluid saturated porous plate. In this paper, core samples having different lithology, petrophysical properties and wettability are analysed by counter current spontaneous imbibition, starting at initial water saturation (Swi), at net confining pressure and elevated temperature. Synthetic brine is used as the wetting phase and Isopar L mineral oil as the non-wetting phase. This methodology is applied to investigate and evaluate how to obtain more reliable, more efficient and faster saturation imbibition data combined with electrical measurements, during spontaneous imbibition measurements. Resistivity index (RI), saturation exponent (n) (by single saturation equilibrium point using Archie’s second law RI= Sw-n) and wettability information using representative fluids, confining pressure and temperature are also obtained by applying this specific counter current imbibition technique and improved procedural approach.

Comparison of micro- and macro-wettability measurements and evaluation of micro-scale imbibition rates for unconventional reservoirs: Implications for modeling multi-phase flow at the micro-scale

Significant advances have been made in the evaluation of micro- and nano-scale variations of pore structure in low-permeability (unconventional) reservoirs using imaging techniques. In parallel, digital rock physics (DRP) methods have been advanced so that pore structure information extracted from these images may be used, in combination with pore-scale modeling, to predict critical petrophysical rock properties such as porosity and permeability. Recent work using DRP applied to multi-phase flow of unconventional reservoirs has suggested that wettability variations at the micro-scale caused by mineralogical heterogeneity or aging can have a profound effect on simulated capillary pressure and relative permeability curves. However, wettability is typically measured at the macro-scale, with the resulting contact angles used for populating DRP models. Further, fluid imbibition rates are usually measured at the macro-scale to compare, for example, the impact of fracturing fluid additives on oil recovery.This study compares water contact angle measurements made at the micro-scale, using an environmental field emission scanning electron microscope (E-FESEM) combined with innovative procedures for contact-angle extraction, with a conventional macro-scale approach (sessile drop) for low-permeability samples obtained from the Montney Formation in Western Canada. For the first time, quantification of imbibition rates at the micro-scale is demonstrated. Two micro-wettability evaluation procedures developed previously are applied to these samples to evaluate water micro-contact angles: 1) imaging of condensation/evaporation experiments and 2) imaging of injected fluids using a micro-injection system. Micro contact angles were first estimated by extracting sessile droplet profiles (with user-guided software developed in-house) and then fitting a parameterized Young-Laplace equation to the droplet profile. For some of the micro-injection experiments, the geometry of the micro-droplet, as captured with the parameterized Young-Laplace equation, was used to compute the volume of the micro-droplet at different stages of imbibition, which in turn was used to evaluate imbibition rates at this scale. Macro contact angles were evaluated using the parameterized Young-Laplace equation and commercial software.This study suggests that laboratory-derived macro-droplet contact angles cannot be confidently and consistently applied at the micro-scale for use in DRP models for tight heterogeneous formations such as the Montney. Significant errors in simulating fluid displacement processes, fluid saturation distributions, capillary pressure and relative permeability curves using DRP methods will result if micro-scale variations in wettability are not taken into account. Finally, the study demonstrates that fluid imbibition measurements may be performed at the micro-scale, enabling fine-scale rock composition/pore structure controls on fluid imbibition to be explored.

Microcorona Discharge-Mediated Nonthermal Atmospheric Plasma for Seed Surface Modification

By exploiting the physical effect of a highly nonuniform localized electric field and electron-initiated impact ionization on space charge, we generated homogeneous nonthermal plasma under ambient atmosphere. We evaluated the physical characteristics and evolution of microcorona discharge-induced nonthermal atmospheric plasma (NAP) based on a point-to-plane electrode in open air with two distinct configurations. High-voltage pulses were employed as the primary power source of corona discharge generation to reveal the fundamental mechanism, polarity effect and feasibility of using NAP for organic surface modification. Consequently, we employed NAP to modify the surface of rice (Oryza sativa L.) seeds to improve their wettability. The surface modification of the rice seeds was investigated via water apparent contact angle (ACA) and water imbibition (WI) measurements. The ACA and WI measurements revealed not only the improvement in the wetting properties but also the mutual relationships between and limitations of ACA and WI analysis. We found that the WI time reached saturation after a certain treatment time, called the threshold treatment time. Because vacuum conditions are not required, well-established NAP technology will garner interest in many fields, ranging from the life, environmental, and biomedical sciences to solid-state electronics applications.

Estimation of relative permeability and capillary pressure from mass imbibition experiments

We perform spontaneous imbibition experiments on three carbonates - Estaillades, Ketton, and Portland - which are three quarry limestones that have very different pore structures and span wide range of permeability. We measure the mass of water imbibed in air saturated cores as a function of time under strongly water-wet conditions. Specifically, we perform co-current spontaneous experiments using a highly sensitive balance to measure the mass imbibed as a function of time for the three rocks. We use cores measuring 37 mm in diameter and three lengths of approximately 76 mm, 204 mm, and 290 mm. We show that the amount imbibed scales as the square root of time and find the parameter C, where the volume imbibed per unit cross-sectional area at time t is Ct1/2. We find higher C values for higher permeability rocks. Employing semi-analytical solutions for one-dimensional flow and using reasonable estimates of relative permeability and capillary pressure, we can match the experimental data. We finally discuss how, in combination with conventional measurements, we can use theoretical solutions and imbibition measurements to find or constrain relative permeability and capillary pressure.

Wettability Alteration by Salinity and Calcium Bridge in a Crude Oil/Brine/Rock System

Wettability alteration has been considered to be a key factor behind low salinity water effect. Though the wettability alteration is widely accepted to be determined by oil components, mineral surfaces and ions in aqueous phase, how the brine chemistry (ionic type and strength) impacts the wettability is still unknown. In this study, the auhtors conducted spontaneous imbibition, contact angle, and zeta potential measurements to investigate: (a) how the ions of the thin film of water between oil and mineral interact with oil and rock to alter the wettability of crude oil/brine/rock system and (b) the mechanism of wettability alteration behind low salinity water effect.

Synthesis and characterization of polyvinyl alcohol based semi interpenetrating polymeric networks

Polymeric networks in the form of hydrogels offer possibilities to achieve desirable combination of properties that are generally not available in a single polymeric material. With these objectives, the present work focus on the synthesis of polyvinyl alcohol (PVA) based novel semi-IPNs of varying compositions by redox polymerization method using N,N'-methylene bisacrylamide (MBA) as the crosslinker and acrylonitrile as the monomer. The prepared semi-IPNs have been examined for structural confirmation, by FTIR analysis. Crystalline features of the semi-IPNs were studied by XRD technique which revealed that crystallinity in the membrane was mainly due to PVA. The IPNs of various compositions have also been examined for their water sorption behavior and network parameters like average molecular weight between crosslinks (Mc) and crosslink density were calculated from water imbibition measurements. The kinetics and mechanism of water sorption process were studied and related kinetic parameters were evaluated. The DSC analysis of the prepared semi-IPNs was also performed and it was found that the gels showed well-defined thermal behavior.