Solution For Imbibition Research Articles

Experimental study of adsorption/desorption and enhanced recovery of shale oil and gas by zwitterionic surfactants

Shale reservoirs have the characteristics of low permeability and low porosity. In order to enhance the recovery of shale oil and gas, surfactant flooding is a mature reservoir oil recovery method. However, the adsorption of different surfactants on the reservoir rock surface is restricted, depending on the type of surfactant. Therefore, a zwitterionic surfactant (OPHS) was synthesized from oleic acid, 3-dimethylaminopropylamine and sodium 3-chloro-2hydroxypropanesulfonate, and characterized by FTIR, 1H NMR, and TGA, and the mechanism of the OPHS for enhancing oil and gas recovery on shale surfaces was investigated. The results showed that the critical micelle concentration (CMC) of OPHS surfactant solution is 7.9 × 10-4 mol/L and the γCMC is 27.5 mN/m; the concentration of 0.1 % OPHS surfactant solution could reduce the contact angle of the cores from 127.2° to 38.8°, which resulted in spontaneous imbibition; The absolute Zeta potential of shale particles in the OPHS surfactant solution was measured at 39 mV, whereas in deionized water at 15.3 mV. This difference can be attributed to the formation of a stable hydration film on the surface of shale particles induced by the wetting reversal effect. Spontaneous imbibition experiments showed that a 0.1 % solution of OPHS surfactant was able to increase the recovery rate by more than four times compared to the imbibition solution without added surfactant; In high-pressure gas adsorption/desorption experiments, the OPHS surfactant solution demonstrated a higher affinity for adsorption onto the shale surface. It effectively occupied adsorption sites, ultimately facilitating methane gas desorption from the shale. In summary, OPHS zwitterionic surfactants exhibit the capability to desorb hydrocarbons from shale pores through mechanisms such as wetting reversal and competitive adsorption. This research holds significant potential for advancing the field of shale oil and gas recovery, providing valuable insights for enhancing recovery processes.

Experimental Study on Forced Imbibition and Wettability Alteration of Active Carbonated Water in Low-Permeability Sandstone Reservoir

Summary Imbibition is one of the main mechanisms for fluid transport in porous media. A combination of carbonated water and active water [active-carbonated water (ACW)] has great prospects in enhanced oil recovery (EOR) and carbon reduction processes. To date, the law of hydrocarbon recovery induced by ACW imbibition is not clear. In this paper, the optimal surfactant concentration was first selected through a spontaneous imbibition experiment, and on this basis, CO2 was dissolved to form ACW. The imbibition effects of formation water (FW), surfactant solution DX-1, and ACW under different pressures were compared. The changes in rock wettability in the three imbibition solutions during imbibition were studied by measuring the contact angle. The effect of fracture on ACW imbibition was studied. Finally, the improved NB−1 was calculated to elucidate the mechanism of forced imbibition for EOR. The results show that 0.1% DX-1 produces the optimal imbibition effect. Pressure is positively correlated with imbibition recovery. ACW can significantly improve the imbibition effect due to its wettability reversal ability being better than those of FW and DX-1. CO2 in ACW can be trapped in the formation through diffusion into small rock pores. The contact angles of the three imbibition solutions decrease with increasing pressure. The contact angle between the rock and oil droplet in the ACW is as low as 38.13°. In addition, the fracture increases the contact area between the matrix and the fluid, thereby improving the imbibition effect. The alteration of NB−1 indicates that FW imbibition is gravity-driven cocurrent imbibition. DX-1 and ACW imbibitions are countercurrent imbibitions driven by capillary force and gravity. The above results demonstrate the feasibility of ACW in low-permeability reservoir development and carbon reduction.

Experimental Mechanism for Enhancing Oil Recovery by Spontaneous Imbibition with Surfactants in a Tight Sandstone Oil Reservoir

This study aims to investigate the mechanism behind surfactant enhanced oil recovery under reservoir conditions through experiments on spontaneous imbibition with surfactants. The tight sandstone samples are characterized using cast thin section (CTS), high-pressure mercury intrusion (HPMI), and nuclear magnetic resonance (NMR) to determine their clay mineral composition, pore size distribution, and fluid distribution. Spontaneous imbibition experiments are then conducted using formation water and surfactant solutions as imbibition liquids, with three different types of surfactants─dodecylbenzene sulfonate (DBS), sodium dodecyl sulfate (SDS), and ammonium bromide─at two different concentrations, each to examine the effect of surfactant type. Additionally, the interfacial tension (IFT) between crude oil and different imbibition solutions is measured, and the contact angles of an oil droplet on the core surface in air, formation water, distilled water, and surfactant solution are determined. Finally, the effects of IFT, rock wettability, formation water salinity, and core permeability on final oil recovery by spontaneous imbibition are analyzed. The results indicate that surfactant-assisted spontaneous imbibition primarily operates through IFT reduction, wettability alteration, and emulsification of crude oil. However, ultralow IFT may lead to low ultimate oil recovery. To increase the ultimate oil recovery of spontaneous imbibition, reducing the salinity of the surfactant solution and creating microfractures can be effective strategies.

An analytic solution for Counter-Current spontaneous imbibition in porous media by the perturbation method

Following primary production of hydrocarbon from naturally fractured reservoirs, secondary recovery by waterflooding relies on Spontaneous Imbibition (SI) as the primary mechanism for oil expulsion to the fracture network, where it can be easily transported to neighboring production wells. Thus, a more complete understanding of this phenomenon is warranted and essential for process improvement. The imbibition process, taking advantage of inherent preferential affinity for water contact over oil of high energy solids, is the rate determining step in recovery and can proceed in either co-current or counter-current fashion, depending upon entrance and exit boundary conditions. Due to the prominence of linear flow normal to extensive planar fracture faces, the phenomena can be largely described as one-dimensional displacement. In this study, the nonlinear one-dimensional diffusivity equation, derived by combining Darcy’s law for both wetting and non-wetting phases with the mass conservation equation, is solved for counter-current spontaneous imbibition using a direct regular perturbation scheme. Saturation and phase pressure profiles in time and space were found to agree with literature solutions. In its analytic formulation, the method constitutes a simpler, more accurate, and more direct way to compute spontaneous imbibition performance than previously available. We claim generality with regard to functional forms for relative permeability and capillary pressure and applicability over the entire range of wettability, provided these effects are reflected in the parameterization of capillary pressure and saturation normalization. In particular, the present method avoids the difficulty in solving nonlinear integral equations. Instead, we reduce computations to a set of simple numerical integrations of the diffusion coefficient. Such a streamlined solution method can more easily provide a compute engine for inverse modeling or optimization schemes to recovery rock and fluid properties from displacement experiments. The solution method is benchmarked against oil–water and air–water solutions by alternative techniques and experimental data. The case of spontaneous imbibition into dry diatomite represents extreme contrast in phase mobility and a rigorous test of the perturbation method as an easier and more direct way to model 1D SI. Following method construction and benchmarking of the new streamlined countercurrent spontaneous imbibition solution method, a subsequent parametric study contributes to a greater understanding of controlling factors in fracture-matrix exchange in porous media.

A Closed-Form Equation for Capillary Pressure in Porous Media for All Wettabilities

A saturation–capillary pressure relationship is proposed that is applicable for all wettabilities, including mixed-wet and oil-wet or hydrophobic media. This formulation is more flexible than existing correlations that only match water-wet data, while also allowing saturation to be written as a closed-form function of capillary pressure: we can determine capillary pressure explicitly from saturation, and vice versa. We propose Pc=A+Btanπ2-πSeCfor0≤Se≤1,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P_{{\ ext{c}}} = A + B\ an \\left( {\\frac{\\pi }{2} - \\pi S_{e}^{C} } \\right)\\,{\ ext{for}}\\,0 \\le S_{{\ ext{e}}} \\le 1,$$\\end{document}where S_{{text{e}}} is the normalized saturation. A indicates the wettability: A>0 is a water-wet medium, A<0 is hydrophobic while small A suggests mixed wettability. B represents the average curvature and pore-size distribution which can be much lower in mixed-wet compared to water-wet media with the same pore structure if the menisci are approximately minimal surfaces. C is an exponent that controls the inflection point in the capillary pressure and the asymptotic behaviour near end points. We match the model accurately to 29 datasets in the literature for water-wet, mixed-wet and hydrophobic media, including rocks, soils, bead and sand packs and fibrous materials with over four orders of magnitude difference in permeability and porosities from 20% to nearly 90%. We apply Leverett J-function scaling to make the expression for capillary pressure dimensionless and discuss the behaviour of analytical solutions for spontaneous imbibition.

Germination dynamics of sesame seeds under salt stress

Sesame crops have large economic potential; however, the scarcity of good quality water in the Semiarid region of the Northeast of Brazil can affect production systems, which requires the search for cultivars that can better be adapted to the local conditions. In this context, the objective of this work was to evaluate the germination dynamics of sesame seed lots subjected to different electrical conductivities of the imbibition solution. The experiment was conducted at the Laboratory of Seeds and Seedling Analysis of the Federal

Characteristic Forced and Spontaneous Imbibition Behavior in Strongly Water-Wet Sandstones Based on Experiments and Simulation

Forced and spontaneous imbibition of water is performed to displace oil from strongly water-wet Gray Berea (~130 mD) and Bentheimer (~1900 mD) sandstone core plugs. Two nonpolar oils (n-heptane and Marcol-82) were used as a non-wetting phase, with viscosities between 0.4 and 32 cP and brine (1 M NaCl) for the wetting phase with viscosity 1.1 cP. Recovery was measured for both imbibition modes, and pressure drop was measured during forced imbibition. Five forced imbibition tests were performed using low or high injection rates, using low or high oil viscosity. Seventeen spontaneous imbibition experiments were performed at four different oil viscosities. By varying the oil viscosity, the injection rate and imbibition modes, capillary and advective forces were allowed to dominate, giving trends that could be captured with modeling. Full numerical simulations matched the experimental observations consistently. The findings of this study provide better understanding of pressure and recovery behavior in strongly water-wet systems. A strong positive capillary pressure and a favorable mobility ratio resulting from low water relative permeability were main features explaining the observations. Complete oil recovery was achieved at water breakthrough during forced imbibition for low and high oil viscosity and the recovery curves were identical when plotted against the injected volume. Analytical solutions for forced imbibition indicate that the pressure drop changes linearly with time when capillary pressure is negligible. Positive capillary forces assist water imbibition, reducing the pressure drop needed to inject water, but yielding a jump in pressure drop when the front reaches the outlet. At a high injection rate, capillary forces are repressed and the linear trend between the end points was clearer than at a low rate for the experimental data. Increasing the oil viscosity by a factor of 80 only increased the spontaneous imbibition time scale by five, consistent with low water mobility constraining the imbibition rate. The time scale was predicted to be more sensitive to changes in water viscosity. At a higher oil-to-water mobility ratio, a higher part of the total recovery follows the square root of time. Our findings indicate that piston-like displacement of oil by water is a reasonable approximation for forced and spontaneous imbibition, unless the oil has a much higher viscosity than the water.

Effect of hydration on Pore Structure and Physical Properties of Permian Basalt and tuff in Sichuan Basin during pressurized imbibition

The volcanic rock with developed pores is important reservoir for oil and gas, but its complex pore-fracture structural characteristics lead to the hydration reaction when the volcanic strata is invaded by drilling fluid or fracturing fluid, which brings great challenges to the drilling operation and oil and gas production in volcanic rock reservoir. In order to understand the influence of clay hydration on the pore characteristics and permeability of different types of volcanic reservoirs. In this paper, we selected distilled water as the imbibition solution, and obtained the variation law of pore structure and physical properties of Permian tuff and basalt in Sichuan Basin during pressurized imbibition through a series of indoor test methods. The results show that the clay content of tuff is high, and the clay hydration produces new cracks during soaking, which leads to the increase of nuclear magnetic porosity of tuff after soaking. At the same time, it also makes some unconnected pores connected with each other, resulting in the increase of rock permeability in the later stage of soaking. During soaking, mineral particles peel off, and some clay minerals are transported to pores and fractures under hydrodynamic action, resulting in the reduction of effective porosity of tuff. The basalt is dense with poor physical properties. There are almost no cracks in the rock soaked for 0–24 h. After soaking for 48 h, new cracks are generated in the rock, which may be caused by the increase of pore pressure in the rock. The mineral particles around the crack obviously fall off and block the pore throat, resulting in the reduction of rock permeability after soaking. This study provides not only helps for avoiding the occurrence of lost circulation, well collapse and other accidents, efficient and safe drilling, but also a theoretical basis for the development of hydraulic fracturing in volcanic reservoirs.

Fast Screening Tool for Assessing the Impact of Poro-Mechanics on Fractured Reservoirs Using Dual-Porosity Flow Diagnostics

Summary Accounting for poro-mechanical effects in full-field reservoir simulation studies and uncertainty quantification workflows is still limited, mainly because of their high computational cost. We introduce a new approach that couples hydrodynamics and poro-mechanics with dual-porosity flow diagnostics to analyze how poro-mechanics could affect reservoir dynamics in naturally fractured reservoirs without significantly increasing computational overhead. Our new poro-mechanically informed dual-porosity flow diagnostics account for steady-state and single-phase flow conditions in the fractured medium while the fracture-matrix fluid exchange is approximated using a physics-based transfer rate coefficient, which models two-phase flow using an analytical solution for spontaneous imbibition or gravity drainage. The deformation of the system is described by the dual-porosity poro-elastic theory, which is based on mixture theory and micromechanics to compute the effective stresses and strains of the rock matrix and fractures. The solutions to the fluid flow and rock deformation equations are coupled sequentially. The governing equations for fluid flow are discretized using a finite-volume method with two-point flux-approximation while the governing equations for poro-mechanics are discretized using the virtual element method. The solution of the coupled system considers stress-dependent permeabilities for fractures and matrix. Our framework is implemented in the open-source MATLAB Reservoir Simulation Toolbox (MRST). We present a case study using a fractured carbonate reservoir analog to illustrate the integration of poro-mechanics within the dual-porosity flow diagnostics framework. The extended flow diagnostics calculations enable us to quickly screen how the dynamics in fractured reservoirs (e.g., reservoir connectivity, sweep efficiency, and fracture-matrix transfer rates) are affected by the complex interactions between poro-mechanics and fluid flow where changes in pore pressure and effective stress modify petrophysical properties and hence affect reservoir dynamics. Because of the steady-state nature of the calculations and the effective coupling strategy, these calculations do not incur significant computational overheads. They provide an efficient complement to traditional reservoir simulation and uncertainty quantification workflows because they enable us to assess a broader range of reservoir uncertainties (e.g., geological, petrophysical, and hydromechanical uncertainties). The capability of studying a much broader range of uncertainties allows the comparison and ranking from a large ensemble of reservoir models and select individual candidates for more detailed full-physics reservoir simulation studies without compromising on assessing the range of uncertainties inherent to fractured reservoirs.

Corneal riboflavin gradients and UV-absorption characteristics after topical application of riboflavin in concentrations ranging from 0.1 to 0.5%

Avoiding damage of the endothelial cells, especially in thin corneas, remains a challenge in corneal collagen crosslinking (CXL). Knowledge of the riboflavin gradients and the UV absorption characteristics after topical application of riboflavin in concentrations ranging from 0.1% to 0.5% could optimize the treatment. In this study, we present a model to calculate the UV-intensity depending on the corneal thickness.Ten groups of de-epithelialized porcine corneas were divided into 2 subgroups. Five groups received an imbibition of 10 min and the other five groups for 30 min. The applied riboflavin concentrations were 0.1%, 0.2%, 0.3%, 0.4% and 0.5% diluted in a 15% dextran solution for each subgroup. After the imbibition process, two-photon fluorescence microscopy was used to determine fluorescence intensity, which was compared to samples after saturation, yielding the absolute riboflavin concentration gradient of the cornea. The extinction coefficient of riboflavin solutions was measured using a spectrophotometer. Combining the obtained riboflavin concentrations and the extinction coefficients, a depth-dependent UV-intensity profile was calculated for each group.With increasing corneal depth, the riboflavin concentration decreased for all imbibition solutions and application times. The diffusion coefficients of 10 min imbibition time were higher than for 30 min. A higher RF concentration and a longer imbibition time resulted in higher UV-absorption and a lower UV-intensity in the depth of the cornea. Calculated UV-transmission was 6 percentage points lower compared to the measured transmission.By increasing the riboflavin concentration of the imbibition solution, a substantially higher UV-absorption inside the cornea is achieved. This offers a simple treatment option to control the depth of crosslinking e.g. in thin corneas, resulting in a lower risk of endothelial damage.

Study on the Key Influential Factors on Water Huff-n-Puff in Ultralow-Permeability Reservoir

Ultralow-permeability reservoirs are difficult to effectively develop using conventional technologies, so it generally produces using horizontal wells’ volume fracturing. Besides, oil wells also face the problems of short stable or no production period, rapid decline rate, and extremely low development degree. Water huff-n-puff of oil recovery technology is a quality and efficiency technology to improve the development effect of an ultralow-permeability reservoir. A systematic study on the related key influential factors of water huff-n-puff is done for improving the development effect of ultralow-permeability reservoirs. This manuscript studied the key influential factors of water huff-n-puff and related improving recovery methods using physical simulation experiments to put forward a beneficial condition for water huff-n-puff, combining with the field practice. The results show that imbibition and energy supplement are main mechanisms of water huff-n-puff; imbibition oil recovery is influenced by rock wettability, permeability, boundary condition, fracture length, water injection speed, and imbibition solution type; the stronger the water-wet reservoir rock is, the bigger the core permeability is, the longer the fracture length is, the larger the contacting area between imbibition solution and rock is, the stronger the ability of imbibition solution to change wettability, and to reduce the interfacial tension force between oil and water is, the better effect of water huff-n-puff is. So far, the field practice of water huff-n-puff has been conducted in 38 wells; the success rate can reach 92.1%, cycle oil increment of single well can reach 972 t, and accumulated oil in evaluation period can reach 36936 t, which further proves that water huff-n-puff can achieve a good effect. The effective methods to improve the development effect of an ultralow-permeability reservoir are changing reservoir physical property and supplying reservoir energy. Higher reservoir energy is good for oil flow, and better physical property can improve the displacement effect and imbibition function of injection solution. Artificial fracturing, higher injection-production ratio, and pretreatment of temporary stoppage fracturing are good methods to improve the development effect of water huff-puff.

Insights into the solution of counter-current spontaneous imbibition for tight unconventional reservoirs

Oil production from fractured reservoirs is challenging due to tendency of water to flow through the fractures causing reservoir oil to be bypassed and captured in the matrix. The spontaneous imbibition is a key mechanism to recover these captured reservoir hydrocarbons. This study brings pressure loss calculations to be an addition to the semi-analytical solution of counter-current imbibition. The magnitude of pressure loss was shown to be quite considerable for tight unconventional reservoirs contrary to its insignificancy for conventional reservoirs. The validity of the semi-analytical solution for unconventional reservoirs is discussed in this respect. A material balance check methodology is introduced and implemented to check the accuracy of the calculation by means of semi-analytical method. Comparison of the results of semi-analytical and numerical solutions reveals that the efficiency of the numerical solution is poor in respect to requirement of model partition and computation time. In this connection, error analysis is conducted for both numerical and semi-analytical solution to clarify the reasons for this observation. Invariance of the minimum and maximum phase pressures, the circumstance of pressure losses to be higher in the oil phase, extended variations in phase pressures due to greater capillary pressures are the considerable outcomes of the solution of the counter-current spontaneous imbibition.

Mathematical model of liquid spontaneous imbibition into gas-saturated porous media with dynamic contact angle and gravity

Liquid imbibition with dynamic contact angle is a ubiquitous phenomenon of fluid flow in porous media, but its analytical solution is challenging to derive. In this work, the analytical solution of liquid imbibition in an inclined capillary tube with velocity-dependent contact angle and gravity is first derived. The time required for the liquid-gas interface to reach a certain distance by spontaneous imbibition with static contact angle and dynamic contact angle are provided. Assuming that the porous medium consists of a bundle of tortuous capillary tubes with fractal distribution of pore size, a mathematical model of liquid imbibition in core-scale porous media with dynamic contact angle and gravity is developed. The studies show that the dynamic contact angle can significantly reduce the imbibition velocity at the initial stage of imbibition, especially in large pores, which forms a nonlinear correlation between imbibition velocity and imbibition time in a log-log plot.

Effect of gravity on spontaneous imbibition of the wetting phase into gas-saturated tortuous fractured porous media: Analytical solution and diagnostic plot

Quantitatively evaluating the gravity effect on spontaneous imbibition in fractured porous media is challenging due to the lack of a suitable model and the complex fracture distribution. In this paper, new analytical solutions for spontaneous imbibition in a single fracture with and without gravity are first derived. Then, assuming a fractal distribution of fractures and with the tortuous plate fracture model, a semianalytical model for spontaneous imbibition of the wetting phase into gas-saturated fractured porous media is derived. Expressions of the wetting phase weight imbibed into fractured porous media with and without gravity are derived. Finally, the effects of gravity on spontaneous imbibition in a single fracture and core-scale fractured porous media are quantitatively evaluated with the inverse Bond number. The research results show that our newly derived analytical solutions attain a better performance in predicting the imbibition height over time in a fracture compared with the Lucas-Washburn model or the Fries and Dreyer model, which has been verified with experimental data from the literature. When NB−1 is smaller than 3.57, the relative error of the imbibition height in a single fracture ηLs will be larger than 10%. In core-scale fractured porous media, the relative error of the total imbibition weight ηM is larger than 10% when NBC−1 is smaller than 8.8. A method of determining the critical time when the gravity effect should be considered is also proposed.

Analytical solutions for forced and spontaneous imbibition accounting for viscous coupling

Fluid-fluid momentum transfer can cause higher flow resistance when fluids flow in opposite directions as compared to the same direction. Conventional modelling of flow in porous media using simple, saturation dependent relative permeabilities does not account for such variations.We consider a generalized theory for multiphase flow in porous media based on mixture theory, where fluid mobilities follow from water-rock, oil-rock and water-oil interaction terms defined in momentum equations. Under strictly co- or counter-current flow modes, the generalized model produces explicit relative permeability expressions dependent on the flow mode, saturations, viscosities and interaction parameters. New expressions for counter-current relative permeabilities are derived assuming zero net flux, representative of counter-current spontaneous imbibition. These functions are compared to previously derived co-current relative permeabilities (assuming equal phase pressure gradients). The functions are incorporated into analytical solutions for forced and spontaneous imbibition (FI and SI) using the theory by Buckley and Leverett (1942) and McWhorter and Sunada (1990), respectively.Our results show that when accounting for viscous coupling; Counter-current relative permeabilities are always lower than co-current ones, including the end points. Both phase curves are reduced by the same saturation dependent coefficient. Increased viscous coupling in the FI case led to a more effective displacement, seen as an increased front saturation and average water saturation behind the front. For counter-current SI, increased viscous coupling resulted in lower imbibition rate. Increased viscosities reduces both oil and water counter-current relative permeabilities, and predict greater reduction in imbibition rate than only modifying the viscosities. The analytical solutions for SI were in agreement with numerical solutions of both a conventional and generalized model. The solutions for SI could be scaled exactly to a square root of time curve for arbitrary input parameters in the generalized model, especially including the strength of viscous coupling.

Dehiscence method: a seed-saving, quick and simple viability assessment in rice

BackgroundSeed viability monitoring is very important in ex situ germplasm preservation to detect germplasm deterioration. This requires seed-, time- and labor- saving methods with high precision to assess seed germination as viability. Although the current non-invasive, rapid, sensing methods (NRSs) are time- and labor-saving, they lack the precision and simplicity which are the virtues of traditional germination. Moreover, they consume a considerable amount of seeds to adjust sensed signals to germination percentage, which disregards the seed-saving objective. This becomes particularly severe for rare or endangered species whose seeds are already scarce. Here we propose a new method that is precise, low-invasive, simple, and quick, which involves analyzing the pattern of dehiscence (seed coat rupture), followed by embryonic protrusion.ResultsDehiscence proved simple to identify. After the trial of 20 treatments from 3 rice varieties, we recognized that dehiscence percentage at the 48th hour of germination (D(48)) correlates significantly with germination rate for tested seed lots. In addition, we found that the final germination percentage corresponded to D(48) plus 5. More than 70% of the seeds survived post-dehiscence desiccation for storage. Hydrogen peroxide (1 mM) as the solution for imbibition could further improve the survival. The method also worked quicker than tetrazolium which is honored as a fast, traditional method, in detecting less vigorous but viable seeds.ConclusionWe demonstrated the comprehensive virtues of dehiscence method in assessing rice seed: it is more precise and easier to use than NRSs and is faster and more seed-saving than traditional methods. We anticipate modifications including artificial intelligence to extend our method to increasingly diverse circumstances and species.

A self-similar analytical solution of spontaneous and forced imbibition in porous media

Both viscous and capillary forces control the two-phase flow in porous media. The Buckley Leverett solution for viscous flow in porous media has been proposed for over a half century. While the corresponding studies of capillary dominated solutions are mainly based on the capillary tube based models. The continuum solutions are just prevail in recently years. The analytical solution of the combination of both effects is rarely investigated. A self-similar analytical solution of spontaneous and forced imbibition in porous media is proposed in this work and the corresponding concise algorithms are presented. The proposed solution successfully solves this typical non-linear partial differential equation by introducing a transformation variable and the capillary fractional flow function analog to the fractional flow function of Buckley Leverett solution. Finally, the case study is performed, which demonstrates the feasibility and accuracy of this proposed solution to a general two-phase flow condition. Cited as : Wang, X., Sheng, J.J. A self-similar analytical solution of spontaneous and forced imbibition in porous media. Advances in Geo-Energy Research, 2018, 2(3): 260-268, doi: 10.26804/ager.2018.03.04

Spontaneous imbibition analysis in shale reservoirs based on pore network modeling

Capillary spontaneous imbibition is vital to the successful development of shale reservoirs. The two-phase flow macro-properties of shale are significantly difficult to be measured in the laboratory. A pore network model is proposed in this work. The model is validated in the conventional Bentheimer sandstone and then applied to shale matrix with the consideration of variable wettability. Some representative relative permeability and capillary pressure curves are obtained from this pore network model. Based on an analytical solution of spontaneous imbibition, we propose a computational algorithm to calculate the oil recovery factors using the calculated macro-properties from our pore network model. Combining these two, the effects of wettability and absolute permeability on the spontaneous imbibition are studied. The absolute permeability plays an important role in the oil recovery factor induced by spontaneous imbibition. The recovery factor is proportional to the quartic root of absolute permeability. A relative small portion of oil wet pores (less than 40%) in a mixed wet formation won't prevent water from imbibing into the shale matrix and increasing the oil recovery. However, when the portion of oil wet pores is too large, the imbibition recovery drops dramatically. The attempt of this work is made to investigate the two-phase flow and spontaneous imbibition of shale reservoirs in the perspective of micro-scale.

An explicit, parsimonious, and accurate estimate for ponded infiltration into soils using the Green and Ampt approach

AbstractThe Green and Ampt solution for vertical ponded infiltration is implicit in time, which makes the result often cumbersome to apply. Here we present a simple explicit solution for the position of the wetting front in time based on approximating the term describing early time behavior by means of the sum of gravitational flow and the exact solution for capillary imbibition. The result is within 1% of the exact implicit solution of vertical Green and Ampt infiltration. We also check the overall accuracy of the Green and Ampt approach, and find it to be within 15% of numerical simulation results for the same soils obtained with the Richards equation. Hence, the proposed approximation adds essentially no error to the Green and Ampt approach, but greatly simplifies computation of infiltration. The approximation also makes explicit the role of the representation of capillarity, which can be adjusted in ways not possible with the implicit result. We find that predictions can be markedly improved by adjusting capillary versus gravitational drivers per soil texture, revealing both a limitation of the Green and Ampt approach, but also providing a potential refinement of Green and Ampt predictions per soil type (demonstrated for sandy and clayey soils). Further, the new approximation allows for simple computation of useful quantities such as flux and cumulative infiltration.

Effects of drought stress on seed germination of ornamental sunflowers

The response to drought stress on germination was investigated on three hybrids of ornamental sunflower, ‘Hadar’, ‘Pazit’, and ‘Zohar’. Different levels of water potential [Ψ: 0.0 (control), −0.15, −0.30, −0.45, −0.60, −0.75, and −0.90 MPa] were adopted using polyethylene glycol-6000 (PEG6000) at four germination temperatures (15, 20, 25, and 30 °C). Final germination percentage, mean germination time, germination index, germination rate index, and germination stress tolerance index were used to evaluate the genotype response to PEG-induced water stress. Shoot and root length and fresh and dry weight were measured on seeds germinated at 20 °C under the different levels of water potentials. During germination, the three ornamental sunflowers showed to be more sensitive to suboptimal temperature than to supraoptimal. Decreasing water potential of imbibition solution progressively inhibited and delayed seed germination. Among cultivars, ‘Hadar’ and ‘Pazit’ performed better at temperature lower than 30 °C. ‘Zohar’ showed a lower sensitivity to PEG-induced water stress at all temperature conditions. Water stress during seed germination depressed the following seedling growth under favourable conditions. As a result, shoot and root length and fresh and dry weight was significantly lower in seedlings from seed germinated at ψ ≤ 0.45 MPa.