Imbibition Research Articles

Development trend of marine shale gas reservoir evaluation and a suitable comprehensive evaluation system

At present, shale gas exploration and development in China is faced with some problems, such as the imperfect evaluation system of reservoir effectiveness and the limitations of reservoir evaluation system on efficient development of shale gas. In order to improve the content and the standard of reservoir evaluation, this paper analyzed the shortcomings and challenges in the static evaluation of shale gas reservoirs on the basis of existing reservoir evaluation, and established a method for evaluating shale gas reservoir effectiveness and a scheme for classifying pore systems. Then, the dynamic evaluation parameters after shale fracturing and their effects on drainage and production measures were discussed. In addition, the potential evaluation parameters of “automatic mitigating water blocking” were studied, and a comprehensive reservoir evaluation system of “static–dynamic” combination was established. And the following research results were obtained. First, new challenges to the shale gas reservoir evaluation are emerged as the lack of in-depth study on “reservoir effectiveness, dynamic evaluation parameter system after fracturing and drainage and production measures after fracturing”, which leads to the serious lag of existing shale gas reservoir evaluation system behind production. Second, the evaluation of reservoir effectiveness is mainly presented as the evaluation on the lower limit of effective porosity, and is embodied in the influence of clay bound water and unconnected pores on the development of shale gas. Third, the development of shale gas reservoir evaluation follows the trend of refining the static reservoir evaluation parameters, defining the potential evaluation indexes of “automatic mitigating water blocking” and establishing the reservoir comprehensive evaluation system of “static–dynamic” combination. Fourth, a post-frac dynamic evaluation system is determined for the potential evaluation indexes of “automatic mitigating water blocking” (e.g., wettability, water imbibition retention capacity, water imbibition expansion mode, expansion rate, and water imbibition cracking capacity). Fifth, a reservoir evaluation idea is put forward that “static evaluation of shale gas reservoir is the foundation and postfrac dynamic evaluation is the complement”, and a comprehensive reservoir evaluation system is established of “static–dynamic” combination suitable for the evaluation of marine shale gas reservoirs in China.

A comparative study of ion diffusion during water imbibition in shale, sandstone and volcanic rock

The recovered fracturing fluid is generally high in salinity (close to 200 kppm), which is related to the diffusion of salt ions from shale reservoir to the fracturing fluid. However, it is not clear about the diffusion capacity of salt ions in different types. In this paper, the shale, tight volcanic and sandstone are selected as comparative study and a series of tests are carried out for the porosity, permeability and mineral composition. The results show that the shale immersing in fracturing fluid will cause ions dissolution and diffusion, which will increase the salinity of the fracturing fluid. The solution salinity increases rapidly in the early stage and gradually slows down in the later stage. The salinity of the fracturing fluid has a linear relationship with the square root of time, so the slope of the curve can be used as a characteristic parameter to evaluate the ion diffusion rate. The process of dissolution and diffusion of salt ions will induce the expansion of micro-cracks, increasing the contact area between the fracturing fluid and shale and enhancing the solution salinity. The ion diffusion rate is positively related with the content of clay minerals and carbonate. The soluble ions include mainly SO 4 2− , Ca 2+ , Na + and K + . The Na + /Cl − ratio is closely related to the content of clay minerals and carbonate minerals. It has a positive correlation with content of illite and chlorite, and a negative correlation with carbonate minerals, suggesting NaCl source from illite and chlorite. This study is significant for understanding the salinity characteristics of recovered fracturing fluid and evaluating the fracture network shape. Cited as : Yang, L., Chen, C., Liu, Y., Zheng, Y. A comparative study of ion diffusion during water imbibition in shale, sandstone and volcanic rock. Capillarity, 2020, 3(2): 16-27, doi: 10.46690/capi.2020.02.01

Evaluation of interfacial tension (IFT), oil swelling and oil production under imbibition of carbonated water in carbonate oil reservoirs

Carbonated water injection into oil reservoirs is known as a high-efficiency enhanced oil recovery (EOR) method that can be a solution for increasing the sweep efficiency in CO2 injection projects. The mechanisms of this method include oil swelling, wettability alteration, dissolution of the reservoir rock and reducing interfacial tension (IFT). In this work, carbonated water-oil IFT and oil swelling at various pressures, temperatures and salinities resulted from formation water dilution were measured and studied using pendant drop experiments. The wettability of the reservoir rock was investigated by contact angle tests and the oil recovery by carbonated water imbibition was demonstrated by performing imbibition experiments. The results confirm the capability of carbonated water to change the parameters to the further production, in such a way that oil recovery values at 10.342 MPa and 80 °C, and the salinities of ten and twenty times diluted formation water were 55.68, 62.95 and 68.52%, respectively. Wettability of carbonate rock altered to water-wet and IFT reduced to 5.039 mN/m.

Reserve metabolism and ubiquitin proteasome system are involved in germination progress of wheat grains

To further elucidate the molecular mechanism of the germination in common wheat, a differential proteomic analysis was completed between the F1 hybrid RS5322 and its parental lines (RS53 and SN22) using isobaric tags for relative and absolute quantitation (iTRAQ) based strategy. Rapid grain germination and superior young seedling growth were observed in the F1 hybrid line. A total of 807 differentially abundant proteins (DAPs) were identified by iTRAQ analysis of grains at 48 h after imbibition in distilled water. Bioinformatics analysis shows that 638 DAPs were annotated in 38 Gene Ontology functional groups, 764 DAPs were classified into 23 clusters of orthologous groups of protein categories, and 538 DAPs were enriched in 65 Kyoto encyclopedia of genes and genomes pathways. Real time quantitative PCR of 12 genes encoding different important proteins showed certain transcriptional and translational expression similarities during grain development. In the F1 hybrid, the DAPs were particularly those involved in starch and sugar metabolism, protein metabolism, protein modification, and ubiquitin proteasome system (UPS). It was speculated that UPS might be responsible for a high germination ability in the F1 hybrid by regulating storage substance metabolism. The DAPs identified in this study provide a scope for improving the grain germination trait in agricultural crops.

Performance Comparison of Novel Chemical Agents for Mitigating Water-Blocking Problem in Tight Gas Sandstones

Summary Water blocking can be a serious problem, causing a low gas production rate after hydraulic fracturing, a result of the strong capillarity in the tight sandstone reservoir aggravating the spontaneous imbibition. Fortunately, chemicals added to the fracturing fluids can alter the surface properties and thus prevent or reduce the water-blocking issue. We designed a spontaneous imbibition experiment to explore the possibility of using novel chemicals to both mitigate the spontaneous imbibition of water into the tight gas cores and measure the surface tensions (STs) between the air and chemical solutions. A diverse group of chemical species has been experimentally examined in this study, including two anionic surfactants (O242 and O342), a cationic surfactant (C12TAB), an alkaline solution of sodium metaborate (NaBO2), an ionic liquid (BMMIM BF4), two nanofluids with aluminum oxide and silicon oxide (Al2O3 and SiO2, respectively), and a series of deep eutectic solvents (DES3-7, 9, 11, and 14). Experimental results indicate that the anionic surfactants (O242 and O342) contribute to low STs but cannot ease the water-blocking issue because they yield a more water-wet surface. The high pH solution (NaBO2), ionic liquid (BMMIM BF-4), and sodium chloride brine (NaCl) significantly decrease the volume of water imbibed to the tight sandstone core through wettability alteration, and C12TAB leads to both ST reduction and an air-wet rock surface, helping to prevent water blocking. The different types of DESs and nanofluids exhibit distinctly different effects on expelling gas from the tight sandstone cores through water imbibition. This preliminary research will be useful in both selecting and using proper chemicals in fracturing fluids to mitigate water-blocking problems in tight gas sandstones.

Oil recovery from fractured porous media with/without initial water saturation by using 3-pentanone and its aqueous solution

This paper presents an application of 3-pentanone, a symmetric dialkyl ketone, to enhance the water imbibition in coreflooding of fractured carbonate cores. 3-Pentanone was tested in two ways: 1.1- wt% 3-pentanone solution in reservoir brine (3pRB) and pure 3-pentanone (3p) as a miscible solvent. It was presented previously that 3p is a mutual solvent for oil and water, and can rapidly change the rock wettability to strongly water-wet with its electron-rich oxygen atom through the oil and water phases. The main objective of this research is to investigate how the initial water saturation (Swi) in the matrix affects the imbibition of 3pRB or 3p from the fracture and the resulting recovery of oil from the matrix.The experimental results were analyzed in terms of material balance (mass and volume) with simplifying assumptions. This analysis enabled to estimate how much of the injected components were imbibed into the surrounding matrices from the fracture and the relative contribution of the injected components to displacing oil in the matrix. Results for the 3pRB and 3p injections indicate collectively that 3-pentanone was more effective in enhancing oil recovery when an aqueous phase was initially present in the matrix.

Dynamics of water imbibition through paper with swelling

We present a combined experimental and theoretical investigation of the dynamics of water imbibition through paper with swelling. The Washburn equation has been widely used to describe the dynamics of the liquid absorption in paper, but its prediction of liquid imbibition speed has been reported to be inaccurate. Our recent study (Chang et al., J. Fluid Mech., vol. 845, 2018, pp. 36–50) demonstrated that the internal cavity of cellulose fibres composing the paper is partially responsible for the limited accuracy of the Washburn equation based on oil imbibition experiments. Here we extend the investigation to water absorption through paper with swelling. We demonstrate that the swelling of the cellulose fibre network in addition to the internal voids of the cellulose fibres crucially affects the imbibition dynamics. Based on the microscopic observation that paper swelling is caused by the expansion of inter-fibre space, we suggest a mathematical model for water imbibition which considers both intra-fibre voids and swelling. By introducing parameters that characterize the swelling speed and volume of paper, our model markedly improves prediction of the water imbibition speed. The results provide not only a theoretical background for designing paper-based microfluidic systems, but also new insights into capillary flow through expandable porous media.

Utilização de diferentes tratamentos pré-germinativos para superação de dormência em sementes de Adenanthera pavonina L.

A propagação de espécies florestais empregadas para reflorestamento ou para ornamentação, pode ser realizada través de sementes, onde podem apresentar dormência não favorecendo o processo de germinação. Logo, o presente trabalho teve como objetivo avaliar diferentes tratamentos da superação de dormência em sementes de A. pavovina L. As sementes foram coletas em três matrizes na cidade de Serra Talhada-PE, e submetidas a diferentes superação de dormência: testemunha; imersão em água a temperatura ambiente por 48 horas; imersão em água a temperatura de 100 ºC por 10 segundos e posterior acondicionamento no freezer por 6 horas; escarificação manual com lixa d’água nº 120, nas duas laterais e do lado oposto ao hilo; imersão em NaClO (2,5%) por 24 horas; imersão em solução de soda cáustica de 30% por 30 minutos. As semente foram semeadas em bandejas de isopor com duzentas células, utilizando como substrato vermiculita de granulometria média. O delineamento experimental adotado foi o inteiramente casualizados, constituído de seis tratamentos e quatro repetições de vinte sementes. Os parâmetros analisados foram porcentagem de emergência (PE); índice de velocidade de emergência (IVE) e tempo médio de emergência (TME). Com o tratamento de escarificação manual com lixa d’água nº. 120, nas duas laterais e do lado oposto ao hilo, verifica-se que para o TME a quantidade de dias é maior para formação de uma plântula (1,98 dias) mas, foi o tratamento que apresentou melhor PE (84%) e IVE (1,3375) em sementes de A. pavonina L., por ocasionar rupturas no tegumento, favorecendo o aumento de embebição de água, sendo a mesma, a etapa principal para o início do processo germinativo. A utilização da escarificação manual com lixa d’água nas duas laterais do tegumento e do lado oposto ao hilo é recomendado como tratamento pré-germinativo em sementes de A. pavonina L.

Experimental investigations of fracturing fluid flowback and retention under forced imbibition in fossil hydrogen energy development of tight oil based on nuclear magnetic resonance

Experimental works have proved that imbibition under forced pressure (FP, the difference between hydraulic fluid pressure and original pore pressure) has a positive effect on fossil hydrogen energy development in tight oil reservoir. However, the knowledge of the influence of imbibition under forced pressure (forced imbibition, FI) on fracturing fluid flowback and water retention is still limited. In this paper, experiments were designed and conducted to reveal the mechanism of fracturing fluid flowback and water retention under imbibition effect in tight sandstones. As a comparison, unconsolidated sandstones were also investigated in this study. Core samples were divided into two categories: the imbibition ones (treated by imbibition) and the filtration ones (treated by displacement), in accordance with the real oil-water distribution after well shut-in. An imbibition core and a filtration core were stitched together to conduct a flowback experiment. During the experiment, fluid distribution in different pore sizes was monitored continuously by using a low-field nuclear magnetic resonance device. Results show that the flowback recovery in tight sandstones is much lower than that in unconsolidated sandstones due to the difference of pore structure. Meanwhile, forced imbibition leads to higher oil recovery than spontaneous imbibition (SI) in tight sandstones since forced pressure enhances water imbibition. The water imbibed into small-macro and macro pores contributes the major flowback recovery, but the imbibed water in micro pores is rather difficult to displace and finally retains in these pores during the flowback process. Overall, forced imbibition not only enhances oil recovery but also increases water retention, explaining the mechanism of well productivity increase by using the shut-in method in the field. This study can help to clarify the influence of forced imbibition on fracturing fluid flowback and enhancement of fossil hydrogen development, and further provide guidance for flowback designs.

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.

Plasma mediated disinfection of rice seeds in water and air

The efficacy of seed disinfection utilizing atmospheric pressure non-thermal plasma is still a subject of intensive research. Previously, we found that rice seeds infected by Fusarium fujikuroi (fungus causing bakanae disease) could be disinfected via underwater arc discharge plasma. In this study, we further investigated the mechanism of disinfection and the effect on disease severity. In addition, we evaluated disinfection of rice seeds in air by surface DBD plasma. Disease severity was significantly reduced in seedlings germinated from rice seeds treated with underwater arc plasma, compared to non-treated seeds (44%–62% plasma treated compared to 92% non-treated). A shockwave of 11 atm pressure was generated during arc discharge, which likely caused fungal detachment from the seed surface. Moreover, reactive oxygen species such as atomic oxygen (O) was emitted from the underwater arc discharge plasma and could have contributed to the degeneration of the chemical composition on the seed surface and the inactivation of the fungal spores. Rice seeds treated with surface DBD plasma in the presence of H2O2 at a lower pressure (0.6 atm) for 30 min showed the highest seed disinfection efficiency (about 93% seed disinfection) and a significant reduction in disease severity in the germinated seedlings (23% plasma-treated compared to 100% non-treated). Taken together, our results suggested that underwater arc discharge and surface DBD plasma could be usefully applied to develop control strategies for seed-borne fungal diseases via seed decontamination during dry storage or water imbibition before sowing.

Near-Fracture Capillary End Effect on Shale-Gas and Water Production

Summary Capillary end effect (CEE) develops in tight gas and shale formations near hydraulic fractures during flowback of the fracturing-treatment water and extends into the natural-gas-production period. In this study, a new multiphase reservoir-flow-simulation model is used to understand the role the CEE plays on the removal of the water from the formation and on the gas production. The reservoir model has a matrix pore structure mainly consisting of a network of microfractures and cracks under stress. The model simulates high-resolution water/gas flow in this network with a capillary discontinuity at the hydraulic-fracture/matrix interface. The simulation results show that the CEE causes significant formation damage during the production period by holding the water saturation near the fracture at higher levels than that using only the spontaneous imbibition of water. The effect makes water less mobile, or trapped, in the formation during the flowback, and tends to block gas flow during the production. The effect during the production is more important relative to the changing stress. We showed that the CEE cannot be removed completely but can be reduced significantly by controlling the production rate.

Priming, a Promising Practical Approach to Improve Seed Germination and Plant Growth in Saline Conditions

Salinity as a major constrain of plant productivity affects growth and development at any stage of growth cycle. Under saline conditions, rapid and uniform germination of plants would be necessary to achieve enhanced quality and potential yield. In such situation, seed priming could be an important approach to increase plant germination, growth and consequently yield. Priming is defined as seed presowing in solutions that allow them to imbibe water to improve the first stage of germination; however, this prevents radical protrusion through seed coat. Seed priming improves establishment in many plant species, and include hydro-priming, osmo-priming, halo-priming, thermo-priming and hormo-priming. Overall, accelerated biochemical and physiological process such cell division and starch hydrolysis, induced α-amylase activity, greater germination rate, less Na+ and higher K+ accumulation and induced antioxidative system might be some mechanisms for salinity tolerance in primed plants. Since shortage of water availability due to osmotic stress is the first phase in salt stress, so one of the major mechanisms for improved germination and growth in primed seeds is accelerated water imbibition under saline conditions. In this paper, different seed priming strategies are examined and comprised in different plants growing in saline conditions. Since different types of seed priming have positive effects on germination, emergence, growth, yield as well as biochemical traits and quality of plants, it seems that seed priming could be promising approach for improved salinity tolerance in future world with changed climate. More researches on detail of seed priming for each agent is needed for each plant.

Geotechnical study of a landslide reactivation in clay soils (central Piedmont, NW Italy).

In March 2015, exceptional meteoric events occurred in southern Piedmont caused a remarkable rise of the rivers water level of the Tanaro Basin with flooding and many landslides. The engineering geological study reported here, concerns a triggering of a previous landslide occurred in 1982 in the hills, shaped in the marine sedimentary succession (Lugagnano Clay, lower Pliocene) of the southern Asti Reliefs, near San Martino Alfieri village. Detailed geological, morphological and topographic surveys of this landslide, with the aim to recognize the morphological features linked to the previous landslide and those connected to the triggering of it, have been carried out. The reactivation of the landslide was highlighted by the presence of a main scarp with minor escarpments and tracks. The mechanism activation of the main landslide is due to a rotational movement. To define the engineering geological model of the landslide body, standard cone penetration tests. rotary drilling borings with S.P.T. and geotechnical laboratory tests were performed. Through surveys, both main slip surface and deep-water seepage have been detected. In details, failure mechanism in OC clays was caused by: a) rapid increase in the bulk density or volume weight during rainfall events; b) rise of interstitial pressures along the sliding surface with reduction of normal stress and consequent reduction of the shear strength along this surface (progressive failure); c) reduction of cohesion and friction angle, due to clay softening. The results of the study have highlighted the need, as a primary factor of slopes consolidation, to install sub-horizontal drainage pipes in order both to avoid subsoil imbibition and to control the changes of interstitial pressure. The consolidation works focused on the construction of containment structures with deep consolidation and the execution of drainage works in the landslide area.

On the magnitude of capillary pressure (suction potential) in tight rocks

In this study, we review the concepts of capillary pressure and total suction. We propose that for shales and siltstones, capillary pressure (matric suction) is not the only dominant source of suction. Therefore, total suction, which is the sum of matric and osmotic pressure (electrostatic forces), provides a better description of the physical process behind water imbibition. We investigate the application of a dew-point psychrometer to measure total suction and compare that to mercury injection capillary pressure (MICP) measurements. The MICP method, traditionally used in energy industry, does not capture the impact of pores smaller than 3 nm. It is also limited to measuring only matric suction, ignoring electrostatic forces. Our results indicate that the suction values typically assumed in the literature from MICP tests significantly underestimate the total suction in shales and siltstones. Total suction for samples from the Montney Formation in Canada can be as high as 250 MPa at water saturations between 1 and 5%. The magnitude of suction measured in this work explains the significant water uptake by this class of reservoirs during hydraulic fracturing. Total suction in the present experiments correlate well to mineralogy and porosity of the samples. The results of this paper suggest that measurements of capillary pressure in unconventional reservoirs are generally inappropriate to describe the behavior of rocks. The order of magnitude of suction reported here has major implications in modelling basin-wide fluid migration, water imbibition into tight rocks, and describing rock's mechanical response after hydraulic fracturing.

Physiological and biochemical responses of selected cowpea (Vigna unguiculata (L.) Walp.) accessions to iron toxicity

This study aimed to investigate the effect of iron toxicity in cowpea using physiological and biochemical responses of selected accessions. Fifteen accessions of cowpea were exposed to two treatments of iron using FeSO4 solution (100 mg l-1 and 400 mg l-1) and distilled water at pH 6.2 as control. The results showed that there was a general reduction in germination morphology; germination percentage among the 400 mg l-1 Fe-treated accessions. Seed mortality rates were significantly higher among the 400 mg l-1Fe-treated accessions (> 35 %). Water imbibition capacity and relative mass gained were higher for Fe-treated accessions. Furthermore, significant increase in the total sugar and percentage utilization of sugars was accompanied by an insignificant decrease in chlorophyll a, a significant decrease in chlorophyll b contents and the persistence of foliar chlorosis, among the 400 mg l-1 Fe-treated accessions. MDA levels were significantly increased while proline remained unchanged, mean SOD activity was insignificantly increased, whereas Cat decreased among the 400 mg l-1 Fe-treated accessions. Documentation of these observable changes in physiological and biochemical parameters will be useful in understanding the impact of elevated iron concentrations on the cultivation of cowpea accessions in soils associated with ferruginous ultisols.

Laboratory evaluation of flow properties of Niutitang shale at reservoir conditions

Abstract Absolute and water saturation dependent gas flow under reservoir conditions is important for the exploration of deep energy resources. Steady-state and various unsteady-state argon permeability tests were conducted on dry Niutitang shale during the confinement loading and unloading cycles, then different gases were used for steady-state permeability tests at the final confinement of 20 MPa. Permeability decreased by 36% with the confinement increasing from 5 MPa to 60 MPa, and around 66% of the permeability reductions was recovered after the unloading cycles. The apparent steady-state permeabilities were 38% higher than those derived by unsteady-state methods due to the enhanced slip flow. Two cycles of water imbibition and gas drainage tests were conducted with the long water evaporation process completed in the second gas drainage process. Argon to carbon dioxide permeability ratio ranged from 1.2 to 2.1, while the water permeability was 30–45% of the gas intrinsic permeability. The argon breakthrough pressure of water-saturated Niutitang shale sample was 8 MPa, and the permeability increased by 10 times after the long-term evaporation process. Argon permeability decreased by 90% and increased by 21.6%–29.6% respectively after the first and second gas drainage processes compared with that under dry condition with the residual water saturation being 29.7% and 11.3% respectively, which were caused by the water blockage and cracking respectively. Influences of carbon dioxide adsorption and induced swelling reached a minimum at residual water saturation.

More generalized recovery models for spontaneous imbibition based on Arp decline equation

Spontaneous water imbibition is an important technique to enhance oil recovery in fractured reservoirs, but most existing models do not work well in some cases. Therefore for this reason, in paper, more better generalized recovery models for spontaneous imbibition, including the exponential recovery model and hyperbolic recovery model, were derived theoretically based on the Arp decline equation to find a suitable model. It was found that the proposed models could be reduced to the frequently used Aronofsky model, the Handy model, the Li-Horne model, and the Viksund model. In addition, a new exponential dimensionless time and new hyperbolic dimensionless time associated with initial decline rate were introduced and verified against experimental data from literatures. The fitting results demonstrated that both exponential dimensionless time and hyperbolic dimensionless time could successfully scale the experimental data in all the cases studied in this paper. And thus they were proposed as suitable ones for spontaneous water imbibition to oil recovery enhancement in fractured reservoirs.

Studies of the storage and transport of water and oil in organic-rich shale using vacuum imbibition method

The inorganic pores, organic pores, and kerogen matrix are important media to store water and oil in shale rocks. We present a vacuum imbibition method to identify the volume of water and oil in these media. Before the experiments, comprehensive rock characterizations were carried out on shale samples from Shahejie Formation combining various methods including N2 adsorption, scanning electron microscope (SEM), X-ray diffraction, and RockEval pyrolysis. Total organic carbon (TOC) accounts for 1.59–5.97% of total rock weight. Kerogen thermal maturity (Ro) of the studied samples is 0.62–1.05%. Then, vacuum imbibition experiments were conducted on shale samples using water and n-dodecane. The accurate volumes of water in organic pores, oil in inorganic pores and organic pores, and the volume of dissolved oil were determined from vacuum imbibition experiments. The effects of Ro on shale storage were analyzed. Furthermore, novel mathematical models of oil and water vacuum imbibition in shale were proposed. The water imbibition in inorganic pores is a capillary flow. The oil imbibition in shale includes capillary flow in pore structures and diffusion in kerogen. The pore-kerogen double diffuse layer (PKDDL) physical model was proposed for the mechanisms of the hydrocarbon mass transfer between pore structures and kerogen. The capillary pressure and the dissolution rate constants were obtained by matching mathematical models with experimental results. This study provides new methods to evaluate the water and oil storage and transfer in organic-rich shale and advances the crucial mechanisms for the evaluation and development of shale reservoirs.

Effect of Drying on the Rehydration Properties of Some Selected Shellfish

This study was conducted to evaluate the effect of oven drying on the proximate composition and rehydration characteristics of shellfish. Shellfish studied included rough and smooth periwinkle, oyster and whelk. Proximate composition of the fresh samples were determined. Then dried in the oven to a moisture content of 10% and further rehydrated with distill water in sample water ratio of 1:40 and allowed to equilibrate. Proximate composition of the fresh shellfish showed that moisture content ranged from 82.38 to 69.24% with fresh smooth periwinkle having the highest moisture value while whelk had the lowest. The results also showed that whelk had the highest values for ash (2.92%), crude protein (18.83%) and crude fibre (3.71%) when compared to other samples. On rehydration, a moisture loss of 11.75%, 13.28%, 19.24% and 22.04% were observed for rough periwinkle, smooth periwinkle, oyster and whelk, respectively. The results for rehydration indices revealed that dehydration ratio was significantly (p<0.05) high for whelk (1.44), followed by oyster (1.29), rough periwinkle (1.23) and lastly, smooth periwinkle 1.20. Rehydration ratio of whelk (1.47) was equally significantly higher, followed by oyster (1.33) and the least were rough and smooth periwinkle (1.17). For coefficient of reconstitution, oyster recorded the highest value of 1.03, followed by whelk 1.02, rough periwinkle 0.95 and smooth periwinkle 0.98. Rate of water imbibition revealed a sharp increase in the water content of smooth periwinkle up to 240 min and thereafter, it slowed down until equilibrium was reached. In terms of rough periwinkle, oyster and whelk; water imbibition took place with rehydration time up to 300 min, 210 min and 270 min, respectively, thereafter they slowed down. The results have demonstrated that the rate in which oven drying affect the physical and nutritional qualities of shellfish differs.