Permeability Oil Research Articles

Experimental and simulation investigations of cyclic water injection in low-permeability reservoir

Many studies have been carried out to investigate the cyclic water injection (CWI) in enhancing oil recovery, while most of the target reservoirs are conventional, and the study for CWI in application to ultralow permeability reservoir is limited. In this study, a combination of experiment and numerical simulation was used to evaluate the performances of CWI in ultralow permeability reservoir. The results indicate that short pressurizing period but long depressurizing period gives the low possibility of water breakthrough and sufficient time for oil/water exchanging and redistribution, which achieves better oil recovery efficiency. In addition, high pressurizing pressure is a good compensation to the reservoir energy, and pushes the water into the far region to displace more oil. The optimized operation parameters for the core-scale experiments are further evaluated with numerical simulation of a realistic ultralow permeability reservoir located in Ordos basin, China, and consistent results between experiment and simulation are found. In the simulation, the optimal injection period and injection pressure during the pressurizing cycle are 20 days and 14 MPa, respectively; the optimal injection period and injection pressure during the depressurizing cycle are 60 days and 2 MPa, respectively. Good field response has been achieved after the implementation of the optimized parameters. This work, for the first time, systematically studies the performances of CWI technique in application to ultralow permeability reservoirs both at core scale and reservoir scale, and it provides theoretical and practical implications for enhancing oil recovery in similar types of ultralow permeability oil reservoirs.

Lysozyme-based composite membranes and their potential application for active packaging

Barrier packaging materials are significant in protecting the packaged contents from damage caused by oxygen, fogging, fats and oils in the environment. In this study, an active barrier packaging composite based on lysozyme and plastic films including polyethylene (PE) and biaxially oriented polypropylene (BOPP) were designed. The barrier packaging composites were prepared using a layer-by-layer self-assembly process to deposit lysozyme onto the surface of the plastic films. The bulk structure and morphology of the composites were investigated using X-ray photoelectron spectroscopy and atomic force microscopy. The barrier properties of the packaging composites were analyzed by measuring water vapor permeability, oil permeability, oxygen permeability, light transmittance and chromaticity. The results showed that the lysozyme coating greatly reduced the water vapor permeability, oxygen permeability and oil permeability of the packaging without affecting the appearance of the original packaging films. The barrier properties of the packaging composites were strengthened by increasing the number of coated lysozyme layers. The composite films showed effective antibacterial activity against E. coli and S. aureus during a pasteurized milk storage experiment, indicating a promising application prospect.

Digital imaging of the oil permeation mechanism in an oleophobic textile

Resistance of military clothing to oil permeation is important for effective protection against chemical warfare. In this paper, while a military textile is rendered oleophobic (oil contact angle ≈ 120°) through plasma-assisted deposition of perfluorodecyl acrylate (PFAC8), permeation of the textile by silicon oil is observed. Using high-definition digital imaging, we study the oil permeation dynamics, rationalize the permeation with a plausible mechanism and identify the threshold textile pore size for prevention of the permeation. We find that oil permeates defects of PFAC8 textiles. Our data suggests a linear variation for oil permeation volume ΔV with time t and implies a gravity-driving permeation mechanism. The mechanism comprises three stages involving merging and propagation of oil–yarn contact lines. The threshold pore size dm scales with σ/ P, where σ is the oil surface tension and P is the hydrostatic head exerted by the oil drop. The paper indicates the importance of an undamaged textile structure to ‘robust’ oil resistance.

Laboratory Study of Residual Oil Mobilization by Induce Vibration in Porous Media

The evolution of techniques required to mobilize reservoir fluids at critical saturation is important because of global petroleum needs because of the necessity to conserve the underground water that deteriorated because of the slowness of persistent organic pollutants’ dismantling. The acoustic waves of low-frequency are one of these methods, but the absence of understanding of the vibration effect to displace Oil prevents vibration application in the field until recently. This paper proves that oil permeability increased when the vibration induced in porous media; vibration makes resorting to the rock grains, which stimulates passage for liquid moving through the reservoir. The capillary pressure and reservoir pressure should be taken into consideration to make optimum validation for vibration stimulation.

Study of the oil geopermeation patterns: A case study of ANSYS CFX software application for computer modeling

Mathematical simulation of oil permeation through the porous media is the crucial topical problem in the framework of localization and liquidation of emergency oil spills. The main objective of this study was to establish the oil contamination level and oil contamination depth for different soil types which is of particular relevance from the standpoint of environmental safety. Four types of soils were taken for investigation as follows Cambisol with sand texture (No. 1), Luvisol (gray forest), with loamy sand texture (No. 2), Black Typical Chernozem with sandy loam texture (No. 3), Kastanozem (pine forest terrace under the pines) with sand texture (No. 4). The task of predicting the temporal-spatial indicators of oil permeation in the soil during accidental spills was solved using ANSYS CFX software allowing to simulate the absorption amount of oil into the ground. Visualization of oil concentration and velocity for studied soil samples was carried out. Determination of petroleum hydrocarbons concentration by the gravimetric method indicated a direct correlation between oil content in the soil and the porosity of the investigated soil samples. In order to determine the rate of hydrocarbon permeation through the dry and wet soil layer comparative experiments were carried out for the following systems: oil – dry soil and oil – wet soil. Permeation coefficients for dry samples from No. 1 to No. 4 were set at the rate 0.0073 m ∙ day−1, 0.0077 m ∙ day−1, 0.0083 m ∙ day−1, 0.0067 m ∙ day−1 respectively, and for wet soils 0.0083 m ∙ day−1, 0.0093 m ∙ day−1, 0.0093 m ∙ day−1, 0.0083 m ∙ day−1 consequently. The obtained hydrocarbon permeation coefficients for different systems allow calculating the depth of oil penetration for a given time after the spill, taking into account soil moisture. The dependence of oil concentration and permeation rate distribution through the soil fully reflects reliability of the experimental data, thereby confirming the verification of the adequacy of the computer model based on the ANSYS CFX software.

Application dispersed particle gels as in-situ fluid diversion agent

From year to year, the number of fields in late stages of development is increasing, which is inevitably accompanied by a decrease in oil production rates and an increase in the volume of produced water. One of the most effective technologies for dealing with this problem is the application of flow diverting technologies. The paper presents the synthesis of the dispersed-gel particles (DPG) for modifying the injectivity profile of the well, the displacement front and diverting the filtration flows in the reservoir. A series of experiments were carried out to determine the particle size distribution, resistance factor of the proposed composition, both on sandpack models and on core samples was studied. The use of the DPG composition allows the injection of the solution into the formation without a significant increase in the injection pressure, which was confirmed by the low values of the resistance factor. The composition possesses selectivity of isolation effect, which is proved by more significant decrease of relative water permeability than relative oil permeability. The selectivity of the action provides a significant reduction in the water cut of the production well. Thus, DPG can serve as an effective tool to divert the filtration flows in the reservoir, blocking the highly permeable areas and channels in heterogeneous reservoirs.

Geochemical reactions and their influence on petrophysical properties of ultra-low permeability oil reservoirs during water and CO2 flooding

Complex geochemical reactions can occur during the water and CO2 flooding for improved oil recovery, influencing the reservoir porosity and permeability, especially for low-permeability reservoirs. Core flooding experiments can be adopted to assess this effect, but it usually takes months or even years to accomplish. In this study, scaling and geochemical reaction experiments were firstly conducted to investigate the precipitation and dissolution of the main minerals induced by water and CO2 injection, based on a typical low-permeability oil reservoir in Xinjiang Oilfield China. Secondly, reactive flow simulation models were then established, based on the experimental data, to evaluate the influence of the geochemical reactions on the porosity and permeability in the reservoir. The experimental results show that the injection water can result in severe mineral precipitation after it mixes with the original formation water, while the injected CO2 can acidize the formation water and result in the dissolution of some minerals (e.g. calcite and silicate) and precipitation of dolomite, which can change the composition of the formation water. The simulation results show that severe carbonate precipitation can occur near the injection well, resulting in a decrease in porosity and permeability after 10 years of water injection. However, the change of rock minerals induced by CO2 injection can cause a slight increase in porosity and permeability near the injector, which benefits the injection of ultra-low permeability reservoirs. Therefore, CO2 flooding is recommended for improved oil recovery.

The influence of interfacial tension on rejection and permeation of the oil droplets through a slit pore membrane

The study investigates the influence of interfacial tension between oil and water on permeation and rejection of oil drops during produced water treatment using a slotted pore metallic membrane. It was found experimentally and analytically that rejection and permeation of oil drops through the membrane had a direct relation with the interfacial tension between oil and water. Oil/water emulsions with a wide range of interfacial tension (4, 9, 15, 30, 35 40 and 47 mN/m) were tested experimentally and analytically and a comprehensive set of data is presented. Higher the interfacial tension between oil and water phases provided a better rejection and lower permeation through the slits of the membrane. In a slit structured pore membrane, the oil drops were assumed to be passing through slots by the drag force generated by the flow of the fluid passing around the drops. The drag force push and distorte the spherical shape of the deforming oil drops. On the other hand, the force that is referred as the static force tries to restore the spherical shape of the drops and plays an important role in the rejection of drops. The static force and the interfacial tension are directly associated with each other. The drag force and the static force counter each other at every stage. Higher the drag force than the static force causes permeation of the drops, while, in case of higher static force than the drag force, rejection of drops was dominant. Experimentally higher rejection was achieved with the highest interfacial tension system.

A novel model for oil recovery estimate in heterogeneous low-permeability and tight reservoirs with pseudo threshold pressure gradient

Pseudo threshold pressure gradient (PTPG) is one of the main factors affecting the oil recovery of heterogeneous low-permeability and tight reservoirs. When the pressure gradient between the supply boundary and the bottom hole is less than PTPG, the crude oil in the formation cannot flow. In order to accurately measure the relationship between PTPG and permeability, a novel experimental device has been designed and a series of core flooding experiments using brine and oil have been carried out. The new experimental device eliminates the influence of rubber sleeve in core holder and core end-effect on the results, and greatly improves the accuracy of pressure measurement. The experimental results show the PTPG has a power function relationship with permeability, and has no obvious relationship with the viscosity of the fluid. Based on the equation for PTPG and permeability of crude oil and brine fitted by the experimental data, a new heterogeneous reservoir mathematical model considering PTPG were established. The influence of the coefficient of permeability variation, average permeability, and the production rate on oil recovery factor have been studied by this model. The results clearly show that the coefficient of permeability variation has the greatest influence on oil recovery factor, which represents inhomogeneity in low-permeability and tight reservoirs. Also, when the coefficient of permeability variation is less than a certain value (about 0.2 when average permeability is 1mD, in our model), there is only a slight decline in oil recovery factor, and when coefficient of permeability variation is larger than this value, the oil recovery factor decreases rapidly. The finding is consistent with oil field production and helpful to determine whether to take EOR(enhanced oil recovery) measures for a low-permeability heterogeneous reservoirs.

Study on EOR method in high water cut stage of low permeability A Oilfield

By using coring, logging, testing data and dynamic data of oil and water wells, the geological recognition, drive system evaluation and remaining oil research after infilling adjustment of different well patterns are carried out, the dominant channel of water drive and the existing position of remaining oil in different well pattern periods. It can be used for reference to improve development effect and oil recovery of other low permeability oilfields in high water cut stage A Oilfield is a typical low-permeability oilfield, which has the characteristics of poor physical properties, start-up fracture gradient and natural fracture development. After more than 30 years of waterflooding development, the oilfield has achieved good development results through multiple rounds of comprehensive adjustment of water injection wells and oil well measures. But at present, the oil field has entered the high water cut stage, the remaining oil is more scattered, the effect of adjustment means is poor, and the oil recovery rate is reduced, so it is necessary to explore the technical methods to improve the development effect and further enhance the oil recovery. In this paper, the recovery of oil field is evaluated by using the results of indoor core, empirical formula method and reservoir engineering method, and the potential of readjustment of oil field is clarified. Secondly, the reservoir geological recognition and multi-disciplinary remaining oil recognition are carried out, the dominant channel of water drive is identified, the type, existing position and formation reason of remaining oil are clarified, and the comprehensive treatment countermeasures based on the corresponding adjustment and plugging at both ends of oil and water wells are put forward; the application means of periodic water injection is developed, and the cooperation with deep water adjustment and flooding is explored, so as to further expand the affected volume, Methods of EOR. The typical application well area effect has been obviously improved, which provides reference for other low permeability oil fields to improve development effect and enhance oil recovery.

In-situ characterization of nonlinear flow behavior of fluid in ultra-low permeability oil reservoirs

Correlating velocity-gradient relation is crucial for understanding flow behavior of fluid in low-permeability oil reservoirs. Instead of experimental approaches, this paper utilized downhole pressure data analysis for in-situ characterization of nonlinear flow behavior at low velocity. We introduced a dynamic permeability concept, which connects flow equation and nonlinear flow behavior. We then employed pseudo-linear function, piecewise function and continuous function to characterize the nonlinear flow behavior. The transient pressure type curves response ascended in the late-time flow period with consideration of nonlinear flow effect, suggesting that nonlinear flow equations can affect the characteristic of the type curves. The coefficients of approximation function are considered to be model parameters and are determined by downhole pressure analysis. Through our workflow, we can obtain a velocity-gradient relation, describing the nonlinear flow behavior of in-situ fluid. The practicality and efficiency of our new method are illustrated by comprehensive case studies. The in-situ flow behavior in reservoir scale can be characterized by normalizing multiple velocity-gradient curves derived from individual well analysis. Compared with core-flooding experiments, the proposed method is more convenient and economic to characterize flow behaviors in low-permeability oil reservoirs.

A Game Changer in Scale-Squeeze Technology

Background Field trials using a new scale-inhibitor technology that improves treatment lifetime of scale squeezes have been successfully performed in the Gulf of Mexico. Tomson Technologies, in partnership with Shell, developed proprietary nanoparticle carriers that enhance scale-inhibitor adsorption to the reservoir and control the return rate for extended periods of time. This technology results in less chemical bleed off in the initial flowback and increases the chemical retained in the reservoir, allowing for more effective squeeze treatments. Both nanoparticle-enabled phosphonate and polymer inhibitors have now been developed and successfully squeezed in the field. Phosphonate inhibitors are widely used for squeeze treatment due to their desirable adsorption and release properties in carbonate and sandstone reservoirs. Minor changes have been made to the chemistry, but overall, the fundamentals have remained unchanged for decades. Polymeric scale inhibitors have also been developed for cases in which phosphonates are not applicable. The nano-enhanced technology provides a large improvement of treatment lifetime of 2 to 4 times (200-400%) when compared to incumbents, making this technology advancement attractive even in cases where current squeezes are considered successful. The well selected for this case study is an offshore formation with a predominantly sandstone mineralogy (approximately 80% quartz) with 25-30% porosity and bottomhole temperature of 183°F (83°C). Technology From the Lab to Field A sandpack sample from the trial well was used in the laboratory to deter-mine the adsorption and desorption properties of the nano-enabled inhibitor in realistic rock conditions. Multiple conditioning steps were used before product was injected in a sequence that mimicked field squeeze treatments. Mass-balance results from the sandpack experiment show adsorption of approximately 8 mg of polymer retained per gram of crushed reservoir rock used in the experiment. A typical rule of thumb for phosphonate-scale inhibitors (only as a comparison since this is a polymeric scale inhibitor) is 1-2 mg of inhibitor retained per gram of rock. Therefore, this is considered a large improvement on adsorption. There are challenges associated with measuring polymers in brine as residuals; however, multiple methods, both in-house and external, were com-pared to ensure accuracy. The results using the nano-enhanced scale inhibitor show concentrations higher than 1 mg/L of active polymer for over 7,000 pore volume of return in the sandpack experiment. Complete intact core experiments were also conducted with reservoir fluids and showed no formation damage during the injection of the product with regained oil permeability of 96%. Oil permeability was in the 150-200 mD range for the intact core experiments. Third-party coreflood testing was performed with nitrified and foamed stages to ensure compatibility with the nano-enabled chemistry. No formation damage was observed with the nitrification of the stages containing the nano-enabled chemistry. Field Application Case Study After extensive lab validation of the product and supporting corefloods to de-risk the technology, Well A was selected by Shell to be the first well treated with the new nano-enabled extended-lifetime inhibitor.

Research and application of asynchronous injection-production in ultra-low permeability horizontal well area

When using horizontal wells to exploit ultra-low permeability oil fields, the development effect is usually ensured by increasing the scale of fracturing reconstruction. However, it also leads to the increasing difference of seepage capacity between matrix and fracture, which makes it easier to see water in horizontal wells after water injection and difficult to recover after water cut rises. Therefore, asynchronous injection-production test was carried out in the ultra-low permeability horizontal well area, making full use of the artificial fracture of horizontal well as the high permeability channel, and performing oil-water replacement through full imbibition between high and low permeability layers, so as to improve oil recovery. On the basis of theoretical guidance, during the summary of practice, the main factors affecting the implementation effect of asynchronous injection and production are gradually analyzed, and the reasonable parameters in the implementation process are clearly defined, so as to explore a new treatment method for the middle and high water cut stage in the ultra-low permeability horizontal well area.

Analysis of large scale fracturing effect and influencing factors in low permeability oil reservoir

H Oilfield is a complex fault field. Due to poor physical properties, it is still difficult to effectively inject wells after fracturing. In addition, the repeated fracturing effect has deteriorated year by year. Most of the blocks are generally low in production, and the oil recovery speed is less than 0.31 %. Since 2014, large-scale fracturing field tests have been carried out in H Oilfield. By analyzing the influence of various factors on fracturing effect, the grey correlation method was used to analyze the influence of various factors on oil production after fracturing. The results showed that the main factors influencing the fracturing effect in the test area were formation coefficient, porosity, oil saturation, amount of sand carrying fluid, amount of fracturing fluid, and amount of sand added. The research results can be used for reference and guidance to improve the development level of low-permeability oil fields.

Studying the effect of carbon dioxide oil solubility on asphaltene aggregation under conditions of the Bashkortostan Republic fields

The purpose of this work is to study the effect of carbon dioxide oil solubility on the aggregation of asphaltene associates and decrease of oil permeability of sandstones. Consideration is given to the interaction variants of oil and carbon dioxide in a free volume before being injected into a porous medium and immediately in the porous medium. The influence of oil composition on the aggregation of asphaltene associates is studied. The effect of the dissolved carbon dioxide on associate dispersion in oil is examined through oil filtering in sandstones. If asphaltene aggregation occurs in a porous medium it causes pore plugging leading to reduced permeability, complicates the development of carbon dioxide injection wells and, as a result, prevents from achieving the planned indicators of oil production and oil recovery. It is found that in the case when oil interacts with carbon dioxide in the free volume before being injected into a porous medium, the increase in the volume of filtered oil and the concentration of carbon dioxide dissolved in oil, and decrease in sandstone permeability reduce the relative mobility of oil with the dissolved carbon dioxide. The significant influence of sandstone permeability on the experimental results indicates that the sizes of asphaltene aggregates are comparable to the sizes of small pores. We have not observed complete attenuation of filtration after passing of oil with dissolved carbon dioxide through sandstones. Based on the analysis of changes in oil composition and properties carried out in the laboratory experiments on oil displacement by carbon dioxide rims, it has been determined that aggregation of asphaltene associates takes place under immediate contact of oil and carbon dioxide in a porous medium. The higher the asphaltene content in oil, the lower the formation permeability, whereas tight formations feature a more significant decrease in permeability.

Mechanisms on the Injection Conformance Reversion during Polymer Flooding of Offshore Heterogeneous Heavy-Oil Reservoirs

Injection conformance reversion commonly observed during polymer flooding in offshore heterogeneous heavy-oil reservoirs weakens the volumetric sweep of polymer solution and compromises its EOR results. To investigate its mechanisms and impact factors, one mathematical model to predicate injection conformance behavior is constructed for heterogeneous reservoirs based on the Buckley-Leverett function. The different suction capability of each layer to polymer solution results in distinct change law of the flow resistance force, which in turn reacts upon the suction capability and creates dynamic redistribution of injection between layers. Conformance reversion takes place when the variation ratio of flow resistance force of different layers tends to be the same. The peak value and scope of conformance reversion decrease and reversion timing is advanced as oil viscosity or permeability contrast increases, or polymer concentration or relative thickness of low permeable layer decreases, which compromises the ability of polymer flooding to improve the volumetric sweep and lower suction of the low permeable layer. The features of offshore polymer flooding tend to make the injection conformance V-type and create low-efficiency circulation of polymer in a high permeable layer more easily. These results can provide guidance to improve the production performance of polymer flooding in offshore heterogeneous heavy-oil reservoirs.

Effect of Displacement Pressure on Oil-Water Relative Permeability for Extra-Low-Permeability Reservoirs.

The oil–water relative permeability is an important parameter to characterize the seepage law of fluid in extra-low-permeability reservoirs, and it is of vital significance for the prediction and evaluation of the production. The pore throat size of extra-low-permeability reservoirs is relatively small, and the threshold pressure gradient and capillary pressure cannot be negligible. In this study, the oil–water relative permeability experiments with three different displacement pressures were carried out on the same core from the extra-low-permeability reservoir of Chang 4+5 formation in Ordos basin by the unsteady experimental method. The results show that the relative permeability of oil increases, while the relative permeability of water remains unchanged considering the capillary pressure and oil threshold pressure gradient compared with the JBN method. As the displacement pressure enlarges, the relative permeability of oil and water both increases; the residual oil saturation decreases, therefore the range of the two-phase flow zone is improved. Moreover, the isotonic point of water–oil relative permeability curves moves to the upper right region, and the reference permeability improves as well with the increasing pressure.

Study of a low-damage efficient-imbibition fracturing fluid without flowback used for low-pressure tight reservoirs

The oil production from the low-pressure tight reservoirs in China decreases sharply after fracturing under natural depletion. To supply the formation energy and displace oil through imbibition instead of flowback, a novel nanoparticle-enhanced supramolecular fracturing fluid (NESF) was developed. It consisted of 0.10 wt% hydrophobically modified hydroxypropyl guar (HMHPG), 1.00 wt% synthesized hydrophilic gemini surfactant (HGS), and 0.05 wt% hydrophobically fumed nanosilica (HNS). A series of experiments were conducted to characterize the molecular structure of HGS and evaluate the heat/shear resistance, rheological property, proppant suspension and transportation, formation damage, and imbibition efficiency of NESF. Finally, the oilfield practical application of NESF fracturing without flowback was carried out. The results showed that the heat resistance and the interfacial property of NESF were improved by HNS and HGS respectively. Besides the favorable common properties, a low oil permeability loss rate of 9.40%, a high fracture conductivity retainment rate of 95.11%, and a high imbibition recovery factor of 19.43% were realized by NESF. The accumulative oil production of the well stimulated by NESF without flowback was increased by 13.55% and the decline rate of oil production was reduced from 14.70% to 5.22% in the first 6 months.

Recovery Method and Parameter Optimization of a Pilot Test for Conformance Control Flooding and Thermal Recovery in the Offshore Heavy Oilfield

NB35-2 oilfield is a typical offshore sandstone reservoir with viscous crude oil and high permeability. Due to the inherent severe heterogeneity, the efficiency of conventional water flooding is pretty low and usually accompanied with early water breakthrough. In order to recover the residual oil and better realize its potential, applications of enhanced oil recovery (EOR) technology are necessary. However, the selection of EOR method and related parameters may directly impact the final results and can be noticeably different for different reservoirs; therefore, to optimize the oil production rate and final oil recovery, systematical optimization of every detail based on the condition of a specific reservoir is of key importance. In this paper, physical simulations were first conducted to select the best recovery methods for the target area based on the static geophysical model under the guidance of reservoir engineering theory. Then, detailed development variants for each method were determined by numerical simulation with the support of data obtained from previous pilot tests (polymer gel flooding and thermal fluid huff and puff) conducted in this area. Three exploitation methods were developed for the target well group, including polymer gel flooding (conformance control, Pattern 1), steam huff and puff (thermal recovery method, Pattern 2), and a combination of polymer gel flooding and steam huff and puff (conformance control and thermal recovery, Pattern 3). The numerical simulation result also showed that Pattern 3 yielded the highest oil recovery. Moreover, the amount of additional oil being recovered by applying Pattern 3 was even higher than the total additional oil being extracted by Patterns 1 and 2. In addition, sensitivity analysis was conducted to rank the most important parameters based on the three Patterns. At last, it is thought that the synergistic effect between conformance control and thermal recovery made more oil recovered, which was intuitively clarified in the mechanism analysis.

Brief descriptions of the principles of prominent methods used to study the penetration of materials into human hair and a review of examples of their use.

Consumers are attracted to the latest fashion trends and different looks. This drives the search for novel hair treatments. Some chemicals present in hair treatment products can penetrate the hair shaft. These materials can either nourish or injure the hair cortex. Different techniques have been used to investigate the mechanism of molecule penetration and the conditions under which penetration occurs. This article reviews the techniques applied for this purpose. Various microscopy techniques are used to capture clear and colourful images to determine the diffusion pathways and the exact location of the molecules under study. However, the laborious sample preparation often leads to sample destruction since cross-sectioning is often required. While various other techniques have been successfully used for investigating the penetration methods, most of these require different amounts of work to be put in for sample preparation and instrumentation. Several spectroscopic techniques have been used to study the penetration of the molecules because of the high levels of accuracy and the quick response time of these techniques. Moreover, the samples are not damaged during the investigation.