Water Saturation Coefficient Research Articles

An integrated approach to the substantiation of the boundary values and the assessment of the character of saturation in the deposits of the Tyumen formation

Background. The Tyumen formation is characterized by the complexity of the structure of deposits and consists of the sediments of different facies groups. To build hydrodynamic models, improve the development system and identify prospective zones, the conditions of sedimentation must be taken into account. Objective. Increasing the reliability of reservoir permeability assessment and clarifying critical resistivities when assessing the nature of saturation, which requires new approaches to petrophysical modeling. Materials and methods. The work uses the results of core studies and interpretation of well-logging data for the JV2 formation considering the facies. Results. The wettability of extracted and nonextracted samples is studied, the dependence of the saturation parameter on the water saturation coefficient is corrected taking into account the wettability of reservoirs, and the relative phase permeabilities are calculated for drainage conditions in the “oil–water” system. Conclusions. An integrated approach makes it possible to clarify the values of permeability, critical resistivities and oil and gas saturation of reservoirs, which can be used to identify prospecting zones when drilling new wells.

Relationship between consistency and compaction of clay soils (Saint-Petersburg)

Clay soils are often found under building foundations, construction properties of which depend on many factors. One of them is the natural soil compaction, which is relevant in the construction classification of soils. This paper analyzes the relationship between the consistency and compaction of clay soils of different genesis and consistency using the Priklonskii soil compaction index. Water saturation of clay soil affects the relative discrepancy between the consistency coefficient and compaction index for soils of different genesis and consistency. It is noted that for soils with the water saturation coefficient lower than one, the consistency coefficient differs from the compaction index. This difference increases with decreasing water saturation coefficient. It is essential that significant differences can also appear when the water saturation coefficient is equal to 0.95 or more, approaching to unity. It is shown that the assessment of the natural compaction of clay soils should be based on their formation conditions. A study of various genetic types of clay soils affecting natural densification and consistency provides a reasonable approach to use of soil densification in the construction classification of soils.

Capillary model – complex geological and petrophysical representation of the deposit when calculating geological reserves of hydrocarbons

The basis for solving almost all geological problems are models, which are a reflection of the structure of deposits. This places high demands on the detail and accuracy of the models. One of the most important parameters in the calculation of reserves is the oil saturation factor, observed in most cases using Dakhnov-Archie models. Despite the widespread use of this technique, it has a number of significant limitations. An alternative way to assess oil saturation in this case is to use a capillary model obtained from the results of capillary measurements of the core. The capillary model is a continuous multidimensional function of the dependence of the water saturation coefficient on the free water level, porosity and permeability. A well-compiled capillary model is a reflection of the geological model of the reservoir – with information about the water saturation of the reservoirs by the altitude of the structure, the levels of fluid contacts, fluid densities, surface and reservoir properties. This paper discusses the capabilities of capillary models, which are widely used in three-dimensional modeling of the degree of saturation of the interwell space, the calculation of the volume of oil-saturated rocks, geological reserves of hydrocarbons, as well as dynamic characteristics in the construction of hydrodynamic models.

Weakening Effect of Water on Mechanical Properties of Brittle Shale under Triaxial Compression

Abstract The mechanical properties of rock materials are remarkably affected by water. To reveal the effect of water on the mechanical properties of shale, the conventional triaxial compression tests were implemented for shale with the five kinds of water saturation coefficient. According to the test results, the influence of the saturation coefficient on strength and deformation parameters was analyzed. Based on the fitting result of the Mohr-Coulomb criterion, the relationship between the strength parameters and the water saturation coefficient was analyzed. The softening effect of water on shale is mainly due to the decrease of cohesion and internal friction coefficient with increasing of water saturation coefficient. The strength criterion considering the influence of water weakening was established according to the function relationship between the fitting parameters and the water saturation coefficient. In addition, three kinds of brittleness indexes were selected to quantitatively analyze the influence of the saturation coefficient on shale brittleness. The results indicated that the brittleness indexes all decreased with the increase of the saturation coefficient, and the brittleness of shale is weakened after water absorption. The research results can provide a reference for the evaluation of saturated shale brittleness.

Assessment of the quality reservoirs for some deposits of the Baku Archipelago

The article discusses methods for assessing the quality of reservoirs using core data and geophysical methods of well surveys. Identifying the presence (or absence) of relationships between the analyzed parameters, a comparison between the parameters characterizing the filtration capacity of reservoir rocks was made with their lithological composition, water saturation coefficient, porosity, and content of carbonate material. On the example of data from some fields in the northern part of the Baku archipelago, an improved method for assessing permeability was applied and the quality of reservoirs was assessed based on data from borehole geophysics. Keywords: reservoir; core; porosity; permeability; logging; quality of reservoir rocks.

Special considerations of determining the gas saturation factor of reservoir rocks of Dnieper-Donets depression gas fields on the basis of petrophysical studies

Introduction. The gas saturation coefficient is one of the most important parameters for calculating gas reserves. The parameter can be determined by laboratory petrophysical methods applying the residual water saturation coefficient. The latter, in turn, is determined by direct or indirect methods. The direct method is used extremely rarely, while indirect methods are very common - primarily the methods of a semipermeable membrane and centrifugation. The first method is considered the most reliable. Formulation of the problem. When applying the semi-permeable membrane method, the issue of setting the maximum displacement pressure is the key factor that determines the result, as it determines the value of the residual water saturation, and, consequently, the value of the gas saturation coefficient of the reservoir. There are numerous cases when the results of laboratory studies of residual water, and hence the gas saturation coefficient, are clearly discordant with the whole set of geophysical and geological data. This problem is possibly caused by the wrong choice of the laboratory research modes, and specifically, the maximum pressure that is created in the course of the experiment. The research objective is to analyze the ways of setting the maximum water displacement pressures during the experiment in terms of the most reasonable, basic method of a semipermeable membrane; to evaluate their applicability taking into account the best practices and propose their optimal combination for practical work. Previous research. The paper considers various approaches to setting the maximum pressure, including an attempt to model the process of deposit formation, achieving irreducible water saturation, an express method using a centrifuge, determining water-holding capacity, limiting pressures by the size of filter pores, and calculating pressures on the basis of the deposit height. Main material. Two approaches have been distinguished from the considered ones: calculation of the maximum pressure on the basis of the deposit height and calculation on the basis of the maximum pore radius, at which a meniscus can be formed. It is shown that it is rational to combine these two approaches into one, which will allow obtaining more reliable values of the residual water saturation, and hence the gas saturation coefficient. The ultimate maximum displacement pressure for the semi-permeable membrane method, which should be created during the experiment, has been determined. The limiting height of the deposit has also been determined. Any calculation above this parameter does not make sense. The discrepancies between theoretical calculations and actually observed heights of capillary rise and the influence of the layered structure of the reservoir have also been considered. The area of possible practical application of the method has been determined. It is noted that extensive knowledge of the reservoir geometry is crucial for the practical application of the method. Besides, the data on the deposit height should be included in the research proposal. Practical value. The application of the method of calculating the maximum displacement pressure on the basis of the deposit height, taking into account the restrictions on the maximum pore diameters, at which a meniscus can be formed, will certainly increase the reliability of gas reserves calculations in the gas fields of Ukraine.

Two-dimensional numerical simulation of spontaneous potential logging data with account to clay content of a reservoir by finite element method

Spontaneous polarization potential (SP) logging remains one of the most widely used geophysical methods of borehole investigation. However, for a long time its interpretation was based on empirical dependences and analytical solutions in simplified formulations. At present the development of the method is associated with the development of new approaches to numerical modeling and quantitative interpretation of SP logging data. Application of numerical algorithms makes it possible to considerably increase information content and resolution of SP method. Nevertheless, most of the currently proposed approaches rely on a simplified description of SP signal formation, which may lead to errors in data interpretation for complex reservoir intervals. In this work, we propose an algorithm for numerical simulation of SP logging data as applied to the study of clayed fluid-saturated reservoirs. The physical and mathematical model of SP signal formation in terms of coupled fluxes for the case of electrochemical SP source is considered. The software realization of the algorithm includes a two-dimensional numerical simulation of SP signals based on the application of the finite element method in the axially symmetric model of the geological medium. The character of SP signals for reservoirs of different thickness at four values of the reservoir water saturation coefficient is studied, as well as the dependence of the shape and amplitude of the SP anomaly in a water- and oil-saturated clayed reservoir on the content and type of clay mineral. The obtained results, aimed at the development of the SP method, improve the quality of SP diagrams interpretation for the study of clayed reservoirs.

Reliability of results of use of complex geophysical studies in the process of control of development of oil and gas deposits

The paper considers modern methods for determining the position of gas-liquid contacts in terrigenous deposits at oil and gas condensate fields in Ukraine. The results of laboratory studies of a representative core collection (87 samples) in the petrophysical laboratory of IFNTUOG made it possible to establish the reservoir parameters and lithological characteristics of reservoir rocks of Carboniferous and Neogene sediments, which made it possible to reliably estimate the reservoir parameters of productive formations. The results of well studies, in particular, obtained during the isolation of oil and gas-saturated reservoir rocks and monitoring the dynamics of changes in oil-water and gas-water contacts, made it possible to form an optimal informative complex of geophysical methods for effective prospecting and development of oil and gas fields. Direct studies of the identified reservoir rocks made it possible to establish that the geological sections of the Jurassic, Cretaceous and Neogene systems of prospecting areas are filled with both hydrophilic and hydrophobic lithotypes of rocks, which have different effects on the readings of electrical and radioactive methods. Reasonably, the maximum value of the electrical resistivity, the maximum oil saturation coefficient (Кo), as well as the minimum value of the water saturation coefficient (Кw), which is typical for oil and gas-saturated formations, must correspond to the condition for displaying these parameters in completely water-saturated rocks. In this case, the boundary of the transition zone will be displayed by the bottom of the maximum radio-saturated layer and the top of the aquifer in this rock. Confirmation of the above is seen from the fragments of geophysical data processing, electrical and neutron studies in the presence of low and high salinity, drilling fluids and drilling fluids. The analysis of the efficiency of using the methods of pulsed neutron-neutron logging (PNNL) and neutron gamma-ray logging (NGL) when monitoring the change in the position of the GLC to prevent watering of productive formations is carried out. According to the research results, it is proposed to use a complex of nuclear physical methods in the process of monitoring the dynamics of changes in NWC, in particular, neutron gamma logging, repeated neutron logging, as well as in the process of drilling conducting electrical methods of imaginary resistance and unauthorized potentials.

Development of a Methodological Approach to Identifying Petrophysical Types of Complicated Carbonate Rocks According to Laboratory Core Studies

Petrophysical typification of productive hydrocarbon deposits is one of the main stages of building a petrophysical model of a reservoir. For carbonate reservoirs characterized by a heterogeneous complex structure of the void space, the problem of identifying petrotypes is very relevant. An extensive literature review of existing methods of petrophysical typification showed that the most well-known and widely used of them were based on simple theoretical models of the structure of the void space of rocks, which did not allow a full description of complex carbonate deposits. Moreover, the petrotypes identified on the basis of these methods did not agree with the results of microdescription of thin sections. A new methodological approach to the identification of petrophysical types of complex carbonate rocks was proposed, based on the integration of the results of standard (determination of the absolute gas permeability and open porosity coefficients) and special (nuclear magnetic resonance studies) core studies and data obtained in the lithological description of thin sections. The developed approach took into account the main petrophysical properties of rocks that characterize its reservoir potential, as well as the structural features of the void space and the influence of secondary transformations. The proposed methodological approach was applied to distinguish petrophysical types in the section of the Assel-Sakmara deposits of the Yareyuskoye field: six petrotypes were identified and described in detail, combined into four zones (zone of development of healed fracturing, zone of development of leaching, zone of development of leaching and open fracturing, zone of development open fracturing), for each of them, individual dependences of the absolute gas permeability coefficient on the open porosity coefficient and the Leverett J-function on the water saturation coefficient were constructed. The information obtained would allow a differentiated approach to geological and hydrodynamic modeling of a hydrocarbon reservoir.

Ecogeomorphogenesis of the Nura river basin under conditions of changing climate and anthropogenic impact

The economic activity of human society is the main factor contributing to the development of the modern landscape. In order to preserve the high ecological quality of the human environment, protect nature and effectively use natural resources, it is necessary to comprehensively take into account and consider any (direct and indirect) man-made changes in the natural environment. That is why today the study of ecogeomorphogenesis in a changing climate and anthropogenic impact is more urgent than ever and the primary task for the preservation of the environment in a supportive state. In this regard, the purpose of this work was to consider the situation of ecogeomorphogenesis in the territory of the Nura River basin, i.e. to show the current state of assessment and accounting of anthropogenic impact for the disclosure of ecogeomorphogenesis of the river basin. The article considers the types of modern processes in the Nura River basin. The data on cartographic and textual material on the geology and morphology of the Nura River basin for the modern period of time were used as the research material, geographical and comparative methods were used. In this paper, the main characteristics and the current state of ecogeomorphogenesis of the Nura River basin are investigated. Based on the results of the study, engineering-geological complexes of rocks were identified based on a set of geological and genetic features, including porphyry-tuff-porphyry, limestone, conglomerate-sandstone-mudstone, mudstone- sandstone-siltstone-coal, clay-gypsum, loam-clay, sandy loam-loam, loam-clay-sand-gravel, mudstone-sand-gypsum and sand and gravel complexes. The current state of ecogeomorphogenesis of the Nura River basin suggests that the rocks have some modifications and deformations as a result of anthropo- genic impact and climate change, with the representation of such formations as effusive, carbonate in the group of rocks, upper terrigenous in the composition of semi-rock. Of the modern geological processes, physical weathering is widely developed. Weathered marls from the surface to the state of heavy loams (up to a depth of 0.5-6 m) have the following physical and mechanical characteristics: natural humidity 16.4-26.1%, porosity coefficient 0.48-0.82, water saturation coefficient 0.82-0.95, total moisture capacity 24.8-29.2, calculated resistance 3.5-4 kg/cm2. Key words: ecogeomorphogenesis, river basin, geology, geomorphology, geological and lithological features.

On the Incorporation of Pristine and Pre-vitrified Alkaline Battery Waste into Non-structural Clay Bricks

The purpose of this work was to explore the incorporation of black manganese oxide powder extracted from alkaline batteries into sintered-clay bricks. The black manganese oxide powder was added into the clay mixture in two different states: pristine and pre-vitrified. Three levels of addition were evaluated according to the final wt% of manganese in the bricks: 0.0, 0.1, and 2.5. The resulting test-bricks were then assessed to determine the following physical and mechanical properties: color change, water absorption, water saturation coefficient, compressive strength, and leaching/efflorescence tendency. The results were statistically tested for significance and compared to a standard industrial formulation for non-structural sintered-clay bricks used locally in Giron, Santander (Colombia). In general, the properties of the test-bricks deviated slightly from the standard formulation only when the final content of manganese in the test-bricks reached 2.5 wt%. In particular, the test-bricks with 2.5 wt% of manganese added in the pre-vitrified state, showed a darker brown color, 1.7 % less water absorption, and a 68 % increase on compressive strength, when compared to the industrial reference red-clay bricks. It is worth to point out that none of the test-bricks studied showed efflorescence tendency. In conclusion, the work proves that the Mn-oxides contained in spent alkaline batteries can be successfully incorporated into nonstructural red clay bricks. These findings would help to ease the adoption of novel circular economy strategies in developing countries with no access to metallurgical facilities for battery recycling.

Water Infusion on the Stability of Coal Specimen under Different Static Stress Conditions

Underground coal mines are frequently subjected to water infusion, resulting in many mining hazards. This study investigated the effect of water infusion on the stress and energy evolution characteristics of coal specimens representing isolated pillars under different initial axial stress conditions using the discrete element method. A water infusion distribution model was developed, in which random functions were employed to describe water distribution for the purpose of realizing the dispersion of results for a better reliability. Based on the results, a stress-level classification was presented to evaluate the water effect on pillars’ instability. For the investigated coal specimens, the water weakening effect on stress and energy remains stable when the axial geo-stress on pillars is less than 65% of uniaxial compressive strength (UCS). In contrast, when the axial stress coefficient is greater than 65%, pillars become unstable eventually. A higher axial stress coefficient is more likely to introduce a lower critical instability point of the water saturation coefficient for pillars in the process of water infusion. However, the instability point remains random to some extent for specimens following the same water distribution rule under the identical test condition. Two instability types, which also happened randomly, were observed in the numerical results for damaged coal specimens under different water saturation coefficients and axial geo-stresses, namely free-falling and step-falling.

Study on influence of two-phase filtration transformation on formation of zones of undeveloped oil reserves

In order to study the process of fluid filtration during flooding of an oil field, article uses Rapoport – Lis model of non-piston oil displacement by water. During plane-radial filtration in a homogeneous formation, radii of disturbance zones are determined with and without taking into account the end effect. Influence of changes in value of capillary pressure gradient on distribution of water saturation coefficient in the non-piston displacement zone for high and low permeability reservoirs is revealed. Application of an element model for a five-point injection and production well placement system showed that, using traditional flooding technology, flat-radial fluid filtration is transformed into rectilinear-parallel. At solving equation of water saturation, Barenblatt method of integral relations was used, which allows determining the transformation time. By solving the saturation equation for rectilinear-parallel filtration, change in the value of water saturation coefficient at bottomhole of production well for an unlimited and closed deposit is determined. It is shown that an increase in water cut coefficient of a production well is possible only for a closed formation. To determine coefficient of water saturation in a closed deposit, a differential equation with variable coefficients is obtained, an iterative solution method is proposed. In the element of the five-point system, oil-saturated zones not covered by development were identified. For channels of low filtration resistance, conditions for their location in horizontal and vertical planes are established. It is shown that, at maintaining formation pressure, there is an isobar line in formation, corresponding to initial formation pressure, location of which determines direction of fluid crossflow rates. Intensity of crossflows affects application efficiency of hydrodynamic, physical and chemical, thermal and other methods of enhanced oil recovery.

Deriving the Oil-Water Seepage Pressure Distribution from Two-Phase Oil-Water Flow Stress Gradient

The characteristics of oil-water two-phase flow in low-permeability reservoirs have been insufficiently studied. In the present article, we estimate the oil-water seepage parameters using a flow stress gradient model with a nonuniform radial distribution of the water saturation coefficient in a low-permeability reservoir. We apply the oil-water relative permeability curves and the Buckley-Leverett equation to determine the oil-water mobility ratio and the functional relationship between the two-phase flow stress gradient, the radial distribution, and the oil saturation. In this way, we construct an oil-water radial flow model based on the oil-water two-phase flow stress to derive the pressure distribution equation. Calculation results show that there is a linear relationship between the oil-water two-phase flow stress gradient and the oil saturation and a quadratic relationship between the oil-water two-phase mobility ratio and the oil saturation. The strata/ pressure distribution for low-permeability reservoirs is highly sensitive to the oil-water two-phase flow stress gradient, and the effect is more noticeable near the wellbore.

ЕЛЕКТРИЧНІ ПАРАМЕТРИ ПОРІД ВЕРХНЬОГО КАРБОНУ РУНОВЩИНСЬКОЇ ПЛОЩІ ДНІПРОВСЬКО-ДОНЕЦЬКОЇ ЗАПАДИНИ

The main objective of this article is to study electrical parameters of sandstones and argillites of the Upper Carbon rocks in the Runovshchynska area of the Dnieper-Donets basin. It has been determined that specific electrical resistivity of dry rock samples (specific electrical resistivity of rock matrix) varies from 44,802 kΩ·m to 6,115 МΩ·m (average 751,328 kΩ·m). Specific electrical resistivity of sandstones is 3,45 times more than argillitesdue to different shaliness of studied rocks. Specific electrical resistivity of saturated rocks samples varies from 0,54 Ω·m to 10,46 Ω·m (average 1,23 Ω·m). Specific electrical resistivity of argillites is 2,46 times more than sandstones because the latter had high content of reservoir water in their pores (sandstones had better conductivity). It has been determined that formation resistivity factor of sandstones in atmospheric conditions varies from 6,05 to 33,71 (argillites 11,8), and argillites – from 4,76 to 51,47 (average 17,4). Physical modelling of reservoir conditions (temperature t = 78,5°С, pressure p = 31–31,9 MPa, mineralization M= 170 g/l) showed that specific electrical resistivity varies from 0,3 Ω·m to 3,0 Ω·m (average 0,75 Ω·m). Sandstones in reservoir conditions had the range from 0,3 Ω·m to 2,3 Ω·m (average 0,7 Ω·m), and argillites – from 0,5 Ω·m to 3,0 Ω·m (average 1,2 Ω·m). In this case, specific electrical resistivity of argillites is 1,6 times more than sandstones. Due to the closure of microcracks and the deformation of the pore space, the electrical resistance of rocks increases with increasing pressure. The dependence of formation resistivity enlargement factor on pressure for the studied rocks is expressed by 2-order polynomials. The formation resistivity factor of the studied rocks in reservoir conditions has been determined. It was defined that sandstones in reservoir conditions had the range of the formation resistivity factor from 5,4 to 63,3 (average 20,3), and porosity coefficient – from 0,038 to 0,175 (average 0,113). The range of the formation resistivity factor for argillites was from 13,4 to 88,7 (average 34,3), and porosity coefficient – from 0,043 to 0,115 (average 0,086). Analysis of data of laboratory electrometric investigations has allowed establishing correlations between the porosity coefficient and formation resistivity factor. In addition, the correlation of electrical parameters of rocks in atmospheric and reservoir conditions and the formation resistivity enlargement factor from the water saturation coefficient, taking into account the lithological varieties of the studied rocks, was established.

On modeling of non-stationary two-phase filtration

Based on the basic mechanics equations of continuous medium, the author’s model of non-stationary two-phase oil filtration and water pumped into the reservoir was developed, based on the dependence of the water saturation coefficient on the pressure of water entering the reservoir. The substantiating for applying the proposed dependence was given. To solve the system of non-linear differential equations, the integral relations method was used, which allowed obtaining an approximate analytical solution of the water pressure disturbance distribution in the two-phase filtration area. The radius of the perturbation area (front of the displacement of oil by water) was defined, and the boundaries of the perturbation region were determined for the given boundary conditions at the bottom of the injection well. Examples allowing the quantify assessment the application of the model proposed by the authors were considered.

Effect of water and temperature on short-term and creep mechanical behaviors of coal measures mudstone

In the present study, a series of uniaxial compression tests and multistage creep tests were performed on specimens of coal measures mudstone with different water contents and at different temperatures using an electrohydraulic servo-controlled testing system (MTS816), a specially developed cantilever-type multiarm lever creep testing device and a thermostatic water tank. The effects of water and temperature on short-term strength, failure mode, and creep properties of the mudstone were systematically analyzed. The uniaxial compression test results showed that the presence of water has a significant effect on the mechanical strength and weakens the short-term mechanical properties of the mudstone specimens, whereas high temperatures can exacerbate this water-weakening effect. The uniaxial compressive strength of the specimens decreased exponentially, as the water saturation coefficient increased at room temperature, whereas the strength of saturated specimens decreased linearly with the increase in temperature. The multistage creep test results indicated that increases in the water saturation coefficient and temperature accelerate the creep deformation and creep strain rate of the mudstone specimens. Under different water and temperature conditions, the creep strain rate increased exponentially, as the creep stress level increased. The sensitivity of the creep strain rate to the creep stress level increased with the increase in water saturation coefficient and temperature. Based on the creep test results, linear rheological models were employed to fit the creep behavior of the mudstone. The results showed that the Burgers model can replicate the primary and secondary creep behaviors of the mudstone under different water content and temperature conditions. The parameters of the Burgers model (E m , E k , and η m ) generally decreased with the increase in water saturation coefficient and temperature. The reasons why water and temperature affect the short-term and long-term mechanical behaviors of the mudstone are the physicochemical effects and mechanical effects.

Modeling of Dielectric Relaxation Processes in Moist Sand Rocks

The results of experimental measurements in the frequency range 10 kHz – 1 GHz of the complex dielectric permittivity of quartz granule powders of various sizes moistened with distilled water and a salt solution are presented. On the basis of these results, a relaxation model has been constructed that makes it possible to separate the influence of relaxation processes caused by polarization of the water–mineral and water–air interfaces on the complex dielectric permittivity. The model parameters are found for various granule sizes and solution concentrations. It is shown that the relaxation time of both processes decreases with decreasing granule size and increasing the concentration of the solution. A different character of the dielectric permittivity hysteresis at different frequencies with a decrease/increase in the water saturation coefficient is explained. The prospects of using the dielectric method for determining the petrophysical characteristics of rocks are discussed.

Freezing and thawing resistance of aerial lime mortar with metakaolin and a traditional water-repellent admixture

We prepared four mortar mixtures with lime, metakaolin and linseed oil, the latter added as an admixture to impart water-repellency. The mortar mineralogy, microstructure, mechanical strength and resistance against freeze-thaw cycles were evaluated. The addition of oil reduced the water saturation coefficient and capillarity absorption rate. Oil also hampered crack development during curing, thanks to the development of large spherical pores. The mechanical strength slightly decreased with the addition of oil to lime mortar but increased when added to lime-metakaolin. The mortar composed of lime, metakaolin and oil showed the highest resistance against freeze-thaw cycles.

Further developments of a poultice for electrochemical desalination of porous building materials: minimization of side effects

Salt induced deterioration of buildings is a frequently present problem and is in connection with traditional buildings a source for increased maintenance and costs. Especially in connection with Cultural Heritage (e.g. murals) even surface deterioration of original materials is unacceptable and should be avoided. Previously, an electrochemical method has been adapted and optimized for desalination of brick masonry and a high efficiency was obtained. Unfortunately, an accelerated weathering was seen among others in shape of crumbling of mortar below the cathode poultice and further developments were needed. The present paper reports further development of the cathode poultice from a single layer to a three layered poultice. The three layered poultice neutralized the produced hydroxides at the cathode and ensured precipitation of the buffering agent within the cathode poultice and still a high desalination was maintained. Possible side effects were examined with SEM-EDX, water saturation coefficient, saturation coefficient, open porosity, water and acid soluble calcium content, pH and electrical conductivity.