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Tar content in gasification products is a serious problem for fuel gas utilization in downstream applications. Catalytic steam reforming of tar to syngas is a promising way for the removal of tar from the gas products. Nickel-based catalysts, dolomite, and olivine have been widely investigated for tar cracking and reforming by various researchers. This paper presents a review of biomass gasification, tar composition, and its elimination process by using the above three catalysts. This paper summarizes the knowledge in the published literature associated with tar elimination during the biomass gasification including discussion on the effects of different support, promoter on the catalytic performance. The aim of this paper is to collect information on the performance of above catalysts to make them accessible to readers within one paper. Comparative studies on these catalysts carried out by some researchers have also been presented here which show that the nickel-based catalyst is much more active than dolomite and olivine, but they are more expensive and can be also deactivated. Compared to olivine, the dolomite shows better catalytic performance with much higher gas yield and H2. Calcination of these catalysts improves the catalytic activities but the amount of coke deposited on the surface of the dolomite is reported higher than that of the olivine, which may be resulted from the different Fe amount of the catalyst. [ABSTRACT FROM AUTHOR]

Enhanced oil recovery in carbonates due to wettability alteration has received much attention recently. In contrast to sandstones reservoirs, carbonates are neutralwet or preferentially oil-wet. The use of CO2 dissolved into water has emerged as an alternative method for EOR operations in carbonates reservoirs. In the present paper, oil recovery from two carbonate outcrop rocks was evaluated with different brines containing CO2. The evaluation included a qualitative approach by spontaneous imbibition tests and a quantitative assessment by the Amott-Harvey index. The rocks tested were limestone and dolomite samples known as analogous to Brazilian pre-salt reservoirs. The testing fluids were a medium gravity crude oil, seawater concentration brine, formation equivalent brine and the carbonated version of these brines. Results shown additional oil recovery directly associated with wettability alteration driven by brine concentration switches. Oil recovery increases were observed independently if the brine concentration decreased or increased over the water replacement process. Wettability alteration took place in both carbonate types starting at oil-wet to neutral-wet conditions. Similar tests carried out with equivalent carbonated brines showed similar alterations in the wetting properties, trending no dependence on salt concentration. However, CO2 and its derived ions dissolved in the brines seem to inhibit the wettability alteration mechanism. [ABSTRACT FROM AUTHOR]

The analysis of mechanisms which affect the formation of agglomerates and determine the granulation process in a broad sense encounters difficulties related to the many ways of the formation of granules. The aim of the study was to perform a qualitative and quantitative analysis of granulation mechanisms with special reference to agglomerates' disintegration in the disc granulation process. This paper contains an analysis of disintegration mechanisms (abrasion and crushing) of agglomerates during the disc granulation of dolomite. The analysis of the mechanisms taking place during the process concerns the granulation stage after wetting. During the research, each time after the wetting stage, the size fraction 10-12.5 mm was substituted with an analogous fraction wetted by means of an aqueous solution of a coloring agent and the process was continued. After the specified time of granulation, the obtained product was sieved through laboratory sieves and then the content of the provided coloring agent in different size fractions was analyzed by means of a spectrophotometer. Measuring the absorbance of the analyzed samples and granulometric composition of the bed, the level and cause of the migration of material of the tested fraction into other size classes were determined, and at the same time, the occurring granulation mechanisms were analyzed. The proposed model and measurement method consisting of determining the absorbance of the tested granulometric fraction enable the qualitative and quantitative analysis of granulation mechanisms are encountered during the carrying-out of the process after wetting the bed. [ABSTRACT FROM AUTHOR]

Many buried karst areas in Iran, and in other parts of the world have not yet been mapped using detailed geological or geophysical studies to delineate susceptibility to sinkhole development. The purpose of this paper is to investigate the possibility of using the results of hydrogeochemical analysis with routine measurements of physicochemical parameters to evaluate and detect areas prone to sinkhole develop. Sixteen spatial maps were prepared using analyzed data from 77 water samples from monitoring water wells in the Kabudar Ahang, Razan, and Qahavand (KRQ) sub-catchments of the Hamadan province, western Iran. By use of geographic information system tools 16 thematic maps for physicochemical parameters (EC, pH., TDS, and groundwater temperature), major cations (Ca2+, Mg2+, Na+, and K+), anions (HCO−3, SO42−, NO3−, and Cl−), and calcite, dolomite, gypsum, and partial pressure of CO2 saturation indices (SIC, SID, SIG, and SIpCO2) were prepared. It was hypothesized that the anomalies of each parameter concentration could be consistent with sinkhole prone areas. To evaluate this assumption, the area under the Receiver Operating Characteristic (ROC) curve was calculated by 100 points as a true sinkhole pixel (50 positive true) and non-sinkhole point (50 true negative). The areas under curve of ROC for these thematic maps were calculated for the 16 variables. Results show that the dolomite and calcite saturation indices (0.49 and 0.43, respectively) are poor indicators, whereas HCO−3 and pCO2 saturation indexes (0.83 and 0.78, respectively) are good indicators of sinkhole susceptibility in the study area. The result confirmed application of hydrogeochemical anomaly analyses and the ROC validation method in covered karst can be a useful tool for prediction of sinkhole prone zones forming in region, where sparse data are available. [ABSTRACT FROM AUTHOR]

Air-gasification has emerged as preferred means of converting biomass to valuable synthesis gas (syngas). In present work, the gasification characteristics of pine sawdust were studied in a small-scale fluidized bed using calcined dolomite as in-bed material. Dolomite is characterized by higher tar conversion and H 2 production during biomass gasification. Different operation conditions, equivalence ratios, reaction temperatures and dolomite contents, are studied for their influence on the gas compositions, gas yields, tar yields and higher heating values of producer gas. The results show that increasing either temperature or dolomite content enhances the tar conversion, where the latter accounts for the syngas with the lowest tar content. At 850 °C, the addition of 50 wt% dolomite can increase the gas yield from 1.48 to 1.85 Nm3/kg, and lowering the tar yield from 11.5 to 4.6 g/Nm3. Furthermore, the addition of more dolomite enhances the quality of the product gas, as indicated by increased values of the higher heating values of producer gas. Increasing the dolomite content within the 0–50% range resulted in higher H 2 and CO contents, whereas the CH 4 content declined. A slight change in CO 2 content was observed with increasing dolomite content, which might cause by the limited carbonation. In contrast, the H 2 content enhances non-linearly with the increase of dolomite content, which indicates that the catalytic activity of dolomite improves with the increase of dolomite share in the feedstock, due to the reforming of tar over dolomite. Increasing the ER from 0.14 to 0.3 elevates the gas yield, but decreases the tar yield and increases the H 2 content in the product gas. • This paper evaluates the catalytic activity of calcined dolomite during biomass gasification. • The effect of ER, temperature and dolomite content is studied. • Overall, gasification with higher dolomite content produces more H 2 content. • The lowest tar yield of 4.6 g/Nm3 is obtained at 850 °C, ER of 0.2, and dolomite content of 50%. [ABSTRACT FROM AUTHOR]

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Geopolymer concrete is a sustainable material which can reuse industrial by-products and thereby minimize the emission of greenhouse gases during its production, unlike cement. Blended geopolymer concrete has been made from two industrial waste products, ground granulated blast furnace slag (GGBS) and dolomite, which are obtained from steel industries and rock crushing plants, respectively. This geopolymer concrete is found to develop high strength within a short period of ambient curing. It is observed that the addition of steel fibers enhances the strength and durability characteristics of this concrete. The paper highlights the engineering and durability properties of steel fiber–reinforced GGBS-dolomite geopolymer concrete and explains how the bond strength and impact resistance of GGBS-dolomite geopolymer concrete is improved by the inclusion of steel fibers. A comparison of improvement in durability characteristics between geopolymer concrete with and without steel fiber reinforcement and ordinary portland cement concrete is also presented. The development of GGBS-dolomite geopolymer concrete from industrial by-products minimizes the cost of construction and creates a solution to the waste disposal problems. The high durability of geopolymer concrete will help to reduce the maintenance cost of structures. [ABSTRACT FROM AUTHOR]

Carbonate reservoirs have become one of the key targets of hydrocarbon exploration. In fact, carbonate reservoirs contributed to 50% of oil production. The reservoir properties evaluation can be very complex to understand when it encounters with dolomitization. Most of the ancient dolomites have associated with changing of rock texture through diagenetic processes such as dissolution, recrystallization, precipitation, mineral stabilization and multiphases of fracturing. Thus, qualitative and quantitative data helps to improve the study of dolomite characterization. The aims of this paper is to identify the dolomite groups in Paleozoic Kinta Limestone and discuss on how diagenetic alterations influence porosity in dolomites microfacies. Kinta dolomite is identified as epigenetic dolostone and believed to form by the replacement along post-depositional lineaments of faults and fractures. The dolomite in Kinta Valley is classified as secondary dolomite. There are thirty (30) samples were collected from quarries in Kinta Valley to perform a petrographic analysis. The analysis is conducted by studying the photomicrograph taken from the optical and cathodoluminescence microscopes. Five (5) types of dolomite microfacies are recognized, which are Dolo-I (Microdolomite), Dolo-II (Sucrosic Dolomite), Dolo-III (Fabric Destructive Fine Crystalline Dolomite), Dolo-IV (Fabric Destructive Coarse Crystalline Dolomite) and Dolo-V (Saddle Dolomite). The dolomite facies are grouped into cement and replacive dolomites. The replacive dolomite is associated with lower porosity than cement dolomite. The variation of porosity values in different types of dolomite can be linked to different diagenetic processes. Our data affirm that diagenetic process of pre-dolomitization has destroyed porosity, while post-dolomitization has created porosity. [ABSTRACT FROM AUTHOR]

This paper explores the application of Total Reflection X‐Ray Fluorescence (TXRF) spectrometry for chromate (CrO42−) and phosphate (PO43−) determinations in synthetic solutions after their adsorption onto dolomite. The competition between both contaminants is also evaluated. Adsorption processes are considered an inexpensive, non‐contaminating alternative for retaining, on a selected substrate, a variety of pollutants present in different effluents. For a specific adsorbent, an important factor to be taking into account is the competition among different possible species. Variables such as concentration, temperature, ionic strength and pH were evaluated. Dolomite, a natural mineral based on calcium and magnesium carbonates, was employed as adsorbent. TXRF is an efficient, fast trace element analytical technique and requires only minimum specimen preparation, for that reason is suitable for this study. The experiments were carried out in batch systems; pH and ionic strength of the solution were measured and controlled. The results obtained in individual systems (phosphate‐dolomite or chromate‐dolomite) indicate a 70.5% for phosphate and 22.7% for chromate removal. The adjustment of the ionic strength had no influence on the removal of the anions. According to this study, the adsorption of chromate was reduced to 14% when the pH increased; this fact did not affect phosphate removal. The removal of both ions increased at pH under than 6. The presence of both ions at different concentrations did not change the removal value for the phosphate, whereas the removal of chromate was almost null, indicating a strong interference of the phosphate in the removal of chromate. [ABSTRACT FROM AUTHOR]

In this paper, magnesium hydroxide has been obtained from seawater by a well-known industrial process which involves the chemical reaction between magnesium ions of seawater with dolomite lime to produce the magnesium hydroxide precipitate. Furthermore, the precipitate was modified by ultrasound of high intensity. The purpose was to obtain magnesium hydroxide with high purity and reduced particle size without agglomeration. The precipitated magnesium hydroxide is characterized by the particle size distribution determined by the laser scattering method in the range of 20 nm–2 mm, and by the SEM analysis. Likewise, in order to investigate the effect of particle size on the thermal stability, thermokinetic study of magnesium hydroxide samples was performed by non-isothermal thermogravimetry in an inert atmosphere at different heating rates. The gained thermogravimetric data were utilized for the kinetic analysis, which was performed by using the isoconversional Friedman method in combination with the multivariate nonlinear regression method. For each degradation stage of investigated samples, kinetic parameters (activation energy, pre-exponential factor and kinetic model) were calculated and compared. [ABSTRACT FROM AUTHOR]

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Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Acid-fracture conductivity has a major impact on acid-fracturing effects. In this paper, influences of acid concentration, temperature, and closure-stress loading time on conductivity under different acid-fluid systems have been researched based on experimental analysis for deep limy dolomite reservoirs. The measured conductivity showed high correlation and specific changing patterns with the above factors. Quantified relationships and equations between the conductivity and these factors were suggested in this paper. Additionally, a strong acid-etching effect caused by crosslinked acid and diverting acid has been observed during the tests. This could lead to high conductivity as well as broken rocks due to pressing with high-concentration acid. In this study, a 50-hour long-term conductivity test has been designed under the closure stress of 60 MPa which was closest to the actual reservoir conditions. The results showed that conductivity retention rate for each test group is less than 40%. By establishing assessment criteria of long-term and short-term conductivity based on the conductivity retention rate, linear relationships with high correlation and quantified equations of the conductivity retention rate in the same acid-rock reaction system could be obtained. [ABSTRACT FROM AUTHOR]

The genesis of the fine crystalline dolomites that exhibit good to excellent reservoir properties in the upper fourth member of the Eocene Shahejie Formation (Es) around the Sikou Sag, Bohai Bay Basin, is uncertain. This paper investigates the formation mechanisms of this fine crystalline dolomite using XRD, SEM, thin section analysis and geochemical data. The stratigraphy of the Sikou lacustrine carbonate is dominated by the repetition of metre-scale, high-frequency deposition cycles, and the amount of dolomite within a cycle increases upward from the cycle bottom. These dolomite crystals are 2-30 μm in length, subhedral to anhedral in shape and typically replace both grains and matrix. They also occur as rim cement and have thin lamellae within ooid cortices. Textural relations indicate that the dolomite predates equant sparry calcite cement and coarse calcite cement. The Sr concentrations of dolomites range from 900 to 1200 ppm. Dolomite δO values (−11.3 to −8.2 ‰ PDB) are depleted relative to calcite mudstone (−8.3 to −5.4 ‰ PDB) that precipitated from lake water, while δC values (0.06-1.74 ‰ PDB) are within the normal range of calcite mudstone values (−2.13 to 1.99 ‰ PDB). High Sr/Sr values (0.710210-0.710844) indicate that amounts of Ca and Mg have been derived from the chemical weathering of Palaeozoic carbonate bedrocks. The high strontium concentration indicates that hypersaline conditions were maintained during the formation of the dolomites and that the dolomites were formed by the replacement of precursor calcite or by direct precipitation. [ABSTRACT FROM AUTHOR]

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Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to reduce the environmental impact caused by the migration of heavy metals in electrolytic manganese residue to water, this paper added calcined dolomite sand to electrolytic manganese residue to solidified Mn2+, and analyzed the microstructure and microstructure of dolomite sand before and after calcination by XRD, BET and SEM methods. The stabilization effect of calcined dolomite sand on Mn2+ in electrolytic manganese residue at different dosage was analyzed and evaluated. The results show that with the calcination temperature increasing from 600 °C to 800 °C, the dolomite sand gradually decompositions to form alkaline oxides such as CaO and MgO. The specific surface area, pore volume and pore size of calcined dolomite sand increase continuously, which are 1.16 ~ 3.96 times, 1.7 ~ 4.18 times and 1.99 ~ 16.12 times of uncalcined dolomite sand, respectively. When 10% calcined dolomite sand at 800 °C is added to electrolytic manganese residue, the stabilization efficiency of Mn2+ is 99. 95%, and when 30% calcined dolomite sand at 700 °C is added, the stabilization efficiency of Mn2+ is 99.85%, and the concentration of Mn2+ is as low as 1.66 mg/L. The stabilization effect of calcined dolomite sand on Mn2+ in electrolytic manganese residue is mainly that Mn2+ is solidified in the form of MnO2 and MnOOH. The calcined dolomite sand at 700 * 800 °C can be used as an effective stabilizer to solidified Mn2+ in electrolytic manganese residue. [ABSTRACT FROM AUTHOR]

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The purpose of this paper is to investigate the strength, physical and engineering index parameters of selected dolomitic rocks with emphasis on grain size. For this purpose, three groups of dolomite from north western Iran, with the same mineral composition but different grain size, were selected; fine grain, medium grain and coarse grain. Three sets of laboratory experiments are performed on 32 samples: first; petrography tests for determining mineral composition and their percentage, and microstructure of rock containing grain size and grain size distribution, second; experiments to determine the physical properties of the rocks included density, compressional and shear wave velocity, and the third category of experiments included uniaxial compressive strength test, Brazilian tensile strength and point load strength. According to the results; there are significant positive correlation between grain size and uniaxial compressive strength (r = 0.89), point load strength (r = 0.58), Brazilian strength (r = 0.69), and average Young's modulus (r = 0.64). Also, with increasing grain size, density decreases (r = -0.77). There is strong correlation between compressional wave velocity and shear velocity (r = 0.88). There are also a strong correlation among the uniaxial compressive strength, Brazilian tensile strength and point load strength. [ABSTRACT FROM AUTHOR]

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Copyright of Romanian Journal of Materials / Revista Romana de Materiale is the property of Foundation for Materials Science & Engineering Serban Solacolu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Late Mesolithic in Southern Europe is dated to the 7th and the first part of the 6th millennia BCE and is marked by profound changes which are mostly evident in the technical know-how and tool-kit of the last hunter-fisher-gatherer societies. The significance of this phase also relates to the fact that it precedes the Early Neolithic, another period of major transformations of human societies. Nonetheless, the Late Mesolithic still remains a poorly known age in this area. A burial discovered at Mondeval de Sora (Northern Italy) in 1987, represents a unique window into this period. In this paper, we provide a detailed analysis of more than 50 lithic and osseous artifacts associated with this burial. We highlight important contextual data regarding the techno-economic dimension and the notion of personal burial possessions. Based on the association and location of some items, we propose a new interpretation of the social status of this individual and the possible impact of technological innovation on the social organization and symbolic sphere of Late Mesolithic groups. [ABSTRACT FROM AUTHOR]

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Dolomite is the most important component of the prolific reservoirs in the Ma55 to Ma51 submembers of the Ordovician Majiagou Formation in the central Yishan Slope, Ordos Basin. However, the origins of the different types of dolomite are unclear because of the different diagenetic environments and complex diagenetic fluids. This paper mainly focuses on the diagenetic environment and diagenetic fluid associated with the dolomite. The petrographic features of the dolomite were studied on the basis of core observation and thin section identification. Geochemical characteristics were analyzed according to the O, C and Sr stable isotopes and major and trace elements. The results demonstrate that, petrographically, the dolomite can be divided into four types, namely, type 1, type 2, type 3 and type 4. Type 1 is mainly characterized by dolomite with gypsum and salt dissolution as well as breccia structures with no clay minerals filling between breccia clasts. Type 2 is characterized by powder-fine crystalline dolomite with apparent residual textures and residual intergranular and intercrystal pores. Type 3 is characterized by leopard limestone or dolomite with leopard textures and massive bioborings. Finally, type 4 is characterized by karst breccia dolomite with many fractures and caves filled by abundant terrigenous clay minerals. In combination with the petrographic data, analysis of the geochemical data reveals that the type 1 dolomite formed in an early near-surface diagenetic environment and the diagenetic fluid might have been early freshwater. Type 2 and type 3 dolomite formed in a shallow-burial diagenetic environment. The diagenetic fluid of type 2 dolomite might have been hypersaline brine that was influenced by freshwater, but that of type 3 dolomite might have been a mixed fluid consisting of seawater and freshwater, which was less saline than the type 2 dolomite fluid. Type 4 dolomite formed in an epidiagenetic near-surface environment and the diagenetic fluid might have been superficial freshwater carrying abundant terrigenous clay minerals. The study shows that the analysis of the diagenetic environment and fluid of dolomite has great significance for research on dolomite origins. The porosity and permeability values of the four types of dolostone reservoirs indicate that type 1 dolomite reservoirs are the best reservoir, type 2 dolomite reservoirs have good physical properties, type 4 dolomite reservoirs are relatively good reservoirs, and the worst reservoir is the type 3 dolomite reservoirs. [ABSTRACT FROM AUTHOR]

Platform carbonates diagenesis in salt basins could be complex due to potential alterations of fluids related and non‐related to diapirism. This paper presents the diagenetic history of the Hettangian to Pliensbachian platform carbonates from the Tazoult salt wall area (central High Atlas, Morocco). Low structural relief and outcrop conditions allowed to define the entire diagenetic evolution occurred in the High Atlas diapiric basins since early stages of the diapiric activity up to their tectonic inversion. Precipitation of dolomite and calcite from both warmed marine‐derived and meteoric fluids characterised diagenetic stages during Pliensbachian, when the carbonate platforms were exposed and karstified. Burial diagenesis occurred from Toarcian to Middle Jurassic, due to changes of salt‐induced dynamic related to increase in siliciclastic input, fast diapir rise and rapid burial of Pliensbachian platforms. During this stage, the diapir acted as a physical barrier for fluid circulation between the core and the flanking sediments. In the carbonates and breccias flanking the structures, dolomite and calcite precipitated from basinal brines, whereas carbonate slivers located in the core of the structure, were affected by the circulation of Mn‐rich fluids. The final diagenetic event is characterised by the income of meteoric fluids into the system during uplift caused by Alpine orogeny. These results highlight the relevant influence of diapirism on the diagenetic modifications in salt‐related basins in terms of diagenetic events and involved fluids. [ABSTRACT FROM AUTHOR]

Most of the phosphate ore in southern China is contained within siliceous dolomite phosphate rock, and more than 90% of it is medium and low‐grade collophane. Reverse flotation of carbonate gangue minerals (dolomite) from phosphate in acidic media is still the most economical method for the reduction of carbonate in collophane concentrates. It has been recognized that the collophane and dolomite in acidic media affect the surface properties of minerals, thereby affecting their flotation properties. In this paper, HCl and H3PO4 were used as regulators or inhibitors to study the flotation behaviour of collophane and dolomite. The inhibition mechanism of collophane and dolomite in two acid media was studied by time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) and X‐ray photoelectron spectroscopy (XPS) analyses. It was found that the addition of an inhibiting acid can partially depress the collophane and improve the flotation of dolomite, thus achieving their flotation separation, and the inhibition effect of H3PO4 on collophane is better than that of HCl. And it was found by TOF‐SIMS analysis that the increase in acid concentration did not reduce the adsorption concentration of the collector, and the main reason for the inhibition was not the decrease in the adsorption concentration of the collector. The adsorption capacity of collector on dolomite surface with H3PO4 is greater than that with HCl. The XPS test indicated that metaphosphate (PO3−1) is the pivotal ion for depressing collophane under acid conditions. [ABSTRACT FROM AUTHOR]

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Design block size is of vital importance for rockfall countermeasure design. According to the Austrian normative document ONR 24810, the design block is specified as fractile (V95-V98) of the block size distribution depending on rockfall frequency. For rock formations, which form very large rockfall blocks (> 10 m3), the use of fractiles V95–V98 appears too high with regard to economically justifiable protective measures. The paper deals with the determination of design blocks for the Dachstein Formation on the basis of data from three Austrian test regions. The formation's bedded limestone represents a key rock of the eastern part of the Northern Calcareous Alps and is very common along some major transport routes. A range of design blocks is derived from a synopsis of block size distributions, magnitude-frequency relations, and considerations about the rockfall barriers' service life. In the process, the knowledge of the return period of the determinated design block is considered more important than the overall rockfall frequency. Analyzing available rockfall event data and block size distributions, it is possible to identify a return period of 21–26 years for a rockfall event ≥ 1 m3/1000 m route section. Thus, such events are rare. Events that affect the V97–V100 fractiles of the block size distribution are even rarer; they yield very large design block volumes, which show return periods > 100 years. For the bedded Dachstein limestone of the test areas, the application of the fractiles V95–V96 (0.15–2.25 m3) is useful for adapting the return period of the design block to the working life of the rock fall barrier (25–50 years). [ABSTRACT FROM AUTHOR]

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Water in Central Asia is a precious resource in the semiarid and arid environments in which people live in the region. Understanding the groundwater quality is important as it is the main factor determining its suitability for drinking and agricultural purposes. This paper presents results of a groundwater hydrochemical assessment in the Herat City by measuring its physicochemical parameters: major cations and anions, pH, total dissolved solids and electrical conductivity. In the light of progressive depletion of groundwater reservoirs and water quality deterioration, an investigation of dissolved major constituents in 27 groundwater samples was performed. The objective was detection of processes for geochemical assessment throughout the area. Herat City has been intensively inhabited during the last decenniums, leading to expansion of the residential and agricultural areas. Besides semi-aridity, rapid social and economic development stimulates greater demand for water, which is gradually fulfilled by groundwater extraction. Groundwater of the study area are characterized by the dominance of Ca + Mg over Na + K. , which was found to be the dominant anion, followed by Cl– and . The hydrochemical types in the area can be divided into two major groups: the first group includes mixed Ca–Mg–Cl and Ca–Cl types. The second group comprises mixed Ca–Na–HCO3 and Ca–HCO3 types. Calcite and aragonite have high SI values, which indicates precipitation as the result of evaporation, whereas dolomite shows an undersaturation state. Most of the samples are within the permissible limit of WHO standards. Interpretation of data suggests that weathering, ion exchange reactions, and evaporation to some extent are the dominant factors that determine the groundwater chemistry in the study area. [ABSTRACT FROM AUTHOR]

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True formation resistivity Rt measurement is one of the fundamental logs in the calculation of hydrocarbon resources. That is why it is very important to have the most reliable resistivity data possible. In this paper, the various outcomes obtained by Polish well log analysts and engineers for the proper determination of hydrocarbon saturation in the Main Dolomite deposits in the Polish Lowland are presented. The long history of efforts directed to make proper exploitation decisions in wells where the Groningen effect has been observed is illustrated, starting with the standard measurement and interpretational approach, through the modified construction of a reference electrode in a Laterolog device and ending with an examination of HRLA (High Resolution Laterolog Array) or Array Compensated Resistivity Tool) ACRt results. The processing of resistivity logs with the special Poprawki software is included. [ABSTRACT FROM AUTHOR]

Methods of composite mechanics were used to evaluate the effective elastic moduli and Biot's parameter of porous media. Natural composites — dolomites and hyaloclastites — were considered as examples, which were also examined experimentally. The microscopic structure of the rocks was studied under a microscope, and their mineral composition was determined by the X-ray diffractometry. A comparison of experimental and calculated elastic moduli of dolomites showed their good agreement, which proved that the averaging method can be used to rapidly evaluate their effective elastic properties. For dolomites, Young's modulus and Biot's parameter were determined as functions of porosity using the calculation results and experimental data. The computation method described in this paper allows one to calculate Biot's tensor in the general case of an anisotropic and inhomogeneous matrix and to evaluate the influence of pore shape on stresses and strains at the microlevel, which is not possible by experimental methods. Using samples of hyaloclastites with round and angular pores, the effect of pore shape on the elastic moduli and the effective stress coefficient was investigated. The effect of pore orientation was also studied using anisotropic dolomite samples with elongated pores. [ABSTRACT FROM AUTHOR]

The paper presents experimental results obtained in the process of making glass foam from glass waste using a cheap foaming agent (natural dolomite). The originality of the work is the application of the microwave energy, unlike the conventional techniques commonly used in the world. The main advantage highlighted by the experiments is the very low specific energy consumption (below 1.5 kWh/kg), due to the peculiarities of the microwave heating technique. The foamed product has physical, mechanical and morphological characteristics (density between 0.30-0.32 g/cm³, thermal conductivity between 0.064-0.067 W/m·K, compressive strength in the range 2.2-2.6 MPa), which are similar to those of foams made by conventional methods and are suitable for its use as insulating material in construction. [ABSTRACT FROM AUTHOR]

In this paper, two types of reinforcement agents of fibrous palygorskite (PAL) and rhombohedral dolomite (DOL) have been used together by simply mixing in order to improve the mechanical and thermal properties of waterborne polyurethane (WPU). A great synergistic effect between 1D PAL and 3D DOL on reinforcing WPU matrix has been observed. In comparison to neat WPU, the tensile strength of such three components WPU-based composite has been significantly improved by 178% with an addition of 4 wt% PAL and 6 wt% DOL. Furthermore, its initial decomposition temperature also has been increased 55 °C. The formation of 3D conjugated filler network with 1D PAL inserted into the 3D DOL network could be attributed to such synergistic reinforcement of WPU. This work provides a good example and eco-friendly pathway for the preparation of high performance polymer composites by simply using micro/nano-fillers with different dimension together. [ABSTRACT FROM AUTHOR]

The effective mass transfer coefficient of hydrogen ion is an important basic parameter of acid rock reaction kinetics, and it is an essential basic parameter for acid fracturing design of carbonate reservoir. It is usually measured by rotating rock disk instrument or conventional size parallel rock plate flow test, but the rotating rock disk instrument cannot simulate the reaction of acid in the formation, and there is a deviation in the test results of high viscosity liquid. In the parallel plate flow experiment, if the size of rock plate is short, then calculating the hydrogen ion mass transfer coefficient will cause large error by using the difference of the rock plate quality or the difference of acid concentration. In this paper, a new method for measuring H+ effective mass transfer coefficient in fractures by large scale linear dynamic displacement is designed. Three-dimensional laser scanning of large size rock plates before and after peracid is carried out, and the acid etching volume of the rock plates is measured, then the acid consumption rate and H+ effective mass transfer coefficient are calculated. In this paper, the H+ effective mass transfer coefficients of gelling acid and diverting acid in the dolomite of west Sichuan permian Qixia formation are tested, which are between (1.50-2.31)×10-5 m/s. The results provide key dynamic parameters for fracture simulation, acid fracturing design and acid fracturing effect evaluation. [ABSTRACT FROM AUTHOR]

This paper takes the thick and widely distributed crystal dolomite of Xixiangchi Formation, Upper Cambrian in Southeastern Sichuan basin as an example, the reservoir characteristics and main controlling factors of crystal dolomite have been analyzed systematically, and the genesis and reservoir formation mechanism of crystal dolomite have been discussed. It shows that the main reservoir rocks of crystal dolomite include powder crystalline dolomite and finely crystalline dolomites, and the intercrystal pores and dissolved intercrystal pores are the main reservoir spaces, with few dissolved vugs and fractures developed in the reservoir. The pore structure analysis shows that the throats of crystal dolomite reservoir are mainly lamellar, reflecting a good configuration between pores and throats, medium- low porosity and low permeability, representing typical porous-type reservoir. Dolomitization analysis indicates that the dolomitization occurred in the penecontemporaneous or early diagenetic stage. The degree of dolomitization decreased gradually from the top to the bottom in each sedimentary cycle, and distribution of dolomite in the study area shows that the content of dolomites decreases from the west to the east, which reflects the degree of dolomitization weakening eastward. Combined with the geochemical research of crystal dolomite, the C and O isotope data reflect the same characteristics of seawater during the late Cambrian. It indicates that the dolomitization might be related to the seepage-reflux of seawater in the early time. Recrystallization played an important role in the genesis of the crystal dolomite, because most of crystal dolomites remain residual granular texture. The intercrystal pores formed by seepage–reflux dolomitization acted as superior seepage channels for the reservoir transformation, and the recrystallization adjusted the previous pores and made them better, while the karstification was the key to the dissolved pore formation. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Geoscience is the property of Natural Gas Geoscience and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Development of geopolymer concrete (GPC) with industrial by-products is a solution to the disposal of the industrial wastes, thus making the concreting process sustainable. This paper focuses on the development of GPC using ground-granulated blast-furnace slag (GGBS) and dolomite (by-product from rock crushing plant) as source materials. Strength properties of slag-based GPC are studied with different proportions of dolomite. It is observed that the addition of dolomite into slag-based GPC reduces the setting time, enhances workability, and rapidly improves the early-age strength. Addition of dolomite into slag GPC also improves the durability properties, such as high resistance towards water absorption, sorptivity, marine attack, and chemical attack. [ABSTRACT FROM AUTHOR]

The study of the critical zones (CZs) of the Earth link the composition and function of aboveground vegetation with the characteristics of the rock layers, providing a new way to study how the unique rock and soil conditions in karst regions affect the aboveground vegetation. Based on survey results of the rocks, soils and vegetation in the dolomite and limestone distribution areas in the karst area of central Guizhou, it was found that woody plant cover increases linearly with the number of cracks with a width of more than 1 mm, while the cover of herbaceous plants shows the opposite trend (p<0.01). The dolomite distribution area is characterized by undeveloped crevices, and the thickness of the soil layer is generally less than 20 cm, which is suitable for the distribution of herbaceous plants with shallow roots. Due to the development of crevices in the limestone distribution area, the soil is deeply distributed through the crevices for the deep roots of trees, which leads to a diversified species composition and a complicated structure in the aboveground vegetation. Based on moderate resolution imaging spectroradiometer (MODIS) remote sensing data from 2001 to 2010, the normalized differentiated vegetation index (NDVI) and annual net primary productivity (NPP) results for each phase of a 16-day interval further indicate that the NDVI of the limestone distribution area is significantly higher than that in the dolomite distribution area, but the average annual NPP is the opposite. The results of this paper indicate that in karst CZs, the lithology determines the structure and distribution of the soil, which further determines the cover of woody and herbaceous plants in the aboveground vegetation. Although the amount of soil in the limestone area may be less than that in the dolomite area, the developed crevice structure is more suitable for the growth of trees with deep roots, and the vegetation activity is strong. At present, the treatment of rocky desertification in karst regions needs to fully consider the rock-soilvegetation- air interactions in karst CZs and propose vegetation restoration measures suitable for different lithologies. [ABSTRACT FROM AUTHOR]

The use of geothermal energy, which comes from both deep geothermal systems and the shallow underground, has been developing rapidly in the last few decades. The purpose of the paper is to present the results of measurements of the thermal properties of all rock samples and sediments that were available from boreholes, two tunnels and numerous surface locations in Slovenia in the period from 1982 to the end of 2022. In relation to the shallow geothermal potential, a special effort is needed to characterize the thermal properties of the rocks and sediments and to implement thermal energy transfer technology. In this sense, knowledge of the thermal conductivity of rocks and sediments is required to assess the possibility of low-enthalpy heat exchange in a given local area. The largest number of measurements was taken to determine thermal conductivity. Determinations of thermal diffusivity were carried out on a much smaller number of rock and sediment samples, as well as determinations of radiogenic heat production in rocks. The results of thermal conductivity measurements on 430 samples from 119 wells, 20 samples from two tunnels and 156 samples from surface locations are shown. The highest thermal conductivities are shown by samples of dolomite, quartz conglomerate and conglomerate, phyllonite, quartz phyllite and gneiss, while the lowest are measured in sediments such as clay, lignite with clay, peat and dry sand. The determined radioactive heat generation is the lowest for milonitized dolomite and highest for dark grey sandstone with shale clasts. Our results are comparable to those already published worldwide, and they could be the basis for the possible future Slovenian standard for the thermal properties of measured rocks and sediments. [ABSTRACT FROM AUTHOR]