Diatomite Samples Research Articles

Study on the Influence of Diatomite with Different Shapes on the Moisture Absorption and Release Performance in Changbai Region of Jilin Province

In this paper, different morphologies of diatomaceous earth (disc, cylindrical) were purified, and characterized by SEM, BET and pore size distribution, and moisture absorption and desorption tests were carried out. The results show that the humidity control performance of the cylindrical diatomite sample is better than that of the disc-shaped diatomite sample. Its 24h moisture absorption, 24h moisture release, volumetric moisture content ratio, average volumetric moisture content and other indicators all exceed Disc-shaped diatomite samples; the specific surface area of cylindrical diatomite samples is higher than that of disc-shaped diatomite samples, and the pore size distribution is more reasonable. Combined with the analysis of humidity control performance, cylindrical diatomite samples are more suitable As an excellent humidity control material.

ИНДИКАТОР Ge/Si ДЛЯ ОЦЕНКИ ИНТЕНСИВНОСТИ ХИМИЧЕСКОГО ВЫВЕТРИВАНИЯ НА ГРАНИЦЕ ПАЛЕОЦЕНА И ЭОЦЕНА В ДРЕВНЕМ ЗАУРАЛЬСКОМ БАССЕЙНЕ

Актуальность. Диатомиты и их переходные разности, сформировавшиеся в условиях палеоцен-эоценового морского бассейна, являются одними из самых широко распространённых в приповерхностном залегании осадочных пород на обширной территории Зауралья. При этом применительно к генетическим аспектам таких пород актуальной остается дискуссия о фундаментальных источниках кремнезема для формирования опал-кристобалитовых отложений. Актуальной задачей остается анализ роли каждого из факторов – континентального выветривания и деятельности апвеллингов – в происхождении горных пород. Соотношение Ge к Si потенциально может рассматриваться как инструмент расшифровки источника кремнезема в биогенных кремнистых породах, так как германий доставляется в породу путем внедрения в биогенный опал; привнос Ge в породу за счет других источников во время диагенеза несущественен, что делает результаты индикационно ценными. Цель: оценка интенсивности химического выветривания на рубеже палеоцена и эоцена в Зауралье на основе изучения соотношения Ge и Si в разновозрастных диатомитах. Методы: полевые исследования, рентгенофлуоресцентный анализ, масс-спектрометрия с индуктивно-связанной плазмой, сканирующая электронная микроскопия. Результаты. Работа содержит первые результаты оценки интенсивности химического выветривания на рубеже палеоцена и эоцена в Зауралье с помощью анализа расчетных соотношений германия и кремния в валовых образцах диатомитов и препаратах биокластики, из которых удален глинистый материал. Соотношения Ge/Si в препаратах биокластики из палеоценовых (Брусяна) и эоценовых (Ирбитское месторождение) диатомитов отличаются практически двукратно. Полученные значения стоит рассматривать как индикатор, что интенсивность химического выветривания претерпевает на этом рубеже серьезные изменения: интенсивное химическое выветривание, усиление гидрологического цикла в период PETM определили увеличение поставки растворенного кремнезема в морской бассейн при накоплении биокремнистых пород на территории современного Зауралья. Ослабление тектонических движений и пенепленизация суши в пределах Восточно-Уральского обрамления способствовали усилению процессов выветривания. Это обеспечило дополнительный трансфер кремнистого вещества в форме истинных и коллоидных растворов в бассейн седиментации для накопления биокремнистых пород. Объем привноса кремнезема с суши на протяжении относительного короткого периода времени стал более заметен в общем балансе поставляемой в бассейн седиментации кремнекислоты. По этой же причине, т. е. из-за наличия дополнительного источника кремнекислоты, валовое содержание SiO2 в палеоценовых диатомитах несколько выше, чем в эоценовых.

Synthesis and Antibacterial Activity of (AgCl, Ag)NPs/Diatomite Hybrid Composite.

In the present research, hybrid (AgCl, Ag)NPs/diatomite composites were synthesized by direct impregnation with aqueous silver nitrate solutions. The silver chloride nanoparticles (AgCl-NPs) were formed as an effect of the exchange reaction when silver interacted with the diatomite mineral impurity halite. Nanoparticles of metallic silver (AgNPs) were created by the reduction of silver ions under the influence of hydrogen peroxide. The content of silver chloride nanoparticles in the (AgCl, Ag)NPs/diatomite composite was limited by the content of the halite in the used diatomite. Samples of natural diatomite and synthesized (AgCl, Ag)NPs/diatomite composites were examined by using scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, infrared spectroscopy and thermogravimetric analysis. Moreover, the antibacterial potential of synthesized composites was also studied using the MIC (minimal inhibitory concentration) method against the most common drug-resistant microorganisms in the medical field: Gram-positive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae. The obtained hybrid (AgCl, AgNPs)/diatomite composites were shown to have antimicrobial potential. However, widespread use requires further study by using various microorganisms and additional cytotoxic studies on eukaryotic systems, e.g., cell lines and animal models.

Activation of Diatomaceous Earth Low-Temperature Plasma

In residential and industrial buildings, a special air environment is formed, which contains gas shaped toxic chemical compounds. A significant part of such substances comes from finishing polymer containing materials. Virtually all polymeric materials release certain toxic chemical compounds into the air. The methods and methods of air cleaning are different. One of the ways to solve the problem associated with providing the required standards for the quality of indoor air is the development and use of new efficient building materials using aggregates that have a high sorption capacity. The paper presents the results of a study of the effect of low temperature non-equilibrium plasma on the sorption characteristics of aggregates based on diatomite earth. Studies have been conducted on samples of natural diatomite and quartz sand. When activated by low temperature nonequilibrium plasma, the structure changes, which leads to an increase in the sorption characteristics of the samples under study.

МИКРОЭЛЕМЕНТНЫЙ СОСТАВ ВОДНЫХ ЭКСТРАКТОВ НЕКОТОРЫХ ОБРАЗЦОВ ДИАТОМИТОВ И ЛИДИТОВ КАРЕЛИИ

Актуальность исследования обусловлена необходимостью получения достоверной информации об элементном составе водных экстрактов диатомитов и лидитов. В настоящее время диатомиты используются в различных отраслях промышленности, в том числе медицинской и фармацевтической. Однако детального изучения состава их водных экстрактов практически не проводилось. Цель: изучить микроэлементный состав водных экстрактов нескольких образцов диатомитов и лидитов. Объекты: три образца диатомитов и два образца лидитов территории Республики Карелия. Методика: лабораторный эксперимент, водная экстракция, масс-спектрометрия с индуктивно-связанной плазмой (ICP MS). Результаты. Изучен элементный состав водных экстрактов нескольких образцов диатомитов и лидитов территории Республики Карелия методом ICP MS. Во всех исследованных экстрактах образцов диатомитов и лидитов преобладающими элементами являются Mg, Na, Ca, K и Al (до нескольких тысяч мкг/л). Экстракты образцов диатомитов имеют однородный состав. Максимальные содержания в них других, наиболее значимых, элементов составляли: P – до 650, Fe – до 1700 (образец № 1) и Mn – до 3300 (образец № 3) мкг/л. Концентрации в диапазоне от 10 до 100 мкг/л характерны для ряда элементов (Li, B, Ti, Cr, Co, Ni, Cu, Zn, Sr, Y, Zr и Ba) в экстрактах всех образцов диатомитов. Экстракты образцов диатомитов № 1 и 2 имели максимальные концентрации легких редкоземельных элементов (РЗЭ): Nd (до 247), Ce (до 230), La (до 156 мкг/л). Химический состав экстрактов образцов лидитов заметно отличался, как между собой, так и от экстрактов диатомитов. Кислая среда (рН 4,5–4,6) экстракта образца № 4 способствовала накоплению ряда элементов: Ni, Sr, Be, Mn, U, Tl, и особенно V, Co, Cu, Zn, Y, Ba. В то же время в экстракте образца № 5 в слабощелочных условиях (рН 7,4–7,5) наблюдались максимальные концентрации Mo, W, Zr, Hf. В исследованных экстрактах образцах диатомитов и лидита № 4 концентрации Al, Mn, Fe, Co, Ni, Cu, Zn превышали значения предельно допустимых концентраций (ПДК) рыбохозяйственных водоемов. Водные экстракты образцов диатомитов показали значительное содержание элементов, которые могут оказать влияние на формирование состава маломинерализованных карельских вод. При этом содержание ряда полезных для развития растений микроэлементов (Ca, Mg, К, Р, Cu, Zn, V, Mn, Sr, Y, Zr) предполагает возможность их использования как «мягких» удобрений (или добавок к минеральным удобрениям).

Macroporous monoliths based оn natural mineral sources, clay аnd diatomite

Macroporous silica ceramic was obtained using clay and diatomite. Boric acid as a low-cost additive in the amount of 1 wt% was used. These porous materials were obtained at low forming pressure (40-80 MPa) and lower sintering temperature (850-1300 ?C) for 4h in air. The influence of boric acid, forming pressure, and sintering temperature on the microstructure, porosity parameters, and mechanical properties of obtained porous monoliths were investigated. As-received and the modified samples were characterized by X-ray diffraction, FTIR, SEM, and mercury porosimetry measurements. As for modified clay and diatomite, they were pressed at 60 MPa and then sintered at 1150 ?C, obtaining porosities of about 10 % and 60 %, respectively. Both of the analyzed samples had the pore diameter in the range of macroporous materials. The pore diameters of clay samples are ranging from 0.1-10 ?m, whereas the pore diameter of diatomite samples was slightly lower with values ranging from 0.05-5 ?m. Modified diatomite samples have a lower Young modulus in comparison to modified clay samples.

Use of pure diatomite for the sorption of heavy metal ions

This article presents results according to purification of water based on diatomite sorbents.The results of the study of diatomite samples from two different regions shows thatadsorption capacity, specific surface and the degree of extraction of the sorbent of Republicof Kazakhstan higher than Iranian diatomite.

Thermochemical Purification, Technical Properties, and Characterization of Ethiopian Diatomite from Adami-Tulu Deposit

This article presents the purification and characterization of several application-oriented properties of Ethiopian diatomite mineral collected from Adami-Tulu deposit. The diatomite samples were purified by thermochemical method conducted in 6 M H2SO4 at 360–368 K for 48 h. The chemical, mineralogical, textural, morphological and thermal properties of the raw diatomite and treated diatomite were then characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscopy, dynamic light scattering particle size analyzer, Fourier transform infrared spectroscopy, thermogravimetry analyzer, Inductively coupled plasma optical emission spectrometry, N2 sorption techniques, and Mercury intrusion porosimetry. Based on the results, the diatomite was composed of mainly amorphous silica, and a small amount of quartz, feldspar, cristobalite and montmorillonite. The diatom frustules showed cylindrical and platy morphological shapes. The treatment for 24 h decreased the impurities, and increased the silica content and Brunauer–Emmett–Teller surface area to 95 wt% and 29 m2/g, respectively. Moreover, interconnected mesopores and a significant amount of macropores were found. From the obtained results, it can be concluded that the diatomite from Adami-Tulu region is moderate in quality, and the application of a hot acid leaching was a valid approach to produce high-quality diatomite, which can be used in several industrial applications.

To blend is a good solution to improve the heat insulation applicability of diatomite ores

BackgroundThe idea of mixing different grades of diatomite ores with certain ratios to obtain blends with tailored minerals constitution that can help on improving their thermal insulation applicability is introduced in this study. In this respect, three diatomite samples were collected for investigation from El-Masakheet, Kasr El-Sagha, and Demia deposits, El-Fayoum, Egypt. Complete chemical and phase analyses of these samples were carried out. The analyses showed that El-Masakheet sample was of low-grade diatomite with excess calcite content. In addition, Kasr El-Sagha and Demia samples were of high-grade diatomite with minor calcite contents. By firing the dried Kasr El Sagha and Demia yellow samples specimens at different temperatures for 1 h, they showed complete destruction at 900 °C. Different amounts of El-Masakheet sample was blended with Kasr El-Sagha and Demia yellow samples. The specimens were subjected to firing at different temperatures for 1 h. The physical properties of the fired mixed specimens were followed up.ResultsResults showed that by blending El-Masakheet sample with 50% mass ratio with Kasr El-Sagha or Demia yellow samples, a pronounced increase in the thermal applicability of the fired blends from 900 to 1100 °C was achieved. In addition, a notable increase in their open porosity was recorded. This improvement was attributed to the change in the minerals constitution ratios in the blends due to the increase in their calcite contents after El Masakheet addition, especially the Ca/Si and Ca/(Al + Si) atom ratios. This change served in forming high melting points minerals like α-wollastonite and akermanite on firing the blends specimens instead of low melting point minerals like cristobalite and alkali aluminosilicate which were formed on firing the high-grade ores alone. Consequently, an increasing in the porosity and the thermal applicability of the new specimens from 900 to 1100 °C was achieved.ConclusionsThe idea of mixing different grades of diatomite ores with certain ratios to obtain blends with tailored minerals constitution can help on improving their thermal insulation applicability and their open porosity. Besides, this concept gave a good solution to get use of the unexploited low-grade diatomite ores, especially of high calcite content.

Immobilization kinetics and mechanism of bovine serum albumin on diatomite clay from aqueous solutions

In this research, adsorption properties of bovine serum albumin (BSA) on diatomite clay, which is an oxide mineral, were studied as a function of BSA, sodium phosphate buffer and protein concentration and pH and the thermodynamic parameters of adsorption process were investigated. The BSA adsorption experiment onto diatomite clay indicated that the BSA solution reached the maximum adsorption value at pH 5.5. It was observed that the maximum adsorption capacity (qm) of the data obtained from the adsorption studies showed a great dependence on pH. The maximum amount of adsorption in adsorption experiments can be considered as points where the electrostatic interaction for pH is appropriate. Both structural and electrostatic interaction in regions outside of the isoelectric point may have caused a decrease in BSA absorbance. The structural influences were associated with different conformational states that while BSA molecules accept changes with pH, electrostatic effects can be observed in BSA molecules behaved like soft particles. In this case, it is not possible to explain the independence of the qm–pH curves of the amount of adsorption. The protein molecules at this point are very stable. Because this value is close to the isoelectric point of serum albumin. The surface structural change of BSA and diatomite clay was studied. For this, Fourier transform infrared spectroscopy (FTIR) spectroscopy values were compared before and after the experiment. The diatomite samples used as support material were characterized by FTIR, scanning electron microscopy, thermogravimetric analysis and Brunauer Emmett–Teller surface area analysis. The thermodynamic functions such as enthalpy, entropy, Gibbs free energy and activation energy were investigated in their experimental work. The thermodynamic parameters such as Gibbs free energy (ΔG*), Ea, ΔH* and ΔS* were calculated as − 67.45, 15.41, − 12.84 kJ mol−1 and − 183.28 J mol−1 K−1 for BSA adsorption, respectively. We can deduce that the adsorption process from the data obtained from the thermodynamic parameters is spontaneous and exothermic. The adsorption of the process was investigated using Eyring and Arrhenius equations, and its adsorption kinetic found to be coherent with the pseudo-second-order model. As a result, we reached that the diatomite clay is a suitable adsorbent for the BSA. Experimental results showed that diatomite clay has the potency to be used for rapid pretreatment in the process of identifying proteins.

Separation of azodicarbonamide from surface of diatomite by froth flotation

The separation of azodicarbonamide (AC) from the surface of diatomite by froth flotation is investigated in this research. Pure samples of diatomite, AC and 1:1 mixtures of the two were floated in a lab-scale flotation cell with collector dosage, frother type and dosage, and pH varied to determine the optimum experimental conditions. The diatomite sample and products from flotation tests were characterized using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX). The results of the flotation tests indicate that there is less AC on the surface of diatomite after flotation compared to the feed, while the AC present in diatomite pores remains unchanged. Additionally, Fourier transform infrared spectroscopy (FT-IR) was employed to study the mechanism of interaction between reagents and minerals.

Сравнительная характеристика различных образцов Мугалжарского диатомита

Сравнительная характеристика различных образцов Мугалжарского диатомита

Separation of aflatoxin B1 from synthetic physiological fluids using talc and diatomite: Kinetic and isotherm aspects.

The objective of the study was to examine adsorption of the aflatoxin B1 from synthetic gastric fluid and synthetic intestinal fluid by talc, raw and calcined diatomite. The kinetic and equilibrium adsorption processes were studied in the batch adsorption experiments applying high performance liquid chromatography for the aflatoxin B1 determination. The kinetic study showed a very fast adsorption of the aflatoxin B1 onto the selected adsorbents from the both physiological fluids with reaching equilibrium within 1-15min. The aflatoxin B1 was almost completely adsorbed in initial linear step of the kinetic process that can be described well by the zero-order kinetics model. The experimental data of the equilibrium adsorption were characterized using the Langmuir and Freundlich isotherm models. The high adsorption effectiveness was found in a range of 90%-100% and 60%-100% for the diatomite samples and the talc respectively at the initial concentrations of the aflatoxin B1 as 31-300ng/mL. The possible mechanisms of the aflatoxin adsorption onto the used mineral adsorbents are also discussed in the work.

Characterization of natural and treated diatomite by Laser-Induced Breakdown Spectroscopy (LIBS)

Differences and similarities between natural diatomite from Mascara, Algeria and its acid washed and microwave irradiated product have been assessed in this study using Laser Induced Breakdown Spectroscopy (LIBS). LIBS is demonstrated as a multi-elemental analysis technique of geological samples with a fast response. Diatomite is commonly used as filtration aid, mild abrasive in products such as metal polishes, adsorbent for liquids, and as porous support for chemical catalysts. LIBS analyses confirmed the reduction of calcium, magnesium, iron or sodium in treated diatomite with respect to natural one, which improves its characteristics as filters or as adsorbents. In the present study, the contents of Ca, Mg and K in the diatomite samples were analyzed with LIBS. Finally, Field Emission Scanning Electron Microscopy (FESEM) was employed for describing the morphology and microstructure of these materials.

Remediation of Phenanthrene-Contaminated Soil by Persulfate Activated with Fe-Modified Diatomite: Kinetic and Statistical Approaches

An innovative diatomite-supported iron catalyst has been developed by using an impregnation process with a mixture of ferrous (Fe2+) and ferric (Fe3+) ions in the form of precipitated iron hydroxides. Raw and modified diatomite samples have been characterized by X-ray fluorescence and scanning electron microscopy. The main characterization results have revealed that modified diatomites are amorphous and have higher iron concentrations than raw diatomite. The results also indicate that the modified materials provided significant catalytic activity on phenanthrene degradation by using sodium persulfate. Satisfactory results were obtained with 45 g/L of sodium persulfate and 1 g of modified diatomite, thus degrading 98% of phenanthrene during 168 h of treatment. Kinetic and statistical approaches were developed for the remediation process herein, which have been validated with experimental data, thence yielding suitable results.

Diatom community and palaeoenvironmental properties of Karacaören diatomite deposits (Nevşehir, Central Anatolia, Turkey)

The diatom community and palaeoenvironmental properties of volcano genetic diatomite deposits that outcrop in the Karacaören (Nevşehir) area are described. Two stratigraphic sections were measured in the study area. One of these sections was measured in Quaternary lake units (K1), and the other in lacustrine sediments of the late Miocene-Pliocene Ürgüp Formation's Bayramhacılı Member (K2). According to stratigraphic and chemical characteristics of the sections, two distinct paleogeographic domains were determined in the study area. One of these, the shallow lacustrine to fluvial area (Quaternary) which is represented by an alternating sequence of diatomite, silt/mud, and tuffite. The other was the deeper lacustrine stage (late Miocene) which is represented by diatomites with some interbedded mud facies, chert and volcanics. From the diatomite samples of these sections, twenty-five species of 10 different diatom genera were identified. When evaluated together, the ecological properties and the distribution of numerical values of the determined diatom genera and species, showed that the study area's diatomite was generally deposited in shallow, high temperature, nutrient-rich water, where nitrogen and phosphorus were abundant and which was an alkaline (pH > 7) freshwater lake environment. Over time the pH value of the environment decreased (pH < 7), and the environment became acidic.

Influence of pore structure on humidity control performance of diatomite

The moisture adsorption and desorption performance of five diatomite samples with different pore structures were tested under high and low relative humidity (98% and 11% relative humidity) and constant temperatures of 20°C and 30°C. The mineral compositions and surface morphologies of diatomite samples were characterized by x-ray diffraction and scanning electron microscopy, respectively. The pore structure of diatomite samples were analyzed by nitrogen gas adsorption and mercury intrusion porosimetry. The relationship of pore structure and humidity control performance were analyzed and discussed. It is indicated that the humidity control performance of diatomite in general enhances as the environmental temperature increases. The Shengxian diatomite presents better humidity control performance among these five samples. According to the dynamics study, the moisture adsorption and desorption performance follow the pseudo-second-order model. The mesoporous in diatomite is vitally important for the humidity controlling. The specific surface area and mesoporous volume are the two key factors for the moisture adsorption and desorption ability. Diatomite with high specific surface area and large mesoporous volume has better humidity control performance. Moreover, the impurities could change the pore structure, then further affect the humidity control performance of diatomite.

In English

The effect of microstructural changes caused by chemical modification of diatomite with aluminosilicate nanoparticles on its adsorption properties with respect to fluorine has been elucidated. The surface modification of diatomite with aluminosilicate is accompanied with significant changes in its structure and chemical properties – a growth of specific surface area, a shift of electro-superficial properties and an increase of adsorption capacity for fluorine. Moreover, some kind of synergism takes place after modification: adsorption capacity of aluminosilicate species grafted on the diatomite surface is higher than that of bulk aluminosilicate. The surface-chemical modification of diatomite has been carried out by heating it in a NaOH solution and subsequent treatment with a solution of aluminum salt and after that with ammonia. Amorphous surface silica partially dissolves during the treatment with NaOH and due to addition of an aluminum salt it forms an aluminosilicate compound. The obtained product is further denoted as DMA. The increase in the specific surface area of DMA is connected with variation of the ratio of the micro- and mesopores through the filling of the large mesopores with aluminosilicate and its own microporous structure increment; the specific surface area gets 81.8 m 2 /g, which is 2.5 times larger than the corresponding value of the initial unprocessed diatomite (37.5 m 2 /g). Partial substitution of Si atoms in silicates of diatomite surface by Al atoms creates as a result of their different valences an excess negative charge, and pH PZC of the sorbent surface shifts to higher values compared to initial diatomite sample that facilitates the attraction of more negatively charged ions from solution. Both these phenomena lead to that adsorption capacity of modified diatomite (DMA) with respect to fluorine is considerably increased from 10 to 58 mmol/g. Aluminosilicate in the DMA composition has 1.3 times greater adsorption capacity with respect to fluorine compared to bulk synthetic aluminosilicate. Since the reactive sites responsible for the adsorption are essentially surface aluminum ions, it is expected that their concentration is closely associated with the content of Al 2 O 3 in aluminosilicate. I t is easy to understand that not all the silica in diatomite matrix, but the surface only was subjected to the substitution of Si atoms with Al, so the surface aluminosilicate composition must contain the increased ratio of Al 2 O 3 / SiO 2 ; it is 0.5 according to some calculation compared to the volume ratio which is 0.33; besides, t he surface aluminosilicate is more or less uniformly distributed on the pore material surface, so more aluminum sites are accessible for interaction with fluoride ions. Furthermore, molecular aluminum and silicon precursors are preferentially grafted on sites that enable the formation of Al(IV) coordination form, and deposited aluminum species on silica are Al(IV) tetrahedrally coordinated species. This specific surface site connectivity eventually enables the formation of Brønsted acid sites. Such acid sites may be formulated as bridging hydroxyls in connection with Al(IV) species, such as pseudo-bridging silanol in Al/SiO 2 , therefore more fluorine is involved in complexes with Al. Apparently, all of the above facts together should be responsible for an increased adsorption capacity of the surface aluminosilicate in the DMA composition.

Corrosion behavior of concrete produced with diatomite and zeolite exposed to chlorides

Chloride induced reinforcement corrosion is widely accepted to be the most frequent mechanism causing premature degradation of reinforced concrete structures. The electrochemical impedance of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sodium chloride was assessed. Chemical, physical and mineralogical properties of three concrete samples (20% diatomite, 20% zeolite, and a reference containing neither) were correlated with corrosion investigations. The steel-reinforced samples were exposed to 3.5% NaCl solution for 500 days, and measured every 15 days via EIS method. Results indicated that porosity and capillary spaces increase the diffusion rate of water and electrolytes throughout the concrete, making it more susceptible to cracking. Reinforcement in the reference concrete was the most corroded compare to the zeolite and the diatomite samples.

Coupled geomechanics and flow modeling of thermally induced compaction in heavy oil diatomite reservoirs under cyclic steaming

Shallow, heavy oil diatomite reservoirs produced using cyclic steaming are often associated with significant subsidence. In cases where the pore pressure is not allowed to deplete noticeably, observed subsidence suggests a mechanism other than pressure decline is responsible. We perform coupled flow and geomechanics modeling to determine whether thermally induced compaction of the reservoir rock could play an important role in subsidence. First, we model laboratory-scale tests on diatomite samples subjected to mechanical and thermal loads. During these tests, substantial non-recoverable thermal compaction was measured. Using the modified Cam-clay model as a basis, thermally induced compaction is implemented by reducing the size of the yield surface as a function of temperature. This leads to a satisfactory modeling of the test results. Second, this new approach is used to model a symmetric pattern of wells in a generic heavy oil diatomite field produced using cyclic steaming. Results from simulations that consider or neglect thermally induced diatomite compaction show that thermal effects can potentially induce significant inelastic pore volume reduction and substantial subsidence.