Search for: calcite
Total 50 records
The effect of calcite cementation on the mechanical behavior of gravely sands, Article 14th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, 23 May 2011 through 27 May 2011, Hong Kong ; 2011 ; Sharif University of Technology
The behavior of a cemented gravely sand is studied using triaxial tests. Undrained tests were performed on saturated specimens, and stress-strain characteristics of the soil, along with volumetric and pore pressure changes, were recognized. Artificially cemented samples are prepared using calcite crystallization as the cementing agent in different percentages. The tests were done in usual range of confining pressures, from 50 to 1200 kPa. The results shows that dilation occurs even at highest confining pressure and least cement content. Also the friction angle of soils increases slightly with cement content, but cohesion intercept increasing is more noticeable
Molecular dynamics simulation investigation of hexanoic acid adsorption onto calcite (1014)surface, Article Fluid Phase Equilibria ; Volume 387 , 2015 , Pages 24-31 ; 03783812 (ISSN) ; Koleini, M. M ; Ayatollahi, S ; Sharif University of Technology
In this paper we report the results of classical molecular dynamics (MD) simulation of hexanoic acid adsorption on calcite (101-4) surface plane using Pavese and AMBER force fields for calcite and hexanoic acid, respectively. Pair correlation function, strictly suggests a well-structured adsorption. Density profile indicates the adsorption occurs through double-bonded O atom of the acid head group by direct interaction with Ca atom at calcite surface. Adsorption orientation of H and double-bonded O atoms was found to be as lock and key with respect to calcite surface Ca and O atoms, facilitating an effective adsorption. Adsorption time evolution indicates that O atom adsorption is...
An atomistic insight into the implications of ion-tuned water injection in wetting preferences of carbonate reservoirs, Article Journal of Molecular Liquids ; Volume 293 , 2019 ; 01677322 (ISSN) ; Badizad, M. H ; Ghatee, M. H ; Ayatollahi, S ; Sharif University of Technology
Elsevier B.V 2019
The efficiency of water flooding methods is known to improve by applying ion-tuned water injection. Although there is a consensus that such improvement happens through reversing reservoir wettability characteristics to more water-wet state, the true impact of ions is still ambiguous among contradictory debates. The well-known molecular dynamics (MD) simulation techniques would shed light on such ambiguities to gain deep atomic-scale understanding of the process. Results from MD simulations show that the presence of Na+ and Cl¯ ions leads to the formation of an electrical double layer in adjacency of calcite surface while Mg2+ ions dominantly make complexes with hydrocarbons throughout the...
Experimental investigation of dynamic asphaltene adsorption on calcite packs: The impact of single and mixed-salt brine films, Article Canadian Journal of Chemical Engineering ; Volume 97, Issue 7 , 2019 , Pages 2028-2038 ; 00084034 (ISSN) ; Ghotbi, C ; Jafari Behbahani, T ; Bakhshi, P ; Sharif University of Technology
Wiley-Liss Inc 2019
In this study, the dynamic adsorption of asphaltene on a calcite surface is investigated. This study investigates the effect of mixed-salt brines on asphaltene adsorption. The results of this work can facilitate the understanding of the complex wettability behaviour of carbonate reservoirs. All experiments were performed in porous media, which were sand-packs filled with calcite powder, to study the influence of the type and concentration of salt on adsorption. The experiments were conducted with asphaltene concentration of 500 mg/L for brines of NaCl, Na2SO4, and a mixture of the two at various ionic strengths. In addition, two tests were performed with an asphaltene concentration of 2000...
Pore-scale simulation of calcite matrix acidizing with hydrochloric acid, Article SPE Journal ; Volume 26, Issue 2 , 2021 , Pages 653-666 ; 1086055X (ISSN) ; Sharif University of Technology
Society of Petroleum Engineers (SPE) 2021
A continuum hydrodynamic model with immersed solid/fluid interface is developed for simulating calcite dissolution by hydrochloric acid (HCl) at the pore scale, and is most accurate for a mass-transfer-controlled dissolution regime under laminar flow conditions. The model uses averaged Navier-Stokes equations to model momentum transfer in porous media and adopts a theoretically developed mass-transfer formulation with assumptions. The model includes no fitting parameter and is validated using experimental results. The findings of previous research and existing models are briefly discussed and their shortcomings and advantages are elucidated. The present model is used in some pore-scale...
Constructing Calcite Core by Microbially Induced Calcite Precipitation (MICP) Usable in Oil and Gas Tests, M.Sc. Thesis Sharif University of Technology ; Yaghmaei, Soheila ; Bazargan, Mohammad ; Ghobadi Nejad, Zahra
Acidizing is the most widely performed job to remove the formation damage, and enhance the oil recovery. Different models have been introduced to design the optimized condition for acidizing. However, none of them are able to predict the optimum injection flow rate in the actual application. As a result, Calcite cores are extracted from reservoirs for conducting experiments and modifying the present models. Nevertheless, acidizing is an intrusive technique destroying the costly extracted cores. Thus, there is a need to construct calcite cores of various porosities and permeabilities to take advantage of them in acidizing modelling.Microbially induced calcite precipitation is a well-known...
The Static Behavior of Calcite Cemented Gravely Sand – Tehran Alluvium Case Study, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen
An understanding of the effect of degree of cementation on static behavior of cemented soils in becoming increasingly important in design and analysis of geotechnical engineering problems. Naturally cemented coarse-grained soils are widely present in many parts of the world. Misunderstanding of the behavior of such soils could lead to under or overestimate of the soil parameters. Previous studies conducted by Prof. Haeri and his co-workers show that most of the alluvial deposit of Tehran, the capital city of Iran. The amount and characteristics of the cementation of the deposit varies in different parts from highly cemented in the north to non-cemented in the south. This deposit consists of...
The Dynamic Behavior of Calcite Cemented Gravelly Sand – A Case Study of Tehran Soil, Ph.D. Dissertation Sharif University of Technology ; Haeri, Mohsen ; Sajjadi, Ali Akbar
An understanding of the effect of degree of cementation on static and dynamic behaviour of cemented soils is becoming increasingly important in design and analysis of geotechnical engineering problems. Naturally cemented coarse-grained soils are widely present in many parts of the world. Misunderstanding of the behaviour of such soils could lead to underestimate or overestimate of the soil parameters. Previous studies conducted by Haeri and his co-workers show that most of the alluvial deposit of Tehran, the capital city of Iran, has a soil with cemented nature. The amount and characteristics of the cementation of the deposit varies in different parts from highly cemented in the north to...
Improvement of Collapsible Soils Using Biocementation Method (Case Study of Gorgan Loess), M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen
Collapsible soils have been encountered in many parts of the world such as Gorgan (a city in North of Iran). In these soils, sudden and large volume changes occur while the water content, loading pressure or both, are passed a threshold limit. One of the serious problems that may occur in the structures constructed on collapsible soils is the catastrophic settlements resulting from increase of water content in the soils. In this research, improvement of mechanical properties of loessial collapsible soil taken from Gorgan has been investigated using biocementation method. There are some microbial processes that can lead to biocementation, which one of them is microbially induced calcite...
Production of Biodiesel Using Calcite Stone as Support Catalyst, M.Sc. Thesis Sharif University of Technology ; Khorasheh, Farhad ; Larimi, Afsanehsadat
The aim of this study is developing and investigating heterogeneous catalysts based on natural calcite for the transesterification of canola oil and methanol in order to produce biodiesel as a renewable and alternative fuel for fossil fuels. At first calcite was calcined at high temperature to decompose calcium carbonate to calcium oxide. Afterward, Mg-Zr/CaO catalysts were prepared with mass ratio of 2:1 Mg:Zr and different weight percent(2.5, 5,7.5 and 10 wt%) on calcite supported by impregnation method. In order to characterized synthesized catalysts used different analysis such as energy dispersive X-ray (EDX) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy...
Wettability alteration modeling for oil-wet calcite/silica nanoparticle system using surface forces analysis: contribution of DLVO versus non-DLVO interactions, Article Industrial and Engineering Chemistry Research ; Volume 57, Issue 43 , 2018 , Pages 14482-14492 ; 08885885 (ISSN) ; Ghazanfari, M. H ; Kazemeini, M ; Jamialahmadi, M ; Helalizadeh, A ; Sharif University of Technology
American Chemical Society 2018
In this work, application of silica nanoparticles for wettability alteration of initially oil-wet calcite was investigated through analysis of surface forces and DLVO theory. Doing so, the wettability and zeta potential of calcite surfaces were measured through the sessile drop method and an in-house experimental setup, respectively. Primary evaluation indicated that incorporating DLVO terms in the Frumkin-Derjaguin model was not sufficient to describe the wettability in an oil-wet calcite/nanofluid system. Sensitivity analysis showed that calculating the double-layer interaction using constant potential-constant potential boundaries along with structural hydrophobic forces (non-DLVO...
A deep look into the dynamics of saltwater imbibition in a calcite nanochannel: temperature impacts capillarity regimes, Article Langmuir ; Volume 36, Issue 31 , 2020 , Pages 9035-9046 ; Koleini, M. M ; Greenwell, H. C ; Ayatollahi, S ; Ghazanfari, M. H ; Sharif University of Technology
American Chemical Society 2020
This research concerns fundamentals of spontaneous transport of saltwater (1 mol·dm-3 NaCl solution) in nanopores of calcium carbonates. A fully atomistic model was adopted to scrutinize the temperature dependence of flow regimes during solution transport under CaCO3 nanoconfinement. The early time of capillary filling is inertia-dominated, and the solution penetrates with a near-planar meniscus at constant velocity. Following a transition period, the meniscus angle falls to a stabilized value, characterizing the capillary-viscous advancement in the calcite channel. At this stage, brine displacement follows a parabolic relationship consistent with the classical Lucas-Washburn (LW) theory....
An experimental study on mechanical behavior of a calcite cemented gravelly sand, Article Geotechnical Testing Journal ; Volume 41, Issue 3 , May , 2018 , Pages 494-507 ; 01496115 (ISSN) ; Haeri, S. M ; Shahrabi, M. M ; Khosravi, A ; Sajadi, A. A ; Sharif University of Technology
ASTM International 2018
In the study presented herein, a simple method for laboratory calcite cementation of a reconstituted gravelly sand was presented. This method was used to prepare cemented gravelly sand specimens, which have similar natural characteristics to alluvial deposit of the city of Tehran. The formation and distribution of calcite bonds, as well as the effectiveness of the presented calcite cementation method in increasing interparticle cohesion, as observed in weakly to moderately cemented soil in Tehran, were evaluated by means of chemical analysis, X-ray diffraction technique, and unconfined compressive strength tests. The cementation technique was used to prepare triaxial specimens with calcite...
Direct insights into the pore-scale mechanism of low-salinity waterflooding in carbonates using a novel calcite microfluidic chip, Article Fuel ; Volume 260 , 15 January , 2020 ; Mahani, H ; Sharif University of Technology
Elsevier Ltd 2020
One of the key open questions in the area of low or controlled salinity water flooding (LSWF or CSWF) is how the observed oil recovery at macro-scale (e.g. Darcy or core-scale) can the explained and what underlying microscopic mechanisms drive it. Thus far, the micromodel investigation of LSWF has been limited to sandstones, remaining challenging to apply to carbonates. In this paper we aim to i) extend the capability to fabricate a novel calcite micromodel using Iceland spar calcite crystal, ii) investigate the pore-scale mechanisms leading to oil recovery from carbonates. A target crude oil-brine-rock (COBR) system was first selected. To screen potential brines which can produce...
Investigation of Interface Phenomena in Low Salinity/Smart Waterflooding by Applying Molecular Dynamics Simulation, Ph.D. Dissertation Sharif University of Technology ; Ayatollahi, Shahab ; Ghazanfari, Mohammad Hossein ; Koleini, Mhammad Mehdi
Low salinity/smart waterflooding is simple to apply and a promising enhanced oil recovery method in which ion-tuned saltwater is injected into subsurface oil reservoirs. Many aspects of this operation, in particular those pertaining to nano-scale, are not yet fully understood. The present dissertation is an attempt to shed light on the microscopic properties and behavior of rock/brine/oil interfaces throughout low salinity/smart waterflooding. Several simulations were carried out for oil/brine and calcite/brine categories each containing various ions and hydrocarbons compounds. The surface contribution of non-functional oil compounds (aromatics and aliphatics) near brine medium was...
Wettability alteration of oil-wet carbonate porous media using silica nanoparticles: Electrokinetic characterization, Article Industrial and Engineering Chemistry Research ; Volume 58, Issue 40 , 2019 , Pages 18601-18612 ; 08885885 (ISSN) ; Ghazanfari, M. H ; Sharif University of Technology
American Chemical Society 2019
Application of nanoparticles for wettability alteration offers a practical approach to resolve some surface-related problems encountered in the nowadays technological process. Examples are underground/subsurface engineering implications, including the enhanced oil recovery from the oil-wet carbonate reservoirs. However, the common wettability evaluating techniques such as contact angle and flotation cannot be representative of the dynamic phenomena occurring at the pore scale and hence are unable to give accurate information about the process. Therefore, in the present work, the electrokinetic evaluations are utilized to explore the wettability alteration of initially oil-wet carbonate rock...
An atomistic insight into interfacial properties of brine nanofilm confined between calcite substrate and hydrocarbon layer, Article Applied Surface Science ; Volume 490 , 2019 , Pages 89-101 ; 01694332 (ISSN) ; Badizad, M. H ; Ayatollahi, S ; Sharif University of Technology
Elsevier B.V 2019
Molecular dynamics simulation was applied in this study to scrutinize the interfacial properties of water nano-film confined between calcite mineral and hydrocarbon layer, as two intrinsically different media. Such system resembles the environment experienced by water molecules in the pore spaces of underground carbonate reservoirs. The interplay between water film and confining phases, oil and mineral, strongly influences hydrocarbon production process; however, there is a lack of detailed understanding of the involved interactions. MD simulations indicate development of several layers with different water densities in the confined brine. Water molecules form well-ordered structure in three...
Interactions between Rock/Brine and Oil/Brine interfaces within thin brine film wetting carbonates: A molecular dynamics simulation study, Article Energy and Fuels ; Volume 33, Issue 9 , 2019 , Pages 7983-7992 ; 08870624 (ISSN) ; Badizad, M. H ; Kargozarfard, Z ; Ayatollahi, S ; Sharif University of Technology
American Chemical Society 2019
The thin brine film that wets rock surfaces governs the wettability of underground reservoirs. The ionic composition and salinity of this nanosized brine film influence the wetting preference of the rock pore space occupied by hydrocarbons. Despite numerous investigations over the last decades, a unanimous fundamental understanding that concerns the contribution of ions in the original wetting state of the reservoir is lacking and hence the mechanisms responsible for the wettability reversal of the mineral are still unclear. This wettability reversal is the main consequence of ion-Tuned waterflooding. Although the method is widely accepted in practice, there is no universal consensus on the...
The impact of salinity on the interfacial structuring of an aromatic acid at the calcite/brine interface: an atomistic view on low salinity effect, Article Journal of Physical Chemistry B ; Volume 124, Issue 1 , December , 2020 , Pages 224-233 ; Badizad, M. H ; Hartkamp, R ; Ayatollahi, S ; Ghazanfari, M. H ; Sharif University of Technology
American Chemical Society 2020
This study aims to elucidate the impact of salinity on the interactions governing the adsorption of polar aromatic oil compounds onto calcite. To this end, molecular dynamics simulations were employed to assess adsorption of a model polar organic molecule (deprotonated benzoic acid, benzoate) on the calcite surface in NaCl brines of different concentration levels, namely, deionized water (DW), low-salinity water (LS, 5000 ppm), and sea water (SW; 45,000 ppm). Calcite was found to be completely covered by several well-ordered water layers. The top hydration layer is very compact and prevents direct adsorption of benzoates onto the substrate. Instead, Na+ ions form a distinct positively...
Theoretical and experimental study of foam stability mechanism by nanoparticles: Interfacial, bulk, and porous media behavior, Article Journal of Molecular Liquids ; Volume 304 , 2020 ; Ghotbi, C ; Ashoori, S ; Moghadasi, J ; Kharrat, R ; Sharif University of Technology
Elsevier B.V 2020
Foam flooding has been applied as a promising method in enhanced oil recovery to obviate the challenges of gas flooding such as fingering, channeling and overriding. However, long-term foam stability is crucial for mobility control. In this work, the effective mechanisms on foam stability in the presence of CaCO3 nanoparticles were assessed both theoretically and experimentally. The static and dynamic behaviors of cationic surfactant (HTAB) foam in the presence of CaCO3 nanoparticles with different hydrophobicity were evaluated. The CaCO3 nanoparticles were treated with a series of long-chain fatty acids to generate a range of wettability. Afterward, the underlying mechanisms were revealed...