Sharif Digital Repository

This research provides an atomistic picture of the role of ions in modulating the microstructural features of an oil-contaminated calcite surface. This is of crucial importance for the rational design of ion-engineered waterflooding, a promising technique for enhancing oil recovery from carbonate reservoirs. Inspired by a conventional lab-scale procedure, an integrated series of molecular dynamics (MD) simulations were carried out to resolve the relative contribution of the major ionic constituent of natural brines (i.e., Na+, Cl-, Mg2+, Ca2+, and SO42-) when soaking an oil-bearing calcite surface in different electrolyte solutions of same salinity, namely, CaCl2, MgCl2, Na2SO4, MgSO4, and... 

Low salinity water flooding (LSWF) has the potential to enhance the oil recovery by affecting the fluid-fluid and rock-fluid interactions. Therefore, a systematic investigation on the effect of initial wetting state (water-wet or oil-wet) of pure calcite is conducted to study the importance of these interactions on the effectiveness of LSWF. In the case of initially water-wet cores, more oil recovery efficiency is observed for more saline water cases. To shed light on the possible involved mechanisms, dynamic IFT, dynamic contact angle (CA), oil/brine and rock/brine surfaces zeta potentials, and effluent pH are measured. It is shown that the short-term effect of IFT reduction and long-term... 

In this study, some new aspects of adsorption of a fluorochemical onto carbonate rocks as a wettability alteration agent to a gas wetting condition with the potential application for reduction of condensate blockage in gas condensate reservoirs are presented. To achieve this, kinetics, equilibrium, and thermodynamic of the adsorption process besides contact angle, imbibition, and characterization tests are investigated. Results of adsorption experiments revealed that kinetics behavior of the utilized fluorochemical–calcite system obeyed the pseudo-second order kinetics model. There was no change in adsorption after about 20 h. Also, the intraparticle diffusion mechanism was not the only rate... 

In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,... 

In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,... 

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... 

As an important precursor of crystalline phases, amorphous calcium carbonate (ACC), especially ultrasmall ACC clusters, have been attracting great interest in fundamental research, materials chemistry, as well as industrial applications. However, it is still challenging to synthesize stable ACC clusters in water that can be isolated and concentrated without severe aggregation. Herein, we report a facile dialysis method for producing colloidally stable ACC clusters that are well dispersed in water with the protection of specific polycarboxylic acids, which could be also easily deprotected by small-molecule acids like sodium citrate. Inherent proto-calcite short-range order is found to be... 

In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,... 

Wettability alteration analysis form gas-repellent to gas-wet with the aid of chemical agents has been subjected of numerous studies. However, fundamental understanding of the effect of surface tension of liquid on repellency strength, the change in the intermolecular forces due to the adsorption of nanoparticles onto the rock surfaces, and exposure of treated rock in brine are not well discussed in the available literature. In this study, X-ray diffraction, Atomic Force Microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were applied to characterize the treated and fresh samples. Dynamic and static contact angle measurements were then combined with six methods... 

In this work, sessile drop and low-bond axisymmetric drop shape analysis methods were coupled to provide some new aspects on stick-slip behavior as well as stick time of a drop on calcite surfaces. Slightly hydrophobic calcite surfaces typified with three irregular roughnesses were used to create irregular surfaces to mimic defects for the water-calcite-air systems. Polishing papers of 200, 600, and 1200 grit and a polishing machine were used to prepare surfaces. X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared, and atomic force microscopy techniques were employed to evaluate the chemical and physical properties of surfaces. A model was developed to predict... 

Dynamic contact angle measurement; as a standard method for surface wettability analysis, is usually conducted through the analysis of sessile drops formed following the low rate injection of fluid from beneath through a drilled hole via an injection needle. However, understanding/characterizing the changes of drop contact angle from the point where the flat solid surface begins is not well discussed yet. Moreover, during the evaluation of size-dependent behavior of contact angle of millimeter-scale drops, the effect of the drilled hole is ignored. In this regard, in the current study, the experimental and thermodynamic characterizations of the sessile drop advancing contact angle... 

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.... 

Characterization and calcination behavior of a low-grade manganese ore, as a part of Mn ferroalloys production, was studied by XRF, ex-situ XRD, in-situ XRD, and SEM-EDS techniques. Calcination experiments were carried out at and up to 900 °C (1173 K) in air and argon atmospheres. The samples were in particles and powder forms. The results indicated that both quartz and calcite phases in the ore exhibit a bimodal spatial distribution; as relatively large regions and finely distributed in the Mn- and Fe-containing phases. By Rietveld analysis of the in-situ XRD data, the reactions occurring upon heating during the calcination process were deduced. Thermal decomposition and reactive diffusion... 

In upstream oil industry, microorganisms arise some opportunities and challenges. They can increase oil recovery through microbial enhanced oil recovery (MEOR) mechanisms, or they can increase production costs and risks through reservoir souring process due to H2S gas production. MEOR is mostly known by bioproducts such as biosurfactant or processes such as bioclogging or biodegradation. On the other hand, when it comes to treatment of reservoir souring, the only objective is to inhibit reservoir souring. These perceptions are mainly because decision makers are not aware of the effect microorganisms’ cell can individually have on the wettability. In this work, we study the individual effect... 

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... 

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... 

The petroleum industry suffers from reservoir souring phenomena, which has negative impacts on production facilities, health, and environment. Injection of incompatible water into the reservoir (waterflooding), which is considered as an enhanced oil recovery (EOR) method, is one of the most common causes of reservoir souring. In general, injected brine, especially seawater, contains high amounts of sulfate ion (SO42−). A high concentration of sulfate in the presence of sulfate-reducing bacteria (SRB) leads to the microbial reservoir souring. During this phenomenon, sulfide, specifically hydrogen sulfide gas (H2S) appears in the producing fluid of the reservoir. In this paper, a coupled... 

Gas flooding is a practical secondary scenario for enhanced oil recovery. Channeling and fingering of the injected gas are the major problems facing this technique. These challenges can be mitigated by the injection of gas as foam. However, foam stability influences the overall efficiency of the process, which could be improved by nanoparticles (NPs). This work provides a theoretical and experimental analysis of the NPs wettability effects on foam behavior, in both static and dynamic states. The treated calcite (CaCO3) NPs along with a cationic surfactant (HTAB) were used for this purpose. By comparison of theoretical and experimental data, it was shown that the foam stability in the... 

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... 

A new type of collapsible soil was encountered in Southern Iran and caused some serious technical problems including subsidence, collapse and sinkholes during the construction of Zahedan-Chabahar railway. Field observations indicated that in-situ soil contains excessive amount of salts resulting in dispersive features in response to seepage forces in addition to its collapsibility. Therefore, a systematic research plan including field sampling and laboratory testing was carried out to investigate the observed geotechnical features. Results of physio-chemical tests revealed the dominance of Sodium in excess of 70% relative to total dissolved salts, which results in high dispersive potential....