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The impact of ultrasonic radiation, as an emerging enhanced oil recovery technique, on reservoir fluid properties is of great importance in petroleum engineering. Although the effect of sonication on fluid properties has been widely investigated, the wettability alteration of carbonate rocks via different solutions under ultrasonic radiation has not been considered. In this study, the synergic impact of ultrasonic radiation on the wettability alteration of carbonate rocks was studied by using distilled water, seawater, SDS surfactant, silica nanoparticles, and SDS surfactant–silica nanoparticles solutions. Variance analysis showed that all parameters under ultrasonic radiation, including types of water, surfactant solution, nanoparticles, sonication time, and temperature, were meaningful and had influences on the wettability alteration. The contact angle decreased notably by raising the temperature and sonication time. Ultrasonic waves improved the elimination of chemisorbed fatty acids on the surface, and this could be one of the mechanisms of wettability alteration by the ultrasonic application.

Asphaltene precipitation and its adsorption on different surfaces are challenging topics in the upstream and downstream of the oil industries and the environment. In this research, the phenomenon of asphaltenes adsorption in the presence and absence of water on the surface of magnetite, hematite, calcite, and dolomite nanoparticles (NPs) was investigated. Five asphaltenes of different origins, four NPs as adsorbents and Persian Gulf water were used for three-phase (asphaltene/toluene solution + NPs + water) experiments. Characterization of asphaltenes and NPs was performed using Fourier transform infrared spectroscopic (FTIR), dynamic light scattering (DLS), elemental analysis, and field emission scanning electron microscopy (FESEM). Adsorption experiments were performed in two- (asphaltene/toluene solution + NPs) and three-phase systems. The results showed that the most effective parameters for asphaltene adsorption onto these NPs are the asphaltene composition, namely nitrogen content, and the aromaticity of asphaltenes. The significant effects of these parameters were also confirmed by the relevancy factor function as a sensitivity analysis. In the competition of asphaltene adsorption capacity by NPs, iron oxide NPs had the highest adsorption (Magnetite NPs > Hematite NPs > Calcite NPs > Dolomite NPs). From the results of the experiments in the presence of water phase, it could be pointed out that the asphaltenes adsorption onto the NPs was accompanied by a decrease compared to the experiments in the absence of water. The modeling also showed that physical adsorption has a significant contribution to the asphaltenes adsorption on the surface of iron oxides and lime NPs. The results of this research can assist in a better understanding of the asphaltene adsorption phenomenon and the role of iron oxide and lime NPs in solving this problem.

Rate of penetration management is a matter of importance in drilling operations and it has been used in some research studies. Although conventional approaches for rate of penetration management are mainly focused on analytical and semi-analytical models, several correlations have also been developed for this purpose. The history of rate of penetration management studies extends back more than half a century and ever since, research interest in this concept has never declined, making it a focus of industry and academic studies. In this article, some of these studies are reviewed to achieve a better understanding of rate of penetration management concept, its financial benefits and also its research capacities. This review reveals the most common rate of penetration management methods which applied analytical, semi-analytical and empirical correlations in different fields around the world. In other words, the main purpose of this study is to evaluate the research studies in which different models and correlations have been used as the main approach for rate of penetration management. Based on the results of this review, the best models for performing rate of penetration management studies and the best objective functions for optimization algorithms are introduced. Cited as: Najjarpour, M., Jalalifar, H., Norouzi-Apourvari, S. A review on half a century of experience in rate of penetration management: Application of analytical, semi-analytical and empirical models. Advances in Geo-Energy Research, 2021, 5(3): 252-273, doi: 10.46690/ager.2021.03.03

Asphaltene adsorption on reservoir rock minerals causes wettability alteration and pore plugging which subsequently reduces crude oil production. Also, it has a negative effect on the efficiency of production and enhanced oil recovery operations. In this study, the adsorption of extracted asphaltenes of two samples of Iranian oil fields on dolomite, quartz, and magnetite was investigated in two-and three-phase systems in both static and dynamic flow modes. Mineral adsorbents were analyzed by Brunauer–Emmett–Teller and X-ray fluorescence methods. Also, several laboratory tests including elemental analysis, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy were carried out to characterize asphaltenes. The results showed that in addition to the effect of known parameters such as asphaltenes concentration and specific surface area of the solid phase, the water phase also affects the amount of asphaltenes adsorption. The adsorption amount of asphaltenes increases with increasing the specific surface area of adsorbent (decreasing particle size) and increasing the initial concentration of asphaltenes, and decreases with the addition of water to the two-phase system. The static adsorption amount of asphaltenes in a two-phase system can be up to 90% higher than the adsorption amount in a three-phase system. Doubling the fluid flow rate in dynamic adsorption significantly (by about 20%) reduces the asphaltenes adsorption, which could be a sign of physical adsorption of asphaltenes on adsorbents. The structure and elemental composition of asphaltenes also have a significant effect on asphaltenes adsorption. The asphaltene sample, which had a more aromatic nature and high nitrogen content, had higher adsorption on reservoir rock minerals. Finally, fitting the adsorption equilibrium models with experimental data reveals that the adsorption isotherm model depends on the type and particle size of the adsorbents and the concentration and type of asphaltenes. Cited as : Mohammadi, M.R., Bahmaninia, H., Ansari, S., Hemmati-Sarapardeh, A., Norouzi-Apourvari, S., Schaffie, M., Ranjbar, M. Evaluation of asphaltene adsorption on minerals of dolomite and sandstone formations in two and three-phase systems. Advances in Geo-Energy Research, 2021, 5(1), 39-52, doi: 10.46690/ager.2021.01.05

Optimum acid selection based on reservoir condition is one of the key elements in achieving a successful treatment in carbonate matrix acidizing. High reaction and corrosion rate of regular hydrochloric acid especially in tight reservoirs with high temperatures is considered as a limitation of this acid. One alternative in a high-temperature reservoir is to use in-situ generated hydrochloric. The objective of this study is to simulate acidizing treatment using both regular hydrochloric and in-situ generated hydrochloric acid. A continuum two-scale model for linear and radial flow geometry was used to simulate dissolution pattern. A finite-volume method with an implicit backward Euler scheme was used to solve the governing equations. The results of the simulation in a linear system showed that, due to low face dissolution, the in-situ generated hydrochloric at low injection rates could create longer wormholes with less pore volume to breakthrough. The results also proved that using the in-situ generated hydrochloric acid could lead to less face dissolution and deeper penetration of acid into the reservoir. This acidizing system is very suitable in situations where a low injection rate is needed and regular hydrochloric cannot be used due to higher pore volume to breakthrough and high corrosion rate. Cited as : Kiani, S., Jafari, S., Apourvari, S. N., Mehrjoo, H. Simulation study of wormhole formation and propagation during matrix acidizing of carbonate reservoirs using a novel in-situ generated hydrochloric acid. Advances in Geo-Energy Research, 2021, 5(1): 64-74, doi: 10.46690/ager.2021.01.07

Image-based simulations at pore scale provide direct insight into the impact of the microstructure on flow and transport processes in porous media. Diffusion is an important mechanism of mass transfer in gas or liquid phases, confined in porous media. Similar to fluid flow, the diffusive transport in porous media is a strong function of pore size and structure. Although the effect of porosity, pore connectivity and constrictivity of homogeneous porous media on macroscopic properties is clear, this is not well understood for heterogeneous porous media. This study uses a dual-structural-scale medium to analyze the effect of topological and morphological parameters on effective properties such as permeability and the effective diffusivity. A synthetic porous medium was created by two sizes of small and large glass beads, and 3D pore structure image of the sample was captured by X-ray computed tomography technique. The Stokes and diffusion equations were directly solved on the extracted pore geometry of sample, using a finite element method. The results show a strong nonlinear relationship between constrictivity, as a morphological parameter, with permeability and effective diffusivity. Based on the results obtained from pore-scale imaging and modeling, the connectivity of the pore space is increased by decreasing the Euler number and consequently the permeability and effective diffusivity is increased. Good agreement between image-based computed effective diffusivity with that estimated by van Brakel and Heertjes empirical relation confirms the reliability of this relation for heterogeneous porous medium, which includes constrictivity in addition to porosity and tortuosity, as three important morphological properties.

In reservoir simulation, the fluid composition is usually assumed uniform for the whole reservoir, while in many reservoirs, oil and gas composition changes with depth. This phenomenon which is known as compositional grading could be significant in heavy and super heavy oil reservoirs. In these reservoirs, biodegradation and asphaltene precipitation are considered as the main reasons behind this phenomenon. Compositional grading in heavy oil reservoirs could affect fluid viscosity and vaporizing–condensing mechanism in steam-assisted gravity drainage (SAGD) operations. In this paper, through a simulation study, one of the Iranian heavy oil reservoirs which have a significant compositional grading was selected to investigate the effect of compositional grading on the performance of simulated SAGD method. The reservoir is a fractured carbonate reservoir, and its compositional grading is maintained because of the lack of convection inside the reservoir. To verify the importance of compositional grading, the performance results of the SAGD method for compositional grading case were compared with that of uniform composition case. The result showed that ignoring compositional grading would lead to underestimation of ultimate recovery in the fractured model. The study of SAGD process in a non-fractured reservoir model showed that considering compositional grading has an insignificant effect on SAGD performance.

Magnetic field exposure could change the properties of fluids, such as water. The application of the magnetic field for wettability alteration of carbonate rocks was investigated in the first part of our study. In this part, however, the interfacial tension of surfactant with crude oil and its static adsorption onto calcite surfaces under the magnetic field application were studied. From the results of this study, it can be pointed out that the magnetic field-treated water, the so-called magnetized water decreased the surface tension. The interfacial tension between crude oil and magnetized water did not significantly change. The value of the CMC for SDS surfactant solution with magnetized water as the solvent was decreased by about 7%. However, magnetic field treatment of surfactant solutions did not change the value of CMC. Besides, the interfacial tension between surfactant solutions and crude oil did not remarkably change via the magnetic field application. Magnetized water increased the equilibrium adsorption of surfactant solutions onto calcite at concentrations above the CMC. As for kinetic behaviors of the surfactant solutions, the pseudo-second-order kinetic model was found to be the best one to predict the kinetic behavior of surfactant solutions prepared with magnetized water and deionized water. Moreover, magnetized water increased the adsorption rate at early times and expedited it onto the adsorbent. The magnetic field could increase the SDS surfactant adsorption (at concentrations above the CMC) onto calcite surfaces only if the adsorbent was maintained in the solutions during the magnetic field treatment.

Fluid loss during cementing operation in depleted reservoirs or in deep wells of reservoirs with low breakdown pressure is a major concern for maintaining well integrity. To overcome this problem, the weight of cement slurry is usually reduced. Although various slurry formulations have been proposed during the last decade, the cost and availability of required additives is still an important concern, especially when the oil price is low. The objective of this study is to make lightweight cement slurry with a density of 105 lb/ft 3 , using the combination of natural pozzolan and API class G cement. In this study, a new formulation based on the optimum amount of a natural pozzolan and other additives is proposed. Based on the results of 24-hour compressive strength test and free water volume, 30% replacement of cement powder with pozzolan was selected as an optimal amount. Addition of more pozzolan into the slurry reduces its pumpability even at room temperature. Bottom-hole condition was simulated by increasing the temperature to 150°F and chemical additives were used to maintain the rheological properties of this slurry. Fluid loss control agent, dispersant and retarder were used at optimum values 0.5, 0.08 and 0.05 (%bwoc), respectively. The compressive strength of the cement rock was monitored at 3, 7 and 30 days, reaching 3528 psi after 30 days. Cited as : Larki, O., Norouzi Apourvari, S., Schaffifie, M., Farazmand, R. A new formulation for lightweight oil well cement slurry using a natural pozzolan. Advances in Geo-Energy Research, 2019, 3(3): 242-249, doi: 10.26804/ager.2019.03.02

Wettability alteration in carbonate reservoirs is the main objective of surfactant flooding. While studies confirm that a magnetic field changes the properties of solutions and water, its application for increasing the effectiveness of surfactant solutions for wettability alteration purposes has not been investigated. In this paper, therefore, the wettability alteration of carbonate rocks is investigated via applying a magnetic field on water and surfactant solutions. Based on experimental measurements conducted and results obtained in this study, the magnetic field-treated water, the so-called magnetized water, reduced the contact angle more than the double distilled water after 30 min of contact time. The effect of salinity on the affinity of magnetized water was also investigated for 0.2 wt% NaCl, and similar results were observed. Wettability alteration was also examined by magnetized water as a solvent of Sodium Dodecyl Sulfate (SDS) surfactant solutions. At surfactant concentrations above the Critical Micelle Concentration (CMC), magnetized water as the solvent decreased not only the contact angle remarkably after long contact time (64.5% reduction at 0.245 wt %) but also the surfactant concentration required for the same amount of reduction. The same behavior was also observed for the 0.25 wt% of surfactant solutions (sodium dodecylbenzenesulfonate and sodium C14-16 olefin sulfonate). The effect of the magnetic field treatment on SDS surfactant solutions was also studied. The impact of one-hour magnetic field treatment on surfactant solutions was negligible. However, the treatment of that on immersed rocks in surfactant solutions resulted in the reduction of contact angle, even more than magnetized water as the solvent.

Successful acid fracturing operation could reduce formation damage and increase production rate in a carbonate reservoir. Final fracture conductivity is a critical parameter that determines the success of the acid fracturing operation. A wide range of parameters could affect the fracture conductivity, making its prediction quite difficult. The effect of contact time, type of acid, and rock type has been evaluated before. In this study, however, the effect of concentration of hydrochloric acid (HCl), rock strength, injection rate, acid type, and rock type on the conductivity of the fracture was investigated. Based on our observations, for calcite rock types, greater fracture conductivities were achieved by using HCl 15% compared to HCl 7%. For dolomite, the result was completely different and lower concentration of HCl had better outcome. Depending on the type of acid that was used, different results achieved for rocks with different strength. When low concentration of HCl, HCl 7%, was used as an injection fluid, dolomite with higher strength had better conductivity. However, for strong acid, HCl 15% and emulsified acid, the best results were obtained for calcite with low strength. Injection rates resulted in two different outcomes. At low concentration, the injection rate of 4 ml/min created better fracture conductivity while at high concentration, the injection rate of 10 ml/min generated better results, when injection fluid was HCl. As for emulsified acid, higher injection rate resulted in proper conductivity. In most cases, emulsified acid had better final fracture conductivity. Based on experimental results obtained, three models for three different acid types were developed. The conductivity of rocks after acid etching was predicted based on injection rate, rock strength, and closure stress. Statistical and graphical analysis proved that developed models have a good performance.

Rate of penetration (ROP) management is a matter of importance in drilling operations and it has been considered in different studies. Different machine learning methods such as simple and optimized artificial neural networks (ANNs), support vector machines (SVMs), fuzzy logic (FL) or adaptive neuro-fuzzy inference system (ANFIS), ensemble methods of machine learning and meta-heuristic algorithms have been used for this purpose so far. In this article, some of the studies by using these methods as the main approach for ROP management are reviewed to achieve a better understanding of this concept, its economic benefits and also its research capacities. Results indicate that ANNs are the most popular machine learning method in ROP management, while simple ANNs excel the modified types in this regard. Still, modified ANNs outperform simple ones in terms of prediction accuracy, but as ANNs fall short in superior prediction performance, other machine learning approaches of ROP management such as linear regression (LR), random forest (RF) and gradient boosting method (GBM) have compensated this shortcoming and proved their efficiency and applicability.

Rate of penetration (ROP) management is a matter of great importance in drilling operations, therefore it has been considered in different field management projects and research studies. In this way, several drilling technologies and concepts such as managed pressure drilling (MPD) and mechanical specific energy (MSE) have found their applications in this category. Moreover, some studies have used the bit management approach, while some other authors have developed special computer software and expert systems for this purpose. The history of ROP management studies reaches to more than half a century. In this article, some of these studies are reviewed to achieve a better understanding of this concept, its economic benefits and also its research capacities. Results indicate that among different methods which are discussed in this paper, bit management have the most field applications in ROP management studies.

The nature of asphaltene and mineralogy of reservoir rock affect the adsorption of asphaltene onto the rock surface. The basic goal of the present study is to assess the adsorption of different asphaltenes on quartz as the main mineral of sandstone formations. For this purpose, asphaltenes were separated from four crude oil samples from different Iranian oil reservoirs and their specifications were analyzed applying various methods including Fourier-transform infrared spectroscopy, elemental analysis, dynamic light scattering, and field emission scanning electron microscopy. Also, X-ray fluorescence and Brunauer–Emmett–Teller methods were carried out to analyze the quartz mineral. Adsorption experiments were performed both statically and dynamically and the effects of the water phase and hydrophobicity of quartz on the adsorption of asphaltene on the mineral were evaluated. The calculated H/C ratios of asphaltenes are in the range of 1.2–1.3, and their average particle size is between 46 and 380 nm. The results of static tests showed that asphaltenes uptake by quartz adsorbents is from 1.16 to 6.78 mg/m2. The results of this work indicated that the adsorption amount of asphaltenes on the quartz surface is directly related to the nitrogen content and polarity of asphaltene, but it is not related to the average particle diameter of asphaltenes and their aromatic nature. By double increasing the flow rate in the dynamic adsorption process, the asphaltene uptake by quartz is reduced by about 35%, which could be an indication of the physical nature of asphaltene adsorption on quartz. Finally, compared to the asphaltene uptake by quartz in the two-phase system, the uptake in the three-phase system on average shows a decrease of more than 30%, which indicates the effect of the competitive presence of water with asphaltene for the surface-active sites. Also, the uptake of asphaltene onto the quartz samples increased with increasing the initial asphaltene concentration and decreasing quartz particle sizes. The effect of wettability on asphaltene adsorption in two- and three-phase systems was investigated using hydrophilic and hydrophobic quartz nanoparticles. In both systems, the adsorption of asphaltene on hydrophobic nanoparticles was higher and the adsorption reduction in the three-phase system was calculated to be between 5 and 10%, which was very small compared to hydrophilic nanoparticles with an adsorption reduction of 30–60%. Wettability of nanoparticles compared to their specific surface area showed more importance in asphaltene adsorption.

Successful implementation of nanofluid-assisted enhanced oil recovery (EOR) operation mainly depends on proper determination of the main factors that control both transport and retention of nano-sized particles in porous media. In this study, a new transport scheme using the kinetic Langmuir model was first developed and validated by some experimental data from the literature. This model was then used to investigate the effect of reservoir rock type, clay content, grain size, brine type, and reservoir temperature on distribution of nanoparticles on the rock surface and in the injected fluid in relation to EOR methods. Moreover, a two-phase approach was derived to simulate the effect of these parameters on both wettability alteration and mobility control. Results confirmed that the deposition tendency of silica nanoparticles on limestone is higher than that on sandstone. By increasing clay content, both surface area and deposition sites increases and consequently more nanoparticles were found to retain. In the case of polyethylene glycol (PEG) stabilized silica nanoparticles, the amount of oil recovery increased by increasing the salinity of brine. Increasing the salinity of brine resulted in considerable deposition of silica nanoparticles on the rock surface and made them more water wet. These phenomena eventually increased the final recovery factor from 62% to 79%. Since the temperature simultaneously affects the deposition and detachment kinetics of nanoparticles and the reservoir fluid properties, its effect on oil recovery in nanoassisted-EOR technique cannot be generalized.

Wettability as related to an oil reservoir represents a fluid ‘s propensity to adsorb or stick to a solid surface in the presence of another immiscible liquid. Therefore, wettability is a key aspect in assessing the degree of recovery of oil from the reservoir. This paper aims at the investigation of the effect of resin, asphaltene, anionic surfactant, and hydrophilic nanoparticles on the wettability alteration of calcite and dolomite rocks. In order to provide a better insight into wettability alteration, several laboratory tests were carried out including energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FTIR), and Scanning electron microscopy (SEM). The contact angles measured on the calcite and dolomite rock surfaces for resin (1000 ppm in toluene) after three weeks were 88° and 93°, respectively. The results of contact angle analyses as a screen for two rocks (calcite and dolomite) wettability showed that resin altered the wettability of rock samples to oil-wet. Also, asphaltene as a heavy and polar component has more influence than resin on the wettability alteration towards oil-wet state. The polarization interaction mechanism is the principle method for altering the wettability of samples by asphaltene and resin. EDX analysis illustrated that the amount of carbon and oxygen after aging rocks in oil, asphaltene, and resin increased, and the heteroatoms N and S were appeared on the calcite and dolomite surfaces. Afterwards, the combination of silica (SiO2) nanofluid and anionic surfactant (sodium dodecyl sulfate (SDS)) for modification of wettability of oil-wet carbonate surface was investigated. The most significant changes were observed after 24 h of contacts of rocks with a mixture of nanofluid and anionic surfactant. The contact angle decreased from about 88° to 16° for calcite and from 93° to 15° in the case of dolomite. The main mechanisms responsible for wettability modification by SiO2-SDS surfactant are: first) hydrogen bonding between the hydroxyl groups of silica nanoparticles and the tail of the anionic surfactant, second) the adsorption of SiO2-nanoparticles to the carbonate rock substrate due to a high degree of negative charges.

Asphaltene deposition in the wellbore is considered as a major operational challenge while producing some crude oils. It has been claimed that, external fields, such as electric field and ultrasonic radiation, could help tackling this issue. Although the effect of electric field on the aggregation size and the aggregation rate of asphaltene particles has been investigated before, its correlation with asphaltene deposition in the presence and absence of ultrasonic radiation is not known. In this study, the asphaltene deposition on metal surfaces was first mimicked using an electrodeposition process, and then the effect of ultrasonic radiation on electrodeposition of asphaltene were measured and analysed. Our observations showed that the electric filed itself does not unstable the dissolved asphaltene, and the asphaltene deposition on electrodes, under the effect of DC electric filed, first requires the formation of asphaltene aggregates. The maximum deposition was generated at 2 kV/cm, the exposure time of 300 s to the electric field, and the weight ratio of toluene to heptane 4.2%. It was also found that the structure and composition of asphaltenes, especially their polarity and aromaticity, affect asphaltenes deposition. Among different adsorption kinetic models, the nth-order kinetics model was selected to estimate the amount of deposited asphaltene. Finally, simultaneous ultrasound radiation during the process of electrodeposition, reduced the deposition rate on the metal blades from an average of 65 wt % of the total asphaltene content to 10 wt%. The findings of this study highlight the role of composition and structural properties of asphaltene on its surface deposition in the wellbore. More importantly, simultaneous radiation of ultrasonic waves during electrodeposition process confirms the effectiveness of ultrasonic radiation, as a quite new asphatene remediation technique.

Asphaltene deposition in porous media has a destructive effect on well productivity during primary and secondary oil recovery. Previous research studies have presented models for permeability reduction due to particle deposition in porous media. In this study, a semi-experimental model was modified and a new model was introduced to predict permeability changes due to asphaltene retention in early times of precipitation. The modified model unlike common models considers the size of asphaltene particles, porous media grain size, fluid flow properties and precipitation in pore throat. A set of experiments are done to obtain the parameters needed for modeling and check the validity of model. Crude oil is used as fluid sample and a sand pack filled with glass beads is used as an artificial porous media in flood tests. To identify the size of asphaltene particles, microscopic technique is used. The results of experiments are used to investigate asphaltene deposition in porous media and evaluate model prediction. A new procedure based on the modified model is applied to obtain model parameters and simplify the calculations. The new model can eliminate the deficiencies in previous models for prediction of asphaltene deposition in early stages of particle retention. The model also is validated by experimental results that were reported in the literature before. The results show rational accommodation with experimental data.

High resolution images acquired from X-ray μ-CT are able to map the internal structure of porous media on which multiphase flow properties can be computed. While the resolution of a few micrometers may be sufficient for capturing the pore space of many sandstones, most carbonates exhibit a large amount of microporosity; pores which are below the image resolution and are not resolved at specific resolution. Neglecting the effect of micropores on fluid flow and transport properties of these rocks can cause erroneous results in particular at partial saturations. Current image-based pore scale models typically only consider macropores for simulating fluid flow. In this paper, we quantify the effect of microporosity on the effective permeability of the wetting phase for heterogeneous model structures with varying amount of micro-to-macro porosity. A multi-scale numerical approach is proposed to couple an average effect of micropores with an explicit representation of macropores. The Brinkman equation is solved using a lattice Boltzmann formulation to facilitate the coupling of Darcy and Stokes equations in micropores and macropores, respectively. The results show good agreement between the fine scale solution and the results of the upscaled models in which microporous regions are homogenised. The paper analyses in particular the choice of the momentum sink parameter at low wetting phase saturations. It is shown that this parameter can be found using either a flux-based calculation of permeability of microporous regions or chosen purely on the basis of the effective permeability of these regions.

The injection of solid stabilized water-in-crude oil emulsion to displace heavy crude oil is a new EOR method. Although high emulsion stability, which is essential for achieving the maximum process efficiency, can be obtained using nanoparticles, developing an inexpensive and environmentally friendly technique that improves emulsion stability is highly beneficial to this method. Magnetic field and magnetized water technologies have such capabilities. Contact angle reduction on solid surfaces is among the modifications that occur in the properties of water due to the magnetization. Although studies show that using these technologies might be amenable for enhanced oil recovery, there has been no investigation into their use to alter conventional and solid stabilized water-in-crude oil emulsion stability. In this study, the magnetized water, prepared with distilled water, is used in the process of emulsion preparation and the resulting emulsion stability is compared to that prepared with normal water. Our findings show that using magnetized water improves the stability of solid stabilized emulsion made with fumed silica and iron oxide nanoparticles, while it does not impact the stability of conventional emulsions. Lower three-phase contact angle in case of using magnetized water compared to that of normal water implies that the hydrophobic nanoparticles more rigidly stick to the oil-water interface and more energy is required in order to detach them from the interface. This results in more stable solid stabilized emulsion. Results indicate that applying the magnetic field to a prepared conventional emulsion makes it a bit less stable. The reorientation of asphaltene molecules and resulting disturbance of the interface layer, along with the oil viscosity reduction, which accelerates the coalescence of dispersed water droplets, results in less stable emulsions. Although applying the magnetic field to the solid stabilized emulsion, prepared with fumed silica nanoparticles, has no effect on its stability, it significantly reduces the stability of the iron oxide nanoparticle stabilized emulsion. The magnetic force that exists between the magnets and the iron oxide nanoparticles, forcibly separates them from the interface and leads to emulsion breakage. The findings of this study could help in better understanding of the mechanisms involved in the stability of solid stabilized emulsions. Besides, a new field, in which the magnetized water can be successfully applied, is introduced.

Rate of penetration (ROP) is one of the most important parameters in reducing drilling expenditure. In this paper, a ROP management study has been conducted for a well in Southwest of Iran. As a part of this study, the best approach for ROP prediction was determined by comparing the performance of several methods and particle swarm optimization (PSO) algorithm was implemented for optimization of ROP. This paper highlights the effects of formation thickness and the magnitude of working data-set on the performance of different algorithms which are being used for ROP management studies, especially in horizontal and inclined wells. This topic has special importance, when the results show a massive difference in thin and thick formations for some ROP prediction methods. Comparing the results of different ROP prediction methods showed that hybrid Bingham model has the best performance in ROP prediction; only if a powerful mathematical tool like trust-region method is being used for the determination of its unknown coefficients. This superiority was not generalized in all individual formations and there were different results in the cases of thin and thick formations; so, application of the bag-of-algorithms strategy by using the most accurate method in each formation is suggested for the prediction of ROP. Performing this ROP management project resulted in the prediction of ROP with a total relative error of 13.59% and also 48.30% improvement in ROP.

Solid invasion into the near wellbore region could be considered as the main mechanism of formation damage during drilling and completion operations. This challenge could be alleviated, to a high extent, with the correct size tailoring of the solid particle in the intruding fluids. This requires a better understanding of the effect of some pore scale properties of formation rocks on macroscopic properties. In this study, the capability of the X-ray Computed Tomography (XCT) technique was utilized to relate the local morphological and topological characteristics of porous media to macroscopic hydraulic properties. Both homogeneous and heterogeneous porous samples were considered and the damage was induced by injecting particulate fluid of poly-dispersed solid particles. The spatial variation of porosity, permeability, pore size distribution, throat size distribution, and sectional damage ratio evaluated before and after the induced damage in these samples. The results for homogeneous sample showed that the damage distribution does not follow a uniform pattern and it strongly depends on the structure of the pores in each section of the sample. As for heterogeneous sample, a wide range of damage ratios from nearly 90% in the coarse layer to 16% in the fine layer was observed. The longitudinal damage in each layer corresponds well with one-third to one-seventh of throat size at each subsection. Compared to homogeneous sample, the size exclusion effect is more evident in heterogeneous sample in which most of the damage happens near to the inlet face.

Optimal future management of gas condensate reservoirs requires reliable estimation of the dew point pressure (Pd). Due to the limitations of the available Pd determination methods, such as cost and the prohibitive time for experimental approaches, and inaccuracies and lack of generalization for predictive approaches, it is still necessary to establish more accurate and user friendly Pd paradigms. In this study, various methodologies based on soft computing (SC) techniques, optimization algorithms, and generalized reduced gradient (GRG) method were implemented to develop Pd models based on a widespread databank. Two types of artificial neural networks, namely radial basis function (RBF) neural networks and Multilayer perceptron (MLP) are the employed SC methods. To improve the prediction capability of the latter, Levenberg-Marquardt (LM), Bayesian Regularization (BR), and Scaled Conjugate Gradient (SCG) algorithms were used in the training phase of MLP, while three nature-inspired algorithms, namely Genetic Algorithm (GA), Bat Algorithm (BA), and Salp Swarm Algorithm (SSA) were first considered in the RBF learning phase. Then, the four best-found models were assembled beneath a unified paradigm utilizing a committee machine intelligent system (CMIS). Also, a correlation was developed using GRG. The developed CMIS and GRG correlation were compared with four empirical correlations as well as seven equations of state (EOSs). Based on the results obtained, CMIS model exhibits very satisfactory Pd predictions with an overall average absolute percent relative error (AAPRE) of 5.28%, and outperforms largely the other existing predictive approaches. Furthermore, the developed correlation provided more accurate results compared to existing correlations and EOSs.

Wellbore instability is a big challenge in shale formations. The objective of this study is to investigate the effectiveness of a natural additive as a shale inhibitor. The capability of this additive for reducing ion movement into shale and plugging its pore throats has been tested and compared with salts and nano particles. The ions and water movement into shale and resultant swelling was measured by modified gravimetric, swelling and modified immersion tests. The results showed that using Henna extract could reduce the ion and water movement into shale. In addition, the results of pore pressure tests showed that 3 wt % of Henna extract are more effective than nano particles and could completely plug the pore throats of shale while the mud rheological properties are still maintained. The findings of this study show that the Henna extract could be considered as a cost-effective and an environmentally-friendly shale inhibitor.

Abstract Carbonates are typically heterogeneous over multiple length scales. Due to varying connectivity of pore space features at different scales for carbonates, exhibiting bi-modal or multi-modal pore size distributions, the reliability of petrophysical cross-correlations for predicting the transport properties is reduced. The recent emergence of high resolution micro-CT technology in conjunction with robust numerical methods helps to address this problem. Due to the finite resolution of X-ray images current pore scale flow models only consider macro-pores; the pores which are resolved at the image resolution. The importance of micro-pores in fluid flow and solute transport has been proved, although qualitatively, in many applications including hydrocarbon production from carbonate rocks, CO2 storage and subsurface groundwater remediation. In this study we quantify the effect of microporosity on effective permeability for different porous media with exhibiting a varying amount of micro- and macro-porosity. We combine Gaussian random fields (GRF) and particle based models to construct model structures with dual-scale pore types. The Brinkman equation is solved directly on the images to calculate the effective permeability via the lattice Boltzmann method while quantifying the flux through the micro-porous regions. Connectivity analysis conducted on the samples revealed the connectedness of macro-pores through micro-pores. Micro-porosity incorporation increased the connectivity of the macro-pores and consequently the effective permeability of the whole system. This paper introduces a methodology to quantify the effect of microporosity on the fluid flow and incorporate it into the macropores. The approach was first tested on three homogeneous model structures and images of two sandstone rocks, before being implemented on more heterogeneous model structures with bi-modal pore size distribution. The work presented here enables us to couple the effect of sub-resolution pores and macropores in a physically meaningful way. This approach might have important applications to the calculation of permeability for unconventional reservoir rocks.