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Collaborating Authors
Ayatollahi, Shahab
Insights into the Effects of Pore Structure, Time Scale, and Injection Scenarios on Pore-Filling Sequence and Oil Recovery by Low-Salinity Waterflooding Using a Mechanistic DLVO-Based Pore-Scale Model
Namaee-Ghasemi, Arman (Department of Chemical and Petroleum Engineering, Sharif University of Technology) | Ayatollahi, Shahab (Department of Chemical and Petroleum Engineering, Sharif University of Technology (Corresponding author)) | Mahani, Hassan (Department of Chemical and Petroleum Engineering, Sharif University of Technology (Corresponding author))
Summary Despite the proven advantage of the low-salinity waterflooding (LSWF) technique, mechanistic understanding of the underlying phenomena at pore-scale remains uncertain. Hence, the corresponding models have limited predictability. In this study, wettability alteration via electrical double-layer (EDL) expansion is captured in a pore-scale model using a multispecies, multiphase computational fluid dynamics simulator. A combination of a pore-doublet and snap-off model is used to evaluate the low-salinity effect (LSE) in two geometries with different pore-throat size distributions. Contact angle is calculated intrinsically within the model using the concept of disjoining pressure through the implementation of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and augmented Young-Laplace equation. The results illustrate that even in a simple pore structure, various pore-filling sequences and recoveries are obtained based on the pore geometrical factors, time effects, backward mixing, and injection scenarios. Secondary LSWF results in higher ultimate oil recovery since both small and large pores are accessible to flow and breakthrough is delayed, giving more time for more efficient displacement. Regarding the pore-throat geometry, the case with larger pores connected via larger throats generally exhibits higher ultimate recoveries. However, the geometry with larger pores connected by small throats results in higher incremental recovery via tertiary LSWF. Moreover, an optimal time scale exists in secondary LSWF due to the snap-off phenomenon, while faster LSE results in higher recovery in tertiary mode. The proposed model is capable of mechanistically capturing and predicting LSE and its subsequent flow dynamics, which exhibits a higher recovery factor by LSWF compared to the commonly used linear wettability model. Thus, this approach improves the predictive capability of the previous models as it does not require contact angle data and arbitrary interpolation schemes.
- North America > United States (1.00)
- Europe (1.00)
- Asia > Middle East (0.67)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.68)
- Geology > Geological Subdiscipline (0.68)
Pore-Scale Simulation of the Interplay between Wettability, Capillary Number, and Salt Dispersion on the Efficiency of Oil Mobilization by Low-Salinity Waterflooding
Namaee-Ghasemi, Arman (Sharif University of Technology) | Ayatollahi, Shahab (Sharif University of Technology (Corresponding author) | Mahani, Hassan (email: shahab@sharif.edu))
Summary Nonuniform mixing during low-salinity waterflooding (LSWF) is a function of the pore geometry and flow patterns within the porous system. Salinity-dependent wettability alteration (WA) changes the entry capillary pressure, which may mobilize the trapped oil depending on the flow regime and salt dispersion pattern. The complex interplay between the wettability, capillary number (), and salt dispersion caused by pore-scale heterogeneity on the efficiency of LSWF is not well understood. In this paper, direct numerical simulations in a pore-doublet model (PDM) were carried out with OpenFOAM® (OpenCFD, Berkshire, UK) using the volume-of-fluid (VOF) method. Oil trapping and remobilization were studied at relevant as low as under different initial wettability states. Depending on the effective salinity ranges (ESRs) for the low-salinity effect (LSE), three WA models were implemented, and the effects of WA degree and salinity distribution on LSWF flow dynamics were investigated. The slow process of WA by means of thin film phenomena was captured by considering a diffuse interface at the three-phase contact line. Because of the pore structure of the pore doublet, only in nonwater-wet cases, oil is trapped in the narrower side channel (NSC) after high-salinity waterflooding (HSWF) and may be remobilized by LSWF. In strongly oil-wet cases, oil is recovered gradually by LSWF by means of a film-flow mechanism near the outlet. In moderately oil-wet cases, however, the entire trapped oil ganglion can be mobilized, provided that the entry capillary pressure is sufficiently reduced. The degree of WA, ESR, kinetics of WA, and the wettability of pore surface at the outlet are determining factors in the drainage of the trapped oil. The salt dispersion pattern in the flowing region [i.e., wider side channel (WSC)] controls the wettability distribution and the rate and magnitude of oil recovery from the stagnant region (i.e., NSC). The difference between the WA models is more apparent near the outlet, where the salinity profile is more dispersed. The ESR in which WA occurs determines the speed of the entry capillary pressure reduction and, thus, the recovery factor. In cases where WA occurs at a salinity threshold (ST), the highest recovery is obtained, whereas with the full-salinity-range WA model, the oil recovery performance is lowest. From the capillary desaturation perspective, it is found that the LSE becomes more pronounced when is less than , and the dispersion regime is in the power-law interval. Because the adverse effect of salt dispersion in the flowing region is delayed, the LSE is intensified. For the simulations to be representative of the actual conditions in the porous medium, much lower than currently used in many research works must be studied. Otherwise, the simulations may lead to over- or underestimation of the LSE. The synergetic or antagonistic effects caused by the interplay between viscous and capillary forces and dispersion may lead to total recovery or entrapment of oil, regardless of WA. Based on the pore geometry, initial wettability state, and balance of forces, the mobilized oil may flow past the conjunction (favorable) or in the backward direction (unfavorable) to the WSC and get retrapped. Successful drainage of oil from the pore system after WA is essential for observing incremental oil recovery by LSWF.
- North America > United States (1.00)
- Asia > Middle East (0.67)
- Europe > United Kingdom > England > Berkshire (0.24)
- Geology > Rock Type > Sedimentary Rock (0.68)
- Geology > Geological Subdiscipline (0.67)
Summary Diversion in heterogeneous carbonate reservoirs plays the most important role to the success of acidizing. Without the use of diversion, more acid preferentially flows into the high-permeability region and leaves the low-permeability region underreacted. But a clear understanding of diverting agents, such as polymer-based in-situ-gelled acids, can help uniformly stimulate the near-wellbore region. In this paper, we correct the rheological model that was developed by Ratnakar et al. (2013) according to experimental data from Gomaa and Nasr-El-Din (2010b) by considering shear-rate effect in a two-scale continuum model. It is found that the rheology parameters and shear rate are influential parameters in diversion. In addition, the amount of acid required for the breakthrough is found to be strongly dependent on rheology parameters and permeability in single-coreflood simulation. In our study, the viscosity of the spent acid is found to be the key parameter for diversion efficiency. We have constructed a mechanistic model similar to that in Panga et al. (2005) that simulates the acid injection in two dimensions. Then, we extended our simulation to dual-core systems with different permeability contrasts. The results show that there exists an intermediate injection rate that develops a wormhole in low-permeability core. The results suggest that the dissolution pattern in the high-permeability core is dependent on the permeability contrast. It changes from wormhole to uniform shape when the permeability contrast increases. Introduction Carbonate-matrix acidizing is widely used in oil fields to increase well productivity.
- Asia > Middle East (0.68)
- North America > United States > Louisiana (0.28)
- North America > United States > Texas (0.28)
- Research Report > New Finding (1.00)
- Research Report > Experimental Study (1.00)
Evaluation of the Kinetics of Asphaltene Flocculation during Natural Depletion and CO2 Injection in Heptane-Toluene Mixtures
Kord, Shahin (Petroleum University of Technology) | Dashti, Hossein (Curtin University) | Zanganeh, Peyman (Shahid Bahonar University) | Ayatollahi, Shahab (Sharif University of Technology)
Abstract Carbon dioxide miscible flooding is known as a very efficient and challenging enhanced oil recovery (EOR) method. Besides the high oil recovery efficiency, the asphaltene precipitation and deposition is believed to be triggered by a perturbation of the thermodynamic equilibrium present in the reservoir. Asphaltene deposition results in wettability alteration and plugging in the reservoir as well as affecting the production facilities. The complicated mechanism of phase separation in asphaltene-containing systems makes it crucial to study the effects of different parameters on the aggregation of asphaltene particles. In this study, a novel high-pressure visual cell equipped with a high-resolution microscope along with the image processing software was prepared to investigate the growth of asphaltene particles on a sample reservoir rock. The quantity of asphaltene deposition was determined at several pressure depletion steps and different temperatures with and without CO2 injection. This would help to evaluate the kinetics of asphaltene flocculation resulting from CO2 injection or pressure drop due to natural depletion. The results reveal that the amount of asphaltene deposition increases with increasing the concentration of the injected CO2. The results of this study demonstrated that the molecular structure of asphaltene could have a noticeable effect on the asphaltene deposition.
- Asia (0.46)
- North America > United States (0.28)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.66)
- Water & Waste Management > Water Management > Lifecycle > Treatment (0.62)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Chemical flooding methods (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene (1.00)
- Facilities Design, Construction and Operation > Flow Assurance > Precipitates (paraffin, asphaltenes, etc.) (1.00)
Co-optimization of Enhanced Oil Recovery and Carbon Dioxide Sequestration in a Compositionally Grading Iranian Oil Reservoir; Technical and Economic Approach
Mokhtari, Rasoul (Shiraz University) | Ayatollahi, Shahab (Sharif University of Technology) | Hamid, Karim (National Iranian South Oil Company) | Zonnouri, Ashkan (National Iranian South Oil Company)
Abstract Geological sequestration of carbon dioxide through enhanced oil recovery operation has been recognized as one of the more viable means of reducing emissions of anthropogenic CO2 into the atmosphere. The objective of this paper is to find the best EOR scenario for a compositional grading Iranian oil reservoir to be fed by a giant power plant which produces huge amount of CO2 emission, through simulation study. For this purpose a three-dimensional simplified yet realistic model of the reservoir considering compositional grading was built based on long term production data. Various simulation cases to combine different injection schemes and examining the effect of injection rate were conducted to propose an injection-production strategy that can optimize the oil recovery along with CO2 storage. This study is the first attempt to investigate technical and economic aspects of simultaneous CO2-EOR and sequestration for the nominated reservoir. Besides, this approach could be used for any gas cycling and natural gas storage process into this reservoir. The results presented in the study clearly demonstrated that continuous CO2 injection scheme through one injection and one production well, is the best scenario for simultaneous EOR and sequestration/gas storage which lead to higher CO2 storage and oil recovery efficiency. Through continuous CO2 injection, this reservoir has potential for large scale CO2-EOR and storage projects (injection of more than 240 thousand metric tons of CO2 per year with only one injection well without any field development plan). Finally an economic study is performed to confirm the best scenario.
- Asia (1.00)
- North America > United States > California (0.46)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (0.61)
- Geology > Rock Type (0.46)
- Reservoir Description and Dynamics > Storage Reservoir Engineering > CO2 capture and sequestration (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Chemical flooding methods (1.00)
- Health, Safety, Environment & Sustainability > Environment > Climate change (1.00)
- (2 more...)
Comparing Different Scenarios for Thermal Enhanced Oil Recovery in Fractured Reservoirs Using Hybrid (Solar-Gas) Steam Generators, A Simulation Study
Yegane, Mohsen Mirzaie (Sharif University of Technology) | Bashtani, Farzad (PERM Inc) | Tahmasebi, Ali (Digital Core Analysis Laboratory, University of Calgary) | Ayatollahi, Shahab (Petroleum University of Technology) | Al-wahaibi, Yahya Mansoor (Sharif University of Technology)
Abstract The application of the renewable energy sources, especially solar energy, for thermal enhanced oil recovery methods as an economical and environmental valuable technique has received many attractions recently. Concentrated Solar Power systems are capable of producing substantial quantities of steam by means of focused sunlight as the heat source for steam generation. This paper aims to investigate viability of using this innovative technology in fractured reservoirs to generate steam instead of using conventional steam generators. A synthetic fractured reservoir with properties similar to those of giant carbonate oil reserves in the Middle East was designed by using commercial thermal simulator. The dual porosity model was used to account for differences in matrix and fracture parameters. Different cyclic and continuous steam injection scenarios using combination of both solar energy and fossil-fuel to generate steam were designed. The cyclic scenarios were different in terms of contribution of solar energy in steam generation and in case of 100% solar scenario a small nightly steam injection using fossil-fuel was suggested to prevent flow back into the wellbore. It was assumed that total amount of injected steam in 10 year time period is the same for all the scenarios regardless of how steam was generated. Simulation results showed that nightly injection of insignificant amount of fossil-fuel-generated-steam in a 100% solar-generated-steam injection process increases the cumulative oil production compared to 100% solar-generated-steam injection system with no nightly injection. Furthermore, there was no significant difference between the final oil recoveries for all the designed cyclic injection scenarios. Although continuous steam injection scenario had the highest final oil recovery among all scenarios, a detailed economical study showed that net present value for 100% solar-generated-steam scenario is the highest. An environmental analysis on all scenarios also indicated significant reduction of CO2 emission into the atmosphere for the latter scenario. Therefore, hybrid steam generators which utilize solar energy instead of traditional fossil-fuel for steam generation is proposed for Middle East fractured reservoirs where there is abundance of sunshine during day time. The findings illustrate high economic efficiency of solar-generated steam injection and highlight it as a green EOR method.
- Europe (1.00)
- Asia > Middle East > Oman (0.47)
Solar Generated Steam Injection in Hamca, Venezuelan Extra Heavy Oil Reservoir; Simulation Study for Oil Recovery Performance, Economical and Environmental Feasibilities
Yegane, Mohsen Mirzaie (Sharif University of technology) | Ayatollahi, Shahab (Sharif University of technology) | Bashtani, Farzad (University of Clagary) | Romero, C.. (Universidad del Zulia)
Abstract Application of solar energy compared to conventional gas-burning boilers for steam generation in thermal Enhanced Oil Recovery processes is a newly attended technology, which brings significant benefits to the petroleum industry through environmental and economical aspects. This technique is especially designed for the regions in which gas-burning steam generation is not viable in large scale. The objective of this study is to investigate about viability of using solar energy to generate steam instead of using conventional steam generators in a Venezuelan extra heavy oil reservoir. Limited gas production policy of the Venezuelan government is the major challenge for utilizing gas steam generators for extra heavy oil reservoirs in this country. Besides, the efficient daylight duration, economic and environmental advantages, are the main features to propose solar-generated-steam injection in Venezuelan extra heavy oil reservoirs. In this study, various scenarios of steam injection on Hamaca-Venezuelan heavy oil reservoir-have been investigated using commercial thermal simulator software and the main results of oil production for similar time periods (5 years) are compared. To compensate the energy needed for the steam generators during the night time, dual types steam generators were proposed to utilize solar and fossil energies during day-time and night time respectively. The simulation results for this extra heavy oil reservoir indicated that the oil production was not significantly improved when solar method is used regardless of the amount of the nightly injection of fossil-fuel generated steam for flow back prevention. This finding illustrated high economic efficiency for solar-generated steam injection compared to dual type (solar and fossil-fuel) steam generator method. Furthermore, the results indicated that in typical imposed cyclic steam injections in integrated solar thermal projects, there is no significant difference in oil productions in various scenarios with different pattern and rate of steam injection if the total amount of injected steam is constant. In addition, this study shows the significant reduction of CO2 and Sulfur Oxides emissions if this new technology is implemented. Besides, various scenarios (with and without natural gas backup) were designed for exact day light duration profile in vicinity of the reservoir in order to optimize the oil production as well as accurate economic and environmental evaluation for each scenario.
- Asia (0.68)
- South America > Venezuela (0.66)
- North America > United States > California (0.28)
A New Method for Wettability Alteration by Use of Cold Atmospheric Pressure Argon/Oxygen Plasma Torch
Heidari, Mohammad A. (Islamic Azad University Science and Research branch) | Habibi, Ali (University of Tehran) | Ayatollahi, Shahab (University of shiraz) | Sohbatzadeh, Farshad (University of Mazandaran)
Wettability is always an important issue for reservoir engineers. Wettability alteration is one of the significant indexes to show the capability of oil recovery of reservoir. In the recent years, various approaches to change wettability have been suggested by scientists and researchers such as chemical flooding and nanofluid injection. The purpose, in oil wet condition, is to change wettability to water wet condition to obtain more recovery. A lot of different methods for wettability measurement such as Contact Angle, Amott methods and USBM are proposed by Anderson and others. The most accurate method is contact angle for wettability measurement. Plasma is one of the four fundamental states of matter. Heating a gas may ionize its molecules or atoms thus turning it into a plasma which contains charged particles: positive ions and negative electrons or ions. A nonthermal plasma is in general any plasma which is not in thermodynamic equilibrium, either because the ion temperature is different from the electron temperature or because the velocity distribution of one of the species does not follow a distribution. The effect of cold atmospheric argon/oxygen plasma torch based on dielectric barrier discharge was investigated on different surfaces. The experiments were conducted on the mica, glass slide and slice of dolomite core surface which is aged with oil and without oil and on a dolomite core with oil after waterflooding. The time interval of plasma torch treatment on these surfaces were 1, 3 and 5 minutes and contact angle measurements done 1, 14 and 28 minutes after plasma treatment. The range of contact angle decrease is between 5 to 41 degree and Fourier Transform Infrared Radiation (FTIR) spectroscopy was carried out for analysis of surface chemistry. It is worth mentioning, however, that it is a novel method and requires more investigation in order to be feasible in reservoir conditions.
- Asia (0.47)
- North America > United States (0.46)
Effect of Time and Temperature on Crude Oil Aging to do a Right Surfactant Flooding with a New Approach
Heidari, Mohammad A (Islamic Azad University Science and Research branch) | Habibi, Ali (University of Tehran) | Ayatollahi, Shahab (Shiraz University) | Masihi, Mohsen (Sharif University of Technology) | Ashoorian, Sefatallah (Sharif University of Technology)
Dilute Surfactant flooding is one of the significant processes in chemical flooding. Many oil reservoirs became appropriate candidates for surfactant/water flooding when screening criteria developed. Injected surfactant tries to mobilize the residual oil that was trapped in interstice. The main contributing mechanism for oil recovery improvement by surfactant flooding is rock wettability alteration. Wettability is a one of the proper index in choosing the best approach for a successful surfactant flooding which tiny change in wettability alteration will lead to improve oil recovery. This experimental study investigated the effect of different aging time and temperature on wettability alteration with exact soaking time to find the optimum condition. Afterwards, coreflooding experiments were performed to determine the impact of dilute cationic surfactant slug with huff ‘n’ puff(cyclic 7 days) method on displacement sweep efficiency in the carbonate core from one of the Iranian oil field. Besides, contact angle and interfacial tension (IFT) measurements were done to provide the supplementary data for a surfactant/waterflooding. The optimum concentrations of C19tab, were determined by measuring interfacial tension values of the crude oil in contact with surfactant solutions, which were prepared from synthetic saline water. The results obtained from laboratory showed a reduction in residual oil saturation by changing contact angle and IFT reduction between oil and water. Aging is known as important parameter for researcher to alter the wettability. Furthermore it proves effect of wettability alteration is more than IFT reduction.
- Asia (1.00)
- North America > United States > Missouri (0.28)
- Research Report > New Finding (0.49)
- Overview > Innovation (0.40)
- Geology > Mineral (0.70)
- Geology > Geological Subdiscipline (0.49)
Nanotechnology-Assisted EOR Techniques: New Solutions to Old Challenges
Ayatollahi, Shahab (EOR Research Center, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz, Iran (now with Sharif University of Technology, Tehran, Iran)) | Zerafat, Mohammad M. (EOR Research Center, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz, Iran)
Abstract Enhanced Oil Recovery techniques are gaining more attention worldwide as the proved oil reserves are declining and the oil price is hiking. Although many giant oil reservoirs in the world were already screened for EOR processes, the main challenges such as low sweep efficiency, costly techniques, possible formation damages, transportation of huge amounts of EOR agents to the fields especially for offshore cases, analyzing micro-scale multi-phase flow in the rock to the large scale tests and the lack of analyzing tools in traditional experimental works, hinder the proposed EOR processes. Our past experiences on using nanotechnology to the upstream cases, especially EOR processes, revealed solutions to some of the challenges associated with old EOR techniques. This method that utilizes particles in the order of 1 to100nm brings specific thermal, optical, electrical, rheological and interfacial properties which are directly useful to release the trapped oil from the pore spaces in the order of 5 to 50 microns of tight oil formations. Laboratory tests using nanoparticles as the EOR agent, developing nano computational models to explore the surface properties and utilizing nano-scale analyzing tools such as atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) mostly for nanoparticles distribution in the pore spaces and on the surfaces for wettability alteration studies are the main parts of this investigation. This paper summarizes new findings from several different theoretical, analytical and experimental works which shows the effectiveness of traditional methods when assisted by this new technology. Ultimately, based on the past experiences, a roadmap will be proposed to avoid the ongoing trial and error practice in this area.
- North America > United States (1.00)
- Europe (1.00)
- Asia > Middle East > Iran (0.28)
- Geology > Mineral (0.69)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (0.35)
- Energy > Oil & Gas > Upstream (1.00)
- Water & Waste Management > Water Management > Lifecycle > Treatment (0.47)