Raoof Gholami - Academia.edu (original) (raw)
Papers by Raoof Gholami
International Journal of Oil, Gas and Coal Technology
Journal of Petroleum Exploration and Production Technology
The successful drilling operation depends upon the achievement of target drilling attributes with... more The successful drilling operation depends upon the achievement of target drilling attributes within the environmental and economic constraints but this is not possible only on the basis of laboratory testing due to the limitation of time and resources. The chemistry of the mud decides its rheological potential and selection of the techniques required for recycling operations. Conductivity, pH, and photometer testing were performed for the physio-chemical characterization of the grass to be used as an environmental friendly drilling mud additive. In this study, different particle sizes (75, 150, and 300 µm) of grass powder were mixed in mud density of 8.5, 8.6, and 8.7 ppg in the measurement of gel strength and viscosity of drilling mud. The grass additive was added in different weight conditions considering no additive, 0.25, 0.5, and 1 g to assess the contribution of grass on the gel strength and viscosity of the drilling mud. The machine learning techniques (Multivariate Linear Re...
Journal of Natural Gas Science and Engineering
Depleted gas reservoirs are recognized as the most promising candidate for carbon dioxide storage... more Depleted gas reservoirs are recognized as the most promising candidate for carbon dioxide storage. Primary gas production followed by injection of carbon dioxide after depletion is the strategy adopted for secondary gas recovery and storage practices. This strategy, however, depends on the injection strategy, reservoir characteristics and operational parameters. There have been many studies to-date discussing critical factors influencing the storage performance in depleted gas reservoirs while little attention was given to the effect of residual gas. In this paper, an attempt was made to highlight the importance of residual gas on the capacity, injectivity, reservoir pressurization, and trapping mechanisms of storage sites through the use of numerical simulation. The results obtained indicated that the storage performance is proportionally linked to the amount of residual gas in the medium and reservoirs with low residual fluids are a better choice for storage purposes. Therefore, it would be wise to perform the secondary recovery before storage in order to have the least amount of residual gas in the medium. Although the results of this study are useful to screen depleted gas reservoirs for the storage purpose, more studies are required to confirm the finding presented in this paper.
Journal of Petroleum Science and Engineering, 2021
Undesirable water production due to water coning in hydrocarbon reservoirs has been a long-standi... more Undesirable water production due to water coning in hydrocarbon reservoirs has been a long-standing issue. This phenomenon decreases the oil production rate, increases the water cut and ultimately leads to early well-shutdown. Water coning may also interrupt the well testing data acquisition used to determine the reservoir permeability. In this study, attempts are made to propose a new approach which can control the water coning and estimate the reservoir permeability simultaneously. This was done by proposing a new boundary control model that was coupled by the Ensemble Kalman Filter (EnKF). A synthetic case study was considered to evaluate the performance of the EnKF associated boundary control (EnKF-ABC) approach. The results obtained indicated that the water cone development is controlled by the proposed method. In addition, the proposed method was also successful to estimate the reservoir permeability in the presence of water cone with less than 20% error after 12 times of down...
Journal of Mining and Environment, 2014
A good knowledge of the parameters causing casing damage is critically important due to vital rol... more A good knowledge of the parameters causing casing damage is critically important due to vital role of casing during the life of a well. Cement sheath, which fills in the gap between the casing and wellbore wall, has a profound effect on the resistance of the casing against applied loads. Most of the empirical equations proposed to estimate the collapse resistance of casing ignore the effects of the cement sheath on collapse resistance and rather assume uniform loading on the casing. This paper aims to use numerical modeling to show how a bad cementing job may lead to casing damage. Two separate cases were simulated where the differences between good and bad cementation on casing resistance were studied. In both cases, the same values of stresses were applied at the outer boundary of the models. The results revealed that a good cementing job can provide a perfect sheath against the tangential stress induced by far-field stresses and reduce the chance of casing to be damaged.
Sustainable Agriculture Reviews, 2019
CO2 storage in deep geological formations such as depleted hydrocarbon reservoirs, saline aquifer... more CO2 storage in deep geological formations such as depleted hydrocarbon reservoirs, saline aquifers, and methane coal beds has been recognized as an effective method to prevent climate change in the near future. This chapter gives a deeper insight into the major components of the carbon capture and storage technology as a major greenhouse gas mitigation approach implemented worldwide. The mechanisms, challenges, and issues understood so far linked to this technology are discussed. It appears that if a storage project can be safely implemented given the precautions mentioned in this chapter, a great step can be taken towards a better future for the next generation.
There have been many studies on reservoir compaction where different mechanisms being suggested a... more There have been many studies on reservoir compaction where different mechanisms being suggested as the reasons behind the integrity of unconsolidated reservoirs during production. Theory of poroelasticity is often used to evaluate the likelihood of compaction under these circumstances, but it is often failed to explain the creep behavior of unconsolidated formations. In this study, attempts are made to have a closer look into the compaction mechanism of deep-water sandstone reservoirs. The results obtained indicated that depending on the type of clays, confining pressure and the loading rate, sandstone may exhibit a viscoelastic or viscoplastic behavior during compaction. The results of this study suggest that detailed analysis of clays is required for correct simulations and to answer questions related to geomechanical responses of unconsolidated sandstones under different stress conditions.
SPE Production & Operations
Summary Liquid-liquid phase flow in pipes merits further investigation as a challenging issue tha... more Summary Liquid-liquid phase flow in pipes merits further investigation as a challenging issue that has very rich physics and is faced in everyday applications. It is the main problem challenging the fluid flow mechanism in the oil and gas industry. The pressure gradient of liquid flow and flow pattern are still the topics of numerous research projects. In this paper, the emphasis is on further investigation to research the flow pattern, water holdup (HW), and pressure decrease for vertical, horizontal, and inclined flow directions of oil and water flows. Test section lines of 4.19-in. (106.426 mm) inner diameter (ID) and 5-m horizontal, 5-m inclined, and 5-m vertical test sections were serially connected. The experiments were conducted at 40°C using 2-cp viscosity oil and tap water, and oil density of 850 kg/m3, at the standard conditions. Fifty experiments were executed at 250 kPa at the multiphase flow test facility, with horizontal, upward (0.6° and 4°), downward (−0.6° and −4°) ...
Journal of Natural Gas Science and Engineering
Abstract Coupled with the advances in technology, there has been an overabundance of well log dat... more Abstract Coupled with the advances in technology, there has been an overabundance of well log data which are highly dimensional and carries vital information about the reservoir. Hence, to identify the most relevant data that can improve petrophysical parameters prediction is essential in the accurate characterisation of reservoirs. There has therefore been an increased appetite in the application of a suitable machine learning model to make accurate petrophysical parameter estimations due to previous successes. Enhanced data analytics and visualisation techniques were used to pre-process already interpreted wireline logs from the Volve field, North Sea. Descriptive statistics were used to understand the relationship between variables. The Extreme Gradient Boosting (XGBoost) regression model was used to predict reservoir permeability and water saturation from all the input data. A novel ensemble model of Random Forest and Lasso Regularisation with enhanced feature engineering technique has been proposed in this study. The holdout cross-validation technique was used to compared to existing dimensionality reduction technique like Principal Component Analysis (PCA) to predict reservoir permeability and water saturation, the proposed ensemble model outperformed the traditional XGBoost and a hybrid PCA-XGBoost models in terms of likelihood of fit, precision, consistency and accuracy. The immense potential of ensemble modelling to enhance reservoir characterisation has been demonstrated by the success of this research.
Fuel
Abstract The influence of Supercritical CO2 (SCCO2) on geochemical interaction is considered a ke... more Abstract The influence of Supercritical CO2 (SCCO2) on geochemical interaction is considered a key factor affecting CO2 storage capacity in shales. To address this issue, samples from Eagle Ford and Mancos shales were treated with SCCO2 for 30 days at 70 °C and 18 MPa. Analytical methods including X-ray diffraction (XRD), optical microscope, and Fourier Transform Infrared spectroscopy (FTIR) were used. The alteration in shale/water contact angles was evaluated based on Sessile drop method. The results show that SCCO2 treatment can alter the mineral composition of shales. Quartz content generally increased, while clay and carbonate minerals’ contents decreased. Evaluating the dissolution of carbonate minerals, in particular, is beneficial to form an effective mineral carbonation trapping for long-term CO2 storage. The changes in surface morphology suggest that clay-rich shales are more affected by SCCO2 treatment compared to sandy/quartz-rich shales. The aromatic hydrocarbons showed minor changes after SCCO2 treatment compared to the aliphatic hydrocarbons. The increase in oxygen-containing groups after SCCO2 treatment proves the high adsorption capacity of CO2 in shales. However, hydroxyl functional groups showed various trends after SCCO2 treatment, depending on the clay content. Eagle Ford shales displayed a possible turn to CO2-wet behavior, while the surface of Mancos shales remained strongly hydrophilic. In conclusion, quartz-rich shales could be favorable for CO2 adsorption and providing more storage capacity.
International Journal of Greenhouse Gas Control
Abstract Surface wettability is a key factor controlling the CO2 seal capacity and defines the CO... more Abstract Surface wettability is a key factor controlling the CO2 seal capacity and defines the CO2 storage potential. Limited studies have addressed the shale/water wettability behavior during CO2 injection, thus considerable attention is needed to understand this concept. In this paper, an ample number of supercritical CO2 exposure experiments were conducted to evaluate the alteration of shale/water contact angles. Different types of shales with various mineralogy from Eagle Ford, Wolfcamp, and Mancos fields, were exposed to SCCO2 at different durations, pressures, and temperatures. Shale mineralogy and surface were analyzed using X-ray diffraction and scanning electron microscope. The results indicated a strong relationship between mineral composition and the alteration in shale/water wettability. Clay-rich shales displayed a possible turn in wetting behavior to CO2-wet with extending the SCCO2 treatment time and increasing the treatment pressure, caused by SCCO2 dissolution of clay and carbonate minerals. While the wettability of high-quartz contents shales remained strongly hydrophilic after various SCCO2 treatment conditions. Increasing the temperature accelerated the CO2/shale interactions, and a minor effect was observed on the shale hydrophilicity. Increasing the cohesive energy density of CO2 promotes a favorable CO2 wetting environment, which reduced the hydrophilicity of the surface and reduces the surface energy. In conclusion, shales with high quartz contents exhibit strong water wetting behavior after SCCO2 treatment, which leads to better sealing capacity, more efficient integrity of geological storage sites, and higher potential for CO2 containment.
International Journal of Greenhouse Gas Control
Abstract There have been many studies carried out in the past decade to evaluate the long-term in... more Abstract There have been many studies carried out in the past decade to evaluate the long-term integrity of seals in CO2 storage sites. These seals (caprock and faults) are often dominated by shale and may act as a capillary barrier against the CO2 migration. Thus, geochemical reactions, mineral transformations, surface wettability alteration and reduction of capillary pressure that may take place in a geological storage site must be deeply understood. The main objective of this study is to examine the changes in the mineralogy and surface wettability of shales with different clay contents once exposed to supercritical CO2 for 6 months. The results obtained indicated that quartz dissolution and kaolinite precipitation can be induced in the presence of supercritical CO2. It appeared that brine in a concentration less than 4000 ppm could help to maintain the water wettability of the clay surface. Changes of surface wettability in a storage site could be a dynamic process and linked to the reduction of the surface areas in clays and their affinity to absorb CO2. Given that the interactions between CO2 and rocks are very slow and may take place over a long period of time, further studies are needed to ensure the integrity of seals in storage sites during and after injection.
Handbook of Neural Computation
Support Vector Machine (SVM) has been introduced in the late 1990s and successfully applied to ma... more Support Vector Machine (SVM) has been introduced in the late 1990s and successfully applied to many engineering related applications. In this chapter, attempts were made to introduce the SVM, its principles, structures, and parameters. The issue of selecting a kernel function and other associated parameters of SVMs was also raised and applications from different petroleum and mining related tasks were brought to show how those parameters can be properly selected. It seems that the cross-validation approach would be the best technique for parameter selections of SVMs but few other concerns such as running time must not be neglected.
Journal of Dispersion Science and Technology
Journal of Petroleum Science and Engineering
Abstract Exact prediction and controlling of surge/swab pressure are required during drilling of ... more Abstract Exact prediction and controlling of surge/swab pressure are required during drilling of hydrocarbon reservoirs and other geological formations that often leads to well control challenges. The existing methods to predict the surge/swab pressure gradient in the wellbore are much implicitly developed, which further reduces the model accuracy. Therefore, the present research aims to develop a novel analytical model by incorporating the explicit flow velocity equations to further improve the efficiency in predicting the surge pressure gradient. The governing flow velocity equations are developed for a concentric annulus exhibiting Couette–Poiseuille flow phenomenon that subsequently used in designing a new analytical model for yield power-law fluids to predict surge pressure gradient. Detailed analysis for the validation of a newly developed model is performed using existing predictive models and experimental data of surge pressure. The statistical analysis exhibits satisfactory outcomes with a maximum error of 5.61% and R2 of 0.988. A detailed analysis on the effect of relevant parameters on surge/swab pressure is also presented. The impact of fluid behaviour index and diameter ratio is found to be highly dependent on surge pressure under varying tripping speeds compared to other drilling parameters such as fluid yield point and consistency index.
Energies
Carbon capture and storage (CCS) is a developed technology to minimize CO2 emissions and reduce g... more Carbon capture and storage (CCS) is a developed technology to minimize CO2 emissions and reduce global climate change. Currently, shale gas formations are considered as a suitable target for CO2 sequestration projects predominantly due to their wide availability. Compared to conventional geological formations including saline aquifers and coal seams, depleted shale formations provide larger storage potential due to the high adsorption capacity of CO2 compared to methane in the shale formation. However, the injected CO2 causes possible geochemical interactions with the shale formation during storage applications and CO2 enhanced shale gas recovery (ESGR) processes. The CO2/shale interaction is a key factor for the efficiency of CO2 storage in shale formations, as it can significantly alter the shale properties. The formation of carbonic acid from CO2 dissolution is the main cause for the alterations in the physical, chemical and mechanical properties of the shale, which in return aff...
Journal of Natural Gas Science and Engineering
Abstract Geomechanical analysis and integrity assessment of hydrocarbon reservoirs upon depletion... more Abstract Geomechanical analysis and integrity assessment of hydrocarbon reservoirs upon depletion and injection are crucial to ensure that CO2 storage projects can be safely implemented. The Bredasdorp basin in South Africa has a great potential for CO2 storage given its hugely available exploration data. However, there has not been any geomechanical characterization carried out on this basin to determine its integrity issues. The aim of this study is to provide a guideline as to how geomechanical analysis of depleted fields can be done for a safe CO2 sequestration practice. The results obtained from the geomechanical model constructed for the depth of 2570 m indicated that the magnitude of the principal vertical, minimum and maximum horizontal stresses in the field are respectively 57 MPa, 41 MPa and 42–46 MPa, indicating the presence of a normal faulting regime in the caprock and the reservoir. However, according to the pore pressure-stress coupling assessment, this normal faulting is much severe in compartment C3 of the reservoir. Fault reactivation and fracture stability were also investigated after depletion and it was found that faults in the compartments C1 and C2 are stable after depletion. However, normal faults (FNS8 and FNS9) in compartment C3 dipping SW were critically stressed and may be reactivated without a proper injection planning. Fractures in compartment C3 were also critically stressed, highlighting a great potential of leakage from this compartment upon injection. It was also revealed that the sustainable maximum fluid pressure of 25 MPa would not induce any fractures in the reservoir during CO2 storage.
Journal of Petroleum Exploration and Production Technology
Miscible CO 2-based enhanced oil recovery (CO 2-EOR) flooding has been used, on many occasions, t... more Miscible CO 2-based enhanced oil recovery (CO 2-EOR) flooding has been used, on many occasions, to maximize the recovery by mobilizing the residual oil. The success of this method, however, depends highly on the minimum miscibility pressure (MMP), the compatibility of CO 2 with the reservoir rock and fluids. Although there have been several studies on the application of CO 2-EOR, the impact of oil compositions associated with MMP on the feasibility of this technique has not been addressed elsewhere. In this study, a simulation study was carried out to investigate the effect of three different oil compositions on the miscibility and ultimate oil recovery of miscible CO 2-EOR method. The results obtained indicated the oil type does not pose a significant impact on the success of miscible CO 2-EOR. It was also found that the ultimate recovery of oil increases in a short period of time by injecting CO 2 at the miscible conditions at the early stage of natural production. Comparatively, the reservoir with the fluid sample S2 seems to be a suitable choice for the miscible CO 2 flooding once the recovery factor was considered together with the total amount of the fluid injected and produced.
International Journal of Oil, Gas and Coal Technology
Journal of Petroleum Exploration and Production Technology
The successful drilling operation depends upon the achievement of target drilling attributes with... more The successful drilling operation depends upon the achievement of target drilling attributes within the environmental and economic constraints but this is not possible only on the basis of laboratory testing due to the limitation of time and resources. The chemistry of the mud decides its rheological potential and selection of the techniques required for recycling operations. Conductivity, pH, and photometer testing were performed for the physio-chemical characterization of the grass to be used as an environmental friendly drilling mud additive. In this study, different particle sizes (75, 150, and 300 µm) of grass powder were mixed in mud density of 8.5, 8.6, and 8.7 ppg in the measurement of gel strength and viscosity of drilling mud. The grass additive was added in different weight conditions considering no additive, 0.25, 0.5, and 1 g to assess the contribution of grass on the gel strength and viscosity of the drilling mud. The machine learning techniques (Multivariate Linear Re...
Journal of Natural Gas Science and Engineering
Depleted gas reservoirs are recognized as the most promising candidate for carbon dioxide storage... more Depleted gas reservoirs are recognized as the most promising candidate for carbon dioxide storage. Primary gas production followed by injection of carbon dioxide after depletion is the strategy adopted for secondary gas recovery and storage practices. This strategy, however, depends on the injection strategy, reservoir characteristics and operational parameters. There have been many studies to-date discussing critical factors influencing the storage performance in depleted gas reservoirs while little attention was given to the effect of residual gas. In this paper, an attempt was made to highlight the importance of residual gas on the capacity, injectivity, reservoir pressurization, and trapping mechanisms of storage sites through the use of numerical simulation. The results obtained indicated that the storage performance is proportionally linked to the amount of residual gas in the medium and reservoirs with low residual fluids are a better choice for storage purposes. Therefore, it would be wise to perform the secondary recovery before storage in order to have the least amount of residual gas in the medium. Although the results of this study are useful to screen depleted gas reservoirs for the storage purpose, more studies are required to confirm the finding presented in this paper.
Journal of Petroleum Science and Engineering, 2021
Undesirable water production due to water coning in hydrocarbon reservoirs has been a long-standi... more Undesirable water production due to water coning in hydrocarbon reservoirs has been a long-standing issue. This phenomenon decreases the oil production rate, increases the water cut and ultimately leads to early well-shutdown. Water coning may also interrupt the well testing data acquisition used to determine the reservoir permeability. In this study, attempts are made to propose a new approach which can control the water coning and estimate the reservoir permeability simultaneously. This was done by proposing a new boundary control model that was coupled by the Ensemble Kalman Filter (EnKF). A synthetic case study was considered to evaluate the performance of the EnKF associated boundary control (EnKF-ABC) approach. The results obtained indicated that the water cone development is controlled by the proposed method. In addition, the proposed method was also successful to estimate the reservoir permeability in the presence of water cone with less than 20% error after 12 times of down...
Journal of Mining and Environment, 2014
A good knowledge of the parameters causing casing damage is critically important due to vital rol... more A good knowledge of the parameters causing casing damage is critically important due to vital role of casing during the life of a well. Cement sheath, which fills in the gap between the casing and wellbore wall, has a profound effect on the resistance of the casing against applied loads. Most of the empirical equations proposed to estimate the collapse resistance of casing ignore the effects of the cement sheath on collapse resistance and rather assume uniform loading on the casing. This paper aims to use numerical modeling to show how a bad cementing job may lead to casing damage. Two separate cases were simulated where the differences between good and bad cementation on casing resistance were studied. In both cases, the same values of stresses were applied at the outer boundary of the models. The results revealed that a good cementing job can provide a perfect sheath against the tangential stress induced by far-field stresses and reduce the chance of casing to be damaged.
Sustainable Agriculture Reviews, 2019
CO2 storage in deep geological formations such as depleted hydrocarbon reservoirs, saline aquifer... more CO2 storage in deep geological formations such as depleted hydrocarbon reservoirs, saline aquifers, and methane coal beds has been recognized as an effective method to prevent climate change in the near future. This chapter gives a deeper insight into the major components of the carbon capture and storage technology as a major greenhouse gas mitigation approach implemented worldwide. The mechanisms, challenges, and issues understood so far linked to this technology are discussed. It appears that if a storage project can be safely implemented given the precautions mentioned in this chapter, a great step can be taken towards a better future for the next generation.
There have been many studies on reservoir compaction where different mechanisms being suggested a... more There have been many studies on reservoir compaction where different mechanisms being suggested as the reasons behind the integrity of unconsolidated reservoirs during production. Theory of poroelasticity is often used to evaluate the likelihood of compaction under these circumstances, but it is often failed to explain the creep behavior of unconsolidated formations. In this study, attempts are made to have a closer look into the compaction mechanism of deep-water sandstone reservoirs. The results obtained indicated that depending on the type of clays, confining pressure and the loading rate, sandstone may exhibit a viscoelastic or viscoplastic behavior during compaction. The results of this study suggest that detailed analysis of clays is required for correct simulations and to answer questions related to geomechanical responses of unconsolidated sandstones under different stress conditions.
SPE Production & Operations
Summary Liquid-liquid phase flow in pipes merits further investigation as a challenging issue tha... more Summary Liquid-liquid phase flow in pipes merits further investigation as a challenging issue that has very rich physics and is faced in everyday applications. It is the main problem challenging the fluid flow mechanism in the oil and gas industry. The pressure gradient of liquid flow and flow pattern are still the topics of numerous research projects. In this paper, the emphasis is on further investigation to research the flow pattern, water holdup (HW), and pressure decrease for vertical, horizontal, and inclined flow directions of oil and water flows. Test section lines of 4.19-in. (106.426 mm) inner diameter (ID) and 5-m horizontal, 5-m inclined, and 5-m vertical test sections were serially connected. The experiments were conducted at 40°C using 2-cp viscosity oil and tap water, and oil density of 850 kg/m3, at the standard conditions. Fifty experiments were executed at 250 kPa at the multiphase flow test facility, with horizontal, upward (0.6° and 4°), downward (−0.6° and −4°) ...
Journal of Natural Gas Science and Engineering
Abstract Coupled with the advances in technology, there has been an overabundance of well log dat... more Abstract Coupled with the advances in technology, there has been an overabundance of well log data which are highly dimensional and carries vital information about the reservoir. Hence, to identify the most relevant data that can improve petrophysical parameters prediction is essential in the accurate characterisation of reservoirs. There has therefore been an increased appetite in the application of a suitable machine learning model to make accurate petrophysical parameter estimations due to previous successes. Enhanced data analytics and visualisation techniques were used to pre-process already interpreted wireline logs from the Volve field, North Sea. Descriptive statistics were used to understand the relationship between variables. The Extreme Gradient Boosting (XGBoost) regression model was used to predict reservoir permeability and water saturation from all the input data. A novel ensemble model of Random Forest and Lasso Regularisation with enhanced feature engineering technique has been proposed in this study. The holdout cross-validation technique was used to compared to existing dimensionality reduction technique like Principal Component Analysis (PCA) to predict reservoir permeability and water saturation, the proposed ensemble model outperformed the traditional XGBoost and a hybrid PCA-XGBoost models in terms of likelihood of fit, precision, consistency and accuracy. The immense potential of ensemble modelling to enhance reservoir characterisation has been demonstrated by the success of this research.
Fuel
Abstract The influence of Supercritical CO2 (SCCO2) on geochemical interaction is considered a ke... more Abstract The influence of Supercritical CO2 (SCCO2) on geochemical interaction is considered a key factor affecting CO2 storage capacity in shales. To address this issue, samples from Eagle Ford and Mancos shales were treated with SCCO2 for 30 days at 70 °C and 18 MPa. Analytical methods including X-ray diffraction (XRD), optical microscope, and Fourier Transform Infrared spectroscopy (FTIR) were used. The alteration in shale/water contact angles was evaluated based on Sessile drop method. The results show that SCCO2 treatment can alter the mineral composition of shales. Quartz content generally increased, while clay and carbonate minerals’ contents decreased. Evaluating the dissolution of carbonate minerals, in particular, is beneficial to form an effective mineral carbonation trapping for long-term CO2 storage. The changes in surface morphology suggest that clay-rich shales are more affected by SCCO2 treatment compared to sandy/quartz-rich shales. The aromatic hydrocarbons showed minor changes after SCCO2 treatment compared to the aliphatic hydrocarbons. The increase in oxygen-containing groups after SCCO2 treatment proves the high adsorption capacity of CO2 in shales. However, hydroxyl functional groups showed various trends after SCCO2 treatment, depending on the clay content. Eagle Ford shales displayed a possible turn to CO2-wet behavior, while the surface of Mancos shales remained strongly hydrophilic. In conclusion, quartz-rich shales could be favorable for CO2 adsorption and providing more storage capacity.
International Journal of Greenhouse Gas Control
Abstract Surface wettability is a key factor controlling the CO2 seal capacity and defines the CO... more Abstract Surface wettability is a key factor controlling the CO2 seal capacity and defines the CO2 storage potential. Limited studies have addressed the shale/water wettability behavior during CO2 injection, thus considerable attention is needed to understand this concept. In this paper, an ample number of supercritical CO2 exposure experiments were conducted to evaluate the alteration of shale/water contact angles. Different types of shales with various mineralogy from Eagle Ford, Wolfcamp, and Mancos fields, were exposed to SCCO2 at different durations, pressures, and temperatures. Shale mineralogy and surface were analyzed using X-ray diffraction and scanning electron microscope. The results indicated a strong relationship between mineral composition and the alteration in shale/water wettability. Clay-rich shales displayed a possible turn in wetting behavior to CO2-wet with extending the SCCO2 treatment time and increasing the treatment pressure, caused by SCCO2 dissolution of clay and carbonate minerals. While the wettability of high-quartz contents shales remained strongly hydrophilic after various SCCO2 treatment conditions. Increasing the temperature accelerated the CO2/shale interactions, and a minor effect was observed on the shale hydrophilicity. Increasing the cohesive energy density of CO2 promotes a favorable CO2 wetting environment, which reduced the hydrophilicity of the surface and reduces the surface energy. In conclusion, shales with high quartz contents exhibit strong water wetting behavior after SCCO2 treatment, which leads to better sealing capacity, more efficient integrity of geological storage sites, and higher potential for CO2 containment.
International Journal of Greenhouse Gas Control
Abstract There have been many studies carried out in the past decade to evaluate the long-term in... more Abstract There have been many studies carried out in the past decade to evaluate the long-term integrity of seals in CO2 storage sites. These seals (caprock and faults) are often dominated by shale and may act as a capillary barrier against the CO2 migration. Thus, geochemical reactions, mineral transformations, surface wettability alteration and reduction of capillary pressure that may take place in a geological storage site must be deeply understood. The main objective of this study is to examine the changes in the mineralogy and surface wettability of shales with different clay contents once exposed to supercritical CO2 for 6 months. The results obtained indicated that quartz dissolution and kaolinite precipitation can be induced in the presence of supercritical CO2. It appeared that brine in a concentration less than 4000 ppm could help to maintain the water wettability of the clay surface. Changes of surface wettability in a storage site could be a dynamic process and linked to the reduction of the surface areas in clays and their affinity to absorb CO2. Given that the interactions between CO2 and rocks are very slow and may take place over a long period of time, further studies are needed to ensure the integrity of seals in storage sites during and after injection.
Handbook of Neural Computation
Support Vector Machine (SVM) has been introduced in the late 1990s and successfully applied to ma... more Support Vector Machine (SVM) has been introduced in the late 1990s and successfully applied to many engineering related applications. In this chapter, attempts were made to introduce the SVM, its principles, structures, and parameters. The issue of selecting a kernel function and other associated parameters of SVMs was also raised and applications from different petroleum and mining related tasks were brought to show how those parameters can be properly selected. It seems that the cross-validation approach would be the best technique for parameter selections of SVMs but few other concerns such as running time must not be neglected.
Journal of Dispersion Science and Technology
Journal of Petroleum Science and Engineering
Abstract Exact prediction and controlling of surge/swab pressure are required during drilling of ... more Abstract Exact prediction and controlling of surge/swab pressure are required during drilling of hydrocarbon reservoirs and other geological formations that often leads to well control challenges. The existing methods to predict the surge/swab pressure gradient in the wellbore are much implicitly developed, which further reduces the model accuracy. Therefore, the present research aims to develop a novel analytical model by incorporating the explicit flow velocity equations to further improve the efficiency in predicting the surge pressure gradient. The governing flow velocity equations are developed for a concentric annulus exhibiting Couette–Poiseuille flow phenomenon that subsequently used in designing a new analytical model for yield power-law fluids to predict surge pressure gradient. Detailed analysis for the validation of a newly developed model is performed using existing predictive models and experimental data of surge pressure. The statistical analysis exhibits satisfactory outcomes with a maximum error of 5.61% and R2 of 0.988. A detailed analysis on the effect of relevant parameters on surge/swab pressure is also presented. The impact of fluid behaviour index and diameter ratio is found to be highly dependent on surge pressure under varying tripping speeds compared to other drilling parameters such as fluid yield point and consistency index.
Energies
Carbon capture and storage (CCS) is a developed technology to minimize CO2 emissions and reduce g... more Carbon capture and storage (CCS) is a developed technology to minimize CO2 emissions and reduce global climate change. Currently, shale gas formations are considered as a suitable target for CO2 sequestration projects predominantly due to their wide availability. Compared to conventional geological formations including saline aquifers and coal seams, depleted shale formations provide larger storage potential due to the high adsorption capacity of CO2 compared to methane in the shale formation. However, the injected CO2 causes possible geochemical interactions with the shale formation during storage applications and CO2 enhanced shale gas recovery (ESGR) processes. The CO2/shale interaction is a key factor for the efficiency of CO2 storage in shale formations, as it can significantly alter the shale properties. The formation of carbonic acid from CO2 dissolution is the main cause for the alterations in the physical, chemical and mechanical properties of the shale, which in return aff...
Journal of Natural Gas Science and Engineering
Abstract Geomechanical analysis and integrity assessment of hydrocarbon reservoirs upon depletion... more Abstract Geomechanical analysis and integrity assessment of hydrocarbon reservoirs upon depletion and injection are crucial to ensure that CO2 storage projects can be safely implemented. The Bredasdorp basin in South Africa has a great potential for CO2 storage given its hugely available exploration data. However, there has not been any geomechanical characterization carried out on this basin to determine its integrity issues. The aim of this study is to provide a guideline as to how geomechanical analysis of depleted fields can be done for a safe CO2 sequestration practice. The results obtained from the geomechanical model constructed for the depth of 2570 m indicated that the magnitude of the principal vertical, minimum and maximum horizontal stresses in the field are respectively 57 MPa, 41 MPa and 42–46 MPa, indicating the presence of a normal faulting regime in the caprock and the reservoir. However, according to the pore pressure-stress coupling assessment, this normal faulting is much severe in compartment C3 of the reservoir. Fault reactivation and fracture stability were also investigated after depletion and it was found that faults in the compartments C1 and C2 are stable after depletion. However, normal faults (FNS8 and FNS9) in compartment C3 dipping SW were critically stressed and may be reactivated without a proper injection planning. Fractures in compartment C3 were also critically stressed, highlighting a great potential of leakage from this compartment upon injection. It was also revealed that the sustainable maximum fluid pressure of 25 MPa would not induce any fractures in the reservoir during CO2 storage.
Journal of Petroleum Exploration and Production Technology
Miscible CO 2-based enhanced oil recovery (CO 2-EOR) flooding has been used, on many occasions, t... more Miscible CO 2-based enhanced oil recovery (CO 2-EOR) flooding has been used, on many occasions, to maximize the recovery by mobilizing the residual oil. The success of this method, however, depends highly on the minimum miscibility pressure (MMP), the compatibility of CO 2 with the reservoir rock and fluids. Although there have been several studies on the application of CO 2-EOR, the impact of oil compositions associated with MMP on the feasibility of this technique has not been addressed elsewhere. In this study, a simulation study was carried out to investigate the effect of three different oil compositions on the miscibility and ultimate oil recovery of miscible CO 2-EOR method. The results obtained indicated the oil type does not pose a significant impact on the success of miscible CO 2-EOR. It was also found that the ultimate recovery of oil increases in a short period of time by injecting CO 2 at the miscible conditions at the early stage of natural production. Comparatively, the reservoir with the fluid sample S2 seems to be a suitable choice for the miscible CO 2 flooding once the recovery factor was considered together with the total amount of the fluid injected and produced.