R. Arabjamaloei - Academia.edu (original) (raw)
Papers by R. Arabjamaloei
Petroleum Science and Technology, 2011
Sand production prediction has always been an important issue when dealing with production phenom... more Sand production prediction has always been an important issue when dealing with production phenomena. Knowing all significant consequences of precise sand production prediction, different methods were developed using a variety of criteria and material models were implemented to obtain more accurate results. Although sand rate prediction has become a prevalent challenge nowadays, it does not reduce sanding onset prediction. Dealing with different methods and knowing the disadvantages of each one will clarify the necessity of developing a technique having the exactness and accuracy of numerical and experimental methods and simplicity of analytical ones. There was an endeavor in this article to apply powerful tools of an artificial neural network to predict critical bottomhole flowing pressure inhibiting sand production. Comprehensive well data gathered from 38 wells distributed in three oilfields producing from the same source rock were investigated to find the main parameters causing sand production. After verifying the proposed model with test wells, it was evaluated against well-accepted analytical models. The final results illustrate a reliable and more exact method that can predict sand initiation with a high degree of accuracy.
Petroleum Science and Technology, 2011
The advanced technology has made directional drilling widely applicable in the drilling industry ... more The advanced technology has made directional drilling widely applicable in the drilling industry for different purposes. The trajectory of a directional well is such that it hits the desired target, typically located away from the surface location of the well, at a specified depth and angle. The well trajectory's azimuth and inclination have very obvious and important effects on the directional drilling performance. The aim of this study is to optimize the trajectory of the well to achieve maximum rate of penetration (ROP) as well as maximum possible wellbore stability. To achieve this, a model that predicts the ROP in a directional well is developed using artificial neural networks (ANNs) based on the 15 input parameters. In the modeling, in addition to the azimuth and angle of the well trajectory, drilling operation parameters and principal stresses of the region are included as inputs. The optimizing process is then performed to achieve the maximum rate of penetration to propose the related azimuth and angle of trajectory. Finally, the provided well trajectory is checked to examine the stability of the wellbore. As the final result a well trajectory that provides the maximum rate of penetration as well as the best stability of the wellbore is designed and proposed. This work also considers the properties of different formations existing in the well path, controlling the direction to hit the desired target at the specified depth.
Petroleum Science and Technology, 2011
Exact detection of lithologic boundaries is one of the main challenges in exploration, drilling o... more Exact detection of lithologic boundaries is one of the main challenges in exploration, drilling operations, and geology. Investigation of facies discontinuities has been performed using petrophysical data regarding sharp changes along the wellbore. Due to the fact that recorded well logging signals contain lots of high-frequency waves (noise), detection of the layer boundaries comes with some uncertainties that should be eliminated by denoising those signals. Wavelet transform analysis is a good approach to denoise the signals and its ability has been proven in several studies. In this study, implementation of wavelet transform analysis resulted in an innovative approach for exact differentiation of neighborhood lithologic units.
Petroleum Science and Technology, 2012
Abstract Many laboratory studies show that numerous variables related to crude oil, reservoir roc... more Abstract Many laboratory studies show that numerous variables related to crude oil, reservoir rock, and salt water exists that affect production rates. Meanwhile, many observations have shown that the combination of salt-water properties and injection conditions has a prominent effect on the microscopic displacement of crude oil by injecting water. A crucial reduction of injectivity of wells may occur due to formation damage during the process of water injection in petroleum reservoirs. Therefore, study of the effect of ...
Petroleum Science and Technology, 2011
... 10916460903581369 R. Arabjamaloei a , S. Shadizadeh b , M. Ekramzadeh c , A. Hamzei c &am... more ... 10916460903581369 R. Arabjamaloei a , S. Shadizadeh b , M. Ekramzadeh c , A. Hamzei c & M. Azad c pages 1615-1624. ... Abu Dhabi International Conference and Exhibition. October 1013 , Abu Dhabi, United Arab Emirates. Paper No. SPE 88698 View all references). ...
Petroleum Science and Technology, 2011
Skin is one of the most challenging problems in oil and gas production, resulting in a reduction ... more Skin is one of the most challenging problems in oil and gas production, resulting in a reduction in reservoir deliverability. Mechanical skin is introduced to the pay zone during the drilling and completion phase, while rate-dependent skin comes into play as production starts, and is caused by infracting basic Darcy assumptions in a gas reservoir. Dissimilar to conventional gas reservoirs, the formation of condensate jots in a gas condensate reservoir when the bottomhole pressure drops below the dew point causes higher skin, which imposes a greater pressure drop. The authors investigated dependency of skin to flow rate in gas condensate reservoirs through a simulation approach. A radial synthetic reservoir compositional model was developed by using rock and fluid properties and well data based on information from a real gas condensate field in south Iran. A well test analysis was utilized to verify the validity and accuracy of the model. Due to heterogeneity existence in particular field, the authors tried to consider different reservoir and wellbore characteristics in reservoir simulation models. A wide range of rock permeabilities and mechanical skins were examined in different irreducible water saturations. Moreover, all the scenarios were run in two different initial reservoir pressures individually. The result of numerous simulations showed a similarity between the trends of rate-dependent skin versus flow rate for the entire tested model. It was also illustrated that in low-permeable gas condensate reservoirs, the existence of mechanical skin leads to inefficient production. Because mitigation of some kind of mechanical skin types are not efficient, the same simulation study should be performed before starting the drilling operation in a gas condensate reservoir to assess the effect of mechanical skin.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
ABSTRACT Mud filtrate invasion is considered as one of the most common sources of formation damag... more ABSTRACT Mud filtrate invasion is considered as one of the most common sources of formation damage problems in naturally fractured reservoirs. The pore throat aperture is usually believed to be in a consistent trend of change in conventional reservoirs, while fractured reservoirs cannot be dealt with as above since the existence of the fracture. Underbalanced drilling is a drilling operation in which the hydrostatic head of the mud column is maintained at a pressure less than that of fluid in the porous medium. While the well pressure is stabilized at a constant amount lower than the formation pressure, the filtrate invasion can easily occur due to the capillary pressure and fracture opening wideness. As it goes, the same difficulties of conventional reservoirs may be seen in a wider and more intense amount. In this study, there is an endeavor to model the fluid flow behavior of reservoir fluid in the naturally fractured reservoir in order to predict the amount of filtrate invasion into the matrix medium. The modeling is derived according to the validated naturally fractured reservoir models; meanwhile, the hand-developed simulator is run to account for any possible changes of different parameters and concerning the correspondent effect on the final results. The results show a considerable invasion in the case of strong capillary pressure. What seems to be the most determining criteria are the temporary overbalanced and static drilling fluid situations, which in turn they will increase the extent and amount of drilling filtrate invasion. Also, the results show a harsh noticeable damage with low under balanced drilling pressure difference while high under balanced drilling pressure difference leads to nowhere.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
Fracture gradient of formation is a key to determine the casing setting depth in drilling oil/gas... more Fracture gradient of formation is a key to determine the casing setting depth in drilling oil/gas wells. In addition, for projects, such as hydraulic fracturing and enhanced oil recovery injection, knowing the fracture gradient of the injection zone is necessary. Also, the pressure integrity of the exposed open hole dictates the maximum allowed wellbore pressure. Several theoretical and operational methods for predicting fracture pressures have been developed and refined. A Leack-off test, which is the most reliable and common method for evaluating fracture pressure gradient, is performed by too much cost and time and also this test cannot be performed at several points. In the present article, a novel technique is presented to obtain an estimation of fracture pressure gradient from drilling operation data reports. This method is based on the effect of pore pressure and confining pressure on compressive strength of rock and, consequently, on drilling speed. Artificial neural networks were implemented to build a simulator for the rate of penetration and analyze the effect of hydrostatic pressure of wellbore on the rate of penetration. The presented method was performed on field data of an Iranian southern field and the results were satisfactorily close to the actual measured fracture pressure by an average error of about 1%.
Petroleum Science and Technology, 2011
ABSTRACT A polymer flooding technique is developed to reduce the amount of residual oil saturatio... more ABSTRACT A polymer flooding technique is developed to reduce the amount of residual oil saturation that cannot be recovered through waterflooding or gas injection processes. Using polymer flooding in the case of high-viscosity oil has been successful due to reducing mobility ratio (M), whereas there is conflict in efficiency of polymer flooding in the case of low-viscosity oil.In this study, to investigate the behavior of polymer flooding in low-viscosity oil, the transparent materials (glass) were used to construct a micromodel and to study various aspects of micro-displacement. By using a micromodel, the displacement of the fluid and menisci was observed and investigated with the aid of images captured by a camera.In this work, two kinds of quarter five-spot glass micromodel patterns were designed and developed and considered as pores medium. These patterns were saturated with light and low-viscosity oil samples from an Iranian fractured reservoir and then flooded by a polymer slug in low-pressure and low-temperature conditions. Three polymer types, hydrolyzed polyacrylamide (HPAM 25%), very low hydrolyzed polyacrylamide (
Petroleum Science and Technology, 2011
ABSTRACT For drilling optimization, an equation for the rate of penetration (ROP) is necessary. T... more ABSTRACT For drilling optimization, an equation for the rate of penetration (ROP) is necessary. The rate of penetration depends on many factors such as formation properties, mud properties, weight on the bit, rotary speed, mud hydraulics, and size/type of bit. Due to the difficulty of mathematical modeling of ROP, researchers have used experimental results or field data to develop a correlation for ROP. In this study, a new model based on artificial neural networks (ANNs) is designed that is able to predict the ROP using real field data gathered in an Iranian oilfield (Ahwaz oilfield). The new model was successful in predicting ROP. To obtain operating parameters that lead to maximum ROP, the corresponding mathematical equation of an ANN model was implemented in a procedure using a genetic algorithm, which is one of the most reliable methods of optimization, and at different depths the parameters leading to maximum ROP were obtained. This model and its results can be used in Pabdeh and Gurpi formations in all Iranian oilfields and similar shaly formations in the Middle East such as the Iraq, Jaddia, and Aaliji formations corresponding to the Pabdeh formation and the Shiranish formation corresponding to Gurpi.
Petroleum Science and Technology, 2010
ABSTRACT Countercurrent spontaneous imbibition is one of the basic processes in two-phase fluid f... more ABSTRACT Countercurrent spontaneous imbibition is one of the basic processes in two-phase fluid flow in fractured porous media. Many researchers have studied modeling of this phenomenon and analytical and numerical solutions have been presented. Specifying the imbibition face (open face) wetting phase saturation, which acts as a boundary condition, has been one of the main challenges in this area. There is no method to specify the imbibition face boundary condition satisfactorily. In this study a new logical method is introduced to determine the open face boundary condition that is satisfactorily close to experimental results. This method considers different aspects of the process of countercurrent spontaneous imbibition and, based on formulation and effective forces in this process, three pieces of evidence are presented to prove that the wetting phase saturation at the imbibition face is a value that leads to maximum wetting phase and nonwetting phase flow with respect to saturation. Because flow rates in this process are a function of saturation and gradient of saturation with respect to location, the maximum wetting and nonwetting phase flow with respect to only saturation would not lead to maximum reachable flow rates for the process.
Petroleum Science and Technology, 2011
ABSTRACT To simulate multiphase flow in complex recovery processes such as water alternating gas ... more ABSTRACT To simulate multiphase flow in complex recovery processes such as water alternating gas (WAG), it is essential to consider the influences of saturation history on relative permeabilities and capillary pressures of the present phases. This effect, which is known as hysteresis, is generally handled by use of empirical models, and deciding which combinations of hysteresis options and parameters are appropriate for a specific study is required. This study investigates how reservoir simulation results are influenced by the use of different modeling options for hysteresis effect in three-phase flow. Hysteresis models were categorized for wetting and nonwetting phases, and they were applied to relative permeability and capillary pressures. In addition, sensitivity analysis was performed on effective parameters on hysteresis behavior of relative permeability. Laboratory hysteresis data were used in simulation of an immiscible WAG process. It was observed that including hysteresis options in simulation influenced the outputs significantly, mainly on oil recovery and breakthrough times (water and gas). Changing the type of nonwetting model had a negligible influence on the results, whereas the type of wetting hysteresis option had a considerable effect on prediction of recovery and breakthrough times. Furthermore, using hysteresis, capillary pressure was found to have a very weak effect on the outputs. Finally, it was observed that the significance of the hysteresis effect is very sensitive to imbibition residual saturation of oil in the presence of water.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
Tight gas reservoirs are categorized as unconventional gas reservoirs. One of the main characteri... more Tight gas reservoirs are categorized as unconventional gas reservoirs. One of the main characteristics of a tight gas reservoir is the adsorption of gas on the rock surface due to high specific surface area. Desorption is the process of adsorbing gas by the reservoir rock on its surface that is dependent on factors, such as reservoir pressure, reservoir rock type, and temperature. Therefore, analysis of production data using conventional methods is expected to be problematic. In this study, there was an endeavor to model and simulate the desorption phenomena in tight formations to investigate its effect on different properties and to study related reservoirs. The purpose of this work is to model the single-phase radial gas flow in tight gas reservoirs including equilibrium desorption phenomena on the rock surface and Darcy flow in a reservoir. Considering a control volume, the gas desorption rate as a function of time and space is incorporated into the radial continuity equation as a source term. Using a Langmuir-type sorption isotherm, the gas desorption rate is determined at any radius of the reservoir. The resulting governing equation is solved numerically using a finite difference approach. The simulator is used to model a tight reservoir to identify how important parameters affect the performance of a tight gas reservoir. The results suggest that the development of tight gas reservoirs with significant gas desorption can lead to higher production rates and improve the productivity of the gas reservoir. The model developed here can be used as an engineering tool for evaluating the role of adsorbed gases in improving the productivity and extending the life of tight gas reservoirs.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2013
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
ABSTRACT An accurate predictive model for rate of penetration of a drilling bit is crucial for th... more ABSTRACT An accurate predictive model for rate of penetration of a drilling bit is crucial for the drilling optimization procedure. Rate of penetration is a complex function, which is dependent on many factors, such as formation properties, mud properties, weight on the bit, rotary speed, mud hydraulic, and size/type. Due to difficulty of mathematical modeling of the rate of penetration, it seems impossible to present a perfect predictive model for this function. Many researchers have tried to use different approaches to present a model for rate of penetration. These approaches include empirical correlations, statistical models, and artificial neural networks. The proposed models are claimed to work well as predictive tools. In this study, different approaches of prediction of rate of penetration are tested to find the most accurate model and investigate the conditions so that each model works well. A new approach is developed to predict rate of penetration by using fuzzy logic, and this model is used in comparison. The results well illustrate that when having a large amount of data, artificial neural networks work considerably better than other approaches in the prediction of rate of penetration. Moreover, it was found that the presented mathematical equations are weak predictive tools although they are simple to use.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
ABSTRACT Counter-current spontaneous imbibition is one of the main displacement processes in frac... more ABSTRACT Counter-current spontaneous imbibition is one of the main displacement processes in fractured reservoirs. Determination of an imbibition face boundary condition has been the main challenge in this area. A recent work presents a new approach that proposes a solution to specify this boundary condition in the case of infinite core length, which results in a saturation less than the maximum reachable wetting phase saturation. The new method is applicable only in the case of infinite cores and cannot be applied in the case of counter-current spontaneous imbibition in matrix blocks of fractured reservoirs that are finite in length. The case of finite core, which includes a dead end, makes the situation very complex and a new challenge in this area. The present article presents a solution for specifying an imbibition face boundary condition when the imbibition front reaches the dead end of the core. The methodology is based on the investigation of the physics of the counter-current imbibition process in a finite core that includes a dead end. Numerical simulation was used to compare the non-wetting phase recovery rate by implementing different boundary conditions in one- and three-dimensional blocks. The results for the one-dimensional core show that the rate of oil recovery during counter-current spontaneous imbibition is higher when imbibition face saturation is higher, but the recovery fractions reach the same value and rate at late times. For a matrix block, it was illustrated that the new boundary condition leads to a higher recovery rate.
Petroleum Science and Technology, 2011
Sand production prediction has always been an important issue when dealing with production phenom... more Sand production prediction has always been an important issue when dealing with production phenomena. Knowing all significant consequences of precise sand production prediction, different methods were developed using a variety of criteria and material models were implemented to obtain more accurate results. Although sand rate prediction has become a prevalent challenge nowadays, it does not reduce sanding onset prediction. Dealing with different methods and knowing the disadvantages of each one will clarify the necessity of developing a technique having the exactness and accuracy of numerical and experimental methods and simplicity of analytical ones. There was an endeavor in this article to apply powerful tools of an artificial neural network to predict critical bottomhole flowing pressure inhibiting sand production. Comprehensive well data gathered from 38 wells distributed in three oilfields producing from the same source rock were investigated to find the main parameters causing sand production. After verifying the proposed model with test wells, it was evaluated against well-accepted analytical models. The final results illustrate a reliable and more exact method that can predict sand initiation with a high degree of accuracy.
Petroleum Science and Technology, 2011
The advanced technology has made directional drilling widely applicable in the drilling industry ... more The advanced technology has made directional drilling widely applicable in the drilling industry for different purposes. The trajectory of a directional well is such that it hits the desired target, typically located away from the surface location of the well, at a specified depth and angle. The well trajectory's azimuth and inclination have very obvious and important effects on the directional drilling performance. The aim of this study is to optimize the trajectory of the well to achieve maximum rate of penetration (ROP) as well as maximum possible wellbore stability. To achieve this, a model that predicts the ROP in a directional well is developed using artificial neural networks (ANNs) based on the 15 input parameters. In the modeling, in addition to the azimuth and angle of the well trajectory, drilling operation parameters and principal stresses of the region are included as inputs. The optimizing process is then performed to achieve the maximum rate of penetration to propose the related azimuth and angle of trajectory. Finally, the provided well trajectory is checked to examine the stability of the wellbore. As the final result a well trajectory that provides the maximum rate of penetration as well as the best stability of the wellbore is designed and proposed. This work also considers the properties of different formations existing in the well path, controlling the direction to hit the desired target at the specified depth.
Petroleum Science and Technology, 2011
Exact detection of lithologic boundaries is one of the main challenges in exploration, drilling o... more Exact detection of lithologic boundaries is one of the main challenges in exploration, drilling operations, and geology. Investigation of facies discontinuities has been performed using petrophysical data regarding sharp changes along the wellbore. Due to the fact that recorded well logging signals contain lots of high-frequency waves (noise), detection of the layer boundaries comes with some uncertainties that should be eliminated by denoising those signals. Wavelet transform analysis is a good approach to denoise the signals and its ability has been proven in several studies. In this study, implementation of wavelet transform analysis resulted in an innovative approach for exact differentiation of neighborhood lithologic units.
Petroleum Science and Technology, 2012
Abstract Many laboratory studies show that numerous variables related to crude oil, reservoir roc... more Abstract Many laboratory studies show that numerous variables related to crude oil, reservoir rock, and salt water exists that affect production rates. Meanwhile, many observations have shown that the combination of salt-water properties and injection conditions has a prominent effect on the microscopic displacement of crude oil by injecting water. A crucial reduction of injectivity of wells may occur due to formation damage during the process of water injection in petroleum reservoirs. Therefore, study of the effect of ...
Petroleum Science and Technology, 2011
... 10916460903581369 R. Arabjamaloei a , S. Shadizadeh b , M. Ekramzadeh c , A. Hamzei c &am... more ... 10916460903581369 R. Arabjamaloei a , S. Shadizadeh b , M. Ekramzadeh c , A. Hamzei c & M. Azad c pages 1615-1624. ... Abu Dhabi International Conference and Exhibition. October 1013 , Abu Dhabi, United Arab Emirates. Paper No. SPE 88698 View all references). ...
Petroleum Science and Technology, 2011
Skin is one of the most challenging problems in oil and gas production, resulting in a reduction ... more Skin is one of the most challenging problems in oil and gas production, resulting in a reduction in reservoir deliverability. Mechanical skin is introduced to the pay zone during the drilling and completion phase, while rate-dependent skin comes into play as production starts, and is caused by infracting basic Darcy assumptions in a gas reservoir. Dissimilar to conventional gas reservoirs, the formation of condensate jots in a gas condensate reservoir when the bottomhole pressure drops below the dew point causes higher skin, which imposes a greater pressure drop. The authors investigated dependency of skin to flow rate in gas condensate reservoirs through a simulation approach. A radial synthetic reservoir compositional model was developed by using rock and fluid properties and well data based on information from a real gas condensate field in south Iran. A well test analysis was utilized to verify the validity and accuracy of the model. Due to heterogeneity existence in particular field, the authors tried to consider different reservoir and wellbore characteristics in reservoir simulation models. A wide range of rock permeabilities and mechanical skins were examined in different irreducible water saturations. Moreover, all the scenarios were run in two different initial reservoir pressures individually. The result of numerous simulations showed a similarity between the trends of rate-dependent skin versus flow rate for the entire tested model. It was also illustrated that in low-permeable gas condensate reservoirs, the existence of mechanical skin leads to inefficient production. Because mitigation of some kind of mechanical skin types are not efficient, the same simulation study should be performed before starting the drilling operation in a gas condensate reservoir to assess the effect of mechanical skin.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
ABSTRACT Mud filtrate invasion is considered as one of the most common sources of formation damag... more ABSTRACT Mud filtrate invasion is considered as one of the most common sources of formation damage problems in naturally fractured reservoirs. The pore throat aperture is usually believed to be in a consistent trend of change in conventional reservoirs, while fractured reservoirs cannot be dealt with as above since the existence of the fracture. Underbalanced drilling is a drilling operation in which the hydrostatic head of the mud column is maintained at a pressure less than that of fluid in the porous medium. While the well pressure is stabilized at a constant amount lower than the formation pressure, the filtrate invasion can easily occur due to the capillary pressure and fracture opening wideness. As it goes, the same difficulties of conventional reservoirs may be seen in a wider and more intense amount. In this study, there is an endeavor to model the fluid flow behavior of reservoir fluid in the naturally fractured reservoir in order to predict the amount of filtrate invasion into the matrix medium. The modeling is derived according to the validated naturally fractured reservoir models; meanwhile, the hand-developed simulator is run to account for any possible changes of different parameters and concerning the correspondent effect on the final results. The results show a considerable invasion in the case of strong capillary pressure. What seems to be the most determining criteria are the temporary overbalanced and static drilling fluid situations, which in turn they will increase the extent and amount of drilling filtrate invasion. Also, the results show a harsh noticeable damage with low under balanced drilling pressure difference while high under balanced drilling pressure difference leads to nowhere.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
Fracture gradient of formation is a key to determine the casing setting depth in drilling oil/gas... more Fracture gradient of formation is a key to determine the casing setting depth in drilling oil/gas wells. In addition, for projects, such as hydraulic fracturing and enhanced oil recovery injection, knowing the fracture gradient of the injection zone is necessary. Also, the pressure integrity of the exposed open hole dictates the maximum allowed wellbore pressure. Several theoretical and operational methods for predicting fracture pressures have been developed and refined. A Leack-off test, which is the most reliable and common method for evaluating fracture pressure gradient, is performed by too much cost and time and also this test cannot be performed at several points. In the present article, a novel technique is presented to obtain an estimation of fracture pressure gradient from drilling operation data reports. This method is based on the effect of pore pressure and confining pressure on compressive strength of rock and, consequently, on drilling speed. Artificial neural networks were implemented to build a simulator for the rate of penetration and analyze the effect of hydrostatic pressure of wellbore on the rate of penetration. The presented method was performed on field data of an Iranian southern field and the results were satisfactorily close to the actual measured fracture pressure by an average error of about 1%.
Petroleum Science and Technology, 2011
ABSTRACT A polymer flooding technique is developed to reduce the amount of residual oil saturatio... more ABSTRACT A polymer flooding technique is developed to reduce the amount of residual oil saturation that cannot be recovered through waterflooding or gas injection processes. Using polymer flooding in the case of high-viscosity oil has been successful due to reducing mobility ratio (M), whereas there is conflict in efficiency of polymer flooding in the case of low-viscosity oil.In this study, to investigate the behavior of polymer flooding in low-viscosity oil, the transparent materials (glass) were used to construct a micromodel and to study various aspects of micro-displacement. By using a micromodel, the displacement of the fluid and menisci was observed and investigated with the aid of images captured by a camera.In this work, two kinds of quarter five-spot glass micromodel patterns were designed and developed and considered as pores medium. These patterns were saturated with light and low-viscosity oil samples from an Iranian fractured reservoir and then flooded by a polymer slug in low-pressure and low-temperature conditions. Three polymer types, hydrolyzed polyacrylamide (HPAM 25%), very low hydrolyzed polyacrylamide (
Petroleum Science and Technology, 2011
ABSTRACT For drilling optimization, an equation for the rate of penetration (ROP) is necessary. T... more ABSTRACT For drilling optimization, an equation for the rate of penetration (ROP) is necessary. The rate of penetration depends on many factors such as formation properties, mud properties, weight on the bit, rotary speed, mud hydraulics, and size/type of bit. Due to the difficulty of mathematical modeling of ROP, researchers have used experimental results or field data to develop a correlation for ROP. In this study, a new model based on artificial neural networks (ANNs) is designed that is able to predict the ROP using real field data gathered in an Iranian oilfield (Ahwaz oilfield). The new model was successful in predicting ROP. To obtain operating parameters that lead to maximum ROP, the corresponding mathematical equation of an ANN model was implemented in a procedure using a genetic algorithm, which is one of the most reliable methods of optimization, and at different depths the parameters leading to maximum ROP were obtained. This model and its results can be used in Pabdeh and Gurpi formations in all Iranian oilfields and similar shaly formations in the Middle East such as the Iraq, Jaddia, and Aaliji formations corresponding to the Pabdeh formation and the Shiranish formation corresponding to Gurpi.
Petroleum Science and Technology, 2010
ABSTRACT Countercurrent spontaneous imbibition is one of the basic processes in two-phase fluid f... more ABSTRACT Countercurrent spontaneous imbibition is one of the basic processes in two-phase fluid flow in fractured porous media. Many researchers have studied modeling of this phenomenon and analytical and numerical solutions have been presented. Specifying the imbibition face (open face) wetting phase saturation, which acts as a boundary condition, has been one of the main challenges in this area. There is no method to specify the imbibition face boundary condition satisfactorily. In this study a new logical method is introduced to determine the open face boundary condition that is satisfactorily close to experimental results. This method considers different aspects of the process of countercurrent spontaneous imbibition and, based on formulation and effective forces in this process, three pieces of evidence are presented to prove that the wetting phase saturation at the imbibition face is a value that leads to maximum wetting phase and nonwetting phase flow with respect to saturation. Because flow rates in this process are a function of saturation and gradient of saturation with respect to location, the maximum wetting and nonwetting phase flow with respect to only saturation would not lead to maximum reachable flow rates for the process.
Petroleum Science and Technology, 2011
ABSTRACT To simulate multiphase flow in complex recovery processes such as water alternating gas ... more ABSTRACT To simulate multiphase flow in complex recovery processes such as water alternating gas (WAG), it is essential to consider the influences of saturation history on relative permeabilities and capillary pressures of the present phases. This effect, which is known as hysteresis, is generally handled by use of empirical models, and deciding which combinations of hysteresis options and parameters are appropriate for a specific study is required. This study investigates how reservoir simulation results are influenced by the use of different modeling options for hysteresis effect in three-phase flow. Hysteresis models were categorized for wetting and nonwetting phases, and they were applied to relative permeability and capillary pressures. In addition, sensitivity analysis was performed on effective parameters on hysteresis behavior of relative permeability. Laboratory hysteresis data were used in simulation of an immiscible WAG process. It was observed that including hysteresis options in simulation influenced the outputs significantly, mainly on oil recovery and breakthrough times (water and gas). Changing the type of nonwetting model had a negligible influence on the results, whereas the type of wetting hysteresis option had a considerable effect on prediction of recovery and breakthrough times. Furthermore, using hysteresis, capillary pressure was found to have a very weak effect on the outputs. Finally, it was observed that the significance of the hysteresis effect is very sensitive to imbibition residual saturation of oil in the presence of water.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
Tight gas reservoirs are categorized as unconventional gas reservoirs. One of the main characteri... more Tight gas reservoirs are categorized as unconventional gas reservoirs. One of the main characteristics of a tight gas reservoir is the adsorption of gas on the rock surface due to high specific surface area. Desorption is the process of adsorbing gas by the reservoir rock on its surface that is dependent on factors, such as reservoir pressure, reservoir rock type, and temperature. Therefore, analysis of production data using conventional methods is expected to be problematic. In this study, there was an endeavor to model and simulate the desorption phenomena in tight formations to investigate its effect on different properties and to study related reservoirs. The purpose of this work is to model the single-phase radial gas flow in tight gas reservoirs including equilibrium desorption phenomena on the rock surface and Darcy flow in a reservoir. Considering a control volume, the gas desorption rate as a function of time and space is incorporated into the radial continuity equation as a source term. Using a Langmuir-type sorption isotherm, the gas desorption rate is determined at any radius of the reservoir. The resulting governing equation is solved numerically using a finite difference approach. The simulator is used to model a tight reservoir to identify how important parameters affect the performance of a tight gas reservoir. The results suggest that the development of tight gas reservoirs with significant gas desorption can lead to higher production rates and improve the productivity of the gas reservoir. The model developed here can be used as an engineering tool for evaluating the role of adsorbed gases in improving the productivity and extending the life of tight gas reservoirs.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2013
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
ABSTRACT An accurate predictive model for rate of penetration of a drilling bit is crucial for th... more ABSTRACT An accurate predictive model for rate of penetration of a drilling bit is crucial for the drilling optimization procedure. Rate of penetration is a complex function, which is dependent on many factors, such as formation properties, mud properties, weight on the bit, rotary speed, mud hydraulic, and size/type. Due to difficulty of mathematical modeling of the rate of penetration, it seems impossible to present a perfect predictive model for this function. Many researchers have tried to use different approaches to present a model for rate of penetration. These approaches include empirical correlations, statistical models, and artificial neural networks. The proposed models are claimed to work well as predictive tools. In this study, different approaches of prediction of rate of penetration are tested to find the most accurate model and investigate the conditions so that each model works well. A new approach is developed to predict rate of penetration by using fuzzy logic, and this model is used in comparison. The results well illustrate that when having a large amount of data, artificial neural networks work considerably better than other approaches in the prediction of rate of penetration. Moreover, it was found that the presented mathematical equations are weak predictive tools although they are simple to use.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2012
ABSTRACT Counter-current spontaneous imbibition is one of the main displacement processes in frac... more ABSTRACT Counter-current spontaneous imbibition is one of the main displacement processes in fractured reservoirs. Determination of an imbibition face boundary condition has been the main challenge in this area. A recent work presents a new approach that proposes a solution to specify this boundary condition in the case of infinite core length, which results in a saturation less than the maximum reachable wetting phase saturation. The new method is applicable only in the case of infinite cores and cannot be applied in the case of counter-current spontaneous imbibition in matrix blocks of fractured reservoirs that are finite in length. The case of finite core, which includes a dead end, makes the situation very complex and a new challenge in this area. The present article presents a solution for specifying an imbibition face boundary condition when the imbibition front reaches the dead end of the core. The methodology is based on the investigation of the physics of the counter-current imbibition process in a finite core that includes a dead end. Numerical simulation was used to compare the non-wetting phase recovery rate by implementing different boundary conditions in one- and three-dimensional blocks. The results for the one-dimensional core show that the rate of oil recovery during counter-current spontaneous imbibition is higher when imbibition face saturation is higher, but the recovery fractions reach the same value and rate at late times. For a matrix block, it was illustrated that the new boundary condition leads to a higher recovery rate.