Saeed Salehi - Academia.edu (original) (raw)
Papers by Saeed Salehi
ArXiv, 2020
Axiomatizing mathematical structures and theories is an objective of Mathematical Logic. Some axi... more Axiomatizing mathematical structures and theories is an objective of Mathematical Logic. Some axiomatic systems are nowadays mere definitions, such as the axioms of Group Theory; but some systems are much deeper, such as the axioms of Complete Ordered Fields with which Real Analysis starts. Groups abound in mathematical sciences, while by Dedekind's theorem there exists only one complete ordered field, up to isomorphism. Cayley's theorem in Abstract Algebra implies that the axioms of group theory completely axiomatize the class of permutation sets that are closed under composition and inversion. In this article, we survey some old and new results on the first-order axiomatizability of various mathematical structures. We will also review identities over addition, multiplication, and exponentiation that hold in the set of positive real numbers.
Cement sheath, placed between casing and formation, is an important barrier to provide a hydrauli... more Cement sheath, placed between casing and formation, is an important barrier to provide a hydraulic seal and establish zonal isolation, preventing fluid communication in the wellbore. In geothermal wells, the temperature at the bottom hole is high. Thermal stress induced by temperature is one of the major considerations to trigger failure in the cement sheath. In this study, a numerical model was created based on the FORGE geothermal well in Utah to investigate the effect of casing pressure, temperature and thermal related parameters on cement integrity of casing-cement-formation systems. To achieve the object, a 3D finite element numerical model consisting of casing-cementformation was developed. The model assumed that the cement-casing and cement-formation interfaces are bonded. Maximum and minimum horizontal stresses from FORGE geothermal well drilling reports were applied as far-field tectonic stresses. Elastic modulus and mechanical strength used in the model were obtained throu...
Journal of Energy Resources Technology
This study presents a laboratory experimental research to determine the characteristics of lost c... more This study presents a laboratory experimental research to determine the characteristics of lost circulation materials (LCMs) capable of addressing thermal degradation, providing bridging and sealing in geothermal conditions. Eleven different materials were tested: Walnut Fine, Walnut Medium, Sawdust, Altavert, Graphite Blend, Bentonite Chips, Micronized Cellulose (MICRO-C), Magma Fiber Fine, diatomaceous earth/amorphous silica powder (DEASP), Cotton Seed Hulls, and a Calcium Carbonate Blend. The filtration and sealing pressure of the LCMs were measured with HPHT equipment up to 149 °C (300 °F). Besides, the particle size distribution (PSD) of fine granular materials was measured. The results show that the performance of some LCM materials commonly used in geothermal operations is affected by high temperature. Characteristics such as shape and size made some materials more prone to thermal degradation. Also, it was found that the PSD of LCMs is a key factor in the effectiveness of br...
2020 International Conference on Computational Science and Computational Intelligence (CSCI)
Journal of Energy Resources Technology
Energy sustainability is the main motive behind the evolution of the concept of well integrity in... more Energy sustainability is the main motive behind the evolution of the concept of well integrity in the oil and gas industry. The concept of well integrity adopts technical, operational, environmental, organizational, and safety measurements to secure the energy supply throughout the life of the well. Technically, a high quality well performance can be maintained by establishing robust barrier systems that are responsible for preventing, controlling, and mitigating potential risks that could arise during the well life cycle. A barrier system is conventionally nested from one or multiple elements that act individually or collectively to scaffold the well integrity. The protection layers in a wellbore can be lost if the integrity of the barrier system is compromised according to the failure of one or all of its elements. Failure can be triggered by technical or non-technical factors. In this study, technical aspects that drive barrier failure mechanisms have given more emphasis. The fai...
Annals of Pure and Applied Logic
Excessive water production from natural gas reservoirs is a main challenge facing the industry no... more Excessive water production from natural gas reservoirs is a main challenge facing the industry nowadays. Polymeric gelants have been widely applied to seal the water production zones, leading to a more feasible production operation. Nevertheless, conventional treatments fail in reservoirs characterized with the presence of sour gases. In this paper, aluminum-based salts are investigated as potential replacement for the conventional chromium acetate as crosslinkers for polyacrylamide (PAM), where aluminum has the advantage of being more environment-friendly besides its abundance. The investigation covers the whole pH range and examines the rheological behavior of the mature gels in the temperature range between 25 and 100°C. While chromium acetate was proven to be sensitive to the presence of sour gases, namely, CO 2 and H 2 S, because of the inability to produce a stable gel at the acidic conditions, this paper presents aluminum-based crosslinkers that are more tolerable toward high acidity. Unlike the conventional crosslinkers, the gelation rate in aluminum acetate and aluminum aminoacetate systems was found to decrease with the increase in pH. Both the crosslinkers succeeded in producing a strong gel with a storage modulus of more than 2000 Pa. Moreover, this study relates the physical stability of the colloidal aluminum crosslinkers with the viscoelastic behavior of the mature gel. The results reveal that aluminum acetate, among the screened salts, has a controllable gelation time at pH conditions between 3.5 and 8.5 and is the most stable in the temperature range 25−100°C. PAM/AlAc system has a gelation time of around 50 min at 75°C making it suitable for near-wellbore treatments, while the gelation time increased to 80 min upon increasing the pH of the system from 4.1 to 4.6. Moreover, the system showed good stability in saline conditions with NaCl concentration of up to 50,000 ppm. Scanning electron microscopy of freeze-dried samples proved the uniform distribution of colloidal crosslinkers and showed sheets wrapping around the colloidal particles. The performance of the new crosslinker is compared with available commercial crosslinkers.
SPE International Conference and Exhibition on Formation Damage Control
Advances in horizontal drilling and completion techniques have proliferated onshore development o... more Advances in horizontal drilling and completion techniques have proliferated onshore development of unconventional shale fields. These wells can span hundreds of miles across a field for a single operator. Live remote monitoring and automation of operations is ideal but rarely cost-effective. Upstream oil and gas operations face many challenges measuring and sending data from remote well sites. Sensors must operate in remote areas, challenging terrain, and inhospitable environments, making very difficult to implement a wireless data flow collection and transmission. Additionally, data integration and consolidation between many devices, software packages, file sizes, and file types, compounds the challenges for analyzing the data for potential improvements in operational efficiencies. Autonomous remote measurement, transmission, and control of oilfield sensors continuously pursued, but rarely fully implemented. The fast production decline of unconventional shales makes high-cost telem...
Energies
Geothermal well integrity has proven to be of high importance, especially because the geothermal ... more Geothermal well integrity has proven to be of high importance, especially because the geothermal life span is expected to be longer than that of conventional oil and gas wells. Recent studies have demonstrated that cement-casing interfacial bonding is a classical well failure in such wells, but field measurements do not correlate with the simulations. We believe that this discrepancy is due to limitations of the simulation itself, which in most cases assumes a free movement of the casing after the interfacial bonding has been exceeded. Since the casing is cemented using a complex hardware package such as centralizer and other cementing components, the free movement of the casing is only possible when no-cement exists behind the casing. This paper proposes a novel experimental method to understand cement strength properties other than the standardized unconfined cement strength (UCS). The novel setup allows the measurement of interfacial bonding strength between cement and casing and...
Journal of Petroleum Science and Engineering
Abstract Drilling fluid circulation loss is referred to as “the most severe problem in drilling o... more Abstract Drilling fluid circulation loss is referred to as “the most severe problem in drilling of oil and gas wells”, as a routine solution, loss circulation materials are added to fill any fractures and vugs that may have been created during the drilling process. An alternative technology to control drilling fluid loss is “Wellbore Strengthening” as a set of engineering design solutions to seal and plug near-wellbore fractures efficiently. This review presents polymeric systems used as loss circulation materials (LCMs) or in wellbore strengthening applications. Moreover, factors that affect the strength of the polymeric formulations, compatibility with drilling fluid and additives, rheological properties and thermal stability are discussed. In addition to that, the review highlights the use of nano-materials in loss circulation polymeric systems. The performance evaluation methods used to evaluate the polymer gel properties are reviewed and the main characteristic of successful LCM formulations are highlighted. Polymers applied in other oil and gas operations, such as hydraulic fracturing and cementing, that have a potential for use in LCM applications are also included in this review.
Volume 8: Polar and Arctic Sciences and Technology; Petroleum Technology
Ice flexural strength is an important parameter in the assessment of ice loads on the hulls of ic... more Ice flexural strength is an important parameter in the assessment of ice loads on the hulls of ice-class ships, sloped offshore structures or sloped bridge piers. While scale effects are well known for compressive ice strength, there has been debate as to whether or not scale effects in ice flexural strength exist. To investigate scale effects during flexural failure of freshwater ice, a comprehensive up-to-date database of beam flexural strength measurements has been compiled. The data show a considerable decrease in flexural strength as the specimen size increases, when examined over a large range of scales. An empirical model of freshwater ice flexural strength as a function of beam volume has been developed using regression analysis.
Rock Mechanics and Rock Engineering
Drilling mud filtration occurs during an overbalanced drilling activity and concurrently with mud... more Drilling mud filtration occurs during an overbalanced drilling activity and concurrently with mud loss through pore throats and fractures. Mud loss and filtration are increased when the wellbore fluid condition is in a dynamic mode (pipe rotation and/or fluid circulation), rather than static. Formation damage is a critical industry challenge that results from mud loss and filtration. There is a considerable amount of experimental studies with only a few modeling approaches for characterizing dynamic mud filtration. Most of these studies have not accounted for factors that can exacerbate mud filtration which includes but not limited to: temperature, pipe rotation, pip/wellbore geometry/eccentricity, and porous media complexity. In this study, two mathematical and computational modeling approaches that can be used to predict dynamic drilling mud filtration in a radial coordinate system are presented. In the first modeling approach, a mechanistic model that is based on a material balance of filter cake evolution is presented. Critical factors that impact dynamic-radial mud filtration (temperature, rotary speed, rock permeability, and rock porosity) and other factors (wellbore/reservoir dimensions, filter cake properties, and mud/ filtrate rheological properties at reservoir temperature) were accounted for. The model was solved with a numerical approach and commercial software. In the second approach, a scanning electron microscopy image of selected dry core samples, combined with image processing, was used to estimate the pore size and porosity of the internal filter cake. The pore structure of the rock samples and filter cake was modeled using the bundle of curved tubes approach. The deposition probability of mud particles was considered through filtration theories. The modeling results were validated with dynamic-radial filtration experiments. The results from both models closely matched the experimental results. On average, the models revealed no more than 4% relative error in predicting dynamic mud filtration. The novelty in both approaches is the incorporation of critical parameters in the models over a wide range and their responses to cumulative filtrate invasion in different rock types. Keywords Dynamic-radial • Mud filtration • Modeling • Permeability • Filter cake List of Symbols c p Mass of particles per unit volume of carrier fluid in slurry (g/cm 3 mud) h Height of formation/cake height (cm) K Permeability K f Formation permeability (Darcy) K c External mud cake permeability (Darcy) k Consistency index (dynes/cm 2 /s n′) k d Deposition coefficient (dimensionless) k e Erosion coefficient (s/cm) L Length of the porous media n Flow behavior index (dimensionless) P Trapping probability of particles
Flow Measurement and Instrumentation
Abstract The classical sharp-crested weirs are not suitable to implement in irrigation canals wit... more Abstract The classical sharp-crested weirs are not suitable to implement in irrigation canals with high suspended sediment flow. Over the time, sediment deposition occurs in the upstream of sharp-crested weirs and causes a time variant water level raise in the upstream and consequently variable discharge coefficients. A series of laboratory experiments was carried out to test the hypothesis of strong turbulent formation and three-dimensional flow in the upstream of half-cosine sharp-crested weirs to prevent sediment deposition. To verify this hypothesis, a series of laboratory experiment was carried out for different weir heights and top widths in free and submerged flow conditions. Mean flow structure and turbulent characteristics of half-cosine and rectangular sharp-crested weirs were measured using a micro-Acoustic Doppler Velocimeter (ADV) probe. It was found that the streamwise velocities of half-cosine weirs were higher than the corresponding rectangular weirs, however, the velocity fluctuations in this direction were similar for both types of weirs. Velocity fluctuations in vertical and transverse directions were found to be significant in half-cosine weirs. The results showed higher turbulent kinetic energy below the crest level for half-cosine weirs which made them capable of sediment resuspension and sediment removal. In was found that the introduced weir model are suitable structures for passage of small floating debris and sediments. A head-discharge formulation was also developed based on the geometry of half-cosine weir in free flow and a constant discharge coefficient was obtained by solving the Fresnel integrals. For practical purposes, semi-empirical formulations were also developed to estimate flow discharge in both free and submerged flow conditions.
Journal of Petroleum Science and Engineering
Abstract Seal assembly is a critical component of wellhead for maintaining well integrity. Failur... more Abstract Seal assembly is a critical component of wellhead for maintaining well integrity. Failure of seal assembly is often cited as a cause for well control incidents. Comprehensive review of existing literature and industry standards and guidelines indicate that limited information is available in public domain on functional aspects and fitness for service evaluation of elastomer hanger seal assembly. This work presents finite element modelling approach to evaluate performance and fitness-for-service of conventional elastomer hanger seal assembly. Three-dimensional computer models consisting of liner, casing, and seal assembly elements were used for this purpose. Sealability was assessed in terms of the contact stress generated at the seal-pipe interface. An analytical model was used to validate and confirm accuracy of FEA results. Parametric analyses were performed and operating curves were generated to understand the behavior of elastomer seal considering different design parameters, such as dimensions and material properties. Sensitivity analysis was performed to identify critical design parameters. Seal annular fit, amount of energization, elastic modulus, and Poisson's ratio were observed to be the most critical factors affecting sealability. All major predictors were incorporated into an empirical correlation that can be used to estimate contact pressure with ±2% error. Based on all the simulation results, recommendations are provided that will help industry/regulators alike in designing and assessing “fitness-for-service” of seal assemblies.
SPE Oklahoma City Oil and Gas Symposium
Plug and Abandonment, P&A, operation is inevitable for each and every well. Most oil and gas well... more Plug and Abandonment, P&A, operation is inevitable for each and every well. Most oil and gas wells are plugged at lowest cost possible complying with requirements set by regulatory agencies. Geopolymers can be used as an alternative material for P&A operations. Unlike many other alternatives such as resin, they are cost efficient and easy to pump down the wellbore. They can be mixed easily onsite and activated by addition of an alkali activator. The research presented in this paper shows they can have a good pumpability, low shrinkage, and high compressive and shear bond strength. The Geopolymer mixtures in this work were composed of Class F Fly Ash rich in Silicate and Aluminum, with elements of Potassium, Calcium, Iron, Sodium, and Titanium. A mixture of Sodium Hydroxide and Sodium Silicate was used to activate the Fly Ash mixtures. Geopolymer mixture designs tested in this work showed high compressive strength, low shrinkage, and suitable thickening time for applications in well ...
ED322897 - Promoting Equity through Educational Technology Networks.
Journal of Energy Resources Technology, 2016
One of the most critical aspects in the drilling operation is to reduce the nonproductive time an... more One of the most critical aspects in the drilling operation is to reduce the nonproductive time and to avoid the borehole instability issues such as kicks, blow outs, lost circulation, stuck pipe, and breakouts. To investigate these problems, one has to understand the formation properties, fluid hydraulics, and the basic mechanics behind drilling a well. In the previous research on this field, the factors were widely discussed and results obtained were related to the formation properties. However, while considering the stresses in the wellbore, the mechanical factors such as the RPM and contact of casing at different positions in wellbore have usually been neglected. In furtherance to this study, the importance of thermal condition, fluid loss, and filter cake formation study cannot be out ruled. This work includes a new insight toward understanding the stress redistribution due to pipe contact by the wellbore and smear mechanism. Additionally, it presents the numerical analysis of i...
AIP Conference Proceedings, 2008
The quantum dynamics of a driven single-band tight-binding model with Dirichlet boundary conditio... more The quantum dynamics of a driven single-band tight-binding model with Dirichlet boundary conditions is considered as a realization of a deformed parafermionic polynomial algebra.
Rml, 2002
By formalizing some classical facts about provably total functions of intuitionistic primitive re... more By formalizing some classical facts about provably total functions of intuitionistic primitive recursive arithmetic (iP RA), we prove that the set of decidable formulas of iP RA and of iΣ + 1 (intuitionistic Σ1-induction in the language of P RA) coincides with the set of its provably ∆1-formulas and coincides with the set of its provably atomic formulas. By the same methods, we shall give another proof of a theorem of Marković and De Jongh: the decidable formulas of HA are its provably ∆1-formulas.
ArXiv, 2020
Axiomatizing mathematical structures and theories is an objective of Mathematical Logic. Some axi... more Axiomatizing mathematical structures and theories is an objective of Mathematical Logic. Some axiomatic systems are nowadays mere definitions, such as the axioms of Group Theory; but some systems are much deeper, such as the axioms of Complete Ordered Fields with which Real Analysis starts. Groups abound in mathematical sciences, while by Dedekind's theorem there exists only one complete ordered field, up to isomorphism. Cayley's theorem in Abstract Algebra implies that the axioms of group theory completely axiomatize the class of permutation sets that are closed under composition and inversion. In this article, we survey some old and new results on the first-order axiomatizability of various mathematical structures. We will also review identities over addition, multiplication, and exponentiation that hold in the set of positive real numbers.
Cement sheath, placed between casing and formation, is an important barrier to provide a hydrauli... more Cement sheath, placed between casing and formation, is an important barrier to provide a hydraulic seal and establish zonal isolation, preventing fluid communication in the wellbore. In geothermal wells, the temperature at the bottom hole is high. Thermal stress induced by temperature is one of the major considerations to trigger failure in the cement sheath. In this study, a numerical model was created based on the FORGE geothermal well in Utah to investigate the effect of casing pressure, temperature and thermal related parameters on cement integrity of casing-cement-formation systems. To achieve the object, a 3D finite element numerical model consisting of casing-cementformation was developed. The model assumed that the cement-casing and cement-formation interfaces are bonded. Maximum and minimum horizontal stresses from FORGE geothermal well drilling reports were applied as far-field tectonic stresses. Elastic modulus and mechanical strength used in the model were obtained throu...
Journal of Energy Resources Technology
This study presents a laboratory experimental research to determine the characteristics of lost c... more This study presents a laboratory experimental research to determine the characteristics of lost circulation materials (LCMs) capable of addressing thermal degradation, providing bridging and sealing in geothermal conditions. Eleven different materials were tested: Walnut Fine, Walnut Medium, Sawdust, Altavert, Graphite Blend, Bentonite Chips, Micronized Cellulose (MICRO-C), Magma Fiber Fine, diatomaceous earth/amorphous silica powder (DEASP), Cotton Seed Hulls, and a Calcium Carbonate Blend. The filtration and sealing pressure of the LCMs were measured with HPHT equipment up to 149 °C (300 °F). Besides, the particle size distribution (PSD) of fine granular materials was measured. The results show that the performance of some LCM materials commonly used in geothermal operations is affected by high temperature. Characteristics such as shape and size made some materials more prone to thermal degradation. Also, it was found that the PSD of LCMs is a key factor in the effectiveness of br...
2020 International Conference on Computational Science and Computational Intelligence (CSCI)
Journal of Energy Resources Technology
Energy sustainability is the main motive behind the evolution of the concept of well integrity in... more Energy sustainability is the main motive behind the evolution of the concept of well integrity in the oil and gas industry. The concept of well integrity adopts technical, operational, environmental, organizational, and safety measurements to secure the energy supply throughout the life of the well. Technically, a high quality well performance can be maintained by establishing robust barrier systems that are responsible for preventing, controlling, and mitigating potential risks that could arise during the well life cycle. A barrier system is conventionally nested from one or multiple elements that act individually or collectively to scaffold the well integrity. The protection layers in a wellbore can be lost if the integrity of the barrier system is compromised according to the failure of one or all of its elements. Failure can be triggered by technical or non-technical factors. In this study, technical aspects that drive barrier failure mechanisms have given more emphasis. The fai...
Annals of Pure and Applied Logic
Excessive water production from natural gas reservoirs is a main challenge facing the industry no... more Excessive water production from natural gas reservoirs is a main challenge facing the industry nowadays. Polymeric gelants have been widely applied to seal the water production zones, leading to a more feasible production operation. Nevertheless, conventional treatments fail in reservoirs characterized with the presence of sour gases. In this paper, aluminum-based salts are investigated as potential replacement for the conventional chromium acetate as crosslinkers for polyacrylamide (PAM), where aluminum has the advantage of being more environment-friendly besides its abundance. The investigation covers the whole pH range and examines the rheological behavior of the mature gels in the temperature range between 25 and 100°C. While chromium acetate was proven to be sensitive to the presence of sour gases, namely, CO 2 and H 2 S, because of the inability to produce a stable gel at the acidic conditions, this paper presents aluminum-based crosslinkers that are more tolerable toward high acidity. Unlike the conventional crosslinkers, the gelation rate in aluminum acetate and aluminum aminoacetate systems was found to decrease with the increase in pH. Both the crosslinkers succeeded in producing a strong gel with a storage modulus of more than 2000 Pa. Moreover, this study relates the physical stability of the colloidal aluminum crosslinkers with the viscoelastic behavior of the mature gel. The results reveal that aluminum acetate, among the screened salts, has a controllable gelation time at pH conditions between 3.5 and 8.5 and is the most stable in the temperature range 25−100°C. PAM/AlAc system has a gelation time of around 50 min at 75°C making it suitable for near-wellbore treatments, while the gelation time increased to 80 min upon increasing the pH of the system from 4.1 to 4.6. Moreover, the system showed good stability in saline conditions with NaCl concentration of up to 50,000 ppm. Scanning electron microscopy of freeze-dried samples proved the uniform distribution of colloidal crosslinkers and showed sheets wrapping around the colloidal particles. The performance of the new crosslinker is compared with available commercial crosslinkers.
SPE International Conference and Exhibition on Formation Damage Control
Advances in horizontal drilling and completion techniques have proliferated onshore development o... more Advances in horizontal drilling and completion techniques have proliferated onshore development of unconventional shale fields. These wells can span hundreds of miles across a field for a single operator. Live remote monitoring and automation of operations is ideal but rarely cost-effective. Upstream oil and gas operations face many challenges measuring and sending data from remote well sites. Sensors must operate in remote areas, challenging terrain, and inhospitable environments, making very difficult to implement a wireless data flow collection and transmission. Additionally, data integration and consolidation between many devices, software packages, file sizes, and file types, compounds the challenges for analyzing the data for potential improvements in operational efficiencies. Autonomous remote measurement, transmission, and control of oilfield sensors continuously pursued, but rarely fully implemented. The fast production decline of unconventional shales makes high-cost telem...
Energies
Geothermal well integrity has proven to be of high importance, especially because the geothermal ... more Geothermal well integrity has proven to be of high importance, especially because the geothermal life span is expected to be longer than that of conventional oil and gas wells. Recent studies have demonstrated that cement-casing interfacial bonding is a classical well failure in such wells, but field measurements do not correlate with the simulations. We believe that this discrepancy is due to limitations of the simulation itself, which in most cases assumes a free movement of the casing after the interfacial bonding has been exceeded. Since the casing is cemented using a complex hardware package such as centralizer and other cementing components, the free movement of the casing is only possible when no-cement exists behind the casing. This paper proposes a novel experimental method to understand cement strength properties other than the standardized unconfined cement strength (UCS). The novel setup allows the measurement of interfacial bonding strength between cement and casing and...
Journal of Petroleum Science and Engineering
Abstract Drilling fluid circulation loss is referred to as “the most severe problem in drilling o... more Abstract Drilling fluid circulation loss is referred to as “the most severe problem in drilling of oil and gas wells”, as a routine solution, loss circulation materials are added to fill any fractures and vugs that may have been created during the drilling process. An alternative technology to control drilling fluid loss is “Wellbore Strengthening” as a set of engineering design solutions to seal and plug near-wellbore fractures efficiently. This review presents polymeric systems used as loss circulation materials (LCMs) or in wellbore strengthening applications. Moreover, factors that affect the strength of the polymeric formulations, compatibility with drilling fluid and additives, rheological properties and thermal stability are discussed. In addition to that, the review highlights the use of nano-materials in loss circulation polymeric systems. The performance evaluation methods used to evaluate the polymer gel properties are reviewed and the main characteristic of successful LCM formulations are highlighted. Polymers applied in other oil and gas operations, such as hydraulic fracturing and cementing, that have a potential for use in LCM applications are also included in this review.
Volume 8: Polar and Arctic Sciences and Technology; Petroleum Technology
Ice flexural strength is an important parameter in the assessment of ice loads on the hulls of ic... more Ice flexural strength is an important parameter in the assessment of ice loads on the hulls of ice-class ships, sloped offshore structures or sloped bridge piers. While scale effects are well known for compressive ice strength, there has been debate as to whether or not scale effects in ice flexural strength exist. To investigate scale effects during flexural failure of freshwater ice, a comprehensive up-to-date database of beam flexural strength measurements has been compiled. The data show a considerable decrease in flexural strength as the specimen size increases, when examined over a large range of scales. An empirical model of freshwater ice flexural strength as a function of beam volume has been developed using regression analysis.
Rock Mechanics and Rock Engineering
Drilling mud filtration occurs during an overbalanced drilling activity and concurrently with mud... more Drilling mud filtration occurs during an overbalanced drilling activity and concurrently with mud loss through pore throats and fractures. Mud loss and filtration are increased when the wellbore fluid condition is in a dynamic mode (pipe rotation and/or fluid circulation), rather than static. Formation damage is a critical industry challenge that results from mud loss and filtration. There is a considerable amount of experimental studies with only a few modeling approaches for characterizing dynamic mud filtration. Most of these studies have not accounted for factors that can exacerbate mud filtration which includes but not limited to: temperature, pipe rotation, pip/wellbore geometry/eccentricity, and porous media complexity. In this study, two mathematical and computational modeling approaches that can be used to predict dynamic drilling mud filtration in a radial coordinate system are presented. In the first modeling approach, a mechanistic model that is based on a material balance of filter cake evolution is presented. Critical factors that impact dynamic-radial mud filtration (temperature, rotary speed, rock permeability, and rock porosity) and other factors (wellbore/reservoir dimensions, filter cake properties, and mud/ filtrate rheological properties at reservoir temperature) were accounted for. The model was solved with a numerical approach and commercial software. In the second approach, a scanning electron microscopy image of selected dry core samples, combined with image processing, was used to estimate the pore size and porosity of the internal filter cake. The pore structure of the rock samples and filter cake was modeled using the bundle of curved tubes approach. The deposition probability of mud particles was considered through filtration theories. The modeling results were validated with dynamic-radial filtration experiments. The results from both models closely matched the experimental results. On average, the models revealed no more than 4% relative error in predicting dynamic mud filtration. The novelty in both approaches is the incorporation of critical parameters in the models over a wide range and their responses to cumulative filtrate invasion in different rock types. Keywords Dynamic-radial • Mud filtration • Modeling • Permeability • Filter cake List of Symbols c p Mass of particles per unit volume of carrier fluid in slurry (g/cm 3 mud) h Height of formation/cake height (cm) K Permeability K f Formation permeability (Darcy) K c External mud cake permeability (Darcy) k Consistency index (dynes/cm 2 /s n′) k d Deposition coefficient (dimensionless) k e Erosion coefficient (s/cm) L Length of the porous media n Flow behavior index (dimensionless) P Trapping probability of particles
Flow Measurement and Instrumentation
Abstract The classical sharp-crested weirs are not suitable to implement in irrigation canals wit... more Abstract The classical sharp-crested weirs are not suitable to implement in irrigation canals with high suspended sediment flow. Over the time, sediment deposition occurs in the upstream of sharp-crested weirs and causes a time variant water level raise in the upstream and consequently variable discharge coefficients. A series of laboratory experiments was carried out to test the hypothesis of strong turbulent formation and three-dimensional flow in the upstream of half-cosine sharp-crested weirs to prevent sediment deposition. To verify this hypothesis, a series of laboratory experiment was carried out for different weir heights and top widths in free and submerged flow conditions. Mean flow structure and turbulent characteristics of half-cosine and rectangular sharp-crested weirs were measured using a micro-Acoustic Doppler Velocimeter (ADV) probe. It was found that the streamwise velocities of half-cosine weirs were higher than the corresponding rectangular weirs, however, the velocity fluctuations in this direction were similar for both types of weirs. Velocity fluctuations in vertical and transverse directions were found to be significant in half-cosine weirs. The results showed higher turbulent kinetic energy below the crest level for half-cosine weirs which made them capable of sediment resuspension and sediment removal. In was found that the introduced weir model are suitable structures for passage of small floating debris and sediments. A head-discharge formulation was also developed based on the geometry of half-cosine weir in free flow and a constant discharge coefficient was obtained by solving the Fresnel integrals. For practical purposes, semi-empirical formulations were also developed to estimate flow discharge in both free and submerged flow conditions.
Journal of Petroleum Science and Engineering
Abstract Seal assembly is a critical component of wellhead for maintaining well integrity. Failur... more Abstract Seal assembly is a critical component of wellhead for maintaining well integrity. Failure of seal assembly is often cited as a cause for well control incidents. Comprehensive review of existing literature and industry standards and guidelines indicate that limited information is available in public domain on functional aspects and fitness for service evaluation of elastomer hanger seal assembly. This work presents finite element modelling approach to evaluate performance and fitness-for-service of conventional elastomer hanger seal assembly. Three-dimensional computer models consisting of liner, casing, and seal assembly elements were used for this purpose. Sealability was assessed in terms of the contact stress generated at the seal-pipe interface. An analytical model was used to validate and confirm accuracy of FEA results. Parametric analyses were performed and operating curves were generated to understand the behavior of elastomer seal considering different design parameters, such as dimensions and material properties. Sensitivity analysis was performed to identify critical design parameters. Seal annular fit, amount of energization, elastic modulus, and Poisson's ratio were observed to be the most critical factors affecting sealability. All major predictors were incorporated into an empirical correlation that can be used to estimate contact pressure with ±2% error. Based on all the simulation results, recommendations are provided that will help industry/regulators alike in designing and assessing “fitness-for-service” of seal assemblies.
SPE Oklahoma City Oil and Gas Symposium
Plug and Abandonment, P&A, operation is inevitable for each and every well. Most oil and gas well... more Plug and Abandonment, P&A, operation is inevitable for each and every well. Most oil and gas wells are plugged at lowest cost possible complying with requirements set by regulatory agencies. Geopolymers can be used as an alternative material for P&A operations. Unlike many other alternatives such as resin, they are cost efficient and easy to pump down the wellbore. They can be mixed easily onsite and activated by addition of an alkali activator. The research presented in this paper shows they can have a good pumpability, low shrinkage, and high compressive and shear bond strength. The Geopolymer mixtures in this work were composed of Class F Fly Ash rich in Silicate and Aluminum, with elements of Potassium, Calcium, Iron, Sodium, and Titanium. A mixture of Sodium Hydroxide and Sodium Silicate was used to activate the Fly Ash mixtures. Geopolymer mixture designs tested in this work showed high compressive strength, low shrinkage, and suitable thickening time for applications in well ...
ED322897 - Promoting Equity through Educational Technology Networks.
Journal of Energy Resources Technology, 2016
One of the most critical aspects in the drilling operation is to reduce the nonproductive time an... more One of the most critical aspects in the drilling operation is to reduce the nonproductive time and to avoid the borehole instability issues such as kicks, blow outs, lost circulation, stuck pipe, and breakouts. To investigate these problems, one has to understand the formation properties, fluid hydraulics, and the basic mechanics behind drilling a well. In the previous research on this field, the factors were widely discussed and results obtained were related to the formation properties. However, while considering the stresses in the wellbore, the mechanical factors such as the RPM and contact of casing at different positions in wellbore have usually been neglected. In furtherance to this study, the importance of thermal condition, fluid loss, and filter cake formation study cannot be out ruled. This work includes a new insight toward understanding the stress redistribution due to pipe contact by the wellbore and smear mechanism. Additionally, it presents the numerical analysis of i...
AIP Conference Proceedings, 2008
The quantum dynamics of a driven single-band tight-binding model with Dirichlet boundary conditio... more The quantum dynamics of a driven single-band tight-binding model with Dirichlet boundary conditions is considered as a realization of a deformed parafermionic polynomial algebra.
Rml, 2002
By formalizing some classical facts about provably total functions of intuitionistic primitive re... more By formalizing some classical facts about provably total functions of intuitionistic primitive recursive arithmetic (iP RA), we prove that the set of decidable formulas of iP RA and of iΣ + 1 (intuitionistic Σ1-induction in the language of P RA) coincides with the set of its provably ∆1-formulas and coincides with the set of its provably atomic formulas. By the same methods, we shall give another proof of a theorem of Marković and De Jongh: the decidable formulas of HA are its provably ∆1-formulas.