Ramadan Ahmed - Academia.edu (original) (raw)

Papers by Ramadan Ahmed

All Days, 2011

Failure of drillstring components due to torsional stresses are caused by torsional vibrations. T... more Failure of drillstring components due to torsional stresses are caused by torsional vibrations. This paper investigates the response of the drillstring to torsional vibrations through analysis on an elemental stepped-shaft drillstring model in a damped medium. The paper directs its analysis to the stick-slip motion which is the most common form of torsional vibrations in drillstrings; stick-slip motion is defined as the continuous stopping and release of the bit/BHA due to the irregular downhole rotation prompted by the existing relationship between the frictional torque and the torque applied from the surface to free the bit. The interaction between the wellbore and the drill-bit is identified in this paper as the source of excitation, that is, as the downhole vibratory source; hence, the exciting torque or couple is derived from the resolution of forces and reactions at wellbore-drill-bit contact. The response equations obtained from theories of mechanical vibrations and mathemati...

All Days, 2004

Extensive aerated mud experiments were performed in a unique field-scale elevated pressure and el... more Extensive aerated mud experiments were performed in a unique field-scale elevated pressure and elevated temperature flow loop (6″ × 3.5″ annular test section, 73 ft length, horizontal configuration without drillpipe rotation). A view port was installed to observe flow patterns in the test section. Two nuclear densitometers were used to measure steady state mean void fraction. During test runs, the liquid and gas phase flow rates were in the range of 50-250 gal/min and 50-150 scf/min, respectively. For all the test runs, measurements of pressure drop and average liquid holdup over the entire annular section were carried out. The two-phase flow patterns were identified by visual observations through the view port. Stratified and slug flow were the two flow patterns observed over the range of the chosen test matrix. The presence of slug flow does not justify many existing simulation practices, which assume a homogeneous gas-liquid flow. A mechanistic model has been developed for aerate...

Nigeria Annual International Conference and Exhibition, 2010

With the growing trend of pre-salt discoveries, some salt formations cannot be simply bypassed to... more With the growing trend of pre-salt discoveries, some salt formations cannot be simply bypassed to get to the reservoir. A considerable thickness of salt of up to 15,000-ft is usually encountered in the deepwater areas. Salt structures embedded within the hydrocarbon prone formations have contributed to the complexities of well trajectory design and operations. Salt domes are impermeable cap rocks for petroleum accumulation but the stress distribution and geo-mechanical dynamics within and around them limit the success of directional drilling. Creeping is the major behavior of salt formations. This study presents a new stress analysis model for rock salt formations based on the octahedral shear stress theory and von Mises failure criterion. The model determines the second deviatoric stress invariant called octahedral shear stress. The stress model also includes the Maxwell's Creep Model in the formulation of the time-dependent response of salt formations to changes in octahedral ...

Nigeria Annual International Conference and Exhibition, 2011

Drilling dynamic dysfunction condition occurs when dynamic forces in the drillstring cause very h... more Drilling dynamic dysfunction condition occurs when dynamic forces in the drillstring cause very high stresses and fatigue or physical damage to the string and thus reduced bit performance or caused wellbore damage. These forces may generate from vibrations, shocks, oscillations, and BHA dynamic buckling. Failure of drillstring components due to torsional stresses are caused by torsional vibrations. This work investigates the response of drillstring to torsional vibrations through analysis on an elemental stepped-shaft drillstring model in a vibration damping medium. The work directs its analysis on the stick-slip motion, which is the most common form of torsional vibrations of drillstring while drilling. The interaction between the wellbore and the drill-bit is identified in this research as the source of excitation, that is, as the downhole vibratory source. Hence, the exciting torque is derived from the resolution of forces and reactions at wellbore-drill-bit contact. The response...

All Days, 2010

In horizontal and highly deviated portions of an Extended Reach Drilling (ERD) well, cuttings bed... more In horizontal and highly deviated portions of an Extended Reach Drilling (ERD) well, cuttings beds form on the low-side of the annulus. The bed partially blocks the annulus resulting in excessive pressure loss and a higher equivalent circulating density (ECD) that is exacerbated by the increase in length of the annulus. This condition limits hole-cleaning capabilities. As a result, selecting favorable drilling parameters is not always sufficient to overcome the hole cleaning problem. Recently, the use of downhole Mechanical Cleaning Devices (MCDs) has been introduced to the industry to mitigate the problem without inducing excessive ECD. Although the use of these tools is increasing, very limited studies have been conducted to optimize their performance. This paper presents results of an experimental study that was carried out to evaluate cuttings removal efficiency of MCDs and applications of MCDs for optimizing ERD systems. Experiments were carried out in a large-scale flow loop t...

Nigeria Annual International Conference and Exhibition, 2011

Taking drilling beyond the continental shelves further into the great depths of water leaves the ... more Taking drilling beyond the continental shelves further into the great depths of water leaves the drilling industry with no option of avoiding reservoirs lying beneath great masses of salt formations. Presently, salt formations trap rich reservoirs in Brazil, West Africa, Gulf of Mexico, North Sea and off the coasts of eastern Canada. The discovery of producible reserves beneath vast, thick sheets of salt formations challenges the regular drilling and completion practices, making every operation a unique experience. Drilling through salt formations can become successful only when the essential properties of salt formations (e.g. halites) that may cause instability are clearly understood. Instabilities in salt formations arise from the ability of the salt to flow under loading conditions (creep) and the ability to dissolve at certain conditions and elevated temperatures (solubility). This paper presents the checklist of essential contributing properties that must be accounted for in m...

All Days, 2012

Drilling extended-reach horizontal wells (ERHWs) have become a viable option for field developmen... more Drilling extended-reach horizontal wells (ERHWs) have become a viable option for field development because these wells bring additional reserves on line which may not be accessible with conventional well designs. Tubular design for ERHWs must be compatible with the intended well objectives, target location, wellbore trajectory in order to minimize the downhole dynamic events such as torque and drag, buckling and vibrations. Presently, the dynamic models used for calculating expected axial load and torque transfers along tubulars in ERHWs consider only the effect of the contact loads and frictional forces generated from torque, drag and buckling events. The expected axial loads and torque calculated during tubular design process are been underestimated using present dynamic models. However, the contact loads and frictional forces generated by lateral and torsional vibration events are critical to the tubular design for ERHWs and should not be ignored. This study in this paper incorpo...

All Days, 2005

This study presents experimental results and techniques that are developed for measuring in-situ ... more This study presents experimental results and techniques that are developed for measuring in-situ cuttings concentration using nuclear densitometers under dynamic conditions. One of the key problems in borehole hydraulics and cuttings transport is the determination of in-situ cuttings concentration in the borehole while drilling. In order to investigate cuttings transport efficiency with aerated fluids under elevated pressure and temperature conditions, in-situ cuttings concentrations were measured manually (i.e. by flushing out the cuttings into a container and weighing them) and using nuclear densitometers. In-situ cuttings concentrations that were obtained using these two different measuring methods are compared and discussed. The results show good agreement between densitometer readings and cuttings weight measurements. This study is useful for designing in-line monitoring systems that accurately measure the cuttings concentration in drilling applications.

All Days, 2006

Drilling fluid "sweeps" are specific fluids specially formulated to transport cuttings ... more Drilling fluid "sweeps" are specific fluids specially formulated to transport cuttings that cannot be removed by ordinary drilling fluid circulation. There has been a lack of certainty of the "sweep" type selection in the field. Although they are in common use in vertical and deviated drilling operations, not much information is known regarding the use of "sweeps", especially in terms of "efficiency" of the "sweeps" and the specific hydraulics involved. The effect of rheology of the "sweep" fluid on "sweep efficiency" has been investigated under low pressure ambient temperature (LPAT) and elevated temperature elevated pressure (EPET) conditions. The LPAT tests were conducted on a 90-ft-long transparent test section that consists of an 8″ ID casing and 4.5″ OD drill pipe. To investigate the effect of temperature on the "sweep efficiency", EPET experiments were conducted under simulated downhole conditions...

All Days, 2012

Surge and swab pressures generated during well construction operations are critical. As thousands... more Surge and swab pressures generated during well construction operations are critical. As thousands of wells are drilled every year, challenges associated with downhole pressure management have become more important for the oil industry. Inadequate estimation of surge and swab pressures can lead to a number of costly drilling problems such as lost circulation due to formation fracture, fluid influx resulting in kicks, breakdown of the formation at shoe due to limited kick tolerance or blowouts. An accurate surge pressure model is very important in planning drilling operations, mainly in wells with narrow safe pressure window, slimholes, low-clearance casings, deepwater, and extended-reach well applications. Existing surge/swab pressure models assume concentric wellbore. This assumption is hardly ever valid in horizontal and inclined wells with some degree of eccentricity. Ignoring the pressure reducing effect of eccentricity on surge and swab pressures may eventually lead to underesti...

All Days, 2010

A number of field and laboratory studies have been carried out to accurately predict the effect o... more A number of field and laboratory studies have been carried out to accurately predict the effect of drillstring rotation on downhole pressure and equivalent circulating density (ECD). Field studies indicated that drillstring rotation often results in an increased ECD. This is in contradiction with the results obtained from number of laboratory studies and other field studies. Consequently, there is no comprehensive model that accounts for the effect drillstring rotation on wellbore hydraulics. Recently, simple empirical models have been developed based on field measurements alone. Although these models can be very useful as they are based on field measurements, they have no physical basis and are limited to specific ranges of field parameters. This article presents results of field studies and theoretical analysis conducted on the effect of drillstring rotation on wellbore hydraulics. Field measurements during actual drilling operation were obtained from four different wells. Key dri...

SPE Journal, 2007

Summary An experimental investigation on polymer-based drilling foams was carried out. Rheology t... more Summary An experimental investigation on polymer-based drilling foams was carried out. Rheology tests were performed with foams that have different concentrations of hydroxylethylcellulose (HEC) and 1% commercial surfactant. Experiments were conducted in a large-scale flow loop that permits foam flow through 2-, 3-, and 4-in. pipe sections, and a 6×3.5-in. annular section. During the experiments, frictional pressure losses across the pipe and annular sections were measured for different gas/liquid flow rates, polymer concentrations (0, 0.25, and 0.5%), and foam qualities (70, 80, and 90%). Significant rheological variations were observed between aqueous foams containing no polymers and polymer-thickened foams. Experimental data show three distinct flow curves for the 2-, 3-, and 4-in. pipe sections, which indicates the presence of wall slip. The Oldroyd-Jastrzebski approach was used to calculate the wall slip velocity and determine the true shear rate. It has been found that wall sl...

SPE Drilling & Completion, 2009

Summary Cuttings transport in highly deviated wellbores is more challenging and critical than in ... more Summary Cuttings transport in highly deviated wellbores is more challenging and critical than in vertical wells. In inclined wells, the fluid velocity has a reduced vertical component that may not be sufficient to transport all the cuttings to the surface. When cuttings returns do not appear to be sufficient for the drilling rate, hole-cleaning sweeps are applied to clean the borehole or reduce cuttings-bed thickness. Fiber-containing sweeps have been very effective in cleaning highly deviated and extended-reach wells. In addition, substantial torque and drag reduction has been reported when fiber-containing drilling fluids are used in the field. Although field observations are encouraging, very little is known currently about flow behavior, hydraulics, and cuttings-transport efficiency of fiber sweeps. There is a great need for understanding how fiber particles enhance the cleaning capabilities of fiber-containing sweeps. The interaction between fiber particles and drilling fluid i...

SPE Drilling & Completion, 2009

Summary Foam has proved to be effective and economical in underbalanced operations (UBO) and is g... more Summary Foam has proved to be effective and economical in underbalanced operations (UBO) and is gaining wider applications in many areas. It provides the desired flexibility in controlling pressure profile and equivalent circulating density (ECD). However, the knowledge of rheology and hydraulics of polymer-thickened foams is still limited. This paper summarizes the significant effects of polymer on foam rheology and presents a hydraulic model that simulates aqueous and polymer-based foam flow in directional and horizontal wellbores. Experimental studies on the rheology of polymer-enhanced foam were conducted using a specially designed flow-through rotational viscometer and pipe viscometers with different concentrations of hydroxyethylcellulose (HEC) polymer. Correlations have been developed for rheological parameters of aqueous- and polymer-based drilling foams. On the basis of the experimental results of foam rheology and a steady-state momentum balance equation, a foam-flow hydra...

Journal of Petroleum Science and Engineering, 2010

A theoretical solution for radial flow of Yield-Power-Law (Herschel-Bulkley) fluids between two p... more A theoretical solution for radial flow of Yield-Power-Law (Herschel-Bulkley) fluids between two parallel disks is presented. The fundamental equations are based on momentum balance in radial coordinates. The solution encompasses the Newtonian, Bingham Plastic and Power-Law fluids as special cases. The numerical solution has been compared with experimental data obtained from radial flow between two parallel disks. Upon application of mathematical simplifications, a closed form expression for pressure drop for radial flow of Yield-Power-Law (YPL) fluids is obtained and presented as an "approximate analytical" solution. The validity of the approximate solution is examined versus numerical solution. The application of the approximate solution to the prediction of drilling fluid losses in fractured formations is discussed.

Journal of Medical Ethics, 2013

Journal of Energy Resources Technology, 2010

Maintaining optimum circulation rates is important in aerated mud drilling operations. However, r... more Maintaining optimum circulation rates is important in aerated mud drilling operations. However, reliable predictions of the optimum rates require accurate modeling of the frictional pressure loss at bottom-hole conditions. This paper presents a mechanistic model for underbalanced drilling with aerated muds. Extensive experiments in a unique field-scale high pressure and high temperature flow loop were performed to verify the predictions of the model. This flow loop has a 150×89 mm2(6″×3.5″) horizontal annular geometry and is 22 m long. In the experiments, cuttings were introduced at a rate of 7.5 kg/min, representing a penetration rate of 15 m/h in the annular test section. The liquid phase flow rates were in the range of 0.30–0.57 m3/min, representing superficial liquid velocities in the range of 0.47–0.90 m/s. The gas liquid ratio (gas volume fraction under in situ condition) was varied from 0.0 to 0.38. Test pressures and temperatures ranged from 1.28 to 3.45 MPa, and 27°C to 80°...

Conflict Management and Peace Science, 2007

The willingness to forgive was examined in a sample of 517 Kuwaiti citizens, aged 12 to 55 years.... more The willingness to forgive was examined in a sample of 517 Kuwaiti citizens, aged 12 to 55 years. Participants were instructed first to read a certain number of stories (in which a harmful act was committed against a child) and then to express their willingness to forgive in each case. The stories included four factors: intent to harm, religious proximity, presence/absence of apologies, and cancellation of consequences. A high level of willingness to forgive was observed among the Kuwaitis studies, irrespective of participants' age and gender. The impact of the religious proximity factor was limited to a very small fraction of the sample.

Bangladesh Journal of Agricultural Research, 2013

The study was carried out at the farmer's field of Juri Upazilla, Maulavibazar District durin... more The study was carried out at the farmer's field of Juri Upazilla, Maulavibazar District during 2008-2009, 2009-2010, and 2011-2012 to find out the proper combination of fertilizer nutrients that promotes better fruit yield and quality of mandarin (cv. Khashi Kamla). The treatments were Native nutrient i.e., control (TI), N150P50K150Mg30 (T2), N200P75K175Mg40 (T3), N250P100 K200Mg50 (T4), N300P125K225Mg60 (T5), and N200P75K175Mg0 (T6) g/plant/year. In addition, 20 kg cowdung/plant was used as blanket dose. Yield components, yield, and TSS content (%) of mandarin varied significantly due to variation of nutrients in all the test years. Fruit yield/plant was improved significantly with increase in NPK and Mg dose irrespective of years. Application of Mg in combination with NPK increased 17-157% mean fruit yield over magnesium control. Significantly the highest yield and yield attributes were recorded under treatment N300 P125 K225 Mg60 g/plant (T5) along with 20 kg cowdung/plant in...

All Days, 2011

Failure of drillstring components due to torsional stresses are caused by torsional vibrations. T... more Failure of drillstring components due to torsional stresses are caused by torsional vibrations. This paper investigates the response of the drillstring to torsional vibrations through analysis on an elemental stepped-shaft drillstring model in a damped medium. The paper directs its analysis to the stick-slip motion which is the most common form of torsional vibrations in drillstrings; stick-slip motion is defined as the continuous stopping and release of the bit/BHA due to the irregular downhole rotation prompted by the existing relationship between the frictional torque and the torque applied from the surface to free the bit. The interaction between the wellbore and the drill-bit is identified in this paper as the source of excitation, that is, as the downhole vibratory source; hence, the exciting torque or couple is derived from the resolution of forces and reactions at wellbore-drill-bit contact. The response equations obtained from theories of mechanical vibrations and mathemati...

All Days, 2004

Extensive aerated mud experiments were performed in a unique field-scale elevated pressure and el... more Extensive aerated mud experiments were performed in a unique field-scale elevated pressure and elevated temperature flow loop (6″ × 3.5″ annular test section, 73 ft length, horizontal configuration without drillpipe rotation). A view port was installed to observe flow patterns in the test section. Two nuclear densitometers were used to measure steady state mean void fraction. During test runs, the liquid and gas phase flow rates were in the range of 50-250 gal/min and 50-150 scf/min, respectively. For all the test runs, measurements of pressure drop and average liquid holdup over the entire annular section were carried out. The two-phase flow patterns were identified by visual observations through the view port. Stratified and slug flow were the two flow patterns observed over the range of the chosen test matrix. The presence of slug flow does not justify many existing simulation practices, which assume a homogeneous gas-liquid flow. A mechanistic model has been developed for aerate...

Nigeria Annual International Conference and Exhibition, 2010

With the growing trend of pre-salt discoveries, some salt formations cannot be simply bypassed to... more With the growing trend of pre-salt discoveries, some salt formations cannot be simply bypassed to get to the reservoir. A considerable thickness of salt of up to 15,000-ft is usually encountered in the deepwater areas. Salt structures embedded within the hydrocarbon prone formations have contributed to the complexities of well trajectory design and operations. Salt domes are impermeable cap rocks for petroleum accumulation but the stress distribution and geo-mechanical dynamics within and around them limit the success of directional drilling. Creeping is the major behavior of salt formations. This study presents a new stress analysis model for rock salt formations based on the octahedral shear stress theory and von Mises failure criterion. The model determines the second deviatoric stress invariant called octahedral shear stress. The stress model also includes the Maxwell's Creep Model in the formulation of the time-dependent response of salt formations to changes in octahedral ...

Nigeria Annual International Conference and Exhibition, 2011

Drilling dynamic dysfunction condition occurs when dynamic forces in the drillstring cause very h... more Drilling dynamic dysfunction condition occurs when dynamic forces in the drillstring cause very high stresses and fatigue or physical damage to the string and thus reduced bit performance or caused wellbore damage. These forces may generate from vibrations, shocks, oscillations, and BHA dynamic buckling. Failure of drillstring components due to torsional stresses are caused by torsional vibrations. This work investigates the response of drillstring to torsional vibrations through analysis on an elemental stepped-shaft drillstring model in a vibration damping medium. The work directs its analysis on the stick-slip motion, which is the most common form of torsional vibrations of drillstring while drilling. The interaction between the wellbore and the drill-bit is identified in this research as the source of excitation, that is, as the downhole vibratory source. Hence, the exciting torque is derived from the resolution of forces and reactions at wellbore-drill-bit contact. The response...

All Days, 2010

In horizontal and highly deviated portions of an Extended Reach Drilling (ERD) well, cuttings bed... more In horizontal and highly deviated portions of an Extended Reach Drilling (ERD) well, cuttings beds form on the low-side of the annulus. The bed partially blocks the annulus resulting in excessive pressure loss and a higher equivalent circulating density (ECD) that is exacerbated by the increase in length of the annulus. This condition limits hole-cleaning capabilities. As a result, selecting favorable drilling parameters is not always sufficient to overcome the hole cleaning problem. Recently, the use of downhole Mechanical Cleaning Devices (MCDs) has been introduced to the industry to mitigate the problem without inducing excessive ECD. Although the use of these tools is increasing, very limited studies have been conducted to optimize their performance. This paper presents results of an experimental study that was carried out to evaluate cuttings removal efficiency of MCDs and applications of MCDs for optimizing ERD systems. Experiments were carried out in a large-scale flow loop t...

Nigeria Annual International Conference and Exhibition, 2011

Taking drilling beyond the continental shelves further into the great depths of water leaves the ... more Taking drilling beyond the continental shelves further into the great depths of water leaves the drilling industry with no option of avoiding reservoirs lying beneath great masses of salt formations. Presently, salt formations trap rich reservoirs in Brazil, West Africa, Gulf of Mexico, North Sea and off the coasts of eastern Canada. The discovery of producible reserves beneath vast, thick sheets of salt formations challenges the regular drilling and completion practices, making every operation a unique experience. Drilling through salt formations can become successful only when the essential properties of salt formations (e.g. halites) that may cause instability are clearly understood. Instabilities in salt formations arise from the ability of the salt to flow under loading conditions (creep) and the ability to dissolve at certain conditions and elevated temperatures (solubility). This paper presents the checklist of essential contributing properties that must be accounted for in m...

All Days, 2012

Drilling extended-reach horizontal wells (ERHWs) have become a viable option for field developmen... more Drilling extended-reach horizontal wells (ERHWs) have become a viable option for field development because these wells bring additional reserves on line which may not be accessible with conventional well designs. Tubular design for ERHWs must be compatible with the intended well objectives, target location, wellbore trajectory in order to minimize the downhole dynamic events such as torque and drag, buckling and vibrations. Presently, the dynamic models used for calculating expected axial load and torque transfers along tubulars in ERHWs consider only the effect of the contact loads and frictional forces generated from torque, drag and buckling events. The expected axial loads and torque calculated during tubular design process are been underestimated using present dynamic models. However, the contact loads and frictional forces generated by lateral and torsional vibration events are critical to the tubular design for ERHWs and should not be ignored. This study in this paper incorpo...

All Days, 2005

This study presents experimental results and techniques that are developed for measuring in-situ ... more This study presents experimental results and techniques that are developed for measuring in-situ cuttings concentration using nuclear densitometers under dynamic conditions. One of the key problems in borehole hydraulics and cuttings transport is the determination of in-situ cuttings concentration in the borehole while drilling. In order to investigate cuttings transport efficiency with aerated fluids under elevated pressure and temperature conditions, in-situ cuttings concentrations were measured manually (i.e. by flushing out the cuttings into a container and weighing them) and using nuclear densitometers. In-situ cuttings concentrations that were obtained using these two different measuring methods are compared and discussed. The results show good agreement between densitometer readings and cuttings weight measurements. This study is useful for designing in-line monitoring systems that accurately measure the cuttings concentration in drilling applications.

All Days, 2006

Drilling fluid "sweeps" are specific fluids specially formulated to transport cuttings ... more Drilling fluid "sweeps" are specific fluids specially formulated to transport cuttings that cannot be removed by ordinary drilling fluid circulation. There has been a lack of certainty of the "sweep" type selection in the field. Although they are in common use in vertical and deviated drilling operations, not much information is known regarding the use of "sweeps", especially in terms of "efficiency" of the "sweeps" and the specific hydraulics involved. The effect of rheology of the "sweep" fluid on "sweep efficiency" has been investigated under low pressure ambient temperature (LPAT) and elevated temperature elevated pressure (EPET) conditions. The LPAT tests were conducted on a 90-ft-long transparent test section that consists of an 8″ ID casing and 4.5″ OD drill pipe. To investigate the effect of temperature on the "sweep efficiency", EPET experiments were conducted under simulated downhole conditions...

All Days, 2012

Surge and swab pressures generated during well construction operations are critical. As thousands... more Surge and swab pressures generated during well construction operations are critical. As thousands of wells are drilled every year, challenges associated with downhole pressure management have become more important for the oil industry. Inadequate estimation of surge and swab pressures can lead to a number of costly drilling problems such as lost circulation due to formation fracture, fluid influx resulting in kicks, breakdown of the formation at shoe due to limited kick tolerance or blowouts. An accurate surge pressure model is very important in planning drilling operations, mainly in wells with narrow safe pressure window, slimholes, low-clearance casings, deepwater, and extended-reach well applications. Existing surge/swab pressure models assume concentric wellbore. This assumption is hardly ever valid in horizontal and inclined wells with some degree of eccentricity. Ignoring the pressure reducing effect of eccentricity on surge and swab pressures may eventually lead to underesti...

All Days, 2010

A number of field and laboratory studies have been carried out to accurately predict the effect o... more A number of field and laboratory studies have been carried out to accurately predict the effect of drillstring rotation on downhole pressure and equivalent circulating density (ECD). Field studies indicated that drillstring rotation often results in an increased ECD. This is in contradiction with the results obtained from number of laboratory studies and other field studies. Consequently, there is no comprehensive model that accounts for the effect drillstring rotation on wellbore hydraulics. Recently, simple empirical models have been developed based on field measurements alone. Although these models can be very useful as they are based on field measurements, they have no physical basis and are limited to specific ranges of field parameters. This article presents results of field studies and theoretical analysis conducted on the effect of drillstring rotation on wellbore hydraulics. Field measurements during actual drilling operation were obtained from four different wells. Key dri...

SPE Journal, 2007

Summary An experimental investigation on polymer-based drilling foams was carried out. Rheology t... more Summary An experimental investigation on polymer-based drilling foams was carried out. Rheology tests were performed with foams that have different concentrations of hydroxylethylcellulose (HEC) and 1% commercial surfactant. Experiments were conducted in a large-scale flow loop that permits foam flow through 2-, 3-, and 4-in. pipe sections, and a 6×3.5-in. annular section. During the experiments, frictional pressure losses across the pipe and annular sections were measured for different gas/liquid flow rates, polymer concentrations (0, 0.25, and 0.5%), and foam qualities (70, 80, and 90%). Significant rheological variations were observed between aqueous foams containing no polymers and polymer-thickened foams. Experimental data show three distinct flow curves for the 2-, 3-, and 4-in. pipe sections, which indicates the presence of wall slip. The Oldroyd-Jastrzebski approach was used to calculate the wall slip velocity and determine the true shear rate. It has been found that wall sl...

SPE Drilling & Completion, 2009

Summary Cuttings transport in highly deviated wellbores is more challenging and critical than in ... more Summary Cuttings transport in highly deviated wellbores is more challenging and critical than in vertical wells. In inclined wells, the fluid velocity has a reduced vertical component that may not be sufficient to transport all the cuttings to the surface. When cuttings returns do not appear to be sufficient for the drilling rate, hole-cleaning sweeps are applied to clean the borehole or reduce cuttings-bed thickness. Fiber-containing sweeps have been very effective in cleaning highly deviated and extended-reach wells. In addition, substantial torque and drag reduction has been reported when fiber-containing drilling fluids are used in the field. Although field observations are encouraging, very little is known currently about flow behavior, hydraulics, and cuttings-transport efficiency of fiber sweeps. There is a great need for understanding how fiber particles enhance the cleaning capabilities of fiber-containing sweeps. The interaction between fiber particles and drilling fluid i...

SPE Drilling & Completion, 2009

Summary Foam has proved to be effective and economical in underbalanced operations (UBO) and is g... more Summary Foam has proved to be effective and economical in underbalanced operations (UBO) and is gaining wider applications in many areas. It provides the desired flexibility in controlling pressure profile and equivalent circulating density (ECD). However, the knowledge of rheology and hydraulics of polymer-thickened foams is still limited. This paper summarizes the significant effects of polymer on foam rheology and presents a hydraulic model that simulates aqueous and polymer-based foam flow in directional and horizontal wellbores. Experimental studies on the rheology of polymer-enhanced foam were conducted using a specially designed flow-through rotational viscometer and pipe viscometers with different concentrations of hydroxyethylcellulose (HEC) polymer. Correlations have been developed for rheological parameters of aqueous- and polymer-based drilling foams. On the basis of the experimental results of foam rheology and a steady-state momentum balance equation, a foam-flow hydra...

Journal of Petroleum Science and Engineering, 2010

A theoretical solution for radial flow of Yield-Power-Law (Herschel-Bulkley) fluids between two p... more A theoretical solution for radial flow of Yield-Power-Law (Herschel-Bulkley) fluids between two parallel disks is presented. The fundamental equations are based on momentum balance in radial coordinates. The solution encompasses the Newtonian, Bingham Plastic and Power-Law fluids as special cases. The numerical solution has been compared with experimental data obtained from radial flow between two parallel disks. Upon application of mathematical simplifications, a closed form expression for pressure drop for radial flow of Yield-Power-Law (YPL) fluids is obtained and presented as an "approximate analytical" solution. The validity of the approximate solution is examined versus numerical solution. The application of the approximate solution to the prediction of drilling fluid losses in fractured formations is discussed.

Journal of Medical Ethics, 2013

Journal of Energy Resources Technology, 2010

Maintaining optimum circulation rates is important in aerated mud drilling operations. However, r... more Maintaining optimum circulation rates is important in aerated mud drilling operations. However, reliable predictions of the optimum rates require accurate modeling of the frictional pressure loss at bottom-hole conditions. This paper presents a mechanistic model for underbalanced drilling with aerated muds. Extensive experiments in a unique field-scale high pressure and high temperature flow loop were performed to verify the predictions of the model. This flow loop has a 150×89 mm2(6″×3.5″) horizontal annular geometry and is 22 m long. In the experiments, cuttings were introduced at a rate of 7.5 kg/min, representing a penetration rate of 15 m/h in the annular test section. The liquid phase flow rates were in the range of 0.30–0.57 m3/min, representing superficial liquid velocities in the range of 0.47–0.90 m/s. The gas liquid ratio (gas volume fraction under in situ condition) was varied from 0.0 to 0.38. Test pressures and temperatures ranged from 1.28 to 3.45 MPa, and 27°C to 80°...

Conflict Management and Peace Science, 2007

The willingness to forgive was examined in a sample of 517 Kuwaiti citizens, aged 12 to 55 years.... more The willingness to forgive was examined in a sample of 517 Kuwaiti citizens, aged 12 to 55 years. Participants were instructed first to read a certain number of stories (in which a harmful act was committed against a child) and then to express their willingness to forgive in each case. The stories included four factors: intent to harm, religious proximity, presence/absence of apologies, and cancellation of consequences. A high level of willingness to forgive was observed among the Kuwaitis studies, irrespective of participants' age and gender. The impact of the religious proximity factor was limited to a very small fraction of the sample.

Bangladesh Journal of Agricultural Research, 2013

The study was carried out at the farmer's field of Juri Upazilla, Maulavibazar District durin... more The study was carried out at the farmer's field of Juri Upazilla, Maulavibazar District during 2008-2009, 2009-2010, and 2011-2012 to find out the proper combination of fertilizer nutrients that promotes better fruit yield and quality of mandarin (cv. Khashi Kamla). The treatments were Native nutrient i.e., control (TI), N150P50K150Mg30 (T2), N200P75K175Mg40 (T3), N250P100 K200Mg50 (T4), N300P125K225Mg60 (T5), and N200P75K175Mg0 (T6) g/plant/year. In addition, 20 kg cowdung/plant was used as blanket dose. Yield components, yield, and TSS content (%) of mandarin varied significantly due to variation of nutrients in all the test years. Fruit yield/plant was improved significantly with increase in NPK and Mg dose irrespective of years. Application of Mg in combination with NPK increased 17-157% mean fruit yield over magnesium control. Significantly the highest yield and yield attributes were recorded under treatment N300 P125 K225 Mg60 g/plant (T5) along with 20 kg cowdung/plant in...