Ram Mohan | University of Tulsa (original) (raw)
Papers by Ram Mohan
Oil and Gas Facilities, 2016
Summary Looped gas/liquid multiphase-flow pipelines are used by the oil and gas industry to reduc... more Summary Looped gas/liquid multiphase-flow pipelines are used by the oil and gas industry to reduce pressure drop and increase flow capacity. They can be installed alone as a flow splitter or combined in series to form a manifold. Application of looped lines is not unique to the petroleum industry; they are also applied in other industries such as nuclear and chemical. However, there has not yet been a comprehensive fundamental investigation of the flow behavior or predictive methods available for such systems because of the complexity involved with respect to process variables such as flow patterns, fluid properties, phase velocities, and pipe geometry. Uneven splitting of the gas and liquid phases between the two looped lines can cause malfunction of the downstream processing equipment; therefore, a total of 65 experiments at different flow conditions in a looped-lines system using different-diameter looped-line configurations are conducted in this study to investigate the pressure...
Integral Methods in Science and Engineering, 2011
Theoretical and Applied Fracture Mechanics, 1999
Acoustic Emission (AE) sensing technique is used as a tool for on-line monitoring of hydro-abrasi... more Acoustic Emission (AE) sensing technique is used as a tool for on-line monitoring of hydro-abrasive erosion (HAE) of pre-cracked multiphase materials. As reference materials, ®ve types of concrete materials were used for the experimental study. Compression tests were performed to determine the mechanical properties and the failure behavior of these materials. Erosion parameters, such as abrasive particle velocity, local exposure time, and abrasive mass¯ow rate were varied during the experiments and AE-signals were acquired. The trends exhibited by the time domain and frequency domain AE-signals with change in process parameters and material properties were analyzed. The results indicate that acoustic emission signal is capable of revealing the dierent material removal mechanisms occurring in pre-cracked multiphase materials when subjected to hydro-abrasive erosion. Visualization studies performed on the erosion site provide more insight into the physics of the process and verify the observations made from the AE-signals. Finally, it is concluded that due to its capability to quantify the amount of material removed, AE RMS could be considered as a parameter for monitoring the material removal process.
Journal of Energy Resources Technology
ABSTRACT
SPE International Symposium and Exhibition on Formation Damage Control, 2014
ABSTRACT Transport of sand in multiphase pipelines occurs in the petroleum industry as sand is pr... more ABSTRACT Transport of sand in multiphase pipelines occurs in the petroleum industry as sand is produced co-mingled with crude oil. Stationary sand beds are formed at the pipe bottom when the flow velocity is lower than the critical sand deposition velocity. These sand beds reduce reservoir production and affect the integrity of the pipe system due to pipeline plugging and erosion/corrosion produced by sand particles. Therefore, the production system must be designed to operate at a velocity where sand particles are transported along the pipe. For that reason, it is crucial to predict the critical sand deposition velocity in order to maximize reservoir production. Gas-liquid-sand flow hydrodynamics, which is commonly encountered in most reservoirs and also in oil and gas transportation pipelines, is more complex than liquid-sand flow, making the modeling extremely difficult. At present, gas-liquid-sand flow is still not well understood, with limited data available in the literature. In addition, the effect of sand concentration has not been thoroughly studied for two-phase flows transporting sand. Experimental and theoretical investigations have been conducted in this study on gas-liquid-sand stratified flow in horizontal pipes at low sand concentrations. A 4-in experimental facility was designed and constructed and data were acquired utilizing air-water-glass beads flow. The data include measurements of critical sand deposition velocities, namely, the transition between moving and stationary beds. The data reveal that for a constant superficial liquid velocity, the critical mixture and liquid sand deposition velocities increase with increasing sand concentrations. Also, for a given sand concentration, the critical liquid velocity is almost the same for different superficial liquid velocities. The sand deposition correlations of Oroskar and Turian (1980) for single-phase flow and Salama (2000) for two-phase flow are modified and extended in order to develop a new correlation. The developed correlation enables the prediction of critical sand deposition mixture velocity for horizontal stratified flow, as function of sand concentration along with other parameters. Comparison between the predictions of the developed correlation and the experimental data reveal a very good agreement, whereby the relative errors of mixture and liquid critical sand deposition velocities are ±2.5% and < 5%, respectively.
SPE Projects Facilities & Construction, 2010
... Design of the SLHC has relied primarily on empirical experi-ence (Kelsall 1952; Rietema 1961a... more ... Design of the SLHC has relied primarily on empirical experi-ence (Kelsall 1952; Rietema 1961a, 1961b, 1961c, 1961d), and more recently on costly and lengthy CFD modeling (Delgadillo and Rajamani 2005; Narasimha et al. 2005). ...
SPE Journal, 2000
Summary The liquid carry-over phenomenon in gas-liquid cylindrical cyclone (GLCC© **) compact sep... more Summary The liquid carry-over phenomenon in gas-liquid cylindrical cyclone (GLCC© **) compact separators has been studied experimentally and theoretically. Experimental data have been acquired including the operational envelope for liquid carry-over and percent liquid carry-over beyond the operational envelope. The data show that at low gas and high liquid flow rates, under churn flow conditions in the upper part of the cylindrical cyclone, a large amount of liquid can be carried over relatively easily. On the other hand, at high gas and low liquid flow rates, under annular flow conditions, one should exceed the operational envelope significantly in order to have large amount of liquid carry-over. A mechanistic model has been developed for the prediction of the percent liquid carry-over beyond the operational envelope for churn flow conditions. An existing model for the prediction of the operational envelope for liquid carry-over has been extended to high-pressure conditions, includ...
Journal of Energy Resources Technology, 2014
Even though there have been several studies conducted by the industry on the use of different inl... more Even though there have been several studies conducted by the industry on the use of different inlet devices for gas–liquid separation, there have been limited laboratory and field evaluations on the use of external piping configurations as flow conditioning devices upstream of a separator inlet. The results of a systematic study of droplet deposition and coalescence in curved pipe and pipe fittings are reported in this paper. A facility has been designed consisting of two main test sections: a fixed horizontal straight pipe section and an interchangeable 180 deg return pipe section (or curved pipe section) of the same length. Both inlet and outlet to the 180 deg return are horizontal, but the plane of the 180 deg return pipe section can pivot about the axis of the inlet horizontal pipe to an angle as much as 10 deg downwards allowing downward flow in the return section. Various pipe fittings of different radius of curvature can be installed for comparison in the 180 deg return. Fitt...
2001 Annual Conference Proceedings
2002 Annual Conference Proceedings
and the University of Tulsa. The objective of the project is to develop a new curriculum for teac... more and the University of Tulsa. The objective of the project is to develop a new curriculum for teaching undergraduate and graduate students multiphase computational fluid dynamics for advanced design. The impact of multiphase flow research on solving practical engineering problems is an integral part of the learning experience. Industrial participants in the project provide specific design problems related to emerging technologies. Students are taught the fundamentals of computational fluid dynamics (CFD) during a one-week workshop. This is followed by an Internet course on multiphase transport phenomena. The students work in teams on CFD design problems with a faculty and industrial mentor. The salient results of this NSF/CRCD project are presented in this paper.
Journal of Natural Gas Science and Engineering
Journal of Energy Resources Technology
The Gas-Liquid Cylindrical Cyclone (GLCC©*) is a simple, compact and low-cost separator, which pr... more The Gas-Liquid Cylindrical Cyclone (GLCC©*) is a simple, compact and low-cost separator, which provides an economically attractive alternative to conventional gravity-based separators over a wide range of applications. The GLCC© inlet section design is a key parameter, which is crucial for its performance and proper operation. An in-depth evaluation of specific design modifications and their effect on safety and structural robustness are carried out in this study using Finite Element Analysis. Fluid-Structure Interaction (FSI) analysis is also carried out using the results of Computational Fluid Dynamics (CFD) aimed at investigating the effect of fluid flow on the inlet section structural integrity. The selected design modifications are based on feasibility of GLCC© manufacturing and assembly for field applications. Different case studies incorporating sustained GLCC© internal pressure, dead weight loading, forces generated because of slug flow and high temperatures are analyzed and...
Journal of Natural Gas Science and Engineering
International Journal of Multiphase Flow
Spe J, 2002
The liquid-liquid Hydrocyclone (LLHC) has been widely used by the Petroleum Industry for the past... more The liquid-liquid Hydrocyclone (LLHC) has been widely used by the Petroleum Industry for the past several decades. A large quantity of information on the LLHC available in the literature includes experimental data, computational fluid dynamic simulations and field applications. The design of LLHCs has been based in the past mainly on empirical experience. However, no simple and overall design mechanistic model has been developed to date for the LLHC. The objective of this study is to develop a mechanistic model for the de-oiling LLHCs, and test it against available and new experimental data. This model will enable the prediction of the hydrodynamic flow behavior in the LLHC, providing a design tool for LLHC field applications. A simple mechanistic model is developed for the LLHC. The required input for the model is: LLHC geometry, fluid properties, inlet droplet size distribution and operational conditions. The model is capable of predicting the LLHC hydrodynamic flow field, namely, the axial, tangential and radial velocity distributions of the continuous-phase. The separation efficiency and migration probability are determined based on swirl intensity prediction and droplet trajectory analysis. The flow capacity, namely, the inlet-to-underflow pressure drop is predicted utilizing an energy balance analysis. An extensive experimental program has been conducted during this study, utilizing a 2" MQ Hydroswirl hydrocyclone. The inlet flow conditions are: total flow rates between 27 to 18 gpm, oil-cut up to 10%, median droplet size distributions from 50 to 500 ìm, and inlet pressures between 60 to 90 psia. The acquired data include the flow rate, oil-cut and droplet size distribution in the inlet and in the underflow, the reject flow rate and oil concentration in the overflow and the separation efficiency. Additional data for velocity profiles were taken from the literature, especially from the Colman and Thew (1980) study. Excellent agreement is observed between the model prediction and the experimental data with respect to both separation efficiency (average absolute relative error of 3%) and pressure drop (average absolute relative error of 1.6%).
Oil and Gas Facilities, 2016
Summary Looped gas/liquid multiphase-flow pipelines are used by the oil and gas industry to reduc... more Summary Looped gas/liquid multiphase-flow pipelines are used by the oil and gas industry to reduce pressure drop and increase flow capacity. They can be installed alone as a flow splitter or combined in series to form a manifold. Application of looped lines is not unique to the petroleum industry; they are also applied in other industries such as nuclear and chemical. However, there has not yet been a comprehensive fundamental investigation of the flow behavior or predictive methods available for such systems because of the complexity involved with respect to process variables such as flow patterns, fluid properties, phase velocities, and pipe geometry. Uneven splitting of the gas and liquid phases between the two looped lines can cause malfunction of the downstream processing equipment; therefore, a total of 65 experiments at different flow conditions in a looped-lines system using different-diameter looped-line configurations are conducted in this study to investigate the pressure...
Integral Methods in Science and Engineering, 2011
Theoretical and Applied Fracture Mechanics, 1999
Acoustic Emission (AE) sensing technique is used as a tool for on-line monitoring of hydro-abrasi... more Acoustic Emission (AE) sensing technique is used as a tool for on-line monitoring of hydro-abrasive erosion (HAE) of pre-cracked multiphase materials. As reference materials, ®ve types of concrete materials were used for the experimental study. Compression tests were performed to determine the mechanical properties and the failure behavior of these materials. Erosion parameters, such as abrasive particle velocity, local exposure time, and abrasive mass¯ow rate were varied during the experiments and AE-signals were acquired. The trends exhibited by the time domain and frequency domain AE-signals with change in process parameters and material properties were analyzed. The results indicate that acoustic emission signal is capable of revealing the dierent material removal mechanisms occurring in pre-cracked multiphase materials when subjected to hydro-abrasive erosion. Visualization studies performed on the erosion site provide more insight into the physics of the process and verify the observations made from the AE-signals. Finally, it is concluded that due to its capability to quantify the amount of material removed, AE RMS could be considered as a parameter for monitoring the material removal process.
Journal of Energy Resources Technology
ABSTRACT
SPE International Symposium and Exhibition on Formation Damage Control, 2014
ABSTRACT Transport of sand in multiphase pipelines occurs in the petroleum industry as sand is pr... more ABSTRACT Transport of sand in multiphase pipelines occurs in the petroleum industry as sand is produced co-mingled with crude oil. Stationary sand beds are formed at the pipe bottom when the flow velocity is lower than the critical sand deposition velocity. These sand beds reduce reservoir production and affect the integrity of the pipe system due to pipeline plugging and erosion/corrosion produced by sand particles. Therefore, the production system must be designed to operate at a velocity where sand particles are transported along the pipe. For that reason, it is crucial to predict the critical sand deposition velocity in order to maximize reservoir production. Gas-liquid-sand flow hydrodynamics, which is commonly encountered in most reservoirs and also in oil and gas transportation pipelines, is more complex than liquid-sand flow, making the modeling extremely difficult. At present, gas-liquid-sand flow is still not well understood, with limited data available in the literature. In addition, the effect of sand concentration has not been thoroughly studied for two-phase flows transporting sand. Experimental and theoretical investigations have been conducted in this study on gas-liquid-sand stratified flow in horizontal pipes at low sand concentrations. A 4-in experimental facility was designed and constructed and data were acquired utilizing air-water-glass beads flow. The data include measurements of critical sand deposition velocities, namely, the transition between moving and stationary beds. The data reveal that for a constant superficial liquid velocity, the critical mixture and liquid sand deposition velocities increase with increasing sand concentrations. Also, for a given sand concentration, the critical liquid velocity is almost the same for different superficial liquid velocities. The sand deposition correlations of Oroskar and Turian (1980) for single-phase flow and Salama (2000) for two-phase flow are modified and extended in order to develop a new correlation. The developed correlation enables the prediction of critical sand deposition mixture velocity for horizontal stratified flow, as function of sand concentration along with other parameters. Comparison between the predictions of the developed correlation and the experimental data reveal a very good agreement, whereby the relative errors of mixture and liquid critical sand deposition velocities are ±2.5% and < 5%, respectively.
SPE Projects Facilities & Construction, 2010
... Design of the SLHC has relied primarily on empirical experi-ence (Kelsall 1952; Rietema 1961a... more ... Design of the SLHC has relied primarily on empirical experi-ence (Kelsall 1952; Rietema 1961a, 1961b, 1961c, 1961d), and more recently on costly and lengthy CFD modeling (Delgadillo and Rajamani 2005; Narasimha et al. 2005). ...
SPE Journal, 2000
Summary The liquid carry-over phenomenon in gas-liquid cylindrical cyclone (GLCC© **) compact sep... more Summary The liquid carry-over phenomenon in gas-liquid cylindrical cyclone (GLCC© **) compact separators has been studied experimentally and theoretically. Experimental data have been acquired including the operational envelope for liquid carry-over and percent liquid carry-over beyond the operational envelope. The data show that at low gas and high liquid flow rates, under churn flow conditions in the upper part of the cylindrical cyclone, a large amount of liquid can be carried over relatively easily. On the other hand, at high gas and low liquid flow rates, under annular flow conditions, one should exceed the operational envelope significantly in order to have large amount of liquid carry-over. A mechanistic model has been developed for the prediction of the percent liquid carry-over beyond the operational envelope for churn flow conditions. An existing model for the prediction of the operational envelope for liquid carry-over has been extended to high-pressure conditions, includ...
Journal of Energy Resources Technology, 2014
Even though there have been several studies conducted by the industry on the use of different inl... more Even though there have been several studies conducted by the industry on the use of different inlet devices for gas–liquid separation, there have been limited laboratory and field evaluations on the use of external piping configurations as flow conditioning devices upstream of a separator inlet. The results of a systematic study of droplet deposition and coalescence in curved pipe and pipe fittings are reported in this paper. A facility has been designed consisting of two main test sections: a fixed horizontal straight pipe section and an interchangeable 180 deg return pipe section (or curved pipe section) of the same length. Both inlet and outlet to the 180 deg return are horizontal, but the plane of the 180 deg return pipe section can pivot about the axis of the inlet horizontal pipe to an angle as much as 10 deg downwards allowing downward flow in the return section. Various pipe fittings of different radius of curvature can be installed for comparison in the 180 deg return. Fitt...
2001 Annual Conference Proceedings
2002 Annual Conference Proceedings
and the University of Tulsa. The objective of the project is to develop a new curriculum for teac... more and the University of Tulsa. The objective of the project is to develop a new curriculum for teaching undergraduate and graduate students multiphase computational fluid dynamics for advanced design. The impact of multiphase flow research on solving practical engineering problems is an integral part of the learning experience. Industrial participants in the project provide specific design problems related to emerging technologies. Students are taught the fundamentals of computational fluid dynamics (CFD) during a one-week workshop. This is followed by an Internet course on multiphase transport phenomena. The students work in teams on CFD design problems with a faculty and industrial mentor. The salient results of this NSF/CRCD project are presented in this paper.
Journal of Natural Gas Science and Engineering
Journal of Energy Resources Technology
The Gas-Liquid Cylindrical Cyclone (GLCC©*) is a simple, compact and low-cost separator, which pr... more The Gas-Liquid Cylindrical Cyclone (GLCC©*) is a simple, compact and low-cost separator, which provides an economically attractive alternative to conventional gravity-based separators over a wide range of applications. The GLCC© inlet section design is a key parameter, which is crucial for its performance and proper operation. An in-depth evaluation of specific design modifications and their effect on safety and structural robustness are carried out in this study using Finite Element Analysis. Fluid-Structure Interaction (FSI) analysis is also carried out using the results of Computational Fluid Dynamics (CFD) aimed at investigating the effect of fluid flow on the inlet section structural integrity. The selected design modifications are based on feasibility of GLCC© manufacturing and assembly for field applications. Different case studies incorporating sustained GLCC© internal pressure, dead weight loading, forces generated because of slug flow and high temperatures are analyzed and...
Journal of Natural Gas Science and Engineering
International Journal of Multiphase Flow
Spe J, 2002
The liquid-liquid Hydrocyclone (LLHC) has been widely used by the Petroleum Industry for the past... more The liquid-liquid Hydrocyclone (LLHC) has been widely used by the Petroleum Industry for the past several decades. A large quantity of information on the LLHC available in the literature includes experimental data, computational fluid dynamic simulations and field applications. The design of LLHCs has been based in the past mainly on empirical experience. However, no simple and overall design mechanistic model has been developed to date for the LLHC. The objective of this study is to develop a mechanistic model for the de-oiling LLHCs, and test it against available and new experimental data. This model will enable the prediction of the hydrodynamic flow behavior in the LLHC, providing a design tool for LLHC field applications. A simple mechanistic model is developed for the LLHC. The required input for the model is: LLHC geometry, fluid properties, inlet droplet size distribution and operational conditions. The model is capable of predicting the LLHC hydrodynamic flow field, namely, the axial, tangential and radial velocity distributions of the continuous-phase. The separation efficiency and migration probability are determined based on swirl intensity prediction and droplet trajectory analysis. The flow capacity, namely, the inlet-to-underflow pressure drop is predicted utilizing an energy balance analysis. An extensive experimental program has been conducted during this study, utilizing a 2" MQ Hydroswirl hydrocyclone. The inlet flow conditions are: total flow rates between 27 to 18 gpm, oil-cut up to 10%, median droplet size distributions from 50 to 500 ìm, and inlet pressures between 60 to 90 psia. The acquired data include the flow rate, oil-cut and droplet size distribution in the inlet and in the underflow, the reject flow rate and oil concentration in the overflow and the separation efficiency. Additional data for velocity profiles were taken from the literature, especially from the Colman and Thew (1980) study. Excellent agreement is observed between the model prediction and the experimental data with respect to both separation efficiency (average absolute relative error of 3%) and pressure drop (average absolute relative error of 1.6%).