The permeability contrast between the Hot Dry Rock(HDR)reservoir and the surrounding formations is a key factor governing fluid loss in Enhanced Geothermal Systems(EGS).This study thus aims to investigate its impact o...The permeability contrast between the Hot Dry Rock(HDR)reservoir and the surrounding formations is a key factor governing fluid loss in Enhanced Geothermal Systems(EGS).This study thus aims to investigate its impact on system performance under varying operating conditions,and a three-dimensional thermo–hydro–mechanical(THM)coupled EGS model is developed based on the geological parameters of the GR1 well in the Qiabuqia region.The coupled processes of fluid flow,heat transfer,and geomechanics within the reservoir under varying reservoir–surrounding rock permeability contrasts,as well as the flow and heat exchange along the wellbores fromthe reservoir to the surface are simulated.Then,the influence of permeability contrast,production pressure,injection rate,and injection temperature on fluid loss and heat extraction performance over a 35-year operation period is quantitatively assessed.Theresults show that increasing the permeability contrast effectively suppresses fluid loss and enhances early-stage heat production,but also accelerates thermal breakthrough and shortens the stable operation period.When the contrast rises from 1×10^(3) to 1×10^(5),the cumulative fluid loss rate drops from 54.34%to 0.23%,and the total heat production increases by 132%,although the breakthrough occurs 5 years earlier.Meanwhile,higher production pressure delays thermal breakthrough and slows transient temperature decline,but exacerbates fluid loss and reduces heat production power.For instance,raising the pressure from 17 to 21 MPa increases the fluid loss rate from 33.17%to 54.34%and reduces average annual heat production power from 25.43 to 14.59MWth.In addition,increasing the injection rate(46 to 66 kg/s)lowers fluid loss rate but brings forward thermal breakthrough by 9 years and causes a 41 K temperature drop at the end of operation.Notably,under high fluid loss,the dynamic response pattern of heat production power shifts from a temperature-dominated“stable–breakthrough–decline”mode to a novel“rising–breakthrough–decline”mode jointly governed by both production temperature and flow rates.These findings provide theoretical support and engineering guidance for improving EGS performance.展开更多
During ultradeep oil and gas drilling,fluid loss reducers are highly important for water-based drilling fluids,while preparing high temperature-and salt-resistance fluid loss reducers with excellent rheology and filtr...During ultradeep oil and gas drilling,fluid loss reducers are highly important for water-based drilling fluids,while preparing high temperature-and salt-resistance fluid loss reducers with excellent rheology and filtration performance remains a challenge.Herein,a micro-crosslinked amphoteric hydrophobic association copolymer(i.e.,DADC)was synthesized using N,N-dimethyl acrylamide,diallyl dimethyl ammonium chloride,2-acrylamido-2-methylpropane sulfonic acid,hydrophobic monomer,and pentaerythritol triallyl ether crosslinker.Due to the synergistic effects of hydrogen bonds,electrostatic interaction,hydrophobic association,and micro-crosslinking,the DADC copolymer exhibited outstanding temperature-and salt-resistance.The rheological experiments have shown that the DADC copolymer had excellent shear dilution performance and a certain degree of salt-responsive viscosity-increasing performance.The DADC copolymer could effectively adsorb on the surface of bentonite particles through electrostatic interaction and hydrogen bonds,which bring more negative charge to the bentonite,thus improving the hydration and dispersion of bentonite particles as well as the colloidal stability of the drilling fluids.Moreover,the drilling fluids constructed based on the DADC copolymer exhibited satisfactory rheological and filtration properties(FLHTHP=12 m L)after aging at high temperatures(up to200℃)and high salinity(saturated salt)environments.Therefore,this work provided new insights into designing and fabricating high-performance drilling fluid treatment agents,demonstrating good potential applications in deep and ultradeep drilling engineering.展开更多
Wellbore instability is an issue that,if left untreated,can cause wells to collapse,resulting in human,environmental,equipment,and revenue losses.Drilling fluids have been used to enhance the drilling process by lubri...Wellbore instability is an issue that,if left untreated,can cause wells to collapse,resulting in human,environmental,equipment,and revenue losses.Drilling fluids have been used to enhance the drilling process by lubricating and cooling the drill bit,eliminating cuttings,and most importantly,by improving the stability of the well by preventing fluid loss.However,there has been an increase in operational demands and challenges that call for drilling fluids to be more effective,economical,sustainable,and environmentally friendly.With shales that have infinitesimally small pores,nanoparticle additives in drilling fluids can be crucial in providing the properties that are necessary to prevent fluid loss and provide wellbore stability while meeting the operational demands of the present day.Therefore,this paper examines the use of nanoparticle additives including copper(Ⅱ)oxide(CuO),magnesium oxide(MgO),and aluminum oxide(Al_(2)O_(3))where they are tested under three conditions using the permeable plugging tester(PPT),high-temperature high-pressure(HTHP)fluid loss apparatus,and API low-temperature e low-pressure(LTLP)fluid loss apparatus under concentrations of 0.03%and 0.10%.Finally,based on the results,each nanoparticle sample(particle sizes between one and 100 nm)performed well in contributing to the aim of this project.CuO is the most effective inhibitor across all concentrations and under the three different conditions.It contributed to reducing the fluid loss from 37.6 mL to 18.2 and 13.2 mL,which is between 52%and 65%of fluid reduction.For MgO,it contributed to fluid loss reduction to 23.8 mL and 15 mL,which translated to 37%e60%of fluid loss reduction.The use of Al_(2)O_(3) nanoparticles resulted in a fluid loss reduction to 33.6 mL and 17.8 mL,reducing the fluid loss up to 11%,at HTHP and up to 53%at LTLP.Unlike CuO and MgO,Al_(2)O_(3) was less effective under HTHP conditions when compared to LTLP conditions.Al_(2)O_(3) did not suffer as a significant diminishing benefit with increasing concentration in LTLP conditions however which means that at a higher concentration,it may begin to be more effective.Each material used in this study has its own specific and technical characteristics that will help create a progressive amount of property,such as providing stability and withstanding the high-temperature and highpressure condition downhole.展开更多
The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics （CFD） has been used to inv...The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics （CFD） has been used to investigate the relations of porosities, flow velocity and diameter of the holes with the pressure loss. Accordingly, some preliminary results have been obtained that pressure loss increases with porosity descent as nearly a hyperbolic trend, rising flow velocity of the input makes the pressure loss increasing with parabola trend, diameter of holes affects little about pressure loss of the muffler. Otherwise, the holes on the perforated pipes make the air flow gently and meanly, which decreases the air impact to the wall and pipes in the muffler. A practical perforated muffler is used to illustrate the available of this method for pressure loss computation, and the comparison shows that the computation results with the method of CFD has reference value for muffler design.展开更多
CoFe2O4 nanoparticles(NPs)and surface modified with gold(Au)have been synthesized by a thermal decomposition method.The obtained NPs and formation of CoFe2O4@Au core–shell(CS)were confirmed by characterizing their st...CoFe2O4 nanoparticles(NPs)and surface modified with gold(Au)have been synthesized by a thermal decomposition method.The obtained NPs and formation of CoFe2O4@Au core–shell(CS)were confirmed by characterizing their structural and optical properties using X-ray powder diffraction(XRD)patterns,Fourier transform infrared spectroscopy,Raman spectroscopy,UV–Visible and photoluminescence studies.Morphological and compositional studies were carried out using high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy,while the magnetic properties were determined using alternating gradient magnetometer and Mossbauer to define the magneto-structural effects of shell formation on the core NPs.Induction heating properties of CoFe2O4 and CoFe2O4@Au CS magnetic nanoparticles(MNPs)have been investigated and correlated with magneto-structural properties.Specific absorption rate and intrinsic loss power were calculated for these MNPs within the human tolerable range of frequency and amplitude,suggesting their potential in magnetic fluid hyperthermia therapy for possible cancer treatment.展开更多
Aiming at the problems of microfracture development in hard brittle shale gas layer in Fuling block, Chongqing, such as collapse of borehole wall and the existence of permeability loss of microfracture during drilling...Aiming at the problems of microfracture development in hard brittle shale gas layer in Fuling block, Chongqing, such as collapse of borehole wall and the existence of permeability loss of microfracture during drilling, and serious pollution of drilling environment with oil-based drilling fluid, a water-based drilling fluid system for anti-collapse and anti-leakage was studied. A water-based drilling fluid system with anti-collapse and anti-leakage was formed by introducing functional treatment agents, such as polypolysaccharide MEG, polymer emulsion film forming wall cementing agent LFGB, polyamine inhibitor LCFA and deformable particle plugging agent BXLZ, into the conventional water-based drilling fluid. After rolling at 130°C for 16 h, the system has good rheological properties, low filtration loss, good inhibition, lubrication and plugging properties. It has good plugging properties for 0.12 mm, 0.24 mm, 0.38 mm micro-cracks and 400 mD and 800 mD sand plates. The system was successfully tested on site in August 2019 in Fuling Reef Block, showing good rheological properties, solid wall plugging, and strong ability to seal and inhibit fracture expansion. There was no block falling in the drilling process, and the tripping, casing running and well cementing operations were all smooth, which provided a new technical idea and scheme for environmental protection and green drilling in Fuling shale gas exploitation.展开更多
The flow field in junction is complicated due to the ripple property of oil flow velocity and different frequencies of two pumps in aircraft. In this study, the flow fields of T-junction and Y-junction were analyzed u...The flow field in junction is complicated due to the ripple property of oil flow velocity and different frequencies of two pumps in aircraft. In this study, the flow fields of T-junction and Y-junction were analyzed using shear stress transport （SST） model in ANSYS/CFX software. The simulation results identified the variation rule of velocity peak in T-junction with different frequencies and phase-differences, meanwhile, the eddy and velocity shock existed in the corner of the T-junction, and the limit working state was obtained. Although the eddy disappeared in Y-junction, the velocity shock and pressure loss were still too big. To address these faults, an arc-junction was designed. Based on the flow fields of arc-junction, the eddy in the junction corner disappeared and the maximum of velocity peak declined compared to T-and Y-junction. Additionally, 8 series of arc-junction with different radiuses were tested to get the variation rule of velocity peak. Through the computation of the pressure loss of three junctions, the arc-junction had a lowest loss value, and its pressure loss reached the minimum value when the curvature radius is 35.42 mm, meanwhile, the velocity shock has decreased in a low phase.展开更多
In the process of performance prediction of waterjet system,the flow loss of inlet duct is usually reckoned by the rule of thumb. But its value is often overestimated to some extent,resulting in error of prediction ac...In the process of performance prediction of waterjet system,the flow loss of inlet duct is usually reckoned by the rule of thumb. But its value is often overestimated to some extent,resulting in error of prediction accuracy. This paper introduces a new method to determine the flow loss by means of computational fluid dynamic (CFD). Firstly,the fluid field around waterjet system is simulated by solving the Reynolds Averaged Navier-Stokes (RANS) equations using commercial CFD code Fluent. Then an additional User-Defined Scalar (UDS) equation is embedded into Fluent to get the virtual dividing surface between the internal flow ingested into the inlet duct and the external flow beneath the hull,which is named as streamtube. By virtual of the streamtube the flow loss can be calculated according to the difference of total pressure between the duct outlet and the capture area ahead of the intake. The results from CFD calculation show that the flow loss coeflcient of a typical flush-type inlet duct is varying from 0.05 to 0.12 at different operation conditions,being obviously less than the value of 0.2-0.3 from empirical rules. With the results of this paper the prediction accuracy on propulsive performance of the waterjet system can be improved further.展开更多
Accurate determination of hydraulic parameters such as pressure losses, equivalent circulation density (ECD), etc. plays profound roles in drilling, cementing and other well operations. Hydraulics characterization req...Accurate determination of hydraulic parameters such as pressure losses, equivalent circulation density (ECD), etc. plays profound roles in drilling, cementing and other well operations. Hydraulics characterization requires that all factors are considered as the neglect of any could become potential sources of errors that would be detrimental to the overall well operation. Drilling Hydraulics has been extensively treated in the literature. However, these works almost entirely rely on the assumption that the drill string lies perfectly at the center of the annulus—the so-called “concentric annulus”. In reality, concentricity is almost never achieved even when centralizers are used. This is because of high well inclination angles and different string geometries. Thus, eccentricity exists in practical oil and gas wells especially horizontal and extended reach wells (ERWs) and must be accounted for. The prevalence of drillstring (DS) eccentricity in the annulus calls for a re-evaluation of existing hydraulic models. This study evaluates the effect of drilling fluid rheology types and DS eccentricity on the entire drilling hydraulics. Three non-Newtonian fluid models were analyzed, viz: Herschel Bulkley, power law and Bingham plastic models. From the results, it was observed that while power law and Bingham plastic models gave the upper and lower hydraulic values, Herschel Bulkley fluid model gave annular pressure loss (APL) and ECD values that fall between the upper and lower values and provide a better fit to the hydraulic data than power law and Bingham plastic fluids. Furthermore, analysis of annular eccentricity reveals that APLs and ECD decrease with an increase in DS eccentricity. Pressure loss reduction of more than 50% was predicted for the fully eccentric case for Herschel Bulkley fluids. Thus, DS eccentricity must be fully considered during well planning and hydraulics designs.展开更多
Applications of Electro-Rheological (ER) or Magneto-Rheological (MR) fluids as typical smart materials have been widely investigated over the past decades (since their introduction in 40’s). The special applications ...Applications of Electro-Rheological (ER) or Magneto-Rheological (MR) fluids as typical smart materials have been widely investigated over the past decades (since their introduction in 40’s). The special applications of these materials as a means of noise suppression are not yet investigated. Constrained Layer Damping (CLD) sheets can be realized by incorporating EMR (ER/MR) materials. In this way, a multilayered damping sheet is obtained with adaptive (tunable) stiffness and damping characteristics. These properties are easily changed in proportion to the electric (magnetic) field applied upon the EMR layer. This notion has been introduced for semi-active vibration control problems. Herein, such panels incorporating EMR material are proposed for adaptive acoustic treatments. Modeling (simulation) of a 3-layered panel with the middle layer being EMR with adjustable properties is carried out in this paper. The tunability of transmission/absorption characteristics of these composite sheets enables us making smart panels for adaptive noise and acoustic treatments. An adaptive performance can be achieved via changing the properties of such panels, on line, according to some sensor outputs. The main objective is to develop proper models to predict the Transmission Loss (TL) of such panels. Also, the TL of this panel is compared with the middle layer of a Newtonian fluid.展开更多
基金supported by the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(GZC20251944)the National Natural Science Foundation of China(No.52376044)the National Key Research and Development Program of China(2024YFE0100800).
文摘The permeability contrast between the Hot Dry Rock(HDR)reservoir and the surrounding formations is a key factor governing fluid loss in Enhanced Geothermal Systems(EGS).This study thus aims to investigate its impact on system performance under varying operating conditions,and a three-dimensional thermo–hydro–mechanical(THM)coupled EGS model is developed based on the geological parameters of the GR1 well in the Qiabuqia region.The coupled processes of fluid flow,heat transfer,and geomechanics within the reservoir under varying reservoir–surrounding rock permeability contrasts,as well as the flow and heat exchange along the wellbores fromthe reservoir to the surface are simulated.Then,the influence of permeability contrast,production pressure,injection rate,and injection temperature on fluid loss and heat extraction performance over a 35-year operation period is quantitatively assessed.Theresults show that increasing the permeability contrast effectively suppresses fluid loss and enhances early-stage heat production,but also accelerates thermal breakthrough and shortens the stable operation period.When the contrast rises from 1×10^(3) to 1×10^(5),the cumulative fluid loss rate drops from 54.34%to 0.23%,and the total heat production increases by 132%,although the breakthrough occurs 5 years earlier.Meanwhile,higher production pressure delays thermal breakthrough and slows transient temperature decline,but exacerbates fluid loss and reduces heat production power.For instance,raising the pressure from 17 to 21 MPa increases the fluid loss rate from 33.17%to 54.34%and reduces average annual heat production power from 25.43 to 14.59MWth.In addition,increasing the injection rate(46 to 66 kg/s)lowers fluid loss rate but brings forward thermal breakthrough by 9 years and causes a 41 K temperature drop at the end of operation.Notably,under high fluid loss,the dynamic response pattern of heat production power shifts from a temperature-dominated“stable–breakthrough–decline”mode to a novel“rising–breakthrough–decline”mode jointly governed by both production temperature and flow rates.These findings provide theoretical support and engineering guidance for improving EGS performance.
基金the National Natural Science Foundation of China(No.52204023)China Postdoctoral Science Foundation(2022M713465)Postdoctoral Innovation Talent Support of Shandong Province(SDBX2022033)。
文摘During ultradeep oil and gas drilling,fluid loss reducers are highly important for water-based drilling fluids,while preparing high temperature-and salt-resistance fluid loss reducers with excellent rheology and filtration performance remains a challenge.Herein,a micro-crosslinked amphoteric hydrophobic association copolymer(i.e.,DADC)was synthesized using N,N-dimethyl acrylamide,diallyl dimethyl ammonium chloride,2-acrylamido-2-methylpropane sulfonic acid,hydrophobic monomer,and pentaerythritol triallyl ether crosslinker.Due to the synergistic effects of hydrogen bonds,electrostatic interaction,hydrophobic association,and micro-crosslinking,the DADC copolymer exhibited outstanding temperature-and salt-resistance.The rheological experiments have shown that the DADC copolymer had excellent shear dilution performance and a certain degree of salt-responsive viscosity-increasing performance.The DADC copolymer could effectively adsorb on the surface of bentonite particles through electrostatic interaction and hydrogen bonds,which bring more negative charge to the bentonite,thus improving the hydration and dispersion of bentonite particles as well as the colloidal stability of the drilling fluids.Moreover,the drilling fluids constructed based on the DADC copolymer exhibited satisfactory rheological and filtration properties(FLHTHP=12 m L)after aging at high temperatures(up to200℃)and high salinity(saturated salt)environments.Therefore,this work provided new insights into designing and fabricating high-performance drilling fluid treatment agents,demonstrating good potential applications in deep and ultradeep drilling engineering.
文摘Wellbore instability is an issue that,if left untreated,can cause wells to collapse,resulting in human,environmental,equipment,and revenue losses.Drilling fluids have been used to enhance the drilling process by lubricating and cooling the drill bit,eliminating cuttings,and most importantly,by improving the stability of the well by preventing fluid loss.However,there has been an increase in operational demands and challenges that call for drilling fluids to be more effective,economical,sustainable,and environmentally friendly.With shales that have infinitesimally small pores,nanoparticle additives in drilling fluids can be crucial in providing the properties that are necessary to prevent fluid loss and provide wellbore stability while meeting the operational demands of the present day.Therefore,this paper examines the use of nanoparticle additives including copper(Ⅱ)oxide(CuO),magnesium oxide(MgO),and aluminum oxide(Al_(2)O_(3))where they are tested under three conditions using the permeable plugging tester(PPT),high-temperature high-pressure(HTHP)fluid loss apparatus,and API low-temperature e low-pressure(LTLP)fluid loss apparatus under concentrations of 0.03%and 0.10%.Finally,based on the results,each nanoparticle sample(particle sizes between one and 100 nm)performed well in contributing to the aim of this project.CuO is the most effective inhibitor across all concentrations and under the three different conditions.It contributed to reducing the fluid loss from 37.6 mL to 18.2 and 13.2 mL,which is between 52%and 65%of fluid reduction.For MgO,it contributed to fluid loss reduction to 23.8 mL and 15 mL,which translated to 37%e60%of fluid loss reduction.The use of Al_(2)O_(3) nanoparticles resulted in a fluid loss reduction to 33.6 mL and 17.8 mL,reducing the fluid loss up to 11%,at HTHP and up to 53%at LTLP.Unlike CuO and MgO,Al_(2)O_(3) was less effective under HTHP conditions when compared to LTLP conditions.Al_(2)O_(3) did not suffer as a significant diminishing benefit with increasing concentration in LTLP conditions however which means that at a higher concentration,it may begin to be more effective.Each material used in this study has its own specific and technical characteristics that will help create a progressive amount of property,such as providing stability and withstanding the high-temperature and highpressure condition downhole.
文摘The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics （CFD） has been used to investigate the relations of porosities, flow velocity and diameter of the holes with the pressure loss. Accordingly, some preliminary results have been obtained that pressure loss increases with porosity descent as nearly a hyperbolic trend, rising flow velocity of the input makes the pressure loss increasing with parabola trend, diameter of holes affects little about pressure loss of the muffler. Otherwise, the holes on the perforated pipes make the air flow gently and meanly, which decreases the air impact to the wall and pipes in the muffler. A practical perforated muffler is used to illustrate the available of this method for pressure loss computation, and the comparison shows that the computation results with the method of CFD has reference value for muffler design.
基金Author (Sandip Sabale) is thankful to University Grants Commission, New Delhi, India, for Raman Fellowship to work in USA (F. No. 5-105/2016 (IC), February 10, 2016
文摘CoFe2O4 nanoparticles(NPs)and surface modified with gold(Au)have been synthesized by a thermal decomposition method.The obtained NPs and formation of CoFe2O4@Au core–shell(CS)were confirmed by characterizing their structural and optical properties using X-ray powder diffraction(XRD)patterns,Fourier transform infrared spectroscopy,Raman spectroscopy,UV–Visible and photoluminescence studies.Morphological and compositional studies were carried out using high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy,while the magnetic properties were determined using alternating gradient magnetometer and Mossbauer to define the magneto-structural effects of shell formation on the core NPs.Induction heating properties of CoFe2O4 and CoFe2O4@Au CS magnetic nanoparticles(MNPs)have been investigated and correlated with magneto-structural properties.Specific absorption rate and intrinsic loss power were calculated for these MNPs within the human tolerable range of frequency and amplitude,suggesting their potential in magnetic fluid hyperthermia therapy for possible cancer treatment.
文摘Aiming at the problems of microfracture development in hard brittle shale gas layer in Fuling block, Chongqing, such as collapse of borehole wall and the existence of permeability loss of microfracture during drilling, and serious pollution of drilling environment with oil-based drilling fluid, a water-based drilling fluid system for anti-collapse and anti-leakage was studied. A water-based drilling fluid system with anti-collapse and anti-leakage was formed by introducing functional treatment agents, such as polypolysaccharide MEG, polymer emulsion film forming wall cementing agent LFGB, polyamine inhibitor LCFA and deformable particle plugging agent BXLZ, into the conventional water-based drilling fluid. After rolling at 130°C for 16 h, the system has good rheological properties, low filtration loss, good inhibition, lubrication and plugging properties. It has good plugging properties for 0.12 mm, 0.24 mm, 0.38 mm micro-cracks and 400 mD and 800 mD sand plates. The system was successfully tested on site in August 2019 in Fuling Reef Block, showing good rheological properties, solid wall plugging, and strong ability to seal and inhibit fracture expansion. There was no block falling in the drilling process, and the tripping, casing running and well cementing operations were all smooth, which provided a new technical idea and scheme for environmental protection and green drilling in Fuling shale gas exploitation.
基金supported by the National Natural Science Foundation of China(No.51175014)
文摘The flow field in junction is complicated due to the ripple property of oil flow velocity and different frequencies of two pumps in aircraft. In this study, the flow fields of T-junction and Y-junction were analyzed using shear stress transport （SST） model in ANSYS/CFX software. The simulation results identified the variation rule of velocity peak in T-junction with different frequencies and phase-differences, meanwhile, the eddy and velocity shock existed in the corner of the T-junction, and the limit working state was obtained. Although the eddy disappeared in Y-junction, the velocity shock and pressure loss were still too big. To address these faults, an arc-junction was designed. Based on the flow fields of arc-junction, the eddy in the junction corner disappeared and the maximum of velocity peak declined compared to T-and Y-junction. Additionally, 8 series of arc-junction with different radiuses were tested to get the variation rule of velocity peak. Through the computation of the pressure loss of three junctions, the arc-junction had a lowest loss value, and its pressure loss reached the minimum value when the curvature radius is 35.42 mm, meanwhile, the velocity shock has decreased in a low phase.
文摘In the process of performance prediction of waterjet system,the flow loss of inlet duct is usually reckoned by the rule of thumb. But its value is often overestimated to some extent,resulting in error of prediction accuracy. This paper introduces a new method to determine the flow loss by means of computational fluid dynamic (CFD). Firstly,the fluid field around waterjet system is simulated by solving the Reynolds Averaged Navier-Stokes (RANS) equations using commercial CFD code Fluent. Then an additional User-Defined Scalar (UDS) equation is embedded into Fluent to get the virtual dividing surface between the internal flow ingested into the inlet duct and the external flow beneath the hull,which is named as streamtube. By virtual of the streamtube the flow loss can be calculated according to the difference of total pressure between the duct outlet and the capture area ahead of the intake. The results from CFD calculation show that the flow loss coeflcient of a typical flush-type inlet duct is varying from 0.05 to 0.12 at different operation conditions,being obviously less than the value of 0.2-0.3 from empirical rules. With the results of this paper the prediction accuracy on propulsive performance of the waterjet system can be improved further.
文摘Accurate determination of hydraulic parameters such as pressure losses, equivalent circulation density (ECD), etc. plays profound roles in drilling, cementing and other well operations. Hydraulics characterization requires that all factors are considered as the neglect of any could become potential sources of errors that would be detrimental to the overall well operation. Drilling Hydraulics has been extensively treated in the literature. However, these works almost entirely rely on the assumption that the drill string lies perfectly at the center of the annulus—the so-called “concentric annulus”. In reality, concentricity is almost never achieved even when centralizers are used. This is because of high well inclination angles and different string geometries. Thus, eccentricity exists in practical oil and gas wells especially horizontal and extended reach wells (ERWs) and must be accounted for. The prevalence of drillstring (DS) eccentricity in the annulus calls for a re-evaluation of existing hydraulic models. This study evaluates the effect of drilling fluid rheology types and DS eccentricity on the entire drilling hydraulics. Three non-Newtonian fluid models were analyzed, viz: Herschel Bulkley, power law and Bingham plastic models. From the results, it was observed that while power law and Bingham plastic models gave the upper and lower hydraulic values, Herschel Bulkley fluid model gave annular pressure loss (APL) and ECD values that fall between the upper and lower values and provide a better fit to the hydraulic data than power law and Bingham plastic fluids. Furthermore, analysis of annular eccentricity reveals that APLs and ECD decrease with an increase in DS eccentricity. Pressure loss reduction of more than 50% was predicted for the fully eccentric case for Herschel Bulkley fluids. Thus, DS eccentricity must be fully considered during well planning and hydraulics designs.
文摘Applications of Electro-Rheological (ER) or Magneto-Rheological (MR) fluids as typical smart materials have been widely investigated over the past decades (since their introduction in 40’s). The special applications of these materials as a means of noise suppression are not yet investigated. Constrained Layer Damping (CLD) sheets can be realized by incorporating EMR (ER/MR) materials. In this way, a multilayered damping sheet is obtained with adaptive (tunable) stiffness and damping characteristics. These properties are easily changed in proportion to the electric (magnetic) field applied upon the EMR layer. This notion has been introduced for semi-active vibration control problems. Herein, such panels incorporating EMR material are proposed for adaptive acoustic treatments. Modeling (simulation) of a 3-layered panel with the middle layer being EMR with adjustable properties is carried out in this paper. The tunability of transmission/absorption characteristics of these composite sheets enables us making smart panels for adaptive noise and acoustic treatments. An adaptive performance can be achieved via changing the properties of such panels, on line, according to some sensor outputs. The main objective is to develop proper models to predict the Transmission Loss (TL) of such panels. Also, the TL of this panel is compared with the middle layer of a Newtonian fluid.
