Hydrophilicity is critical in Nafion membranes during fuel cell operation as insufficient membrane hydration leads to brittle behavior and a drop in proton conductivity.The incorporation of APTS(3-(aminopro pyl)trieth...Hydrophilicity is critical in Nafion membranes during fuel cell operation as insufficient membrane hydration leads to brittle behavior and a drop in proton conductivity.The incorporation of APTS(3-(aminopro pyl)triethoxysilane)into exfoliated graphene oxide(EGO)by covalent functionalization to be used as filler into Nafion membranes allows higher hydrophilicity for these membranes.This is associated with promoting hydroxyl,carbonyl,siloxane,silane,and amine groups within the EGO-APTS matrix.The incorporation of these materials as Fuel Cell MEAs leads to a significant reduction of the ohmic resistance measured at high frequency resistance(HFR)in electrochemical impedance spectroscopy(EIS)experiments and achieves maximum power densities of 1.33 W cm^(-2)at 60℃ at 100%RH(APTS-EGO,0.2 wt%)and1.33 W cm^(-2)at 60℃ at 70%RH(APTS-EGO,0.3 wt%),which represents an improvement of 190%compared to the commercial Nafion 212 when utilizing low humidification conditions(70%).Moreover,the as-synthesized membrane utilizes lower Nafion ionomer mass,which,in conjunction with the excellent cell performance,has the potential to decrease the cost of the membrane from 87 to 80￡/W as well as a reduction of fluorinated compounds within the membrane.展开更多
Most of the carbonates in the Tarim Basin in northwest China are low-porosity and low-permeability rocks. Owing to the complexity of porosity in carbonates, conventional rock- physics models do not describe the relati...Most of the carbonates in the Tarim Basin in northwest China are low-porosity and low-permeability rocks. Owing to the complexity of porosity in carbonates, conventional rock- physics models do not describe the relation between velocity and porosity for the Tarim Basin carbonates well. We propose the porous-grain-upper-boundary （PGU） model for estimating the relation between velocity and porosity for low-porosity carbonates. In this model, the carbonate sediments are treated as packed media of porous elastic grains, and the carbonate pores are divided into isolated and connected pores The PGU model is modified from the porous-grain-stiff-sand （PGST） model by replacing the critical porosity with the more practical isolated porosity. In the implementation, the effective elastic constants of the porous grains are calculated by using the differential effective medium （DEM） model. Then, the elastic constants of connected porous grains in dry rocks are calculated by using the modified upper Hashin-Shtrikman bound. The application to the Tarim carbonates shows that relative to other conventional effective medium models the PGU model matches the well log data well.展开更多
This paper proposes a novel approach for generating 3-dimensional complex geological facies models based on deep generative models.It can reproduce a wide range of conceptual geological models while possessing the fle...This paper proposes a novel approach for generating 3-dimensional complex geological facies models based on deep generative models.It can reproduce a wide range of conceptual geological models while possessing the flexibility necessary to honor constraints such as well data.Compared with existing geostatistics-based modeling methods,our approach produces realistic subsurface facies architecture in 3D using a state-of-the-art deep learning method called generative adversarial networks(GANs).GANs couple a generator with a discriminator,and each uses a deep convolutional neural network.The networks are trained in an adversarial manner until the generator can create "fake" images that the discriminator cannot distinguish from "real" images.We extend the original GAN approach to 3D geological modeling at the reservoir scale.The GANs are trained using a library of 3D facies models.Once the GANs have been trained,they can generate a variety of geologically realistic facies models constrained by well data interpretations.This geomodelling approach using GANs has been tested on models of both complex fluvial depositional systems and carbonate reservoirs that exhibit progradational and aggradational trends.The results demonstrate that this deep learning-driven modeling approach can capture more realistic facies architectures and associations than existing geostatistical modeling methods,which often fail to reproduce heterogeneous nonstationary sedimentary facies with apparent depositional trend.展开更多
Accurate acid placement constitutes a major concern in matrix stimulation because the acid tends to penetrate the zones of least resistance while leaving the low-permeability regions of the formation untreated.Degrada...Accurate acid placement constitutes a major concern in matrix stimulation because the acid tends to penetrate the zones of least resistance while leaving the low-permeability regions of the formation untreated.Degradable materials(fibers and solid particles)have recently shown a good capability as fluid diversion to overcome the issues related to matrix stimulation.Despite the success achieved in the recent acid stimulation jobs stemming from the use of some products that rely on fiber flocculation as the main diverting mechanism,it was observed that the volume of the base fluid and the loading of the particles are not optimized.The current industry lacks a scientific design guideline because the used methodology is based on experience or empirical studies in a particular area with a particular product.It is important then to understand the fundamentals of how acid diversion works in carbonates with different diverting mechanisms and diverters.Mathematical modeling and computer simulations are effective tools to develop this understanding and are efficiently applied to new product development,new applications of existing products or usage optimization.In this work,we develop a numerical model to study fiber dynamics in fluid flow.We employ a discrete element method in which the fibers are represented by multi-rigid-body systems of interconnected spheres.The discrete fiber model is coupled with a fluid flow solver to account for the inherent simultaneous interactions.The focus of the study is on the tendency for fibers to flocculate and bridge when interacting with suspending fluids and encountering restrictions that can be representative of fractures or wormholes in carbonates.The trends of the dynamic fiber behavior under various operating conditions including fiber loading,flow rate and fluid viscosity obtained from the numerical model show consistency with experimental observations.The present numerical investigation reveals that the bridging capability of the fiber–fluid system can be enhanced by increasing the fiber loading,selecting fibers with higher stiffness,reducing the injection flow rate,reducing the suspending fluid viscosity or increasing the attractive cohesive forces among fibers by using sticky fibers.展开更多
We present lithofacies classifications for a tight gas sandstone reservoir by analyzing hierarchies of heterogeneities.We use principal component analysis(PCA)to overcome the two level of heterogeneities,which results...We present lithofacies classifications for a tight gas sandstone reservoir by analyzing hierarchies of heterogeneities.We use principal component analysis(PCA)to overcome the two level of heterogeneities,which results in a better lithofacies classification than the traditional cutoff method.The classical volumetric method is used for estimating oil/gas in-place resources in the petroleum industry since its inception is not accurate because it ignores the heterogeneities of and correlation between the petrophysical properties.We present the importance and methods of accounting for the heterogeneities of and correlation between petrophysical properties for more accurate hydrocarbon volumetric estimations.We also demonstrate the impacts of modeling the heterogeneities and correlation in porosity and hydrocarbon saturation for hydrocarbon volumetric estimations with a tight sandstone gas reservoir.Furthermore,geoscientists have traditionally considered that small-scale heterogeneities only impact subsurface fluid flow,but not impact the hydrocarbon resource volumetric estimation.We show the importance of modeling small-scale heterogeneities using fine cell size in reservoir modeling of unconventional resources for accurate resource assessment.展开更多
This paper describes the identification of waterflooded zones and the impact of waterflooding on reservoir properties of sandstones of the Funing Formation at the Gao 6 Fault-block of the Gaoji Oilfield,in the Subei B...This paper describes the identification of waterflooded zones and the impact of waterflooding on reservoir properties of sandstones of the Funing Formation at the Gao 6 Fault-block of the Gaoji Oilfield,in the Subei Basin,east China.This work presents a new approach based on a back-propagation neural network using well log data to train the network,and then generating a cross-plot plate to identify waterflooded zones.A neural network was designed and trained,and the results show that the new method is better than traditional methods.For a comparative study,two representative wells at the Gao 6 Fault-block were chosen for analysis:one from a waterflooded zone,and the other from a zone without waterflooding.Results from this analysis were used to develop a better understanding of the impact of waterflooding on reservoir properties.A range of changes are shown to have taken place in the waterflooded zone,including changes in microscopic pore structure,fluids,and minerals.展开更多
In this paper, we describe some recent imaging technologies developed by Schlumberger for oilfield downhole mul- tiphase flow production logging (PL) and cross-well electromagnetic (EM) survey applications. FloScan Im...In this paper, we describe some recent imaging technologies developed by Schlumberger for oilfield downhole mul- tiphase flow production logging (PL) and cross-well electromagnetic (EM) survey applications. FloScan Imager (FSITM) has been introduced as a 3-phase oil/gas/water flow PL tool for deviated and horizontal wells. FSI sensors can map fluid velocity and holdup profiles along a vertical diameter of the wellbore at every survey depth, enabling a robust estimate of the individual phase flow rates in complex flow regimes. The cross-well EM survey is based on cross-borehole induction logging technique and provides resistivity distribution at a reservoir scale. It is a useful tool for reservoir management and is most effective in dynamic fields where fluid saturations are variable in time and space. The tool can be used to identify (water or steam) flooded and bypassed regions. By monitoring changes in the resistivity spatial distribution with time, cross-well EM survey is very effective at mapping inter-well temperature and structure. Some field examples are shown for both FloScan Imager PL tool and cross-well resistivity imaging survey.展开更多
The flow behavior in porous media with threshold pressure gradient(TPG) is more complex than Darcy flow and the equations of motion, and outer boundary and inner boundary with TPG are also different from Darcy flow fo...The flow behavior in porous media with threshold pressure gradient(TPG) is more complex than Darcy flow and the equations of motion, and outer boundary and inner boundary with TPG are also different from Darcy flow for unsteady flow of a producing well in a reservoir. An analytic method to solve this kind of problem is in a need of reestablishment. The classical method of Green's function and Newman product principle in a new way are used to solve the unsteady state flow problems of various shapes of well and reservoir while considering the TPG. Four Green's functions of point, line, band and circle while considering the TPG are achieved. Then, two well models of vertical well and horizontal well are built and simultaneously the function to calculate the moving boundary of each well model is provided. The results show that when considering TPG the pressure field is much different, which has a sudden pressure change, with a moving boundary in it. And the moving boundary of each well model increases with time but slows down rapidly, especially when the TGP is large.展开更多
In this paper, a boundary element formulation in the wave-number space domain for solving the wave equation for a borehole with arbitrary shape in acoustic logging problems is presented. The problem is treated as a tw...In this paper, a boundary element formulation in the wave-number space domain for solving the wave equation for a borehole with arbitrary shape in acoustic logging problems is presented. The problem is treated as a two-dimensional medium with the discrete wave- number method in the vertical direction. The method is validated by comparing the results obtained by this method with those obtained by the finite-difference method. The method is used to study the effect on wave propagation in a vertical borehole of a vertical fracture. For a monopole source, the dispersion curves for Stoneley waves yield three branches. For dipole and quadrupole sources, different orientations of the source yield different results. When the dipole source is orthogonal to the fracture, the dispersion curve is similar to that of the open hole, while the curves are quite different when the source is parallel to the fracture. These characteristics enable us to determine the orientation of the vertical fracture.展开更多
Reservoir impoundment is related to several hydraulic engineering concerns,including irreversible valley contractions,landslides and reservoir-induced earthquakes.However,these phenomena,such as valley contractions,ar...Reservoir impoundment is related to several hydraulic engineering concerns,including irreversible valley contractions,landslides and reservoir-induced earthquakes.However,these phenomena,such as valley contractions,are hardly to be explained by the conventional method.The scientific understanding of water effects during impoundment and their hazards to hydraulic structure are needed.The effective stress law for fissured rock masses is introduced in the elasto-plastic model employing the Drucker-Prager criterion and implemented in the three dimension(3D)nonlinear finite element method(FEM)program Three-dimensional FINite Element(TFINE).The slope deforms towards river-way during impoundment since the increasing pore pressure in fissures changes stress state and leads to additional plastic deformation in the rock materials.The value of Biot coefficient and the influence of water on rock materials are discussed in detail.Thus,the mechanism of slope deformation during the impoundment of Jinping-I arch dam is revealed,and the deformation is accurately measured.The application of the effective stress law provides a method to consider stress assessment,deformation evaluation and stability estimate of hydraulic structures during the impoundment process.This is a beneficial exploration and an improvement of hydraulic engineering design.展开更多
基金financially supported by the UK Research Council EPRSC EP/W03395X/1the Program grant SynHiSel EP/V047078/1the Hydrogen and Fuel Cells Hub(H_(2)FC SUPERGEN)EP/P024807/1。
文摘Hydrophilicity is critical in Nafion membranes during fuel cell operation as insufficient membrane hydration leads to brittle behavior and a drop in proton conductivity.The incorporation of APTS(3-(aminopro pyl)triethoxysilane)into exfoliated graphene oxide(EGO)by covalent functionalization to be used as filler into Nafion membranes allows higher hydrophilicity for these membranes.This is associated with promoting hydroxyl,carbonyl,siloxane,silane,and amine groups within the EGO-APTS matrix.The incorporation of these materials as Fuel Cell MEAs leads to a significant reduction of the ohmic resistance measured at high frequency resistance(HFR)in electrochemical impedance spectroscopy(EIS)experiments and achieves maximum power densities of 1.33 W cm^(-2)at 60℃ at 100%RH(APTS-EGO,0.2 wt%)and1.33 W cm^(-2)at 60℃ at 70%RH(APTS-EGO,0.3 wt%),which represents an improvement of 190%compared to the commercial Nafion 212 when utilizing low humidification conditions(70%).Moreover,the as-synthesized membrane utilizes lower Nafion ionomer mass,which,in conjunction with the excellent cell performance,has the potential to decrease the cost of the membrane from 87 to 80￡/W as well as a reduction of fluorinated compounds within the membrane.
基金supported by the National Basic Research Program of China(2013CB228602)the National High Technology Research Program of China(2013AA064202)the National Science and Technology Major Project of China(Grant No.2011ZX05004-003)
文摘Most of the carbonates in the Tarim Basin in northwest China are low-porosity and low-permeability rocks. Owing to the complexity of porosity in carbonates, conventional rock- physics models do not describe the relation between velocity and porosity for the Tarim Basin carbonates well. We propose the porous-grain-upper-boundary （PGU） model for estimating the relation between velocity and porosity for low-porosity carbonates. In this model, the carbonate sediments are treated as packed media of porous elastic grains, and the carbonate pores are divided into isolated and connected pores The PGU model is modified from the porous-grain-stiff-sand （PGST） model by replacing the critical porosity with the more practical isolated porosity. In the implementation, the effective elastic constants of the porous grains are calculated by using the differential effective medium （DEM） model. Then, the elastic constants of connected porous grains in dry rocks are calculated by using the modified upper Hashin-Shtrikman bound. The application to the Tarim carbonates shows that relative to other conventional effective medium models the PGU model matches the well log data well.
文摘This paper proposes a novel approach for generating 3-dimensional complex geological facies models based on deep generative models.It can reproduce a wide range of conceptual geological models while possessing the flexibility necessary to honor constraints such as well data.Compared with existing geostatistics-based modeling methods,our approach produces realistic subsurface facies architecture in 3D using a state-of-the-art deep learning method called generative adversarial networks(GANs).GANs couple a generator with a discriminator,and each uses a deep convolutional neural network.The networks are trained in an adversarial manner until the generator can create "fake" images that the discriminator cannot distinguish from "real" images.We extend the original GAN approach to 3D geological modeling at the reservoir scale.The GANs are trained using a library of 3D facies models.Once the GANs have been trained,they can generate a variety of geologically realistic facies models constrained by well data interpretations.This geomodelling approach using GANs has been tested on models of both complex fluvial depositional systems and carbonate reservoirs that exhibit progradational and aggradational trends.The results demonstrate that this deep learning-driven modeling approach can capture more realistic facies architectures and associations than existing geostatistical modeling methods,which often fail to reproduce heterogeneous nonstationary sedimentary facies with apparent depositional trend.
文摘Accurate acid placement constitutes a major concern in matrix stimulation because the acid tends to penetrate the zones of least resistance while leaving the low-permeability regions of the formation untreated.Degradable materials(fibers and solid particles)have recently shown a good capability as fluid diversion to overcome the issues related to matrix stimulation.Despite the success achieved in the recent acid stimulation jobs stemming from the use of some products that rely on fiber flocculation as the main diverting mechanism,it was observed that the volume of the base fluid and the loading of the particles are not optimized.The current industry lacks a scientific design guideline because the used methodology is based on experience or empirical studies in a particular area with a particular product.It is important then to understand the fundamentals of how acid diversion works in carbonates with different diverting mechanisms and diverters.Mathematical modeling and computer simulations are effective tools to develop this understanding and are efficiently applied to new product development,new applications of existing products or usage optimization.In this work,we develop a numerical model to study fiber dynamics in fluid flow.We employ a discrete element method in which the fibers are represented by multi-rigid-body systems of interconnected spheres.The discrete fiber model is coupled with a fluid flow solver to account for the inherent simultaneous interactions.The focus of the study is on the tendency for fibers to flocculate and bridge when interacting with suspending fluids and encountering restrictions that can be representative of fractures or wormholes in carbonates.The trends of the dynamic fiber behavior under various operating conditions including fiber loading,flow rate and fluid viscosity obtained from the numerical model show consistency with experimental observations.The present numerical investigation reveals that the bridging capability of the fiber–fluid system can be enhanced by increasing the fiber loading,selecting fibers with higher stiffness,reducing the injection flow rate,reducing the suspending fluid viscosity or increasing the attractive cohesive forces among fibers by using sticky fibers.
基金supported by the Important National Science Technology Specific Projects of China(No.2016ZX05010-001-003).
文摘We present lithofacies classifications for a tight gas sandstone reservoir by analyzing hierarchies of heterogeneities.We use principal component analysis(PCA)to overcome the two level of heterogeneities,which results in a better lithofacies classification than the traditional cutoff method.The classical volumetric method is used for estimating oil/gas in-place resources in the petroleum industry since its inception is not accurate because it ignores the heterogeneities of and correlation between the petrophysical properties.We present the importance and methods of accounting for the heterogeneities of and correlation between petrophysical properties for more accurate hydrocarbon volumetric estimations.We also demonstrate the impacts of modeling the heterogeneities and correlation in porosity and hydrocarbon saturation for hydrocarbon volumetric estimations with a tight sandstone gas reservoir.Furthermore,geoscientists have traditionally considered that small-scale heterogeneities only impact subsurface fluid flow,but not impact the hydrocarbon resource volumetric estimation.We show the importance of modeling small-scale heterogeneities using fine cell size in reservoir modeling of unconventional resources for accurate resource assessment.
基金Project supported by the National Natural Science Foundation of China (No. 41172109)the National Natural Science Foundation of Shandong Province (No. ZR2011DM009)the Research Foundation for the Doctoral Program of Higher Education (No. 20110003110014),China
文摘This paper describes the identification of waterflooded zones and the impact of waterflooding on reservoir properties of sandstones of the Funing Formation at the Gao 6 Fault-block of the Gaoji Oilfield,in the Subei Basin,east China.This work presents a new approach based on a back-propagation neural network using well log data to train the network,and then generating a cross-plot plate to identify waterflooded zones.A neural network was designed and trained,and the results show that the new method is better than traditional methods.For a comparative study,two representative wells at the Gao 6 Fault-block were chosen for analysis:one from a waterflooded zone,and the other from a zone without waterflooding.Results from this analysis were used to develop a better understanding of the impact of waterflooding on reservoir properties.A range of changes are shown to have taken place in the waterflooded zone,including changes in microscopic pore structure,fluids,and minerals.
文摘In this paper, we describe some recent imaging technologies developed by Schlumberger for oilfield downhole mul- tiphase flow production logging (PL) and cross-well electromagnetic (EM) survey applications. FloScan Imager (FSITM) has been introduced as a 3-phase oil/gas/water flow PL tool for deviated and horizontal wells. FSI sensors can map fluid velocity and holdup profiles along a vertical diameter of the wellbore at every survey depth, enabling a robust estimate of the individual phase flow rates in complex flow regimes. The cross-well EM survey is based on cross-borehole induction logging technique and provides resistivity distribution at a reservoir scale. It is a useful tool for reservoir management and is most effective in dynamic fields where fluid saturations are variable in time and space. The tool can be used to identify (water or steam) flooded and bypassed regions. By monitoring changes in the resistivity spatial distribution with time, cross-well EM survey is very effective at mapping inter-well temperature and structure. Some field examples are shown for both FloScan Imager PL tool and cross-well resistivity imaging survey.
基金Project(51304220) supported by the National Natural Science Foundation of ChinaProject(3144033) supported by the Beijing Natural Science Foundation,ChinaProject(20130007120014) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘The flow behavior in porous media with threshold pressure gradient(TPG) is more complex than Darcy flow and the equations of motion, and outer boundary and inner boundary with TPG are also different from Darcy flow for unsteady flow of a producing well in a reservoir. An analytic method to solve this kind of problem is in a need of reestablishment. The classical method of Green's function and Newman product principle in a new way are used to solve the unsteady state flow problems of various shapes of well and reservoir while considering the TPG. Four Green's functions of point, line, band and circle while considering the TPG are achieved. Then, two well models of vertical well and horizontal well are built and simultaneously the function to calculate the moving boundary of each well model is provided. The results show that when considering TPG the pressure field is much different, which has a sudden pressure change, with a moving boundary in it. And the moving boundary of each well model increases with time but slows down rapidly, especially when the TGP is large.
基金Acknowledgements We thank the thoughtful comments from two anonymous reviewers. This work is partly supported by a contract with Schlumberger-Doll Research, Schlumberger and partly by the National Science Foundation of China under D40521002.
文摘In this paper, a boundary element formulation in the wave-number space domain for solving the wave equation for a borehole with arbitrary shape in acoustic logging problems is presented. The problem is treated as a two-dimensional medium with the discrete wave- number method in the vertical direction. The method is validated by comparing the results obtained by this method with those obtained by the finite-difference method. The method is used to study the effect on wave propagation in a vertical borehole of a vertical fracture. For a monopole source, the dispersion curves for Stoneley waves yield three branches. For dipole and quadrupole sources, different orientations of the source yield different results. When the dipole source is orthogonal to the fracture, the dispersion curve is similar to that of the open hole, while the curves are quite different when the source is parallel to the fracture. These characteristics enable us to determine the orientation of the vertical fracture.
基金Projects(51323014,51479097,51279086)supported by the National Natural Science Foundation of ChinaProject(2016-KY-2)supported by the State Key Laboratory of Hydroscience and Hydraulic Engineering,China
文摘Reservoir impoundment is related to several hydraulic engineering concerns,including irreversible valley contractions,landslides and reservoir-induced earthquakes.However,these phenomena,such as valley contractions,are hardly to be explained by the conventional method.The scientific understanding of water effects during impoundment and their hazards to hydraulic structure are needed.The effective stress law for fissured rock masses is introduced in the elasto-plastic model employing the Drucker-Prager criterion and implemented in the three dimension(3D)nonlinear finite element method(FEM)program Three-dimensional FINite Element(TFINE).The slope deforms towards river-way during impoundment since the increasing pore pressure in fissures changes stress state and leads to additional plastic deformation in the rock materials.The value of Biot coefficient and the influence of water on rock materials are discussed in detail.Thus,the mechanism of slope deformation during the impoundment of Jinping-I arch dam is revealed,and the deformation is accurately measured.The application of the effective stress law provides a method to consider stress assessment,deformation evaluation and stability estimate of hydraulic structures during the impoundment process.This is a beneficial exploration and an improvement of hydraulic engineering design.
