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Evaluation of numerical schemes for capturing shock waves in modeling proppant transport in fractures

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Petroleum Science 2017年第4期14卷 731-745页

作者： Morteza Roostaei Alireza Nouri Vahidoddin Fattahpour dave chan Department of Civil and Environmental Engineering University of AlbertaEdmontonCanada

In petroleum engineering, the transport phenomenon of proppants in a fracture caused by hydraulic fracturing is captured by hyperbolic partial differential equations(PDEs). The solution of this kind of PDEs may encounter smooth transitions, or there can be large gradients of the field variables. The numerical challenge posed in a shock situation is that high-order finite difference schemes lead to significant oscillations in the vicinity of shocks despite that such schemes result in higher accuracy in smooth regions. On the other hand, first-order methods provide monotonic solution convergences near the shocks,while giving poorer accuracy in the smooth *** numerical simulation of such systems is a challenging task using conventional numerical methods. In this paper, we investigate several shock-capturing *** competency of each scheme was tested against onedimensional benchmark problems as well as published numerical experiments. The numerical results have shown good performance of high-resolution finite volume methods in capturing shocks by resolving discontinuities while maintaining accuracy in the smooth regions. Thesemethods along with Godunov splitting are applied to model proppant transport in fractures. It is concluded that the proposed scheme produces non-oscillatory and accurate results in obtaining a solution for proppant transport problems.

关键词： Proppant transport Hyperbolic partial differential equations Frac pack Hydraulic fracturing

Relationship between rock macro-and micro-properties and wellbore breakout type

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Underground Space 2021年第1期6卷 62-75页

作者： Hossein Rahmati Alireza Nouri dave chan Hans Vaziri University of Alberta AlbertaCanada BP America Inc. HoustonUSA

This study numerically investigates the effect of material micro-and macro-parameters on the failure mechanisms and geometry of a wellbore *** analysis of the borehole breakout is essential in addressing wellbore stability,well completion,and sand production *** three-dimensional discrete element method(DEM)was used in the *** numerical tool was used in numerical model simulations of drilling through sandstone in cubic samples at the laboratory scale subjected to pre-existing far-field ***,a series of triaxial testing simulations were performed to relate the micromechanical parameters to the macromechanical material *** results showed that the geometry of the breakout is affected,among the material micro-parameters,by the particle contact modulus,bond normal and shear strengths,particle crushing strength,and particle size ***,it was found that the macro-parameters including Young’s modulus,friction and dilation angles,and uniaxial compression strength(UCS)also affect the type of breakout.

关键词： Borehole breakout Numerical simulation Material properties

Theoretical elastoplastic analysis for foundations with geosynthetic-encased columns

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2012年第7期13卷 506-518页

作者： Yuan-yu DUAN Yi-ping ZHANG dave chan Ya-nan YU College of Civil Engineering and Architecture Zhejiang UniversityHangzhou 310058China Department of Civil and Environmental Engineering University of AlbertaEdmontonAlbertaCanada

As a new technique in ground improvement, geosynthetic-encased columns (GECs) have promising applications in soft soil foundation. By assuming yielding occurs in the columns while the surrounding soil and the geosynthetic remain elastic, an elastoplastic analytical procedure for foundations improved by GECs is proposed. The radial stresses that the geosynthetic provides and the elastoplastic deformations of the foundation resting on a rigid base are derived. A comparison with finite element analysis shows that the proposed method is effective and can provide a reasonable prediction of a GEC's deformation. Subsequent parametric analysis indicates that higher geosynthetic stiffness leads to better performance of the composite foundation. The optimum length of encasement is related to the load acting on the foundation and the permissible vertical and radial displacements of the column. Moreover, as the dilation angle of the column increases, the settlement decreases, especially under high loading. The influence of the encasement is more significant in soils with smaller elastic modulus.

关键词： Geosynthetic-encased columns (GECs) Equal vertical strain Elastoplastic deformation Analytical procedure

Numerical investigation of the hydraulic fracturing mechanisms in oil sands

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Underground Space 2021年第2期6卷 195-216页

作者： Siavash Taghipoor Morteza Roostaei Arian Velayati Atena Sharbatian dave chan Alireza Nouri Department of Civil and Environmental Engineering University of AlbertaCanada KGHM International 1010 Lorne StSudburyON P3C 4R9Canada RGL Reservoir Management Inc. 690842 StLeducAB T9E 0R8Canada

This paper presents a numerical investigation of hydraulic fracturing in oil sands during cold water injection by considering the aspects of both geomechanics and reservoir fluid *** to previous studies,the low shear strengths of unconsolidated or weakly consolidated sandstone reservoirs significantly influence the hydraulic fracturing ***,classical hydraulic fracture models cannot simulate the fracturing process in weak sandstone *** the current numerical models,the direction of a tensile fracture is predetermined based on in situ stress ***,the potential transformation of a shear fracture into a tensile fracture and the potential reorientation of a tensile fracture owing to shear banding at the fracture tip have not yet been addressed in the *** this study,a smeared fracture technique is employed to simulate tensile and shear fractures in oil *** model used combines many important fracture features,which include the matrix flow,poroelasticity and plasticity modeling,saturation-dependent permeability,gradual degradation of the oil sands as a result of dilative shear deformation,and the tensile fracturing and shear failure that occur with the simultaneous enhancement of ***,sensitivity analyses are also performed with respect to the reservoir and geomechanical parameters,including the apparent tensile strength and cohesion of the oil sands,magnitude of the minimum and maximum principal stress,absolute permeability and elastic modulus of the oil sands and ramp-up *** these analyses are performed to clarify the influences of these parameters on the fracturing response of the oil sands.

关键词： Smeared fracture Hydraulic fracturing Numerical simulation Oil sand

库水循环加卸载条件下岸坡饱和土体变形特性试验研究

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水利学报 2015年第5期46卷 612-618页

作者：陈勇韦双 dave chan 三峡大学三峡库区地质灾害教育部重点实验室湖北宜昌443002 湖北省地质局冶金地质勘探大队湖北黄石435004

水库运行期水位每年周期性涨落,岸坡土体在库水循环加卸载作用下会发生不同程度的阶梯状变形。为探求循环加卸载对岸坡深部变形的诱发机理,本文以水库防洪限制水位以下岸坡土体为研究对象,在饱和土应力路径三轴试验过程中,控制非等向受... 详细信息

水库运行期水位每年周期性涨落,岸坡土体在库水循环加卸载作用下会发生不同程度的阶梯状变形。为探求循环加卸载对岸坡深部变形的诱发机理,本文以水库防洪限制水位以下岸坡土体为研究对象,在饱和土应力路径三轴试验过程中,控制非等向受压试样的孔隙水压力周期变化,模拟岸坡土体的水力-力学状态,实时测定土体的周期性变形特性及破坏特征。研究结果表明:等偏应力孔压循环加卸载过程中,试样剪应变为台阶式上升趋势,而体应变是循环的弹性变化;孔压持续增大造成试样破坏呈现脆变和剪胀的特征。最后,结合等偏应力孔压增大条件下粉质黏土的破坏特征与常规三轴剪切试验成果,对比两种应力路径下试样的有效应力比和剪应变的发展过程,分析了其强度差异的内在原因。

关键词：循环加卸载非等向受压孔隙水压力应力路径有效应力比

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库岸有限厚度粉质黏土冲蚀演化规律及预测

水科学进展 2023年第6期34卷 938-947页

作者：陈勇张书石 chan dave 三峡大学三峡库区地质灾害教育部重点实验室湖北宜昌443002 Department of Civil and Environmental Engineering University of AlbertaEdmontonAB T6G 2W2Canada

土体冲蚀流失是塌岸发展和库岸再造的重要诱发因素。为准确预测水流作用下岸坡土体流失进程,自主研制了能够实时精确量测土样质量变化的新型冲蚀试验装置,开展三峡库岸粉质黏土冲刷起动和冲蚀进程试验,分析有限厚度土体冲蚀演化规律和... 详细信息

土体冲蚀流失是塌岸发展和库岸再造的重要诱发因素。为准确预测水流作用下岸坡土体流失进程,自主研制了能够实时精确量测土样质量变化的新型冲蚀试验装置,开展三峡库岸粉质黏土冲刷起动和冲蚀进程试验,分析有限厚度土体冲蚀演化规律和影响机制,并建立预测模型。结果表明:有限厚度土体的总冲蚀量随时间增加但增速逐渐趋缓,冲蚀速率逐渐衰减,且冲蚀速率及其衰减程度均与孔隙比或流速成正比;将反映密实度的孔隙比和反映剪切力的水流速度嵌入预测模型能较好地拟合粉质黏土冲蚀演化进程曲线。建立的有限厚度土体冲蚀进程预测模型,为水流冲刷作用下岸坡形态变化趋势预测研究提供参考。

关键词：冲蚀试验有限厚度冲蚀比冲蚀速率预测模型

周期加卸载条件在ABAQUS中的数值实施方法及验证

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水利学报 2014年第S2期45卷 67-72页

作者：陈勇杨贝贝韦双 dave chan 三峡大学三峡库区地质灾害教育部重点实验室湖北宜昌443002 阿尔伯塔大学土木与环境工程学院

水库运行期水位每年周期性涨落,岸坡土体在库水周期加卸载作用下发生不同程度的阶梯状变形。为探求变形的诱发机理、揭示变形的发展规律,本文以参数简单且意义明确的统一硬化模型(UH模型)为基础,建立了该模型的增量关系,并借用ABAQUS软... 详细信息

水库运行期水位每年周期性涨落,岸坡土体在库水周期加卸载作用下发生不同程度的阶梯状变形。为探求变形的诱发机理、揭示变形的发展规律,本文以参数简单且意义明确的统一硬化模型(UH模型)为基础,建立了该模型的增量关系,并借用ABAQUS软件的开发接口,添加该模型的UMAT子程序,从而建立土体在周期加卸载作用下的应力应变演化规律模拟方法。最后,对数值模拟方法和子程序进行了单元测试和试验成果验证,对比分析结论如下:开发的UH模型UMAT子程序是可行的,模拟结果与特殊应力路径下三轴试验中的有效应力变化与应变发展规律等吻合性较好。

关键词：周期加卸载统一硬化模型模型 UMAT子程序应力路径三轴试验

循环脱吸湿与加卸载耦合作用下土体持水性能试验研究

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岩土力学 2019年第8期40卷 2907-2913页

作者：陈勇苏剑谈云志 chan dave 三峡大学三峡库区地质灾害教育部重点实验室湖北宜昌443002 三峡大学防灾减灾湖北省重点实验室湖北宜昌443002

土体所经历的干湿循环和应力历史,对其孔隙结构和持水性能影响明显。为进一步深入研究二者耦合作用的影响,开展了先竖向固结再循环脱吸湿以及先气压脱湿再反复竖向加卸载两种不同加载路径的水分变化测量试验,探索土样持水性能和变形能... 详细信息

土体所经历的干湿循环和应力历史,对其孔隙结构和持水性能影响明显。为进一步深入研究二者耦合作用的影响,开展了先竖向固结再循环脱吸湿以及先气压脱湿再反复竖向加卸载两种不同加载路径的水分变化测量试验,探索土样持水性能和变形能力的演化规律。研究结果表明:(1)脱湿与吸湿路径对比,土体的持水能力具有明显的差异性,且土体越密实,这种差异性越强烈;(2)随着脱吸湿循环次数的增加,土样的进气值略有增大,减湿段和吸湿段的斜率都会减小,但影响趋势随循环次数增多而减弱;(3)对于气压减湿后的非饱和土样,其前期固结压力随气压值增加而增大,而加卸载形成的滞回圈的面积却随之减小,土体的持水性能和变形能力也降低;(4)重塑土样从不同加载路径首次达到同一应力状态时,先固结再脱湿路径下土样的体积收缩更多,而先施加气压再加载路径下土样持水性能减弱的更多。

关键词：循环脱吸湿反复加卸载耦合作用持水性能变形能力

A Stochastic Granule Model of Rockfill Using Combined Finite/Discrete Element Method

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A Stochastic Granule Model of Rockfill Using Combined Finite...