جستجوی مقالات مرتبط با کلیدواژه « rough-walled fractures » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

One of the most important aspects of governing physical processes through rough-walled fractures is the non-linear behavior of flow. The onset of non-linear flow in rock fractures is characterized by critical Reynolds number, which is the main object of this paper. In this paper, the technical aspects of non-linear flow of crude oil through open rock fractures and critical Reynolds number were studied. These issues were studied based on the results of three-dimensional numerical simulation of the Navier-Stokes equations for crude oil flow through rough-walled fractures. The finite volume simulation of crude oil flow through three-dimensional space of rough-walled fractures was performed for a wide range of Reynolds numbers or flow rates. The results of crude oil flow simulations were analyzed based on the Forchheimer’s law. The coefficients of energy losses due to viscous and inertial dissipation mechanisms were derived from the Forchheimer’s law regression on the results. Then, the role of linear and nonlinear energy losses with viscous and inertial dissipation mechanisms was evaluated based on the relation between Reynolds and Forchheimer non-dimension numbers. Finally, the critical Reynolds number was determined for onset of non-linear flow through rough-walled fractures. The results of this study indicate that the Forchheimer’s law appropriately describes the non-linear crude oil flow through rough-walled fractures. By increasing the Reynolds number (or flow rate), the ratio of viscous energy lose from total energy losses decreases non-linearly and simultaneously, the inertial dissipation becomes the dominant mechanism of energy lose. The critical Reynolds number for crude oil is in the range of 30 to 46 for the open fractures of this study. The maximum and minimum of critical Reynolds number follow the minimum and maximum of inertial dissipation coefficient and also the gradient of Reynolds- Forchheimer curve, respectively.

One of the most important aspects of governing physical processes through rough-walled fractures is the non-linear behavior of flow. The main aim of this paper is to investigate the effect of non-linear flow on the hydraulic parameters and deviation from Darcy’s law. To reach this goal, the three-dimensional simulation of crude oil flow inside rough-walled fractures was performed by numerical solving the Navier-Stokes equations supplemented by the continuity equation through application of finite volume technique. The crude oil flow through three-dimensional space of rough-walled fractures was numerically simulated for a wide range of inlet velocity of flow rates. Then, the regime of flow, the deviation of crude oil flow through rough-walled open fractures from Darcy’s law, nonlinear relationship between hydraulic gradient and flow rate, and the effect of non-linear flow on the hydraulic aperture and permeability of fractures were investigated by analysis of crude oil flow simulation. The results of this study indicate that the crude oil flow through rough-walled fractures is non-linear; therefore the hydraulic parameters such as hydraulic aperture and permeability are not constant and highly depend on the flow rate of crude oil. In fact, hydraulic aperture and permeability of fractures decrease non-linearly by increment of flow rate, where these parameters show 10% and 20% of relative decrement, respectively. In addition, the results of regression analysis show that the Forchheimer’s law appropriately describes the behavior of crude oil flow through rough-walled fractures than Darcy’s law. Moreover, the accuracy of Forchheimer’s law is much more than 98%, but the relative error of Darcy’s law reaches to 27%.

This paper investigates the crude oil flow through open and rough-walled fractures. The aim of this paper is to evaluate the effects of surface roughness and spatial arrangement of aperture segment on fluid flow phenomenon through rough-walled fractures. In addition, the validity of classic geometrical equations of cubic law correction was explored by comparing the output results of numerical simulations (in terms of permeability). To reach this goal, the crude oil flow through three-dimensional rough-walled fractures was numerically simulated by simultaneous solving of Navier-Stokes and mass conservation equations and utilizing FLUENTTM computational software. The numerical crude oil flow simulation was performed for six different three-dimensional geometrical models of fractures whit different roughness and aperture arrangements and constant porosity. The results of fluid flow simulation were analyzed with different points of view and then compared with the classic geometrical equations of cubic law correction. The results of this study show that (i) for the open fractures, the effects of roughness on the pressure lose is higher than spatial arrangement of aperture segment, (ii) due to the nonlinearity of flow, the permeability of fractures decreases by increasing the Reynolds number, and (iii) with the classic geometrical equations of cubic law correction encounter with about 5 to 35% error and the accuracy of these equations will be decrease by decrease the permeability of fractures or increase of roughness and spatial variability of aperture. These findings prove useful in proper understanding of crude oil flow in fractures, or inclusions in computational simulation of large-scale flow in fractured petroleum reservoirs.