Non-Darcian radial flow toward a finite-diameter,fully penetrating well in a confined aquifer was analyzed on the basis of the Izbash equation with consideration of the wellbore storage eflect.We derived semi-analytic...Non-Darcian radial flow toward a finite-diameter,fully penetrating well in a confined aquifer was analyzed on the basis of the Izbash equation with consideration of the wellbore storage eflect.We derived semi-analytical solutions of drawdown by using the Boltzmann transform,and obtained approximate analytical solutions of the drawdown at early and late times.MATLAB programs were developed to facilitate computation of the semi-analytical solutions.The turbulence factor v which was directly related to the pumping rate appeared to have negligible influence upon the wellbore well function at early times,but imposed significant influence at intermediate and late times.However,the turbulence factor v imposed non-negligible influence upon the aquifer well function during the entire pumping period,provided that the observation point was not suflciently close to the wellbore.Sensitivity analysis indicated that the power index n in the Izbash equation had less influence on the type curves at the face of the pumping wellbore,but had much greater influence upon the well function in the aquifer.As the n values increased,the drawdown in the aquifer decreased at early times and increased at late times.The Boltzmann transformation could only be used in an approximate sense for radial non-Darcian flow problems.This approximation would provide accurate solutions at early times,and introduce small but consistent discrepancies at intermediate and late times for the wellbore well function.展开更多
Electromagnetic Computer Tomography (ECT) is a method to probe the interior of an inhomogeneous medium via surface measurement in a non-linear way. Due to the great differences in conductivity and permittivity betwe...Electromagnetic Computer Tomography (ECT) is a method to probe the interior of an inhomogeneous medium via surface measurement in a non-linear way. Due to the great differences in conductivity and permittivity between oil and water in the well, Electromagnetic Tomography Well Logging (ETWL), a new flow imaging measurement system, is proposed to describe the distribution and movement of oil/water two-phase flow in the well by scanning the detected region and applying a suitable data processing algorithm. The results of the numerical simulation and physical modeling show that the system could provide a clear image of the flow profile.展开更多
A coupling model is proposed in this paper by using the Green Function and Newman's product principle, and the solution method is provided here as well. This model can be used to describe the reservoir inflow and wel...A coupling model is proposed in this paper by using the Green Function and Newman's product principle, and the solution method is provided here as well. This model can be used to describe the reservoir inflow and wellbore flow for fishbone wells in an unsteady flow or pseudo-steady flow state. A case study indicates that the bottom hole pressure declines quickly in the unsteady flow period which is very short. The pressure drop per unit time remains unchanged under the pseudo-steady flow conditions. The distribution of flow rate along the main wellbore shows a wave shape under the unsteady flow condition, and the flow rate distribution in each branch is similar. The flow rate distribution along the main wellbore is irregular "U" shaped under the pseudo-steady flow condition, and the space-symmetrical branches have the same flow distribution pattern. In the initial production period, the flow rate increases significantly as the length of branches and the angle between branches and the main wellbore increase. As the production continues, the length and angle of branches have only a slight effect on the flow in fishbone wells.展开更多
The Wells turbine is an axial-flow air-turbine designed to extract energy from ocean waves. An important consideration is the self-starting capability of the Wells turbine, a phenomenon encountered where the turbine a...The Wells turbine is an axial-flow air-turbine designed to extract energy from ocean waves. An important consideration is the self-starting capability of the Wells turbine, a phenomenon encountered where the turbine accelerate by itself up to a certain speed for the best turbine performance. In order to clarify the self-starting characteristic and running performance of the Wells turbine in an irregular oscillating flow, a numerical simulation process is established in this paper on the rational assumption of quasi-steady flow conditions, Both self-starting characteristics and running performance are obtained through the numerical simulation and subsequently compared with the experimental data achieved on a computer-controlled oscillating flow test rig which could realize some irregular oscillating flow according to the specified spectrum. Results show that the self-starting time decreases with the increase of the significant wave height and the mean frequency of the irregular oscillating flow, Therefore, it is possible to predict accurately the performance of the Wells turbine by computer simulation.展开更多
This paper examines the two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection by means of a fixed streamlinemodel,The mathematical model of the verical two-dimensio...This paper examines the two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection by means of a fixed streamlinemodel,The mathematical model of the verical two-dimensional flow or oil-water for a horizontal well in a medium with double-porosity is established ,and whose accuratesolutions are obtained by using the characteristic method .The saturation distributionsin the fractured system and the matrix system as well as the formula of the time of water free production are presented .All these results provide a theoretical basis and a computing method for oil displacement by edge water from naturally fracturedreservirs.展开更多
An iterative method was developed for incorporating the well bore boundary into the finite difference model of water flow in variably saturated porous media. Six cases were presented involving groundwater pumping or i...An iterative method was developed for incorporating the well bore boundary into the finite difference model of water flow in variably saturated porous media. Six cases were presented involving groundwater pumping or injection to demonstrate the advantages of the iterative method over the traditional method. For the iterative method, the total flux gradually approached the well discharge and the flux profile was non-uniform. And the iterative method took into account the variation of well bore water table. Compared to the traditional method, the iterative method can simulate the variably saturated flow caused by pumping or injection more realistically.展开更多
A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analyti...A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analytical approach was proposed to model the production performance of full-life cycle in well pad and to investigate the effect of fracture length,flow capacity,well spacing and fracture spacing on estimated ultimate recovery(EUR).Finally,an integrated workflow is developed to optimize drilling and completion parameters of the horizontal wells by incorporating the productivity prediction and economic evaluation.It is defined as nested optimization which consists of outer-optimization shell(i.e.,economic profit as outer constraint)and inner-optimization shell(i.e.,fracturing scale as inner constraint).The results show that,when the constraint conditions aren’t considered,the performance of the well pad can be improved by increasing contact area between fracture and formation,reducing interference between fractures/wells,balancing inflow and outflow between fracture and formation,but there is no best compromise between drilling and completion parameters.When only the inner constraint condition is considered,there only exists the optimal fracture conductivity and fracture length.When considering both inner and outer constraints,the optimization decisions including fracture conductivity and fracture length,well spacing,fracture spacing are achieved and correlated.When the fracturing scale is small,small well spacing,wide fracture spacing and short fracture should be adopted.When the fracturing scale is large,big well spacing,small fracture spacing and long fracture should be used.展开更多
Considering the influence of quadratic gradient term and medium deformation on the seepage equation, a well testing interpretation model for low permeability and deformation dual medium reservoirs was derived and esta...Considering the influence of quadratic gradient term and medium deformation on the seepage equation, a well testing interpretation model for low permeability and deformation dual medium reservoirs was derived and established. The difference method was used to solve the problem, and pressure and pressure derivative double logarithmic curves were drawn to analyze the seepage law. The research results indicate that the influence of starting pressure gradient and medium deformation on the pressure characteristic curve is mainly manifested in the middle and late stages. The larger the value, the more obvious the upward warping of the pressure and pressure derivative curve;the parameter characterizing the dual medium is the crossflow coefficient. The channeling coefficient determines the time and location of the appearance of the “concave”. The smaller the value, the later the appearance of the “concave”, and the more to the right of the “concave”.展开更多
基金the National Natural Science Foundation of China (Nos.50428907 and 50479011)
文摘Non-Darcian radial flow toward a finite-diameter,fully penetrating well in a confined aquifer was analyzed on the basis of the Izbash equation with consideration of the wellbore storage eflect.We derived semi-analytical solutions of drawdown by using the Boltzmann transform,and obtained approximate analytical solutions of the drawdown at early and late times.MATLAB programs were developed to facilitate computation of the semi-analytical solutions.The turbulence factor v which was directly related to the pumping rate appeared to have negligible influence upon the wellbore well function at early times,but imposed significant influence at intermediate and late times.However,the turbulence factor v imposed non-negligible influence upon the aquifer well function during the entire pumping period,provided that the observation point was not suflciently close to the wellbore.Sensitivity analysis indicated that the power index n in the Izbash equation had less influence on the type curves at the face of the pumping wellbore,but had much greater influence upon the well function in the aquifer.As the n values increased,the drawdown in the aquifer decreased at early times and increased at late times.The Boltzmann transformation could only be used in an approximate sense for radial non-Darcian flow problems.This approximation would provide accurate solutions at early times,and introduce small but consistent discrepancies at intermediate and late times for the wellbore well function.
基金This work was supported by the National Natural Science Foundation of China(60472019).
文摘Electromagnetic Computer Tomography (ECT) is a method to probe the interior of an inhomogeneous medium via surface measurement in a non-linear way. Due to the great differences in conductivity and permittivity between oil and water in the well, Electromagnetic Tomography Well Logging (ETWL), a new flow imaging measurement system, is proposed to describe the distribution and movement of oil/water two-phase flow in the well by scanning the detected region and applying a suitable data processing algorithm. The results of the numerical simulation and physical modeling show that the system could provide a clear image of the flow profile.
基金support from the National Science and Technology Major Projects of China(Grant No. 2011ZX05031-003)
文摘A coupling model is proposed in this paper by using the Green Function and Newman's product principle, and the solution method is provided here as well. This model can be used to describe the reservoir inflow and wellbore flow for fishbone wells in an unsteady flow or pseudo-steady flow state. A case study indicates that the bottom hole pressure declines quickly in the unsteady flow period which is very short. The pressure drop per unit time remains unchanged under the pseudo-steady flow conditions. The distribution of flow rate along the main wellbore shows a wave shape under the unsteady flow condition, and the flow rate distribution in each branch is similar. The flow rate distribution along the main wellbore is irregular "U" shaped under the pseudo-steady flow condition, and the space-symmetrical branches have the same flow distribution pattern. In the initial production period, the flow rate increases significantly as the length of branches and the angle between branches and the main wellbore increase. As the production continues, the length and angle of branches have only a slight effect on the flow in fishbone wells.
基金This subject was financially supported by the National Natural Science Foundation of China (Grant No. 59976047)
文摘The Wells turbine is an axial-flow air-turbine designed to extract energy from ocean waves. An important consideration is the self-starting capability of the Wells turbine, a phenomenon encountered where the turbine accelerate by itself up to a certain speed for the best turbine performance. In order to clarify the self-starting characteristic and running performance of the Wells turbine in an irregular oscillating flow, a numerical simulation process is established in this paper on the rational assumption of quasi-steady flow conditions, Both self-starting characteristics and running performance are obtained through the numerical simulation and subsequently compared with the experimental data achieved on a computer-controlled oscillating flow test rig which could realize some irregular oscillating flow according to the specified spectrum. Results show that the self-starting time decreases with the increase of the significant wave height and the mean frequency of the irregular oscillating flow, Therefore, it is possible to predict accurately the performance of the Wells turbine by computer simulation.
文摘This paper examines the two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection by means of a fixed streamlinemodel,The mathematical model of the verical two-dimensional flow or oil-water for a horizontal well in a medium with double-porosity is established ,and whose accuratesolutions are obtained by using the characteristic method .The saturation distributionsin the fractured system and the matrix system as well as the formula of the time of water free production are presented .All these results provide a theoretical basis and a computing method for oil displacement by edge water from naturally fracturedreservirs.
基金Supported by National Natural Science Foundation of China (No. 51079068)
文摘An iterative method was developed for incorporating the well bore boundary into the finite difference model of water flow in variably saturated porous media. Six cases were presented involving groundwater pumping or injection to demonstrate the advantages of the iterative method over the traditional method. For the iterative method, the total flux gradually approached the well discharge and the flux profile was non-uniform. And the iterative method took into account the variation of well bore water table. Compared to the traditional method, the iterative method can simulate the variably saturated flow caused by pumping or injection more realistically.
基金Supported by the China National Science and Technology Major Project(2016ZX05037,2017ZX05063).
文摘A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analytical approach was proposed to model the production performance of full-life cycle in well pad and to investigate the effect of fracture length,flow capacity,well spacing and fracture spacing on estimated ultimate recovery(EUR).Finally,an integrated workflow is developed to optimize drilling and completion parameters of the horizontal wells by incorporating the productivity prediction and economic evaluation.It is defined as nested optimization which consists of outer-optimization shell(i.e.,economic profit as outer constraint)and inner-optimization shell(i.e.,fracturing scale as inner constraint).The results show that,when the constraint conditions aren’t considered,the performance of the well pad can be improved by increasing contact area between fracture and formation,reducing interference between fractures/wells,balancing inflow and outflow between fracture and formation,but there is no best compromise between drilling and completion parameters.When only the inner constraint condition is considered,there only exists the optimal fracture conductivity and fracture length.When considering both inner and outer constraints,the optimization decisions including fracture conductivity and fracture length,well spacing,fracture spacing are achieved and correlated.When the fracturing scale is small,small well spacing,wide fracture spacing and short fracture should be adopted.When the fracturing scale is large,big well spacing,small fracture spacing and long fracture should be used.
文摘Considering the influence of quadratic gradient term and medium deformation on the seepage equation, a well testing interpretation model for low permeability and deformation dual medium reservoirs was derived and established. The difference method was used to solve the problem, and pressure and pressure derivative double logarithmic curves were drawn to analyze the seepage law. The research results indicate that the influence of starting pressure gradient and medium deformation on the pressure characteristic curve is mainly manifested in the middle and late stages. The larger the value, the more obvious the upward warping of the pressure and pressure derivative curve;the parameter characterizing the dual medium is the crossflow coefficient. The channeling coefficient determines the time and location of the appearance of the “concave”. The smaller the value, the later the appearance of the “concave”, and the more to the right of the “concave”.