Centered simple waves for the two-dimensional pseudo-steady isothermal ?ow around a convex corner

The two-dimensional(2D) pseudo-steady isothermal flow, which is isentropic and irrotational, around a convex corner is studied. The self-similar solutions for the supersonic flow around the convex corner are constructed, where the properties of the centered simple wave are used for the 2D isentropic irrotational pseudo-steady Euler equations. The geometric procedures of the center simple waves are given. It is proven that the supersonic flow turns the convex corner by an incomplete centered expansion wave or an incomplete centered compression wave, depending on the conditions of the downstream state.

ANALYSIS ON PSEUDO-STEADY INDENTATION CREEP

Theoretical analysis and finite element （FE） simulation have been carried out for a constant specific load rate （CSLR） indentation creep test. Analytical results indicate that both the representative stress and the indentation strain rate become constant after a transient period. Moreover, the FE simulation reveals that both the contours of equivalent stress and equivalent plastic strain rate underneath the indenter evolve with geometrical self-similarity. This suggests that pseudo-steady indentation creep occurs in the region beneath the indenter. The representative points in the region are defined as the ones with the equivalent stress equal to the representative stress. In addition, it is revealed that the proportionality between indentation strain rate and equivalent plastic strain rate holds at the representative points during the pseudo-steady indentation creep of a power law material. A control volume （CV） beneath the indenter, which governs the indenter velocity, is identified. The size of the CV at the indented surface is approximately 2.5 times the size of the impression. The stress exponent for creep can be obtained from the pseudosteady indentation creep data. These results demonstrate that the CSLR testing technique can be used to evaluate creep parameters with the same accuracy as conventional uniaxial creep tests.

A model for coupling reservoir inflow and wellbore flow in fishbone wells

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.

Study and Application of Horizontal Well Productivity Formula with Continuous Time-Varying Considered

The horizontal well technology has been widely applied to enhanced oil recovery for low permeability and heavy oil reservoir. It is the important basis for designing and optimizing horizontal well to determine the productivity. The productivity determination of horizontal wells in offshore oil fields is mainly based on the actual productivity data of producing directional wells in the similar reservoirs nearby. Considering pressure drop and oil layer thickness to calculate the productivity, this method lacks certain theoretical basis and requires rich working experience for reservoir engineers. The other method is Joshi Formula which needs the known horizontal well control radius to be known. But the control radius is man-made at certain degree. In order to address the shortcomings of existing methods, a new reservoir engineering method was proposed to determine the horizontal well productivity formula, horizontal flow pattern and control radius based on the principle of equivalent flow resistance and conformal transformation. This method has overcome the disadvantage of determining on person. It provided some theoretical basis for getting the horizontal well productivity and is of some guiding meaning for evaluating the productivity of adjustment wells and development wells.

Mean wind load induced incompatibility in nonlinear aeroelastic simulations of bridge spans

Mean wind response induced incompatibility and nonlinearity in bridge aerodynamics is discussed,where the mean wind and aeroelastic loads are applied simultaneously in time domain.A kind of incompatibility is found during the simultaneous simulation of the mean wind and aeroelastic loads,which leads to incorrect mean wind structural responses.It is found that the mathematic expectations (or Iimiting characteristics) of the aeroelastic models are fundamental to this kind of incompatibility.In this paper,two aeroelastic models are presented and discussed,one of indicial-function-denoted (IF-denoted) and another of rational-function-denoted (RF-denoted).It is shown that,in cases of low wind speeds,the IF-denoted model reflects correctly the mean wind load properties,and results in correct mean structural responses;in contrast,the RF-denoted model leads to incorrect mean responses due to its nonphysical mean properties.At very high wind speeds,however,even the IF-denoted model can lead to significant deviation from the correct response due to steady aerodynamic nonlinearity.To solve the incompatibility at high wind speeds,a methodology of subtraction of pseudo-steady effects from the aeroelastic model is put forward in this work.Finally,with the method presented,aeroelastic nonlinearity resulted from the mean wind response is investigated at both moderate and high wind speeds.

Estimating the Properties of Naturally Fractured Reservoirs Using Rate Transient Decline Curve Analysis

Transient rate decline curve analysis for constant pressure production is presented in this pa- per for a naturally fractured reservoir. This approach is based on exponential and constant bottom-hole pressure solution. Based on this method, when In （flow rate） is plotted versus time, two straight lines are ob- tained which can be used for estimating different parameters of a naturally fractured reservoir. Parameters such as storage capacity ratio （co）, reservoir drainage area （A）, reservoir shape factor （CA）, fracture per- meability （ky）, interporosity flow parameter （,~） and the other parameters can be determined by this ap- proach. The equations are based on a model originally presented by Warren and Root and extended by Da Prat et al. and Mavor and Cinco-Ley. The proposed method has been developed to be used for naturally fractured reservoirs with different geometries. This method does not involve the use of any chart and by us- ing the pseudo steady state flow regime, the influence of wellbore storage on the value of the parameters ob- tained from this technique is negligible. In this technique, all the parameters can be obtained directly while in conventional approaches like type curve matching method, parameters such as co and g should be ob- tained by other methods like build-up test analysis and this is one of the most important advantages of this method that could save time during reservoir analyses. Different simulated and field examples were used for testing the proposed technique. Comparison between the obtained results by this approach and the results of type curve matching method shows a high performance of decline curves in well testing.