利用核函数法中的自适应带宽同时对一维空间两个储集层属性参数进行粗化

在多孔介质流体流动模拟中,应用网格粗化方法必须在保留重要储集层参数的空间分布的前提下,首先利用大网格粗化原始地质模型(尤其是孔隙型介质),并用数值方法求解。提出了根据属性参数的空间分布、以核函数的自适应带宽为基础的网格粗化新方法,该方法既减少了网格数量,同时也保留原始精细模型的主要非均质性特征。该方法的关键点在于可以同时对两种储集层属性参数进行网格粗化。首先计算每个储集层属性参数的带宽量或最优门槛值并得到粗化结果,然后根据最大带宽和最小带宽采用两种不同的方法对两个属性参数同时粗化。现在已经能够实现利用不同方法建立储集层两个属性参数的最终粗化模型,不同方法的网格单元数和网格位置都相同。最小带宽法的粗化误差小于最大带宽法。图6表1参29     

A combined Bayesian–wavelet–data fusion approach for borehole enlargement identification in carbonates

Petrophysical logs are usually acquired in most of the drilled wells and some of them have good correlations with mechanical properties of the rock. In this paper, a new multi-variable workflow is proposed in order to identify the location of borehole enlargements along the wellbore in correlation with some of the petrophysical logs acquired using wireline or logging while drilling tools in addition to mud weight and in-situ vertical stress data. This approach employs number of data processing techniques including Bayesian classification, wavelet de-noising, and data fusion to determine borehole intervals with maximum likelihood of enlargement. The application of the proposed method is to identify enlargement zones and does not provide information about stresses orientations and magnitudes. This paper explains the methodology and presents its results in five study wells in a carbonate field. The study confirms the applicability and the generalization capability of the method in carbonate formations with a significant accuracy.     

Hot deformation behaviour of bimodal sized Al2O3/Al nanocomposites fabricated by spark plasma sintering

The deformation behaviour of bimodal sized Al₂O₃/Al nanocomposites were investigated by hot compression tests conducted in the temperature range 350–500°C and strain rates of 0.001, 0.01 and 0.1 s^–1. The dynamic recrystallisation behaviour of the nanocomposites strongly depended on the forming parameters. The bimodal sized Al₂O₃ particles played a crucial role in the recrystallised microstructure. The addition of bimodal sized Al₂O₃ particles led to a significant increase of activation energy of plastic deformation, corroborating the enhanced resistance of the nanocomposite to hot deformation. This was also reflected by the increased compressive yield strength in the nanocomposite due to both dislocation strengthening caused by n‐Al₂O₃ and preventing the grain growth due to the presence of μ‐Al₂O₃ at grain boundaries. It was found that with the decrease of Z values, local strain induced by deformation was released and the grain size of aluminium matrix gradually increased, indicating that the main softening mechanism of the bimodal sized Al₂O₃/Al nanocomposites was dynamic recrystallisation (DRX). The lower the Z value was, the easier the DRX occurred. The highly beneficial role of the bimodal sized Al₂O₃ reinforcement in improving the high‐temperature performance of aluminium matrix nanocomposite was discussed.     

RELATIONSHIP BETWEEN TRUE AND ESTIMATED POSSIBILISTIC SYSTEMS AND THEIR RECONSTRUCTIONS†

This paper is a theoretical contribution to reconstructability analysis of possibilistic systems. A method to estimate a given possibility distribution from the associated observations is derived based on the one-to-one correspondence between possibility distributions and their basic probability assignments. It is shown that in this estimation the possibility value for a state is proportional to the frequency of the state in the observations which are drawn from nested state subsets. The order preservation relationship between a given (true) possibility distribution and its estimation is derived. Based on this preservation property, it is shown that the order in the distance from an original possibilistic overall system of their unbiased reconstructions from two alternative reconstruction hypotheses (structures) is preserved in the estimated systems domain. Particularly, it is proved that systems conceptualized in terms of possibility theory possess an important property: if a possibilistic system is perfectly reconstructable from a specific reconstruction hypothesis, then a system estimated from any data produced by the former system is also perfectly reconstructable from the same hypothesis.     

Investigation of TaC–TaB<Subscript>2</Subscript> ceramic composites

The TaC–TaB₂ composition was sintered by spark plasma (SPS) at 1900–2100°C and applied pressure of 30 MPa. TaC and 2–3 wt% B₄C were used as starting powders. Densification process, phase evolution, microstructure and the mechanical properties of the composites were investigated. The results indicated that the TaC–TaB₂ composition could be SPS to 97% of theoretical density in 10 min at 2100°C. Addition of B₄C leads to an increase in the density sample from 76 to 97%. B₄C nano-powder resists grain growth even at high temperature 2100°C. The formation of TaB₂/carbon at TaC grain boundaries helps in pinning the grain boundary and inhibiting grain growth. The phase formation was associated with carbon and boron diffusion from the starting particles B₄C to form TaB₂ phases. TaC grain sizes decreased with increase in B₄C concentration. Samples with 2.0 wt% B₄C composition had highest flexure strength up to 520 MPa. The effect of B₄C addition on hardness measured by microhardness has been studied. Hardness of samples containing 3.0 wt% B₄C was 16.99 GPa.