基于离散裂缝的多段压裂水平井数值试井模型及应用

水平井压裂技术已经成为开发低渗透油气藏、页岩气藏和致密气场等非常规油气藏的关键技术。基于离散裂缝模型,对裂缝进行简化,建立了二维多段压裂水平井有限导流数值试井模型,利用有限元方法求解模型,获得多段压裂水平井试井理论曲线和压力场特征。分析表明:多段压裂水平井的试井理论曲线一共分为七个阶段:井筒储存段、裂缝线性流段、裂缝-地层双线性流段、裂缝干扰段、地层线性流段、系统径向流段和边界作用段,其中裂缝-地层双线性流段和裂缝干扰是其典型特征。分析了裂缝数量、裂缝间距、裂缝不对称、裂缝不等长和裂缝部分缺失等因素对试井理论曲线的影响,结果表明:裂缝数量和裂缝间距对试井理论曲线的影响最大。较多的裂缝、较大裂缝间距、对称的裂缝和等长的裂缝有利于降低压裂水平井井底的流动阻力,提高产能。将建立的数值试井模型应用于四川盆地一口多段压裂水平井的压力恢复测试的数值试井解释,结果表明:本文建立的模型可以较好的拟合压力恢复测试数据,可以获得裂缝的导流能力和裂缝长度,为压裂效果评价和压裂设计提供指导。      

Toward the Synthesis of Modified Carbohydrates by Conjugate Addition of Propane‐1,3‐dithiol to α,β‐Unsaturated Ketones

Selected 5‐substituted derivatives 4 of 1,1‐diethoxy‐5‐hydroxypent‐3‐yn‐2‐one were treated with propane‐1,3‐dithiol under various conditions. The unprotected hydroxy ketones underwent cyclization during the dithiol addition and gave the corresponding 3‐(diethoxymethyl)‐2‐oxa‐6,10‐dithiaspiro[4.5]decan‐3‐ols 5 in 80–90% yield as the only products (Scheme 3 and Table 1). These products can be regarded as partly modified carbohydrates in the furanose form. When the benzyl‐protected analogues 10‐Bn of the 1,1‐diethoxy‐5‐hydroxypent‐3‐yn‐2‐one derivatives were treated with the same dithiol, however, no cyclization occurred; instead the corresponding 3‐{2‐[(benzyloxy)methyl]‐1,3‐dithian‐2‐yl}‐1,1‐diethoxypropan‐2‐one derivatives 11‐Bn were formed in good yield (up to 99%; Table 4). These 1,3‐dithianes were and are in the process of being converted to a number of new carbohydrate analogues, and here are reported high‐yield syntheses of functionalized molecules 17 belonging to the 5,5‐diethoxy‐1,4‐dihydroxypentan‐2‐one family of compounds (Table 7), via 15‐Bn (Table 5) and 16‐Bn (Table 6 and Scheme 8).     

Tandem isomerization-lactonization of olefinic fatty acids using the Lewis acidic ionic liquid, choline chloride·2ZnCl2

The tandem isomerization-lactonization of unsaturated fatty acids to their corresponding γ-lactones was carried out for the first time in the presence of a Lewis acidic ionic liquid, choline chloride·2ZnCl₂. The ionic liquid initially catalyzes the stepwise migration of the double bond along the carbon chain toward the carboxyl group at the Δ4 position, which subsequently undergoes lactonization resulting in the formation of γ-lactones. This one step process allows the formation of γ-lactone in good yield with little or no formation of δ-lactones. The studied ionic liquid plays the dual role of solvent as well as catalyst.     

Morphology and performance of unsaturated polyester nanocomposites modified with organoclay and thermoplastic polyurethane

<正>Unsaturated polyester(UPR)/thermoplastic polyurethane(TPU)/organoclay nanocomposites were prepared by melt compounding of thermoplastic polyurethane and unsaturated polyester prepolymer,and then mixing with the hybrids of styrene monomers and organoclay at ambient temperature.The crosslinking reaction eventually occurred through the unsaturated polyester prepolymer and styrene monomer.The morphology of the composites was investigated by scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The results show that the impact strength of UPR/TPU/organoclay nanocomposites increases obviously;the cure shrinkage decreases markedly,the glass transition temperature is enhanced and an elastic response to the deformation is prominent at the temperature above 10℃.     

Analogues of cytotoxic squamocin using reliable reactions: new insights into the reactivity and role of the α,β-unsaturated lactone of the annonaceous acetogenins

A small library of squamocin analogues has been prepared and screened biologically (cytotoxicity, inhibition of mitochondrial complex I and complex III). To centre diversity on a crucial part of the molecule (i.e., the α,β-unsaturated lactone), an original and reliable lactone opening reaction has been discovered and exploited among other efficient reactions.     

A priori error analysis of the mortar finite element method for variational inequalities

The mortar finite element method is a special domain decomposition method, which can handle the situation where meshes on different subdomains need not align across the interface. In this article, we will apply the mortar element method to general variational inequalities of free boundary type, such as free seepage flow, which may show different behaviors in different regions. We prove that if the solution of the original variational inequality belongs to H²(D), then the mortar element solution can achieve the same order error estimate as the conforming P₁ finite element solution. Application of the mortar element method to a free surface seepage problem and an obstacle problem verifies not only its convergence property but also its great computational efficiency. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008     

Influence of the presence of a partially saturated layer on the interpretation in field permeability tests

This paper concerns the determination of the soil permeability from water tests performed in the proximity of a partially saturated layer. The objective of the study is the determination of the influence of the presence of a partially saturated zone on the shape factor. The latter is a key parameter for the interpretation of soil permeability from in situ tests. The paper is composed of three parts. The first part describes the water test generally used in the measurement of the permeability in saturated soils, and we discuss difficulties of its use in the presence of unsaturated soils. The second part includes the numerical model used to study the flow of water in partially saturated soils. The last part involves a study of the influence of the presence of a partially saturated soil on the interpretation of the water test.     

放射性惰性气体 37Ar向地表输运的数值模拟

放射性惰性气体 37Ar的监测是全面禁止核试验条约核查体系中现场视察（OSI）的一项重要技术手段。 为在理论上考察地下核爆炸后 37Ar泄漏到地表的时间及泄漏量， 将核试验场区抽象为多孔介质， 在不考虑 37Ar在基岩中吸附、 解吸的情况下， 利用多孔介质渗流模型， 对理想场区地下核爆炸产生的 37Ar在地层中的输运进行数值模拟， 给出了 37Ar泄漏到地表时间及变化量。 计算结果可为OSI惰性气体监测技术的发展及其在地下核爆炸监测中应用的有效性评价提供参考。 Monitoring radioactive gas 37Ar is an important technique for the On Site Inspection(OSI) of the Comprehensive Nuclear Test Ban Treaty (CTBT) verification regime. In order to establish a theoretical model that can be used to calculate the appearing time and radioactivity of 37Ar which transports to the ground after a nuclear explosion， the rock media in the test area is assumed to be a homogeneous porous media， without consideration of gas absorption by and release from the rock media. The seepage model in the porous media is used to calculate 37Ar transportation. Computational results give the time 37Ar leaks to the ground and the variation of its radioactivity with time．And we can analyze and consider the computational results when we have developed OSI noble gas monitoring systems and evaluated their effectiveness.     

An alternative procedure for approximating hyperbolic systems of conservation laws

This work presents an alternative numerical procedure for simulating a class of nonlinear hyperbolic systems, using Glimm's method for advancing in time. The standard procedure to implement this methodology suffers from the disadvantage of requiring a complete solution of the associated Riemann problem—a task, in general, not easily reached. The alternative procedure introduced in this article consists in approximating the solution of the associated Riemann problem by piecewise constant functions always satisfying the jump condition—thus circumventing the difficulty of solving the Riemann problem and giving rise to an approximation easier to implement with lower computational cost. In order to illustrate the good performance of the alternative methodology proposed, two problems are considered—namely the transport of a pollutant in the atmosphere and the dynamics of the filling up of a rigid porous medium, modeled under a mixture theory viewpoint. Comparison with the standard procedure, employing the complete solution of the associated Riemann problem for implementing Glimm's scheme, has shown good agreement.     

Wacker-type oxidative functionalization of β-substituted unsaturated sulfoxides

The Wacker-type oxidation is an important procedure catalyzed by palladium complexes. A mild and general method for the preparation of β-substituted-δ-oxosulfoxides from the corresponding β-substituted-γ,δ-unsaturated sulfoxides is described. The products are versatile synthetic intermediates for the preparation of syn- and anti-1,3-diol and 1,3-aminoalcohol derivatives.