Three-phase measurements of oil and gas trapping in sand packs

We measure the trapped saturations of oil and gas as a function of initial saturation in water-wet sand packs. We start with a water-saturated column and inject octane (oil), while water and oil are produced from the bottom. Once water production has ceased, air (gas) then enters from the top, allowing oil and gas to drain under gravity for different times. Finally water is then injected from the bottom to trap both oil and gas. The columns are sliced and the fluids analyzed using gas chromatography. We find that for high initial gas saturations more gas can be trapped in the presence of oil than in a two-phase (gas/water) system. The residual gas saturation can be over 20% compared to 14% in two-phase flow [Al Mansoori SK, Iglauer S, Pentland CH, Bijeljic B, Blunt MJ. Measurements of non-wetting phase trapping applied to carbon dioxide storage. Energy Procedia 2009;1(1):3173–80]. This is unlike previous measurements on consolidated media, where the trapped gas saturation is either similar or lower to that reached in an equivalent two-phase experiment. For lower initial gas saturation, the amount of trapping follows the initial-residual trend seen in two-phase experiments. The amount of oil trapped is insensitive to initial gas saturation or the amount of gas that is trapped, again in contrast to measurements on consolidated media. More oil is trapped than would be predicted from an equivalent two-phase (oil/water) system, although the trapped saturation is never larger than the maximum reached in two-phase flow (around 11%) [Pentland CH, Al Mansoori SK, Iglauer S, Bijeljic B, Blunt MJ. Measurement of non-wetting phase trapping in sand packs. In: SPE 115697, proceedings of the SPE annual technical conference and exhibition, Denver, Colorado, USA; 21–24 September 2008]. These initially surprising results are explained in the context of oil layer stability and the competition between snap-off and piston-like advance. In two-phase systems, displacement is principally by cooperative piston-like advance with relatively little trapping, whereas in consolidated media snap-off is generally more significant. However, oil layer collapse events during three-phase waterflooding rapidly trap the oil which acts as a barrier to direct water/gas displacement, except by snap-off, leading to enhanced gas trapping.     

预应力蛋形消化池流固耦合有限元分析

与圆柱形储液罐相比,预应力蛋形消化池中流体与固体交界面呈弧形面,且结构横截面为变厚度,这就带来了有限元分析的困难。结合厦门市蛋形消化池的结构设计,采用三维有限元技术对预应力蛋形消化池有限元模型进行了整体的静力、动力分析,分析了蛋形消化池中盛有水体时结构的自振频率及在地震载荷作用下的动应力,与国内首次模拟地震振动台试验结果进行了比较,两者符合良好,表明该有限元计算模型是合理的,可以应用于类似特种结构。     

库车地区高矿化度泥浆影响下的电阻率校正方法研究

为了克服克拉地区膏盐地层垮塌及地层压力对钻井的影响,在钻井过程中往往采用高矿化度、大密度的钻井液.这使得渗透性地层中观测得到电阻率与实际的电阻率存在较大的偏差,给测井解释带来极大的困难.本文针对克拉地区的实际情况,对高矿化度泥浆影响下的电阻率校正方法进行了探索性研究,提出了基于岩心资料的电阻率校正方法及基于泥浆动态侵入的图版校正电阻率方法,最后通过毛管分析饱和度与校正后电阻率计算饱和度对比验证校正电阻率的可信性.结果表明,校正后电阻率更能真实的反映地层电性特征,进一步提高了测井解释符合率.     

周期成层Patchy模型中纵波的频散和衰减研究

本文用孔隙介质力学的方法来研究纵波在介观周期成层Patchy模型的传播问题.相对于White方法,该方法少了不同介质分界面处的流体压力不等的假设,推导过程更为严密;和Dutta的双相方程解耦方法比较,文中方法直接求解双相方程,形式上更为直观.当纵波通过周期成层孔隙模型时,在低频段用孔隙弹性力学得到纵波频散和衰减结果与用White公式得到的结果符合得很好;周期成层的Patchy孔隙模型由于其空间排列的周期性使其成为孔隙弹性声子晶体,在其频散和衰减曲线上的高频段会出现多个禁带和通带,这使得速度不会随频率单调递增,衰减峰也不只一个.对于地震频段,随着渗透率降低模型的衰减峰向低频移动,这和实际观测结果一致,和传统Biot理论预测结果正相反;随着含气量上升纵波衰减峰值先上升后下降,其最大值出现在含气量0.1左右,这和相关实验结果一致.研究结果表明该模型可以定性解释观测到的地震衰减结果.     

基于叠前地震数据和岩石物理的游离气定量估算方法——以印度Krishna-Godavari盆地NGHP01-10A井为例

天然气水合物稳定带下方游离气分布模式、气体含量及其对水合物富集成藏的指示是水合物研究中的难点,而利用振幅随偏移距变化(Amplitude Versus Offset,AVO)与岩石物理模型能够对游离气含量进行地震定量解释.我们对印度Krishna-Godavari(K-G)盆地的地震资料进行了叠前保幅处理,在测井数据和层位标定的基础上,基于等效介质岩石物理模型和AVO正演模拟定量估算了NGHP01-10A井的游离气饱和度,发现水合物下方的游离气饱和度与其分布模式有关.游离气呈均匀分布时饱和度为孔隙空间的0.3%~0.4%,而块状分布时为3%~4%,该结果与NGHP01-10D实测计算的泊松比交汇分析结果吻合很好.最后再根据干燥岩石骨架的泊松比反演结果进一步判断游离气分布为均匀分布,其饱和度为0.3%~0.4%.     

基于康普顿背散射扫描技术的液体安检仪

DLS1201机是一种高度智能化、小型轻便、多功能的检查仪,是国内外唯一的基于康普顿背散射扫描（CBS）技术研制成功的安全检查设备。本文对其技术要点和技术指标作了简要说明,并与国内外其他安检仪作了对比。     

Simplified design method for shear-valve magnetorheological dampers

Based on the Bingham parallel-plate model, a simplified design method of shear-valve magnetorheological(MR) dampers is proposed considering the magnetic circuit optimization. Correspondingly, a new MR damper with a full-length effective damping path is proposed. The prototype dampers are also fabricated and studied numerically and experimentally. According to the test results, the Bingham parallel-plate model is further modified to obtain a damping force prediction model of the proposed MR dampers. This prediction model considers the magnetic saturation phenomenon. The study indicates that the proposed simplified design method is simple, effective and reliable. The maximum damping force of the proposed MR dampers with a full-length effective damping path is at least twice as large as those of conventional MR dampers. The dynamic range of damping force increases by at least 70%. The proposed damping force prediction model considers the magnetic saturation phenomenon and it can realize the actual characteristic of MR fluids. The model is able to predict the actual damping force of MR dampers precisely.     

Viscoelastic representation of surface waves in patchy saturated poroelastic media

Wave-induced flow is observed as the dominated factor for P wave propagation at seismic frequencies. This mechanism has a mesoscopic scale nature. The inhomogeneous unsaturated patches are regarded larger than the pore size, but smaller than the wavelength. Surface wave, e.g., Rayleigh wave, which propagates along the free surface, generated by the interfering of body waves is also affected by the mesoscopic loss mechanisms. Recent studies have reported that the effect of the wave-induced flow in wave propagation shows a relaxation behavior. Viscoelastic equivalent relaxation function associated with the wave mode can describe the kinetic nature of the attenuation. In this paper, the equivalent viscoelastic relaxation functions are extended to take into account the free surface for the Rayleigh surface wave propagation in patchy saturated poroelastic media. Numerical results for the frequency-dependent velocity and attenuation and the time-dependent dynamical responses for the equivalent Rayleigh surface wave propagation along an interface between vacuum and patchy saturated porous media are reported in the low-frequency range (0.1–1,000 Hz). The results show that the dispersion and attenuation and kinetic characteristics of the mesoscopic loss effect for the surface wave can be effectively represented in the equivalent viscoelastic media. The simulation of surface wave propagation within mesoscopic patches requires solving Biot’s differential equations in very small grid spaces, involving the conversion of the fast P wave energy diffusion into the Biot slow wave. This procedure requires a very large amount of computer consumption. An efficient equivalent approach for this patchy saturated poroelastic media shows a more convenient way to solve the single phase viscoelastic differential equations.     

超高效液相色谱-电喷雾串联质谱法同时测定土壤中四环素类抗生素及其降解产物

研究建立了超高效液相色谱电喷雾串联质谱法(UPLC/MS/MS)测定土壤中四环素(TC)、土霉素(OTC)、金霉素(CTC)、多西环素(DC)4种四环素类抗生素(TCs)及5种降解产物的残留分析方法。采用乙腈与EDTA-Mcllvaine缓冲液混合提取土壤样品中TCs,净化采用HLB固相萃取小柱,电离方式为ESI(+),定量方法为多反应监测(MRM)模式。在0.001~0.5 mg/kg范围内, 4种四环素类抗生素及其降解产物的峰面积与质量浓度的线性关系良好( R2>0.99)。仪器检出限为1.085~15.780 μg/kg,方法的定量限为3.617~42.526 μg/kg。在3个添加水平 0.05、0.1和 0.5 mg/kg下,除脱水四环素和差向脱水四环素(其回收率<30%)外,其余四环素类抗生素及代谢产物在土壤中的添加回收率为62.1%~87.6%,相对标准偏差为2.35%~13.42%。该方法线性关系良好,灵敏度高,适用于土壤中四环素类抗生素及其降解产物的残留分析。     

Resistivity saturation in liquid iron–light-element alloys at conditions of planetary cores from first principles computations

We present a comprehensive analysis of electrical resistivity for liquid Fe–Si, Fe–S, and Fe–O alloys from first principles computations, covering the pressure/temperature conditions and major light element candidates inside the cores of terrestrial planets. By fitting optical conductivity with the Drude formula, we explicitly calculate the effective electron mean free path, and show that it becomes comparable to the interatomic distance for high densities and Si/S concentrations (Ioffe–Regel criterion). In approaching the Ioffe–Regel criterion, the temperature coefficient of resistivity decreases with compression for all compositions, eventually vanishes (Fe–Si), or even changes sign (Fe–S). Differences in resistivity and the degree of saturation between the iron alloys studied are explained in terms of iron–light element coordination numbers and their density dependence. Due to competing temperature and pressure effects, resistivity profiles along proposed core adiabats exhibit a small negative pressure gradient.