油气藏水相圈闭损害预测新方法——相圈闭系数法

准确预测水相圈闭损害是储层保护技术和增产改造措施优选的基础。目前的预测方法,如渗透率损害率、水相圈闭损害指数和总水体积等,多用来预测油层水锁损害,且因考虑因素不够全面或使用不够简便,而不能较好地预测水相圈闭损害,尤其是致密气层的水相圈闭损害。根据初始含水饱和度、储层压力、流体性质和储层孔隙结构等对水相圈闭损害的影响机理,提出了预测水相圈闭损害程度的相圈闭系数法,研究了其对渗透率、初始含水饱和度和压差的敏感性,给出了预测标准。相圈闭系数是无因次量,具有考虑因素全面、实用简便、易于推广等特点,已经应用到致密气藏水相圈闭损害预测,并取得了较好效果。

双疏性表面处理预防致密储层水相圈闭损害实验研究

传统的屏蔽暂堵技术不能有效防止致密储层中工作液的侵入,而以往靠降低界面张力排驱液相的方法效果短暂。在工作液中加入氟表面活性剂,增大润湿接触角,是一种降低毛管力减弱毛管自吸的新方法。润湿实验筛选出能将致密砂岩由液润湿改变为气润湿的氟表面活性剂。100℃下将岩心片浸泡在含所选氟活性剂的滤液中处理40 min,岩心片与滤液和水的接触角分别为120°和110°。毛管自吸、岩心流动实验表明,处理后岩心总吸水量降低了60%,自吸速率较处理前降低了40%~50%,驱替速率约是处理前的2倍。表明,氟活性剂能够有效改变储层岩心的润湿性,具有预防水相圈闭损害的应用潜力。

致密火山岩气藏水相和油相圈闭损害实验评价——以南堡凹陷5号构造沙河街组为例

致密火山岩气藏通常与致密砂岩气藏呈互层分布,尽管储层岩石物性与致密砂岩气藏类似,但致密火山岩气藏水相圈闭和油相圈闭损害却未能引起关注。为了揭示致密火山岩气藏水相和油相圈闭损害潜力,选取南堡凹陷沙河街组致密火山岩气藏储层岩心,开展了水相和油相毛管自吸与液相返排实验评价,并与沙河街组致密砂岩气藏液相圈闭损害进行对比。结果表明:(1)致密火山岩气藏储层岩石水相和油相毛管自吸能力弱于致密砂岩,致密砂岩既亲水又亲油,致密火山岩亲油性更强;(2)沙河街组致密火山岩气藏液相圈闭损害呈现"三低"特点,即毛管自吸进液量低、液相返排率低和渗透率损害率低;(3)沙河街组致密火山岩气藏水相圈闭损害比油相圈闭损害更严重。孔喉呈多峰分布、裂缝发育、存在大量溶蚀孔等孔喉结构差异是造成致密火山岩气藏水相和油相圈闭损害显著区别于致密砂岩气藏的重要原因。致密火山岩气藏钻井过程中,需控制裂缝性漏失,避免水基或油基工作液滤液进入裂缝侧面储层深处;控制压裂等增产改造措施规模,以防沟通底水诱发水相圈闭损害;在开发生产过程中要制定合理工作制度,预防凝析油析出引起的油相圈闭损害。

正丁醇-水-氯化钙体系液液平衡的测定和预测

测定了 2 98.15K和 32 3.15K下氯化钙在 1%～ 2 0 % (质量分数 )范围内的正丁醇 -水体系液液平衡。应用作者提出的强电解质混合溶剂体系过量自由焓模型 (1994年 ) ,仅用二元信息回归出参数后 ,对该体系的平衡双液相联结线和盐浓度分布进行预测 。

国内外钻井及储层改造过程中致密砂岩气藏储层保护技术现状研究——论适用于塔里木油田致密砂岩气藏储层保护技术

塔里木油田致密砂岩气藏储量巨大,随着钻井工程技术以及气藏增产改造技术的不断进步,致密砂岩气藏资源的开发将备受重视。致密砂岩气藏与常规油气藏差异较大,普遍具有超低渗透率,超低孔隙度和超低含水饱和度的特点,并且储层岩石性质多变,埋藏较深,温度较高,高压、异常高压井广泛存在。条件的复杂性导致致密砂岩气藏在钻探开发过程中极易受到伤害,导致产量急剧下降甚至丧失的情况。侵入液体的相圈闭伤害以及储层岩石的敏感矿物与侵入液相互作用产生的理化反应是导致致密砂岩气藏产能下降的主要原因。除此以外乳化堵塞、多相流效应、润湿反转效应等因素也会导致气藏渗透率进一步降低。对于天然裂缝发育的致密砂岩气藏,固相颗粒堵塞裂缝通道是储层伤害的一个不可忽视的因素。目前国内致密砂岩气藏储层保护技术发展较慢,可借鉴国内外先进的储层保护技术,提高塔里木油田致密砂岩气藏的开采效果。

Analysis of a new 5-phase bearingless induction motor

This paper addresses the bearingless motor with a single set of multiphase windings. The interaction between M and M±1 pole-pair magnetic fields produces radial force. Based on this principle,a bearingless machine is obtained. Conventional bearingless machine has dual windings,levitation windings and torque windings,which produce the two magnetic fields. In the proposed bearingless motor,the two needed magnetic fields are produced by feeding two groups of currents to a single set of multiphase windings. Taking a 5-phase induction motor as example,the inductance matrices,considering air gap eccentricity,are calculated with the modified winding function method. The radial force analytical model is deduced by virtual displacement,and its results are validated by FEA. The mathematical model of the new bearingless machine is set up,and the simulation results verified the feasibility of this novel bearingless motor.

Influence of relative positions between RF coil and crucible on sapphire crystals by edge-defined film-fed growth(EFG) technique

To obtain the stable temperature field required for growing sapphire crystals, the influence of relative positions between RF coil and crucible on the performances of sapphires produced by edge-defined film-fed growth（EFG） technique was investigated. For comparison, the crucible was located at the top（case A） and the middle（case B） of the RF coil, respectively. Furthermore, the lattice integrities were studied by the double-crystal X-ray diffraction, and the dislocations were observed under the optical microscope and atomic force microscope after corroding in molten KOH at 390 ℃. The crystals in case B exhibit better lattice integrity with smaller full width at half maximum of 29.13 rad·s, while the value in case A is 45.17 rad·s. The morphologies of dislocation etch pits in both cases show typical triangular symmetry with smooth surfaces. However, the dislocation density of 2.8×104 cm-2 in case B is only half of that in case A, and the distribution is more uniform, compared to the U-shaper in case A.

Seasonal changes in TC and WSOC and their ^13C isotope ratios in Northeast Asian aerosols： land surface–biosphere–atmosphere interactions

In order to understand the relative importance of anthropogenic and biological sources of carbonaceous aerosols in Northeast Asia,we measured total carbon(TC)and water-soluble organic carbon(WSOC)and their stable carbon isotope ratios(d^(13)C)in total suspended particulates collected from Sapporo,northern Japan(43.07°N,141.36°E)over a 1-year period(during 2 September 2009and 5 October 2010).Temporal variations of TC showed a gradual decrease from mid-autumn to winter followed by a gradual increase to growing season with a peak in early summer.Both d^(13)C_(TC)and d^(13)C_(WSOC)showed very similar temporal trends with a gradual enrichment of^(13)C from mid-autumn to winter followed by a depletion in the^(13)C to early summer and thereafter it remained stable,except for few cases.Based on the results obtained together with the air mass trajectories,we found that biogenic emissions including biological particles(e.g.,pollen)and secondary organic aerosol formation from biogenic volatile organic compounds are the important sources of carbonaceous aerosols in spring/summer whereas fungal spores from soil and biomass burning and enhanced fossil fuel combustion contribute significantly in autumn/winter and in winter,respectively,in Northeast Asia.

PCCP broken wire detection based on orthogonal electromagnetic principle

Aiming at the major failure mode of prestressed concrete cylinder pipes (PCCP),namely the fracture of prestressed steel wires,the broken wire detection technology based on orthogonal electromagnetic principle is studied. The detection system model is established and optimized by using COMSOL finite element simulation software. Furthermore,the theoretical analysis of the wire-breaking effect is carried out. The influence of factors on broken wire signal characteristics such as edge effect,circumferential relative position of the detector and broken wires,excitation frequency and relative permeability of steel wires is analyzed,which provides a theoretical guidance for the field detection. The influence of the steel cylinder structure on the simulation results is analyzed,which provides a reference for the improvement of calculation efficiency. The corresponding detection system is designed and implemented. Concretely,a high-voltage and high-power sinusoidal signal coil drive scheme based on sinusoidal pulse width modulation technology and an intelligent power module is innovatively proposed and the corresponding protection circuit is designed. The broken wire signal could be effectively extracted through a lock-in amplifier. The experimental results show that this system can effectively identify the broken wires with low cost.

Strengthening the three-dimensional comprehensive observation system of multi-layer interaction on the Tibetan Plateau to cope with the warming and wetting trend

Changes in the water cycle on the Tibetan Plateau(TP)have a significant impact on local agricultural production and livelihoods and its downstream regions.Against the background of widely reported warming and wetting,the hydrological cycle has accelerated and the likelihood of extreme weather events and natural disasters occurring(i.e.,snowstorms,floods,landslides,mudslides,and ice avalanches)has also intensified,especially in the highelevation mountainous regions.Thus,an accurate estimation of the intensity and variation of each component of the water cycle is an urgent scientific question for the assessment of plateau environmental changes.Following the transformation and movement of water between the atmosphere,biosphere and hydrosphere,the authors highlight the urgent need to strengthen the three-dimensional comprehensive observation system(including the eddy covariance system;planetary boundary layer tower;profile measurements of temperature,humidity,and wind by microwave radiometers,wind profiler,and radiosonde system;and cloud and precipitation radars)in the TP region and propose a practical implementation plan.The construction of such a three-dimensional observation system is expected to promote the study of environmental changes and natural hazards prevention.

Application of DC component to select fault branch in arc suppression coil grounding system

When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is much slower. This paper analyses the DC component of fault branch, and has found it is much bigger than that of the normal branches in transient state. All the simulation results obtained from three compensation types, different fault time and different wave cycles show that the DC component of fault branch is much higher than that of those normal branches. These results verify the effectiveness of taking the DC component as the method of fault line selection in the arc suppression coil grounding system.

Trend in Coral-Algal Phase Shift in the Mandapam Group of Islands, Gulf of Mannar Marine Biosphere Reserve, India

The present study revealed proliferation of macro-algae modifying coral reef ecosystems in a different manner due to diseases and sedimentations in the Mandapam group of islands in the Gulf of Mannar. Benthic surveys were conducted with major attack of seven coral reefs diseases with high sedimentation rate, nine species of fleshy macro-algae(Turbinaria ornata, Turbinaria conaides, Caulerpa scalpelliformis, Caulerpa racemosa, Kappaphycus alvarezii, Padina gymnosphora, Sargassum wightii, Ulva reticulata and Calurpa lentillifera) proliferation against major corals life forms(Acropora branching, Acropora digitate, Acropora tabulate, coral massive, coral submassive, coral foliose and coral encrusting). The results confirm that diseased corals most favor to macro-algae growth(15.27%) rather than the sedimentation covered corals(8.24 %). In the degradation of coral life forms, massive corals were more highly damaged(7.05%) than any other forms. Within a short period of time(May to September), coral coverage shrank to 17.4% from 21.9%, macro-algae increased 23.51% and the average sedimentation rate attained 77.52 mg cm^(-2) d^(-1) with persisting coral reef diseases of 17.59%. The Pearson correlation showed that the coral cover decreased with increasing macro-algae growth, which was statistically significant(r =-0.774, n = 100, P < 0.0005). The proliferation of the various macro-algae C. scalpellifrmis, T. ornata, C. racemosa, T. conaides, U. reticulata, S. wightii, K. alvarezii, P. gymnosphora and C. lentillifera increased with percentages of 6.0, 5.8, 5.7, 4.9, 4.2, 3.7, 2.7 and 1.9, respectively. If this trend continues, the next generation of new recruit corals will undoubtedly lead to a phase shift in Gulf of Mannar corals.

The sex ratio of wild Chinese alligators Alligator sinensis

The Chinese alligator Alligator sinensis is one of the most endangered crocodilian species, and typically exhibits temperature-dependent sex determination. It is extremely important to clarify the sex structure of Chinese alligators to implement recovery projects successfully. However, the sex ratio of wild Chinese alligators remains unknown. In this study, we collected 28 years of sex ratio data from Chinese alligators residing in the natural and artificial habitats of Changxing Nature Reserve, China, and examined the differences in the sex ratio dynamics between these two populations. We observed that the sex ratio of wild Chinese alligators is 1 male to 4.507 females, which was significantly lower compared to that of the captive population （1 to 2.040; P 〈 0.001）, and is significantly different to previously documented sex ratios for this species （all P 〈 0.01）. Furthermore, we documented an annually stable （P = 1.000） female-biased sex ratio for wild alligators at hatching [1 male to 4.747 females; 0.174 （0.167~）.182）], in contrast to a dramatically fluctuating sex ratio （P 〈 0.001） in captivity [1 male to 1.674 females; 0.374 （0.246-0.593）], showing a potential mechanism for adjusting the sex structure. Finally, we found that the hatchling sex ratios were similar to that of the population sex ratio （P = 0.748）, with little correlation to air temperature values in the 60-70 day incubation period during the breeding season （July and August; both P 〉 0.05）. Overall, this study indicates that the stabilized female-biased sex ratio of Changxing Chinese alligators might result from selection pressure caused by local mate competition and major inbreeding .

Thermal performances of non-equidistant helical-coil phase change accumulator for latent heat storage

Helical-coil is a common structure of heat exchanger unit in phase change heat accumulator and usually has the equal coil pitch between adjacent coils. Its thermal performances could be improved by improving the uniformity of the phase change material （PCM） temperature distribution. Thus, a novel non-equidistant helical-coil structure was proposed in this study. Its coil pitch decreased along the flow direction of heat transfer fluid, which made the heat exchange area in unit volume increase to match the decreasing temperature difference between the heat transfer fluid and PCM. The structure was optimized using numerical simulation. An experimental system was developed and the experiment results indicated that the proposed non-equidistant helical-coil heat accumulator was more effective than equidistant helical-coil for latent heat storage. The uniformity of the temperaalre distribution was also confirmed by simulation results.

Biosynthetic approach to modeling and understanding metalloproteins using unnatural amino acids

Metalloproteins have inspired chemists for many years to synthesize artificial catalysts that mimic native enzymes.As a complementary approach to studying native enzymes or making synthetic models,biosynthetic approach using small and stable proteins to model native enzymes has offered advantages of incorporating non-covalent secondary sphere interactions under physiological conditions.However,most biosynthetic models are restricted to natural amino acids.To overcome this limitation,incorporating unnatural amino acids into the biosynthetic models has shown promises.In this review,we summarize first synthetic,semisynthetic and biological methods of incorporates unnatural amino acids(UAAs)into proteins,followed by progress made in incorporating UAAs into both native metalloproteins and their biosynthetic models to fine-tune functional properties beyond native enzymes or their variants containing natural amino acids,such as reduction potentials of azurin,O_2 reduction rates and percentages of product formation of HCO models in Mb,the rate of radical transport in ribonucleotide reductase(RNR)and the proton and electron transfer pathways in photosystemⅡ(PSⅡ).We also discuss how this endeavour has allowed systematic investigations of precise roles of conserved residues in metalloproteins,such as Metl21 in azurin,Tyr244 that is cross-linked to one of the three His ligands to CuB in HCO,Tyr122,356,730 and 731 in RNR and TyrZ in PSⅡ.These examples have demonstrated that incorporating UAAs has provided a new dimension in our efforts to mimic native enzymes and in providing deeper insights into structural features responsible high enzymatic activity and reaction mechanisms,making it possible to design highly efficient artificial catalysts with similar or even higher activity than native enzymes.

Thermal convection thinning of the North China Craton: Numerical simulation

We used twodimensional numerical simulations to investigate smallscale convection in the upper mantlelithosphere system with depth and temperaturedependent viscosity. Our aim was to examine the mechanism of craton thinning by thermal con vection. The model domain is 700 km deep and 700 km wide with a resolution of 71x71 nodes and 160000 markers. The ve locity boundary conditions are freeslip along all the boundaries. A thermal insulation condition was applied at the two side walls, with constant temperatures for the top and bottom boundaries. We assumed an initial temperature of 273 K at the upper boundary and 1673 K at the lower boundary, and 1573 K at the bottom of the lithosphere （200 km depth） for the thick, cold, and stable North China Craton （NCC）. We calculated the thermal evolution in the upper mantle when the temperature at its bottom is raised because of lower mantle convection or plumes. The temperature at the bottom of the upper mantle was set at 1773, 1873, 1973, and 2073 K for different models to study the temperature effect on the lithospheric thinning processes. Our endmember calculations show that with the bottom boundary raising the lithosphere can be thinned from a depth of 200 km to a depth of between 100 and 126.25 km. The thinning rates are at mm/y order of magnitude, and the thinning timescale is about 10 Ma.