射流式水力降压实验研究

采用研制的射流式水力降压模拟工具及其相应的试验台架,对一种在常规钻井方式下有效降低井底压力的射流式水力降压方式进行了实验研究。着重研究了工具喷嘴直径、排量及安装位置距钻头距离对降压效果的影响。研究得出如下结论:(1)射流式水力降压工具的降压效果随排量的增加而增加,在排量为9 L/s,工具距钻头距离L=0,喷嘴直径N=2.5 mm情况下,井底环空产生最大压差为0.45 MPa,当L=6 m,N=3.5 mm,工具吸入口处产生最大压差0.58MPa,该处压差平均降低17.74%;(2)工具降压效果与工具安装位置及喷嘴尺寸选择有关,工具安装在近钻头处,降压效果最明显,过于远离井底,降压效果波及不到井底,L>2 m时对井底环空压降趋近于0;(3)射流式水力降压工具可以有效地解决窄密度窗口地层的涌、漏等故障。

射流式水力降压钻井机理与参数研究

窄密度窗口是钻井工程设计中的一个难点。为解决这一问题,提出了一种射流式水力降压原理,利用高速射流产生的抽吸力降低井底压力(循环当量密度),并介绍了工具设计的基本思路。射流式水力降压工具由主副流道组成,副流道流体在喷嘴处的高速低压区对环空产生抽吸作用。通过计算,降压效果随无量纲面积比、排量和喷嘴直径的增大而增大,随钻井速度的增大而降低。在分流量5%、钻井液密度1.25 g/cm3时,最大能降低井底压力1.5 MPa。该研究为射流式水力降压钻井应用打下了基础。

NUMERICAL SIMULATION STUDY ON WUQING GEOTHERMAL RESERVOIR,TIANJIN

In this paper the computer code of AUTOUGH2 is used to carry out numerical simulation study on the Wuqing geothermal reservoir for evaluating reservoir performance upon different exploitation schemes.The simulating calculation and analysis of two main cases,production without reinjection and production with reinjection,were carried out to illuminate and compare the temperature and pressure profiles with distance and time.The water level or pressure will decrease with the time of production,and the reinjection will cause the cooling effect of reinjection on the production zone.

One-dimensional consolidation of visco-elastic aquitard due to withdrawal of deep-groundwater

One-dimensional consolidation of visco-elastic aquitard due to withdrawal of deep-groundwater was studied.Merchant model was used to simulate visco-elastic characteristic of aquitard.General solutions of the governing equation were obtained by applying Laplace transform with respect to time,and then the pore-pressure,strain and deformation of the aquitard could be calculated by Laplace inversion.A case was analyzed to validate the correctness of the present method.Finally,some consolidation properties of the problem were analyzed.Comparison of the average degree of consolidation defined by pore pressure with that defined by settlement shows that they are different and the maximum difference is 22.8%.The influences of parameters of Merchant model and the rate of the water level on the consolidation are great.The smaller the viscosity coefficient is,the later the rate of consolidation decreases.The rate of consolidation is decreased with the decrease of the rate of the water level fall.Therefore,the lagged effect of land subsidence should be considered in the actual project.

Effect of nozzle geometry on pressure drop in submerged gas injection

Submerged gas injection into liquid leads to complex multiphase flow, in which nozzle geometries are crucial important for the operational expenditure in terms of pressure drop. The influence of the nozzle geometry on pressure drop between nozzle inlet and outlet has been experimentally studied for different gas flow rates and bath depths. Nozzles with circular, gear-like and four-leaf cross-sectional shape have been studied. The results indicate that, besides the hydraulic diameter of the outlet, the orifice area and the perimeter of the nozzle tip also play significant roles. For the same superficial gas velocity, the average pressure drop from the four-leaf-shaped geometry is the least. The influence of bath depth was found negligible. A correlation for the modified Euler number considering the pressure drop is proposed depending on nozzle geometric parameter and on the modified Froude number with the hydraulic diameter of the nozzle do as characteristic length.

Composition of stable isotope in precipitation and its influences by different vapor sources in the eastern Qilian Mountains

To better understand the process of precipitation and water cycle, the composition of stable isotope in precipitation and its influences by different vapor sources in the eastern of Qilian Mountains were conducted from June 2013 to May 2014. The total of 100 precipitation samples were collected in Wushaoling national meteorological station located in the eastern of Qilian Mountains. The analysis indicates that the slope of Local Meteoric Water Line is lower than that of Global Meteoric Water Line. The average values of δ18 O and δD in precipitation are higher in summer but lower in winter. Except for negative correlation with relative humidity, the stable isotope values in precipitation are positive correlations with temperature, precipitation and water vapor pressure. Influenced by water vapor source, the values of d-excess are lower for the Westerly wind and the South Asia Monsoon onJuly and the Westerly wind and the East Asia Monsoon on August, but they are higher for the Westerly wind on other months, that they are also influenced by the weather conditions in rainfall process. The variation of stable isotope in precipitation exhibited significant temperature effect, and there is also some precipitation amount effect in spring and summer.

The establishment of a new deliverability equation considering threshold pressure gradient

The flowing mechanism of a low permeability gas reservoir is different from a conventional gas reservoir,especially for that with higher irreducible water saturation the threshold pressure gradient exists. At present,in all the deliverability equation,the additional pressure drop caused by the threshold pressure gradient is viewed as constant,but this method has big error in the practical application. Based on the non-Darcy steady flow equation,the limited integral of the additional pressure drop is solved in this paper and it is realized that the additional pressure drop is not a constant but has something to do with production data,and a new deliverability equation is derived,with the relevant processing method for modified isochronal test data. The new deliverability equation turns out to be practical through onsite application.

Pressure Drop Measurements on Distillation Columns

Pressure drops are of major importance for distillation/absorption columns. This paper mainly discusses how to correctly measure, interpret and use pressure drop data. The possible causes of incorrect pressure drop measurements are studied including the effects of pressure tap dimensions, locations, and vapor condensation etc. The effect of the static head of vapor on the pressure drop data and column pressures is evaluated. Variations of sectional pressure drops along the column are investigated based on the experimental data obtained from commercial size distillation columns at Fractionation Research, Inc. （FRI）. For a packed column, it is found that the spacing between the liquid distributor and the top of the bed affects the overall pressure drop measurements, which is confirmed by a fundamental fluid dynamics analysis.

Numerical Investigation on the Initiation Mechanism of Debris-Flow under Rainfall

Rainfall is an important factor to trigger the debris flow.Numerical simulation on the responses of slopes and the initiation of debris flow under rainfall was processed by using the software FLAC2D based on the soil parameters in Weijia Gully,Beichuan County,Sichuan Province,China.The effects of the slope angle,rainfall intensity,soil parameters on the developments of the stress and pore pressure and deformation of the slope were studied.It indicates that large displacements of the slope are mainly located near the slope toe.With the increase of the rainfall intensity the stability of the slope decreases and so the debris-flow is easy to occur.

Effect of rainfall on a colluvial landslide in a debris flow valley

A colluvial landslide in a debris flow valley is a typical phenomena and is easily influenced by rainfall. The direct destructiveness of this kind of landslide is small, however, if failure occurs the resulting blocking of the channel may lead to a series of magnified secondary hazards. For this reason it is important to investigate the potential response of this type of landslide to rainfall. In the present paper, the Goulingping landslide, one of the colluvial landslides in the Goulingping valley in the middle of the Bailong River catchment in Gansu Province, China, was chosen for the study. Electrical Resistivity Tomography(ERT), Terrestrial Laser Scanning(TLS), together with traditional monitoring methods, were used to monitor changes in water content and the deformation of the landslide caused by rainfall. ERT was used to detect changes in soil water content induced by rainfall. The most significant findings were as follows:(1) the water content in the centralupper part(0~41 m) of the landslide was greaterthan in the central-front part(41~84 m) and(2) there was a relatively high resistivity zone at depth within the sliding zone. The deformation characteristics at the surface of the landslide were monitored by TLS and the results revealed that rainstorms caused three types of deformation and failure:(1) gully erosion at the slope surface;(2) shallow sliding failure;(3) and slope foot erosion. Subsequent monitoring of continuous changes in pore-water pressure, soil pressure and displacement(using traditional methods) indicated that long duration light rainfall(average 2.22 mm/d) caused the entire landslide to enter a state of creeping deformation at the beginning of the rainy season. Shear-induced dilation occurred for the fast sliding(30.09 mm/d) during the critical failure sub-phase(EF). Pore-water pressure in the sliding zone was affected by rainfall. In addition, the sliding L1 parts of the landslide exerted a discontinuous pressure on the L2 part. Through the monitoring and analysis, we conclude that this kind of landslide may have large deformation at the beginning and the late of the rainy season.

Pressure drop of the film-enlarged tube bundles in air-water two-phase cross flow in evaporative air cooler

An experiment was carried out to investigate the relation of the maximum velocity of air passing through narrowest passage, mass flux of spray water in one square meter in one hour and the pressure drop of tube bundles. Twelve equations were obtained for the relation. The results show that the pressure drop of the tube bundles increases with increase of the maximum velocity of air and the mass flux of spray water. Comparing the pressure drop of the bare tube bundles with that of the film-enhanced tube bundles, it is found that the pressure drop of the film-enhanced tube bundles is lower about 11% and the surface roughness of the film-enhanced plates is a main factor that influences the pressure drop. The data and method obtained in the paper can be used to compute the pressure drop of the film-enhanced tube bundles and is helpful for selection of fan.

涡流式水力降低井底压差机制及现状

石油与天然气钻探实践表明,降低井底压差,减小岩屑的压持效应,并尽量实现井底的欠平衡条件,可以显著提高钻井的机械钻速。本文在介绍涡流式水力降压技术的原理的基础上,综述了环空涡流泵、涡流式水力降压短节和涡流钻头等涡流式水力降压工具的结构特点、降压效果和研发应用情况,采用计算流体力学软件对涡流PDC(聚晶金刚石复合片)钻头的井底流场进行了数值模拟研究。结果发现,涡流钻头与井壁间的密封是降压的关键,推荐上返喷嘴的倾角为150°—180°,推荐上返流量为32%以上,为涡流钻头的研发提供理论指导。

Experimental Investigation on Heat Transfer Characteristics of Water in Inclined Downward Tube of a Supercritical Pressure CFB Boiler

In this study, experiments have been performed for an investigation on heat transfer of water in an inclined downward tube with an inner diameter of 20 mm and an inclined angle of 45° from the horizon, with the range of pressure from 11.5 to 28 MPa, mass flux from 450 to 1550 kg/(m2 s), and heat flux from 50 to 585 k W/m2. Based on the experimental data, the temperature distribution in the tube wall was derived. The heat transfer characteristics of inclined downward flow were compared with that of vertical downward flow. The effects of heat flux on wall temperature were analyzed and the corresponding empirical correlations were presented. The results show that heat transfer characteristics of water in the inclined downward tube are not uniform along the circumference from the top surface to the bottom surface. An increase in heat flux exacerbates the non-uniformity. At subcritical pressures, both dry-out and departure from nucleate boiling(DNB) occur at the top surface of the inclined downward tube; inversely, only dry-out takes place on the bottom surface of the inclined downward tube and in the vertical downward tube. At near-critical pressures, DNB and dry-out occur in the comparing tubes with greater possibility. At supercritical pressures, heat transfer gets enhanced in the pseudo-critical enthalpy region; in the high enthalpy region, the top surface temperature of the inclined downward tube decreases obviously.

Leaf hydraulic traits of larch and ash trees in response to long-term nitrogen addition in northeastern China

Aims Atmospheric nitrogen(N)deposition influences tree hydraulic architecture and thus the growth and survival;but the responses of leaf hydraulic traits remain uncertain,and may vary with species or plant functional types.Methods We used the 16-year N addition experiment(10 g N m−2 year−1)on Fraxinus mandshurica(ash,broadleaf angiosperm)and Larix gmelinii(larch,conifer gymnosperm)plantations in northeastern China and examined the effect of N addition on their leaf hydraulics.We measured the leaf pressure–volume traits by the bench drying method and quantified the maximum leaf hydraulic conductance(K_(leaf_max))and resistance to embolism(P50leaf)by the timed rehydration method.Important Findings Larch had higher K_(leaf_max)and stronger drought tolerance(i.e.,lower relative water content at turgor loss point(RWC_(tlp))and modulus of elasticity(ε),and more negative P50leaf)than ash.N addition increased the leaf osmotic potential at turgor loss(πtlp)and full turgor(π0),and leaf capacitance(Cleaf_mass)for ash but not for larch,indicating that ash is more sensitive to N addition.N addition consistently increased K_(leaf_max)and P50leaf values for both species.πtlp andπ0 were positively while Cleaf_mass was negatively correlated with leaf density(LD)for ash.K_(leaf_max)was positively but P50leaf was negatively related with LD for larch.There were negative relationships between K_(leaf_max)and P50leaf for both species.Overall,our findings suggest that long-term N addition decreases the leaf drought tolerance for these two important tree species,which improve the understanding of the tree hydraulic performance under N deposition.