多分支废弃油井层温衰减规律及注入参数对注采性能的影响

利用废弃油井开发地热资源是降低地热开发成本、促进商业推广的有效措施,其中层温衰减规律对地热系统取热效果具有重要影响。为此,以废弃油井储层为研究对象,结合泰森多边形理论对储层裂缝进行了划分,建立了三维油水两相热流耦合数值模型,分析了不同储层条件与布井结构下的层温衰减规律,探究了注入参数等因素对地热注采性能的影响。研究结果表明:(1)低渗透储层抽采30年生产温度最大差值可达22.08 K,高渗透储层(1.0×10^(-13) m^(2))温度过度衰减,长年限采热效率低;(2)储层含油率与生产温度和发电功率呈正相关关系,生产30年后差值最大可达11.57 K与0.12 MW;(3)分支井沿垂直方向会形成低温波谷,层温衰减高于储层其余部分,数量增加对注采影响小;(4)注入速率与发电功率、生产温度分别呈正、负相关关系,但注入速率超过89 kg/s时不利于长年限开采。结论认为:(1)储层取热性能对初始渗透率最为敏感,注入速率与储层含油率次之,优先开发低渗透储层有利于长年限采热;(2)应利用油田地热降低稠油黏度,形成地热辅助采油模式,以实现经济效应最大化;(3)选取6支分支井与89 kg/s的注入速率可得到可观取热效果和较好的经济效益。

地震属性分析技术在小断层识别中的应用

断层解释是开展储层研究工作的重要环节之一,但是受构造背景及地震资料质量的影响,在常规地震剖面上直接解释断距小于λ/4的断层系统比较困难,使得地下储层的情况并不为解释人员所了解,因此,为了有效识别研究区的小断层系统,为断层的解释工作做出指导,本文在具体分析研究区断层识别能力的基础上,利用体属性、沿层构造属性及目的层吸收衰减属性对研究区A的断层系统进行了有效预测,并取得了较好的研究效果。

交流电流衰减法(PCM)在埋地钢质管道防腐检测中的应用

随着城市的建设和发展,埋地管线的种类和数量迅速增多,相应地也出现了涉及地下管线安全运行的各种腐蚀问题。因此开展埋地管道防腐层的非开挖检测非常必要。本文简要介绍了埋地管道非开挖检测常用的方法,然后具体围绕交流电流衰减法(PCM)的工作原理、检测前的准备展开讨论,并且以北京某地区的天然气埋地管道非开挖检测工作为例,介绍一则应用交流电流衰减法(PCM)进行埋地管道防腐层检测的工程实例,根据检测数据和管中电流随测量距离的变化曲线进行分析,确定了破损点的位置,并进行了开挖验证,将评价结果和开挖检测结果做了比较。之后指出了应用该法的局限性并提出相关建议。最后对未来的检测方法进行了展望。

基于左归一化图卷积网络的推荐模型

图神经网络(GNN)应用于推荐领域之后取得了巨大的成功,通过堆叠多层图神经网络层聚合邻居的信息,使节点可以获取更加广阔的协同信息,可以有效解决推荐系统的数据稀疏问题。目前大部分将图卷积网络应用于推荐的工作都遵循对称归一化的设计,对称归一化加强了冷门商品对于用户嵌入的构建,但是会分配给流行度高的商品很低的权重,导致热门商品对于用户节点嵌入影响微乎其微。针对这一问题,提出一种左归一化图卷积网络模型,模型使用了更加灵活的归一化处理方式,加入衰减因子,并且设计了两种针对各图卷积层的衰减机制,相互配合,大幅提高了推荐的效果。在数据集Alibaba、Amazon-book、Yelp2018上与基准模型LightGCN、NGCF(Neural Graph Collaborative Filtering)、PinSage、Bprmf进行了对比实验,结果表明,与LightGCN相比,所提模型的召回率(recall)分别提高9.9%、20.2%、7.5%,归一化折损累计增益(NDCG)分别提高12.7%、24.1%、8.3%,验证了所提模型的有效性。

Wigner-Ville distribution and its application in seismic attenuation estimation

The attenuation of seismic signals is often characterized in the frequency domain using statistical measures of the power spectrum. However, the conventional Fourier transform-based power spectrum estimation methods suffer from time-frequency resolution problems. Wigner-Ville distribution, which is a member of Cohen class time-frequency distributions, possesses many appealing properties, such as time-frequency marginal distribution, time-frequency localization, etc. Therefore, Wigner-Ville distribution offers a new way for estimating the attenuation of seismic signals. This paper initially gives a brief introduction to Wigner-Ville distribution and the smoothed Wigner-Ville distribution that is effective in reducing the cross-term effect, and then presents a method for seismic attenuation estimation based on the instantaneous energy spectrum of the Wigner-Ville distribution. A real data example from central Tarim Basin in western China is presented to illustrate the effectiveness of the proposed method. The results show that the Wigner-Ville distribution-based seismic attenuation estimation method can effectively detect the difference between reef, shoal and lagoon facies by their attenuation properties, indicating that the estimated seismic attenuation can be used for reef and shoal carbonate reservoir characterization.

Analysis of GPS ionospheric scintillation signal amplitude fading characteristics at low latitude

The received satellite signal amplitude is attenuated greatly due to the strong ionospheric scintillation for lowlatitude regions, which causes the GPS tracking loop＇s loss of lock, the positioning errors to increase, and navigation to be interrupted. To solve the above problems, a novel signal processing algorithm is proposed based on the GPS L1 software receiver during strong ionospheric scintillation using the multi-channel intermediate frequency（IF） data sampling system. Tens of thousands of fading events are obtained based on the signal intensity measurement. The amplitude fading characteristics in the lowlatitude region are analyzed,including fading duration, time separation between fades and the numbers of signal intensity fading events. The fading thresholds are set to be 15 and 10 dB, respectively. The main fading time is very short in- 15 dB fading threshold, which generally is less than 20 ms. The main time separation between fades is less than 2 s in a single one-hour period from the time 23： 00 to 24： 00. Therefore, it has the characteristic of a short reacquisition time for the receiver designed to reduce the probability of simultaneous loss of lock for some satellites.Subsequently, the acquisition, tracking and PVT（position,velocity and time） calculations are completed by the customdesigned software receiver. The results show that the impact analysis of ionospheric scintillation on GPS amplitude attenuation in the lowlatitude region is helpful for designing the advanced tracking algorithm and to improve the robustness and accuracy of the GPS receiver.

A study of damping factors in perfectly matched layers for the numerical simulation of seismic waves

When simulating seismic wave propagation in free space, it is essential to introduce absorbing boundary conditions to eliminate reflections from artificially trtmcated boundaries. In this paper, a damping factor referred to as the Gaussian dmping factor is proposed. The Gaussian damping factor is based on the idea of perfectly matched layers （PMLs）. This work presents a detailed analysis of the theoretical foundations and advantages of the Gaussian damping factor. Additionally, numerical experiments for the simulation of seismic waves are presented based on two numerical models： a homogeneous model and a multi-layer model. The results show that the proposed factor works better. The Gaussian damping factor achieves a higher Signal-to-Noise Ratio （SNR） than previously used factors when using same number of PMLs, and requires less PMLs than other methods to achieve an identical SNR.

Deterioration of Water Ballast Tank Coating Systems by Active Substances in Ballast Water Management Systems

Sodium hypochlorite and ozone are the principal active substances and usually employed in ballast water management systems. In the present study, the authors focus on the effect of these active substances to the maaix polymer of coating. In order to obtain such information, the authors investigated the penetration of active substances to the polymer from cross section of specimens introduced by SAICAS （surface and interracial cutting analysis system）, followed by FT-IR-ATR （Fourier transform infrared and attenuated total reflectance） spectroscopy analysis from Z direction of cross section. The corrosion test of coating panels by these active substances （control as artificial seawater） has been conducted for 120 days. The results show that the depth profile of each active substance is around few dozens of micrometers from coating surface. The criteria of corrosion test cannot be determined by these results due to lacking in actual corrosion data immersed for 15 years under active substances. However, the authors evaluated the effect on ballast tank coating systems by active substances using analytical methods of SAICAS and FT-IR-ATR spectroscopy.

Ultrasonic characterization of modified Cr_2O_3 coatings by reflection coefficient spectroscopy

Pores,microcracks and density of plasma sprayed Cr2O3 coatings before and after high-intensity pulsed ion beam(HIPIB) irradiation were investigated using the ultrasonic reflection coefficient spectroscopy(URCS).The URCS was analyzed based on an acoustic transmission model for the multi-layered structure.The longitudinal velocity in the coatings was calculated from the experimental URCS,and the attenuation coefficient expression was deduced by comparing the experimental and numerical fitting amplitude spectral lines.The longitudinal velocity of as-sprayed Cr2O3 coating is 2 002 m/s,and increases to 2 099 and 2 148 m/s after being irradiated by HIPIB with 1 and 5 shots.Correspondingly,the factor A changes from 0.046 to 0.026 and 0.020 and n from 1.702 to 1.658 and 1.649 in the attenuation coefficient expression of α=Af n.It is observed that the surface morphology of Cr2O3 coatings changes from rough and porous to smooth and uniform with the increase of shot number,which accords with the ultrasonic analyses reasonably.The URCS seems to provide a convenient and nondestructive method to characterize surface modification of the plasma sprayed coatings.

Research on attenuation characteristic of sound wave in coal or rock body

In order to using power sound wave increase permeability of coal, rules of attenuation of sound wave in coal should be studied. In this paper, characteristic and mechanism of attenuation of sound wave in coal was researched according to acoustic theory and attenuation coefficients was estimated by acoustic parameter of coal. The research results show that the main attenuation mechanism of sound wave in coal is absorption attenuation and scattering attenuation. The absorption attenuation includes viscous absorption, thermal conduction absorption and relaxation absorption. Attenuation coefficient of sound wave in gaseous coal is 38.5 Np/m. Researches on attenuation characteristic of sound wave will provide the theoretical basis for power sound wave improving permeability of coal and accelerating desorption of coal bed gas.

Experimental study on sliding shaft lining mechanical mechanisms under ground subsidence conditions

Aimed at more than 60 shaft linings damaged in Huaibei, Datun, Xuzhou and Yanzhou mine areas, this paper presents a new type of sliding shaft lining with asphalt blocks sliding layer. By model test, it is obtained that the deformation characteristics and the mechanical mechanisms of the sliding shaft lining under the condition of ground subsidence. The research results provide a testing basis for the sliding shaft lining design. By now, this kind of sliding shaft lining had been applied in 9 shafts in China and Bangladesh.

Enhancement of heat radiative characteristics of coatings by ultra-attenuation

The absorption process of radiative heat in its transmission medium and the effect of ultra-attenuation on the radiative characteristics are analyzed in detail. A method of ultra-attenuation to enhance the radiative characteristics of the medium is proposed. It is proved that decreasing the particle size of coatings can increase the transmission depth of radiative heat and get higher emissivity and absorptivity both theoretically and practically. Ultra-attenuation and nanocrystallization will bring a brilliant prospect to the development of radiative coatings.

Calculation method of prestack FAGVO and its applications

Frequency attenuation occurs when seismic waves propagate through the porous reservoirs containing hydrocarbons. Current researches on the seismic frequency attenuation mainly focus on the post-stack domain instead of the prestack domain. Here we propose the frequency attenuation gradient vs. offset （FAGVO） based on the amplitude variation with offset and frequency attenuation integral equations. We derive the FAGVO equation that equals to zero in a full-elastic medium and is negative in a viscoelastic medium. FAGVO is affected by the viscosity of the medium, the coefficients of reflection, the frequency variation, and high-frequency attenuation. FAGVO uses the differences of partially stacked data to decrease the interference caused by subsurface strata affecting the frequency attenuation, highlights the frequency attenuation gradient anomalies in hydrocarbon-bearing reservoir pores, and finally realizes the hydrocarbon fluid identification. The method was verified using a two-dimensional wave equation forward model and was found to be cost effective. Furthermore, the method does not require well information, which can be applied in the stage of seismic exploration, especially, in the exploration of a none-well project.

GIS-based Evaluation on the Fault Motion-Induced Coseismic Landslides

Earthquake-induced potential landslides are commonly estimated using landslide susceptibility maps. Nevertheless, the fault location is not identified and the ground motion caused by it is unavailable in the map. Thus, potential coseismic landslides for a specific fault motion-induced earthquake could not be predicted using the map. It is meaningful to incorporate the fault location and ground motion characteristics into the landslide predication model. A new method for a specific fault motion-induced coseismic landslide prediction model using GIS （Geographic Information System） is proposed herein. Location of mountain ridges, slope gradients over 45~, PVGA （Peak Vertical Ground Accelerations） exceeded o.15 g, and PHGA （Peak Horizontal Ground Accelerations） exceeded o.25 g of slope units were representing locations that initiated landslides during the 1999 Chi-Chi earthquake in Taiwan. These coseismic landslide characteristics were used to identify areas where landslides occurred during Meishan fault motion-induced strong ground motions in Chiayi County in Taiwan. The strong ground motion （over 8 Gal in the database, 1 Gal = 0.0l m/s2, and 1 g = 981 GaD characteristics were evaluated by the fault length, site distance to the fault, and topography, and their attenuation relations are presented in GIS. The results of the analysis show that coseismic landslide areas could be identified promptly using GIS. The earthquake intensity and focus depthhave visible effects on ground motion. The shallower the focus depth, the larger the magnitude increase of the landslides. The GIS-based landslide predication method is valuable combining the geomorphic characteristics and ground motion attenuation relationships for a potential region landslide hazard assessment and in disaster mitigation planning.

Peripheral bronchogenic carcinoma: Enhancement pattern evaluation on PACS and CT workstations

Objective: The aim of the study was to determine the efficiency and effectiveness of picture archiving and communication system(PACS) workstation in detecting enhancement pattern of peripheral bronchogenic carcinoma. Methods: The 62 patients with peripheral bronchogenic carcinoma underwent two-phase contrast material-enhanced multislices computed tomography(MSCT) of the chest in a single-breath-hold technique. Two spiral CT scans were obtained at 25 s and 90 s respectively after nonionic contrast material was administrated via the antecubital vein at a rate of 4 m L/s by using an autoinjector. Precontrast and postcontrast attenuation on every scan were measured on PACS and CT workstations respectively and peak height was calculated. Enhancement pattern was evaluated on the image obtained at 90 s after injection of contrast medium on PACS and CT workstations respectively. Results: No statistically significant difference in precontrast attenuation, postcontrast attenuation at 25 s and 90 s was found between these measured on a PACS workstation [(40.21 ± 7.03) HU;(55.53 ± 11.09) HU;(75.95 ± 13.45) HU] and those [(39.01 ± 8.95) HU;(56.01 ± 10.91) HU;(76.03 ± 11.95) HU] on a CT workstation(t = 1.140, P = 0.256 > 0.05; t = 1.580, P = 0.149 > 0.05; t = 1.505, P = 0.150﹥0.05). The peak height that calculated on a PACS workstation was 35.74 HU(20 HU). There was not statistically significant difference in peak height between that calculated on a PACS workstation and that on a CT workstation [(37.02 ± 12.05) HU; t = 2.001, P = 0.099 > 0.05]. The tumors showed same enhancement pattern on PACS workstation and CT workstation. Of the 62 cases, 38 showed homogeneous enhancement, 17 showed heterogeneous enhancement, five showed peripheral enhancement, two showed central enhancement, at 90 s. The enhancement pattern revealed on PACS workstation was consistent with feature of peripheral bronchogenic carcinoma. Conclusion: The efficiency and effectiveness of PACS workstation is as same as those of CT workstation in detecting enhancement pattern of peripheral bronchogenic carcinoma.

Novel Technique of Radar Interferometry in Dynamic Control of Tall Slender Structures

Structures of slender shape, like guyed masts, chimneys or TV towers, are exposed to the excitation of dynamic movements. The most common cause of vibration is the wind that reduces generation of vortices. Another important reason is a sudden strike from seismic or para-seismic forces. Structure exposed to wind impact is subjected to harmonically various force, perpendicular to the air stream, which is an effect of vortices, shedding on alternate sides of slructure. Because of the possibility of vibration the damping of a structure has to be designed. Measuring of decay in the oscillation allows to find the logarithmic decrement of the real structure and compare it with the designed value. Apart from damping, the proper designing of tall slender structures has to preserve the significant difference between vortex shedding frequencies and the natural frequencies of the structure shape modes. In the case of guyed masts it is important to analyse the response of a real structure to the exceptional dynamic load, such as a sudden break of guy or fall off a load from a structure, e.g., icing or antennas. The dynamic analysis of a real slructure requires the accurate values describing the dynamic behavior of tall structures （e.g., amplitudes）. The accuracy of 0.1 mm is provided by ground-based interferometric radar. This device is a part of the IBIS-S （image by interferometric survey） system, which calculates the displacement values on the basis of the difference between phases of waves received in consecutive samples. Typically, the measurements of tall structures are performed with several sensors （strain gauges, accelerometers）. Instead, the IBIS-S system allows the quasi-continuous （not limited to points） observation of the entire structure without installation of any sensors or reflectors. The real resolution （along the structure）, which means the minimum distance between two observed points, amounts up to about 0.7 m,

球罐γ射线现场照射的安全防护距离

本文通过一个球罐现场γ射线检测实例,发现安全防护距离理论计算值与实际测量值存在较大误差。经过分析,发现标准中的理论计算公式是在真空的条件下得出的,没有考虑到空气的衰减作用,导致误差较大。如果考虑了空气的作用,标准中的理论计算公式可作修改,能减少现场安全防护距离,并确保安全防护。

井间定向震源正演模拟与特性分析

为减少管波对采集数据的影响,井间地震采用了定向震源,其能量辐射特性影响接收波场的能量分布与后续成像效果.研究定向震源的正演模拟并分析能量辐射特性,为井间地震成像过程中能量补偿提供基础数据.采用圆形震源阵列法,在近源区内按照质点与震源点连线的方向设置振动函数强度,水平方向能量最强,垂直方向能量最弱,模拟的辐射能量具有随方向改变的特点.实际井间地震能量方向性非常强,因而同时采用吸收衰减层法进一步减弱纵向的地震波能量.吸收衰减层法在震源周围设置具有衰减因子的海绵层,通过不同方向设定不同的衰减因子来控制震源的方向特性.衰减因子采用了渐变函数,保证海绵层边界不产生人为反射干扰.将圆形震源阵列法与吸收衰减层法联合进行双层介质模型和实际速度场模拟,得到的炮记录方向性更加明显.两种方法的有机结合,能够更好地模拟井间定向震源.在圆形震源阵列法可行性验证基础上,分析了阵列半径对接收波场能量的影响,初步确定了模拟定向震源的最佳阵列半径.通过分析方向性参数和井间距对接收波场能量分布的影响,获得了定向震源激发下接收波场的能量分布,为在井间地震偏移成像中进行能量补偿建立了基础.

A short comment on the effect of a shear layer on nonlinear water waves

In this paper we study nonlinear periodic deep water waves propagating on a background shear current,which decays exponentially with depth.We extend the study of Cheng,Cang and Liao(2009) by introducing a second parameter which measures the depth of the shear current.A high-order convergent analytical series solution is obtained by the homotopy analysis method(HAM).A detailed analysis of the impact of the depth parameter is given.We find that increasing this parameter so that the shear current is thinner reduces the wave phase speed,smoothes the wave crest,sharpens the trough,and enlarges the maximum wave height for the case of propagating waves on an opposing current;while it produces the opposite effect on an aiding current.

Super-aligned films of sub-1 nm Bi_(2)O_(3)-polyoxometalate nanowires as interlayers in lithiumsulfur batteries

Sub-1 nm nanowires(SNWs) can not only be processed like polymers due to their polymer-analogue properties but also show multifunctions owing to their well-manipulated compositions and structures. Rationally designed and engineered multicomponent heterostructure SNWs can further enhance their multifunction performance while it is very challenging to achieve such SNWs at sub-nanoscale.Herein, we synthesized Bi_(2)O_(3)-polyoxometalate heterostructure SNWs(PMB SNWs), and fabricated super-aligned PMB SNWs films(S-PMB SNWs films), which can serve as interlayers to efficiently suppress lithium polysulfide(LPS)shuttling, intrinsically promote the redox kinetics of the LPS conversion and substantially protect the Li anode. The lithium-sulfur(Li-S) battery with the S-PMB SNWs film as the interlayer showcases an ultralow capacity decay rate with 0.013% per cycle over 850 cycles. This study demonstrates the potential of heterostructure SNWs to improve the performance of Li-S batteries.