基于超声波实验研究压力及流体对致密岩石横波衰减特征的影响

我国致密油气储层勘探前景广阔,开采价值高,但其储层岩石具有低孔、低渗、强非均质性等特征,建立储层波响应与岩石物性参数之间的联系仍面临挑战,针对致密储层波响应规律的研究有待深入开展。孔隙流体性质及围压会影响岩石的剪切模量及横波衰减,本文对部分饱和的8块致密岩石在不同围压条件下开展了超声波实验观测,采用谱比法估算岩石的横波衰减。结果显示,横波衰减随围压上升而下降,且饱水岩石的横波衰减大于饱油,饱气状态衰减最弱。气、水部分饱和岩石的测量结果中,岩石样本的横波衰减在中间含水饱和度达到峰值,此外,横波衰减随孔隙度、渗透率上升均有增大的趋势。基于实验测量的岩石物性参数,结合Voigt-Reuss-Hill(VRH)平均、微分等效介质模型和喷射流模型构建了致密岩石衰减模型,分析了不同围压条件下含流体岩石的衰减特征,结果显示,该模型可合理描述横波衰减特征。在完全饱和与部分饱和条件下,模型预测的横波衰减显示出明显的压力及流体敏感性。以样本TS1-19为例,在完全饱和、变围压条件下,模型预测的横波衰减峰值在11.6~69.5范围内,衰减峰值随着围压增大而降低,且峰值频率有向高频端移动的趋势。在部分饱和、围压30MPa条件下,模型预测的横波衰减峰值在15.5~39.8范围内,衰减峰值随着含水饱和度增大而增大,且峰值频率向低频端移动。对于所有样本,以30MPa围压为例,所预测的横波衰减在5.6~38.6范围内,其中在饱和条件下,模型预测横波衰减随着孔隙度增大而增大,随着围压增大而减小;在气水部分饱和条件下,随着含水饱和度的增大,基于模型及Voigt和Reuss边界法预测的横波衰减整体呈增大的趋势,而实验观测到的横波衰减在中间饱和度达到极大值。

Acceptance of COVID-19 vaccine and its related determinants in Nigeria:An online survey

BACKGROUND Vaccine hesitancy is a major challenge in the fight against the coronavirus disease 2019(COVID-19)pandemic.Identifying the sociodemographic factors associated with vaccine acceptance among Nigerians is crucial for improving vaccine uptake.AIM To assess the acceptance rate of COVID-19 vaccine and its related determinants among Nigerians.METHODS An online cross-sectional survey(observational study)was conducted between February 2021 and May 2021,using a questionnaire hosted on SurveyMonkey.The invitation to take part in the poll was sent out to participants through social networking platforms.A logistic regression was used to determine which sociodemographic factors were associated with vaccine acceptance constructs.RESULTS A total of 1800 persons responded to the survey,a larger proportion of whom were males(53.9%)and within the age group of 21-30 years(29.4%)and earned an average income of less than$500 per month(43.3%).Only 0.56%of participants had a high perceived risk of COVID-19 infection,while only 1.11%had a perceived risk of dying from COVID-19.The perception rate of the COVID-19 vaccine among participants was 51.1%,while the acceptance rate was 63.9%.There was no significant association between the COVID-19 vaccine acceptance rate and related determinants assessed,particularly age(χ²=3.049,P=0.550),sex(χ²=0.102,P=0.749),average income(χ²=3.802,P=0.875),and religion(χ²=2.819,P=0.420).Participants with chronic conditions demonstrated a higher acceptance rate compared to the general population.CONCLUSION Despite the positive perception observed and substantial vaccine acceptance rate among the study participants,more public health interventions are still needed to enhance vaccine acceptability in Nigeria.

一种简化的计算频域有限差分自适应系数的方法

频域有限差分(finite difference frequency domain,FDFD)方法是地震波场模拟的常用方法,FDFD地震波场模拟的关键之一是构造能有效压制数值频散的FDFD系数。在已有的构造地震波场模拟FDFD系数的方法中,随一个网格内的波长个数变化的自适应FDFD系数可以最大程度地压制数值频散。目前计算自适应FDFD系数的方法涉及角度积分、共轭梯度优化、顺序初值选取、光滑正则化等问题,不仅较难实现而且计算效率较低。为了简化自适应FDFD系数的计算并提高相应计算效率,本文提出一种新的计算自适应FDFD系数的方法。所提方法首先将不同离散传播角度的平面波解代入FDFD格式,构造相应的最小二乘问题。由于该最小二乘问题较为病态,常规的基于正规方程组的求解方法难以得到光滑的自适应FDFD系数,本文提出通过QR矩阵分解求解相应超定线性方程组来求解该最小二乘问题。相比已有的基于角度积分、共轭梯度优化、顺序初值选取的计算自适应FDFD系数的方法,所提方法在可以得到光滑自适应FDFD系数的基础上,不仅计算过程更简洁,且计算效率明显提高。数值波场模拟结果表明,基于QR矩阵分解的自适应系数FDFD方法可以达到与基于角度积分、共轭梯度优化、顺序初值选取的自适应系数FDFD方法相同的精度,同时所需的计算时间更少。

非饱和岩石中的纵波频散与衰减:双重孔隙介质波传播方程

本文采用Rayleigh理论描述纵波激励下非饱和岩石中气泡的局域流体流动,从经典力学的哈密顿原理导出了双重孔隙介质中的波传播方程,即Biot-Rayleigh方程.方程的格式简洁,参数少,所有相关参数物理可测,因此,方程具有较好的物理可实现性.基于相同的岩石与前人理论对比,初步验证了本理论的有效性.对三个地区的砂岩储层进行了分析,结果显示:地震频段内纵波对储层是否含气非常敏感,但对含气饱和度指示性不佳,且随着孔隙度降低,纵波频散与衰减在中低频段更为显著;含甲烷与含二氧化碳的砂岩储层均呈第三类AVO响应特征,很难从叠前分析技术中鉴别;理论预测的纵波频散随饱和度与频率变化的趋势与特征,与多频段实验观测结果一致.

Rock physics modeling of heterogeneous carbonatereservoirs： porosity estimation and hydrocarbon detection

In heterogeneous natural gas reservoirs, gas is generally present as small patchlike pockets embedded in the water-saturated host matrix. This type of heterogeneity, also called "patchy saturation", causes significant seismic velocity dispersion and attenuation. To establish the relation between seismic response and type of fluids, we designed a rock physics model for carbonates. First, we performed CT scanning and analysis of the fluid distribution in the partially saturated rocks. Then, we predicted the quantitative relation between the wave response at different frequency ranges and the basic lithological properties and pore fluids. A rock physics template was constructed based on thin section analysis of pore structures and seismic inversion. This approach was applied to the limestone gas reservoirs of the right bank block of the Amu Darya River. Based on poststack wave impedance and prestack elastic parameter inversions, the seismic data were used to estimate rock porosity and gas saturation. The model results were in good agreement with the production regime of the wells.

致密砂岩衰减岩石物理图板分析:储层微裂隙预测

致密砂岩储层普遍具有孔隙度低、微裂隙发育的特点,岩石内部常含有强烈的结构非均质性.致密砂岩发育的微裂隙使储层具有良好的连通性,促成高饱和气的天然气成藏.针对川西某探区须家河组高含气饱和度致密砂岩,本文选取致密砂岩岩心样本,进行了不同围压下的超声波实验测量.考虑储层完全饱气情况下的粒间孔隙、微裂隙双重孔隙结构,采用Biot-Rayleigh双重孔隙方程,构建致密砂岩岩石物理模型,进而分析了裂隙含量对纵波频散和衰减的影响.基于地震波衰减,构建了致密砂岩多尺度岩石物理图板.采用谱比法和改进频移法估算致密砂岩样本及储层衰减,对超声和地震频带下的图板进行校正.将校正后的图板应用到研究工区,选取二维测线和三维区块,进行储层孔隙度和裂隙含量的定量预测.对比实际资料进行分析,结果显示,本文预测的孔隙度和裂隙含量与三口测井的孔隙度曲线和实际产气情况基本吻合,基于孔隙-裂隙衰减岩石物理模型有效地预测了优质储层的分布区域.

意义疗法的理论、方法与技术:基于存在积极心理学的视角

意义疗法是以存在积极心理学为理论基础,以构建个体生命意义为目的,实现生活正负两极性的动态平衡,从而解决其心理困扰获得心理治愈与成长的一种整合性心理咨询与治疗方法。起源于Frankl意义学说的意义疗法是通往人类美好生活的路径,它源于对苦难生活所隐含意义的本质认识。在理论上,意义疗法以意义定向看世界为中心,以意义管理理论和双系统模型为支架;在方法上,为保障意义获得,应遵循8个基本问题和12条原则,充分发挥意义源的作用,实现意义获得的双路径统一;在技术上,灵活采用趋向性(PURE)策略、回避性(ABCDE)策略、以及双视角双通道策略或其它策略的整合。意义疗法因包含了精神成分而超越了心理动力学和个体心理学等传统心理治疗方式。未来研究还需明确意义疗法整合了哪些流派的具体方法和技术,细化意义疗法主要的技术与策略的操作步骤,考察成熟幸福感量表在中国文化下的适用性,以及充分整合质性与量化研究方法检验意义疗法在中国的适用性。

有效应力变化对致密砂岩孔隙结构及弹性波响应的影响规律

致密砂岩气藏具有裂缝发育和有效应力高的特征,研究不同有效压力下孔、裂隙介质地震波传播特征,有利于地震解释与地下储层的识别.但是前人的研究较少考虑岩石内部微观孔隙结构特征与孔隙、裂隙间流体流动的关系.本文首先通过选取四川盆地典型致密砂岩岩样,在不同有效压力下对岩石样本进行超声波实验测量.然后基于实验测得的纵、横波速度进行裂隙参数反演,得到不同有效压力下致密砂岩样本的裂隙孔隙度.再将裂隙孔隙度和样本岩石物理参数代入双重孔隙介质模型,模拟得到不同有效压力下饱水致密砂岩样本纵横波速度频散和衰减的变化规律.结果表明模型预测的速度频散曲线与纵波速度实验测量结果能够较好的吻合.最后统计分析了致密砂岩裂隙参数,得到了致密砂岩储层裂隙参数随有效压力及孔隙度变化特征.依据实际岩石物理参数建立模型,其裂隙参数三维拟合结果能够较好描述致密砂岩裂隙结构与孔隙度、应力的关联,可为实际地震勘探中预测储层裂缝性质提供基础依据.

影像式线棒材在线表面检测系统

为应对市场对钢材表面质量要求越来越高的挑战,开发了完全不同于涡流探伤设备的线棒材用在线表面质量检测系统,利用光学摄像原理对线棒材表面实施无间断地高速连续拍摄,经专用软件处理后实时判别线棒材表面的缺陷,具有检测能力强、信息丰富等特点,使用效果良好。

龙马溪—五峰组富有机质页岩三维岩石物理模板分析及“甜点”预测

为识别四川盆地丁山区龙马溪—五峰组目的层富含页岩气的“甜点区”,本文对页岩的有机碳含量、脆性、孔隙度及微裂隙等核心指标进行分析研究.对页岩展开岩石物性特征和岩石物理分析,结果显示“甜点区”具有TOC含量高、高孔隙度、低密度、脆性高(石英含量高)的特点,此外储层的拉梅常数和密度的乘积λρ分布范围是18~30 GPa·g·cm^(-3),泊松比υ范围是0.18~0.22,剪切模量μ范围是13~18 GPa.根据储层的岩石物理特征,同时考虑孔隙度、裂隙纵横比和矿物组分对优质页岩敏感弹性参数的影响,采用等效嵌入体应力平均(EIAS)理论模型构建适合页岩气储层的三维岩石物理模板,进而预测储层的孔隙度、裂隙纵横比和石英矿物含量.基于测井数据,对构建的三维岩石物理模板进行校正,将校正后的模板应用到研究工区,选取过三口井的二维测线和三维区块,进行孔隙度、裂隙纵横比和石英矿物含量的定量预测.对比实际资料分析得出的优质页岩储层孔隙度预测范围与测井结果吻合较好,过三口井的目的层产气情况与预测结果一致性良好,目的层页岩具有高孔隙度、低裂隙纵横比和高石英含量的特征,可有效地指示优质页岩储层分布.

Dispersion and attenuation of compressional waves in tight oil reservoirs: Experiments and simulations

We performed ultrasonic experiments in specimens from a tight oil reservoir. The P-wave attenuation of fl uid-saturated specimens was estimated by the spectral ratio method. The results suggest that at ultrasonic frequencies, most specimens have stronger attenuation under gas-saturated conditions than at water- or oil-saturated conditions. The P-wave attenuation positively correlates with permeability. Scanning electron microscopy observations and the triple-porosity structure model were used to simulate the wave propagation. The P-wave velocity dispersion and attenuation are discussed on the basis of the Biot, Biot– Rayleigh double-porosity medium, and the triple-porosity structure models. The results suggest that the Biot and Biot–Rayleigh models cannot explain the attenuation, whereas the triple-porosity structure model is in agreement with the experimental data. Furthermore, we infer that microcracks are common in a porosity of 5%–10%, and the size of microcracks increases in samples with higher porosity. However, the volume ratios of microcracks and clay inclusions remain constant regardless of porosity variations. The size of microcracks is signifi cantly larger than the clay inclusions, and the bulk modulus of microcracks is lower than the bulk modulus of clays.

Modelling of microbial enhanced oil recovery application using anaerobic gas-producing bacteria

Microbial enhanced oil recovery （MEOR） methods apply injection of bacteria to depleted oil reservoirs to produce oil, which had remained unrecovered after the conventional methods of production. The ability ofthermophilic anaerobic bacteria to produce gas as the main mechanism in potential MEOR in high salinities of 70-100 g/L was investigated in this study. Maximum gas production of up to 350 mL per 700 mL of salty solution was produced at a salinity of 90 g/L stably during 2-4 days of experiment. The experimental results were upscaled to the Snorre Oilfield, Norway, and simulated using ECLIPSE software for 27 months. The best scenarios showed that the increase in oil recovery on average was at 21% and 17.8% respectively. This study demonstrated that anaerobic bacteria used in biogas plants could be an attractive candidate for MEOR implementation due to their ability to withstand high temperature and salinity, and produce gas in large volumes.

A patchy-saturated rock physics model for tight sandstone based on microscopic pore structures

The wave-induced local fluid flow mechanism is relevant to the complex heterogeneity of pore structures in rocks.The analysis of the local fluid flow mechanism is useful for accurately describing the wave propagation characteristics in reservoir rocks.In the exploration and production of hydrocarbon reservoirs,the real stratum may be partially saturated with a multi-phase fluid mixture in general.Therefore,it is of great significance to investigate the wave velocity dispersion and attenuation features in relation to pore structures and fluids.In this work,the characteristics of fabric microstructures are obtained on the basis of pressure dependency of dry rock moduli using the effective medium theory.A novel anelasticity theoretical model for the wave propagation in a partially-saturated medium is presented by combining the extended Gurevich squirt-flow model and White patchysaturation theory.Numerical simulations are used to analyze wave propagation characteristics that depend on water saturation,external patchy diameter,and viscosity.We consider a tight sandstone from the Qingyang area of the Ordos Basin in west China and perform ultrasonic measurements under partial saturation states and different confining pressures,where the basic properties of the rock are obtained at the full gas saturation.The comparison of experimental data and theoretical modeling results shows a fairly good agreement,indicating that the new theory is effective.

Possible Multiple Sources of the Strong 1117 Po Plain Earthquake, Inferred from the Plio-Quaternary Evolution of the Northern Adriatic Area

The strongest documented seismic disaster ever occurred in the Po Plain area (January 3, 1117, M = 6.5) involved significant damage over a large zone. The genetic mechanism of such an event, most probably caused by more than one earthquake, is still an object of debate. Above all, the sources so far proposed cannot account for significant features of the observed macroseismic field. In this work, we suggest that the damage in the Verona zone was caused by the activation of a fault in the Lessini tectonic district, while damage in the central Po Plain may be related to a thrust fault located beneath the Giudicarie belt. The effects felt in northern Tuscany might derive from the seismic activation of the presumed SW-ward buried prolongation of the Giudicarie fault. The presence of such transpressional lithospheric discontinuity in the Adriatic domain since the upper Miocene and its reactivation (Pliocene-Pleistocene) as a thrust zone is mainly suggested by an accurate analysis of the observed deformation pattern in the central Mediterranean region. The proposed Giudicarie source may also help to explain the damage observed in the central Po Plain on December 25, 1222, which is not compatible with the seismic sources so far proposed.

Targeted Sub-Attomole Cancer Biomarker Detection Based on Phase Singularity 2D Nanomaterial-Enhanced Plasmonic Biosensor

Detection of small cancer biomarkers with low molecular weight and a low concentration range has always been challenging yet urgent in many clinical applications such as diagnosing early-stage cancer,monitoring treatment and detecting relapse.Here,a highly enhanced plasmonic biosensor that can overcome this challenge is developed using atomically thin two-dimensional phase change nanomaterial.By precisely engineering the configuration with atomically thin materials,the phase singularity has been successfully achieved with a significantly enhanced lateral position shift effect.Based on our knowledge,it is the first experimental demonstration of a lateral position signal change>340μm at a sensing interface from all optical techniques.With this enhanced plasmonic effect,the detection limit has been experimentally demonstrated to be 10^(-15) mol L^(−1) for TNF-α cancer marker,which has been found in various human diseases including inflammatory diseases and different kinds of cancer.The as-reported novel integration of atomically thin Ge_(2)Sb_(2)Te_(5) with plasmonic substrate, which results in a phase singularity and thus a giant lateral position shift, enables the detection of cancer markers with low molecular weight at femtomolar level. These results will definitely hold promising potential in biomedical application and clinical diagnostics.

Aerosol Microphysical and Radiative Effects on Continental Cloud Ensembles

Aerosol-cloud-radiation interactions represent one of the largest uncertainties in the current climate assessment. Much of the complexity arises from the non-monotonic responses of clouds, precipitation and radiative fluxes to aerosol perturbations under various meteorological conditions. In this study, an aerosol-aware WRF model is used to investigate the microphysical and radiative effects of aerosols in three weather systems during the March 2000 Cloud Intensive Observational Period campaign at the US Southern Great Plains. Three simulated cloud ensembles include a low-pressure deep convective cloud system, a collection of less-precipitating stratus and shallow cumulus, and a cold frontal passage. The WRF simulations are evaluated by several ground-based measurements. The microphysical properties of cloud hydrometeors, such as their mass and number concentrations, generally show monotonic trends as a function of cloud condensation nuclei concentrations. Aerosol radiative effects do not influence the trends of cloud microphysics, except for the stratus and shallow cumulus cases where aerosol semi-direct effects are identified. The precipitation changes by aerosols vary with the cloud types and their evolving stages, with a prominent aerosol invigoration effect and associated enhanced precipitation from the convective sources. The simulated aerosol direct effect suppresses precipitation in all three cases but does not overturn the aerosol indirect effect. Cloud fraction exhibits much smaller sensitivity （typically less than 2%） to aerosol perturbations, and the responses vary with aerosol concentrations and cloud regimes. The surface shortwave radiation shows a monotonic decrease by increasing aerosols, while the magnitude of the decrease depends on the cloud type.

Experiments on excitation and data processing of low-frequency vibroseis in permafrost area of the tibetan plateau

Few seismic exploration work was carried out in Tibetan Plateau due to the characteristics of alpine hypoxia and harsh environmental protection needs.Complex near surface geological conditions,especially the signal shielding and static correction of permafrost make the quality of seismic data is not ideal,the signal to noise ratio(SNR)is low,and deep target horizon imaging is difficult.These data cannot provide high quality information for oil and gas geological survey and structural sedimentary research in the area.To solve the issue of seismic exploration in Tibetan Plateau,this test used low frequency vibroseis wide-line and high-density acquisition scheme.In view of the actual situation of the study area,the terrain,the source and the diff erent observation system were simulated,and the processing technique was adopted to improve the quality of seismic data.Low-frequency components with a minimum of 1.5Hz of vibroseis ensure the deep geological target imaging quality in the area,the seismic profi le wave group is clear,and the SNR is relatively high,which can meet the needs of oil and gas exploration.Seismic data can provide the support for the development of oil and gas survey in the Tibet plateau.

Water Chemistry and Hydrometeorology in a Glacierized Catchment in the Polar Urals,Russia

This study aims to determine the relationships between local meteorological conditions,proglacial river discharge and biogeochemical processes operating in a periglacial basin located in the Polar Ural mountain range, Russia. Fieldwork was conducted in the catchment of Obruchev Glacier(13 km2) during the summer peak flow period in 2008. River discharge was dominated by snowmelt and changed from 3300 l s-1 to less than 1000 l s-1. The mean daily air temperatures of stations situated in the mountain tundra and near Obruchev Glacier from July 11 th to August 1st 2008 were 14.4°C and 10.3°C, respectively. The glacial river had low total dissolved solids varying from 4.5 to 9 mg l-1 and coefficients of correlation between Na+ and Cl-, K+ and Cl-, as well as NH4+ and Cl- were 0.94, 0.90 and 0.84, respectively. Rainfall events affected the snowmelt initiation and provided an essential part of the discharge during the intense snowmelt period, which occurred from July 11 th to July 18 th 2008. Data showed that Na+ and K+ in the surface water derived from snowmelt rather than chemical weathering of silicates. Also, it was obtained that NO3- derived from the melting snowpack, whereas ammonification occurring under the snowpacks was the primary source for NH4+.

Impact Analysis of EV Charging with Mixed Control Strategy

EVs （electric vehicles） have been widely accepted as a promising solution for reducing oil consumption, air pollution and greenhouse gas emission. The number of EVs is growing very fast over the years. However, the high adoption of EVs will impose a burden on the power system, especially for neighborhood level network. In this paper, we propose a mixed control framework for EV charging scheduling to mitigate its impact on the power network. A metric for modeling customer＇s satisfaction is also proposed to compare the user satisfaction for different algorithms. The impacts of the proposed algorithms on EV charging cost, EV penetration and peak power reduction are evaluated with real data for a neighborhood level network. The simulation results demonstrate the effectiveness of the proposed algorithms.

Results About Parabolic-Like Mappings

In this paper we present the most important definitions and results of the theory of parabolic-like mappings, and we will give an example. The proofs of the results can be found in [2,4] and [3].