随钻脉冲中子-伽马密度测井响应数值模拟

随钻过程中采用D-T可控中子源和2个NaI晶体探测器系统,记录两个探测器的非弹性散射和俘获伽马射线,采用俘获伽马计数比值进行含氢指数校正后,建立非弹性散射伽马计数比和地层密度的响应关系,从而实现脉冲中子-伽马密度测井.利用蒙特卡罗方法模拟地层条件下非弹性散射和俘获伽马分布,得到非弹伽马计数与地层密度和含氢指数都有关,但近、远探测器俘获伽马计数比反映含氢指数灵敏度高,利用其对含氢指数校正后就可以得到非弹伽马计数与地层密度的关系;通过二元回归方法得出地层密度校正后的响应公式,校正后视密度和真密度值相差很小.研究结果表明,在随钻过程中利用脉冲中子伽马测井方法可以确定地层密度.      

Macroscale and mesoscale analysis of concrete as a multiphase material for biological shields against nuclear radiation

The overall thermo‐hygro‐mechanical behavior of concrete is to be investigated, because its bearing capacity is required together with its shielding properties, specifically when concrete structures are exposed to high‐energy neutron fluxes, which represent the next generation facilities designed for the production of high energy radioactive ion beams in physics research. Irradiation in the form of either fast and thermal neutrons, primary gamma rays or gamma rays produced as a result of neutron capture, are learnt to affect concrete as well as neutron fluences of the order of 10¹⁹ n/cm² and gamma radiation doses of 10¹⁰ rad seem to become critical for concrete strength. The collection of data on concrete samples, variously exposed to neutron radiation, has allowed for defining a law for radiation damage within the FEM research code NEWCON3D, assessing the 3D coupled thermo‐hygro‐mechanical behavior of concrete, modeled as a multiphase porous medium, both at the macroscale and the mesoscale level. The required damage law is thought to be a function of the neutron flux impinging the concrete shielding wall, and a good estimate of this quantity has been provided by means of a Monte Carlo code developed by CERN and the National Institute of Nuclear Physics of Milan, Italy; this code handles radiation transport calculations and represents at this day one of the most reliable procedures for dealing with the interaction of radiation and matter. The suggested procedure for the radiation damage evaluation has allowed for discussing on differences between mesolevel and macrolevel approaches. Stochastic contour maps of the expected radiation field, properly interfaced with the numerical FE code, have allowed for obtaining a more precise evaluation of the radiation damage front as well as its evolution in time. Copyright © 2013 John Wiley & Sons, Ltd.     

水灰炭地层各孔隙度中子随能量时间分布MonteCarlo模拟

作者在MCNP的基础上，开发了中子测井，中子通量随能量、时间分布蒙特卡罗（MC）模拟软件包，对裸眼井、井眼里无下井仪器、淡水饱和灰岩地层、井眼注淡水，用该软件计算了井轴和井壁一确定点,各孔隙度中子量通量，时间分布。即孔隙度对中子通量随量、时间分布和热中子、超热中子时间谱的影响。     

Gamma and resistivity logs for characterization of Gondwana coal seams at the Northwestern part of Bangladesh

Different parameters obtained through geophysical borehole logging using self potential, resistivity, gamma–gamma, neutron, natural gamma, and acoustic tools, help in the identification of strata and estimation of the physical, electrical, and acoustical properties of the subsurface lithology. In the coal mining industry, currently, the main application for the logs is to determine coal seam depth, thickness together with coal seam quality, qualitatively. Gamma and resistivity logging in seven boreholes at the Phulbari Coal Basin show high resistivity value and low gamma count rate data in coal seams than the interbeds. An attempt has been made to identify and characterize Gondwana coal seams to a limited extent of seam depth, thickness, and quality in seven boreholes together with draw relationship between resistivity, gamma count rate, and ash content of coal at the Phulbari Coal Basin of Bangladesh.     

Vertical electrical sounding to delineate the potential aquifer zones for drinking water in Niamey city,Niger, Africa

Niger is a landlocked African country and the only source of surface water is the Niger River which flows in the western part of Niger and only few villages near to the river gets benefited from it, leaving most of the areas dependent on groundwater solely. The groundwater resources in Niger are mainly used for drinking, livestock and domestic needs. It can be observed that the water exploitation is minimal there due to several factors like undeveloped areas, less population, limited wells, rain-fed irrigation, etc. The delineation of potential aquifer zones is an important aspect for groundwater prospecting. Hence, the direct current (DC) resistivity soundings method also known as vertical electrical sounding (VES) is one of the most applied geophysical techniques for groundwater prospecting that was used in the capital city, Niamey of Niger. Twelve VES surveys, each of AB spacing 400 m were carried out in lateritic and granitic rock formations with a view to study the layer response and to delineate the potential zones. Potential aquifer zones were at shallow depth ranging from 10 to 25 m for the drilled borehole depth of 80–85 m in every village. Analysis of the result showed a good correlation between the acquired data and the lithologs.     

Some features of the streamer belt in the solar corona and at the Earth’s orbit

The rays of enhanced brightness making up the structure of the coronal-streamer belt can be traced to the lowest atmospheric layers in the Sun, with the angular size remaining nearly constant, d ≈ 2.5° ± 0.5°. This suggests that the physical mechanism generating the slow solar wind in the rays of the streamer belt differs from the mechanism giving rise to the fast solar wind from coronal holes. At distances of R < (4–5) R _⊙, the rays of the streamer belt are not radial in the plane of the sky and show deviations toward the corresponding pole. They then become essentially radial at R > (4–5) R _⊙. A transverse cross section of streamers in the corona and its continuation into the heliosphere—a plasma sheet—can be represented as two radially oriented, closely spaced rays (d ≈ 2.0°–2.5°) with enhanced density and an angular size of d. We also show that the ray structure of the streamer belt is involved in the development of coronal mass ejections (CMEs). The motion of a small-scale CME occurs within a magnetic flux tube (ray of enhanced brightness) and leads to an explosive increase in its angular size (rapid expansion of the tube). It seems likely that large-scale CMEs are the result of the simultaneous expansion of several magnetic tubes. We suggest that a small-scale CME corresponds to a “plasmoid” (clump of plasma of limited size with its own magnetic field) ejected into the base of a magnetic tube, which subsequently moves away from the Sun along the tube.     

Well log data analysis for lithology and fluid identification in Krishna-Godavari Basin,India

Well log analysis provides the information on petrophysical properties of reservoir rock and its fluid content. The present study depicts interpretation of well log responses such as gamma ray, resistivity, density and neutron logs from six wells, namely W-1, W-2, W-9, W-12, W-13 and W-14 under the study area of Krishna-Godavari (K-G) basin. The logs have been used primarily for identification of lithology and hydrocarbon-bearing zones. The gamma ray log trend indicates deposition of cleaning upward sediment. Coarsening upward, clayey-silty-sandy bodies have been evidenced from the gamma ray log. Gas-bearing zones are characterised by low gamma ray, high deep resistivity and crossover between neutron and density logs. Total 14 numbers of hydrocarbon-bearing zones are identified from wells W-9, W-12, W-13 and W-14 using conventional log analysis. Crossplotting techniques are adopted for identification of lithology and fluid type using log responses. Crossplots, namely P-impedance vs. S-impedance, P-impedance vs. ratio of P-wave and S-wave velocities (Vp/Vs) and lambda-mu-rho (LMR), have been analysed to discriminate between lithology and fluid types. Vp/Vs vs. P-impedance crossplot is able to detect gas sand, brine sand and shale whereas P-impedance vs. S-impedance crossplot detects shale and sand trends only. LMR technique, i.e. λρ vs. μρ crossplot is able to discriminate gas sand, brine sand, carbonate and shale. The LMR crossplot improves the detectability and sensitivity of fluid types and carbonate lithology over other crossplotting techniques. Petrophysical parameters like volume of shale, effective porosity and water saturation in the hydrocarbon-bearing zones in these wells range from 5 to 37%, from 11 to 36 and from 10 to 50% respectively. The estimated petrophysical parameters and lithology are validated with limited core samples and cutting samples from five wells under the study area.     

利用测井数据解析含煤地层渗透特性

研究受采动影响含煤地层渗透特性的变化规律,结合电视钻孔成像技术综合分析覆岩破坏高度,对煤矿开采瓦斯抽放系统钻孔位置合理布置具有重要意义。根据测井资料（密度、伽马）,解析地层边界、泥质含量及纯岩段夹层、弱层的存在及其对含煤地层渗透特性的影响。理论分析与现场实测表明:原始地层伽马曲线和泥质含量可以解析泥岩、粘土层和夹层、弱层的位置;含煤地层渗透率受采动影响,渗透率增高区由采前泥岩、粘土与其他岩体层交界和原始裂隙区向采后纯岩夹层、弱层区演化;被研究含煤地层冒落带顶点深度433 m,裂隙带顶点深度382 m。      

Planktic foraminiferal biostratigraphy of the Maastrichtian-Paleocene succession at the north Farafra Oasis,Western Desert,Egypt

Seven planktic foraminiferal zones are distinguished in the Maastrichtian-Paleocene succession at the north Farafra Oasis. These are the Rugoglobigerina hexacamerata (CF8b), Gansserina gansseri, and Contusotruncana contusa zones in the Maastrichtian topped by a well-known unconformity across the Cretaceous/Paleogene (K/Pg) boundary. The Danian is subdivided into two biozones: Globanomalina compressa/Praemurica inconstans-Praemurica uncinata Subzone (P1c) and Praemurica uncinata–Morozovella angulata (P2) Zone. The Late Paleocene is divided into two zones: Morozovella angulata-Globanomalina pseudomenardii (P3) and Globanomalina pseudomenardii (P4). A minor hiatus between the Danian/Selandian and Selandian/Thanetian boundaries are also recorded. These time gaps across the stage boundaries may be related to the tectonic events that affected the sedimentation regime throughout the Upper Cretaceous–Lower Paleogene interval in the Farafra Oasis.     

Wolf-Rayet stars and relativistic objects: Distinctions between the mass distributions in close binary systems

The observed properties of Wolf-Rayet stars and relativistic objects in close binary systems are analyzed. The final masses M _CO ^f for the carbon-oxygen cores of WR stars in WR + O binaries are calculated taking into account the radial loss of matter via stellar wind, which depends on the mass of the star. The analysis includes new data on the clumpy structure of WR winds, which appreciably decreases the required mass-loss rates $\dot M_{WR}$ for the WR stars. The masses M _CO ^f lie in the range (1–2)M _⊙–(20–44)M _⊙ and have a continuous distribution. The masses of the relativistic objects M _x are 1–20M _⊙ and have a bimodal distribution: the mean masses for neutron stars and black holes are 1.35 ± 0.15M _⊙ and 8–10M _⊙, respectively, with a gap from 2–4M _⊙ in which no neutron stars or black holes are observed in close binaries. The mean final CO-core mass is $\overline M _{CO}^f = 7.4 - 10.3M_ \odot$ , close to the mean mass for the black holes. This suggests that it is not only the mass of the progenitor that determines the nature of the relativistic object, but other parameters as well-rotation, magnetic field, etc. One SB1R Wolf-Rayet binary and 11 suspected WR + C binaries that may have low-mass companions (main-sequence or subgiant M-A stars) are identified; these could be the progenitors of low-mass X-ray binaries with neutron stars and black holes.     

The structure and microstructure of α-cristobalite and its relationship to β-cristobalite

Recent transmission electron microscopy (TEM) electron diffraction investigation of β-cristobalite has revealed a strong characteristic diffuse intensity distribution. In this work a similar, but less intense, diffuse scattering is reported for synthetic α-cristobalite. This material also displays both tetragonal twinning and characteristic striations correspond to planar boundaries which may exist on any {1, 0, l}_tetragonal plane.     

The stratigraphical distribution of mid-Cretaceous Foraminifera near Ventnor, Isle of Wight

Ventnor No. 2 Borehole, located near Ventnor, Isle of Wight, penetrated the basal part of the Chalk Group and the Selborne Group before terminating in the upper part of the Lower Greensand Group (Sandrock Formation). The borehole was examined for Foraminifera, and although they were not seen in the Sandrock Formation and Monks Bay Sandstone Formation, the remainder of the borehole yielded moderately low diversity assemblages dominated by agglutinated species. Foraminiferal zones 3-6 (H dentatus to M. fallax/M. rostratum macrofaunal zones) were identified in the Gault Formation and zones 6 (lower) to 6a (M. fallax/M. rostratum to A. briacensis macrofaunal zones) were identified in the Upper Greensand Formation. Assemblages from the overlying West Melbury Marly Chalk Formation were used to identify foraminiferal zones BGS1-BGS3 (M. mantelli and M. dixoni macrofaunal zones).     

Wavelet Analysis of Geophysical Well-log Data of Bombay Offshore Basin, India

Geophysical well-log (bore-hole) data facilitate understanding of the physical properties of the subsurface formations as a function of depth measured in a well. In the present study, the wavelet transformation technique was applied to the well-log data of three wells in the Bombay High oil field, India, in order to identify depths to the tops of oil and/or gas formation zones (pay zones). Continuous wavelet transformation (CWT) was performed on gamma-ray, resistivity, neutron porosity and velocity log data sets in order to determine the space-localization of the oil and/or gas formation zones. The choice of a mother wavelet is important and largely depends on the data under investigation. We have applied a variety of wavelets to the different log data sets to not only identify the depths to the tops of formation zones, but also to determine the optimum wavelet that best characterizes the pay zones. On examination of scalogram plots of each log corresponding to each wavelet for their better resolution in identifying the formation boundaries, we have found that the scalograms corresponding to the Gaus1 wavelet appeared to give the best resolution in identifying the depths of pay zones in all the well-log data sets of all three wells. To further validate the above observation, a histogram analysis of CWT coefficients is made. This showed that, of all the wavelets considered for the present study, Gaus1 wavelet is the most appropriate and optimum for determining the space-localization of pay zones in all the well-log data sets considered in the present study. The depths of pay zones estimated from scalogram plots of logs agree well with those provided by the Oil and Natural Gas Corporation Ltd., India.     

Estimation and scaling of hydrostratigraphic units: application of unsupervised machine learning and multivariate statistical techniques to hydrogeophysical data

Numerical models provide a way to evaluate groundwater systems, but determining the hydrostratigraphic units (HSUs) used in constructing these models remains subjective, nonunique, and uncertain. A three-step machine-learning approach is proposed in which fusion, estimation, and clustering operations are performed on different data sets to arrive at HSUs at different scales. In step one, data fusion is performed by training a self-organizing map (SOM) with sparse borehole hydrogeologic (lithology, hydraulic conductivity, aqueous field parameters, dissolved constituents) and geophysical (gamma, spontaneous potential, and resistivity) measurements. Estimation is handled by iterative least-squares minimization of the SOM quantization and topographical errors. Application of the Davies-Bouldin criteria to k-means clustering of SOM nodes is used to determine the number and location of discontinuous borehole HSUs with low lateral density (based on borehole spacing at 100 s m) and high vertical density (based on cm-scale logging). In step two, a scaling network is trained using the estimated borehole HSUs, airborne electromagnetic measurements, and numerically inverted resistivity profiles. In step three, independent airborne electromagnetic measurements are applied to the scaling network, and the estimation performed to arrive at a set of continuous HSUs with high lateral density (based on sounding locations at meter (m) spacing) and medium vertical density (based on m-layer modeled structure). Performance metrics are used to evaluate each step of the approach. Efficacy of the proposed approach is demonstrated to map local-to-regional scale HSUs using hydrogeophysical data collected at a heterogeneous surficial aquifer in northwestern Nebraska, USA.     

Nuclear geophysical logging for Gondwana coal exploration: a case study at Phulbari Coal Basin, northern part of Bangladesh

Different methods of lithology predictions from geophysical data have been developed in the last 15 years, among which the conventional logs are as follows: sonic, neutron–neutron, natural gamma, and density (backscattered gamma–gamma). This article concentrates on the nuclear geophysical suite, in particular, gamma and gamma–gamma logging, which, to date, provide the most accurate geophysical means of identifying coal seams and estimating their thickness. From the gamma and gamma–gamma logs of boreholes AEN 002, 007, 044, 045, 063, 085, and 105, which were carried out at the Phulbari Coal Basin of Bangladesh, two coal seams—upper and main with two lower seams of limited occurrence and of varying thickness—were identified, together with their regional occurrence.     

Effects of a mudcake on Stoneley waves in a fluid-filled porous formation around a borehole

A mudcake formed on the borehole wall between a fluid-filled porous formation and the borehole fluid can affect Stoneley wave propagation used to estimate the formation permeability. The mudcake effect on the permeability dependence of radial oscillations of borehole fluid is investigated in a system with a source generating radial acoustic waves in the borehole and hydrophones (pressure sensors) that record the respective attenuating oscillations of the borehole fluid. The permeability of the porous formation is estimated from theoretical permeability dependence of the attenuation exponent, knowing the time dependence of the exponential attenuation of borehole fluid oscillations.     

断层破碎带综合地球物理找水模式——以干田坝村探采结合井为例

乌蒙山贫困缺水区水资源严重缺乏,找水需求大、难度大。为确定了ZK12探采结合井位置,本文首先分析了工区找水环境因素的地层时代、含水介质类型、构造背景、水源条件和水动条件等5个条件;其次,对富水特征的含水岩组、蓄水构造和富水地貌进行研究;最后,重点分析地球物理特征找水因素,介绍了视电阻率联合剖面法、大地电磁测深法、瞬变电磁法、激电测深和地球物理测井等“多方法”应用效果,通过视电阻率、视极化率、衰减度、半衰时等“多参数”,确定断层裂隙水的地球物理特征,建立由浅入深的“多层次”地球物理模式。最终,创新性提出了乌蒙山连片贫困缺水区重点村镇的“多方法、多参数、多层次”地球物理找水模式,克服单一物探方法找水的局限性,精准定井位,对地下水勘查起到示范作用。      

On the correlation between spectra of solar microwave bursts and proton fluxes near the Earth

Studies of the extreme solar proton event of January 20, 2005 intensified the contest over of a long-standing problem: are solar cosmic rays arriving at the Earth accelerated by solar flares or by shocks preceding rapidly moving coronal mass ejections? Among the most important questions is the relationship between the energy spectra of the solar cosmic rays and the frequency spectra of flare microwave bursts. Some studies of previous solar-activity cycles have shown that such a relationship does exist, in particular, for protons with energies of tens of MeV. The present work analyzes this relation using data for 1987–2008. For flare events observed in the western half of the disk, there is a significant correlation between the index δ, which is equivalent to the power-law index of the integrated energy spectrum of 10–100 MeV protons detected near the Earth’s orbit, and radio burst parameters such as a ratio of peak fluxes S at two frequencies (for example, at 9 and 15 GHz) and a microwave peak frequency f _m . Proton fluxes with hard (flat) energy spectra (δ ≤ 1.5) correspond to hard microwave frequency spectra (S ₉/S ₁₅ ≤ 1 and f _m ≥ 15 GHz), while flares with soft radio spectra (S ₉/S ₁₅ ≥ 1.5 and f _m ≤ 5 GHz) result in proton fluxes with soft (steep) energy spectra (δ ≥ 1.5–2). It is also shown that powerful high-frequency bursts with the hardest radio spectra (f _m ≈ 30 GHz) can point at acceleration of significant proton fluxes in flares occurring in strong magnetic fields. These results argue that solar cosmic rays (or at least their initial impulses) are mainly accelerated in flares associated with impulsive and post-eruptive energy release, rather than in shocks driven by coronal mass ejections.