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101.
地磁偏角实时自动修正技术在油田定向钻井中的应用 总被引:2,自引:1,他引:2
在油田定向钻井的磁导向定位系统中,地磁偏角校正是一个不可缺少的基本要素,同时在磁偏角校正值精度直接影响定向井的导向定位精度。因此,作者提出了提高地磁偏角校正值精度的方法,并试图将地磁偏角实时自动修正技术引入我国油田定向钻井领域。 相似文献
102.
Isabelle Letard Philippe Sainctavit Catherine Deudon 《Physics and Chemistry of Minerals》2007,34(2):113-120
Pyrrhotite (Fe7S8) is a natural iron sulphide that can participate in rock magnetisation. Its electronic structure is not yet surely described.
X-ray magnetic circular dichroism (XMCD) at Fe L2,3 edges on Fe7S8, coupled with multiplet calculations, shows that iron is present only as Fe2+ in this magnetic iron sulphide. It reveals a strong magnetic orbital moment. XMCD at Fe and S K edges shows the quite strong
polarization of both Fe and S in Fe7S8. 相似文献
103.
The primary factors that control the concentration of total reduced (inorganic) sulfide in coastal sediments are believed
to be the availability of reactive iron, dissolved sulfate and metabolizable organic carbon. We selected nine sites in shallow
(<3 m), close to sub-tropical, estuaries and bays along the central Texas coast that represented a range in sediment grain
size (a proxy for reactive iron), salinity (a proxy for dissolved sulfate), and total organic carbon (a proxy for metabolizable
organic carbon). Based on these parameters a prediction was made of which factor was likely to control total reduced sulfide
at each site and what the relative total reduced sulfide concentration was likely to be. To test the prediction, the sediments
were analyzed for total reduced sulfide, acid volatile sulfide, and citrate dithionate-extractable, HCl-extractable and total
Fe in the solid phase. Using solid-state gold–mercury amalgam microelectrodes and voltammetry, we determined pore water depth
profiles of Fe(II) and ΣH2S and presence or absence of FeS(aq). At five of the nine sites the calculated degree of sufildization of citrate dithionite-reactive-iron was close to or greater
than 1 indicating that rapidly reactive iron was probably the limiting factor for iron sulfide mineral formation. At one site
(salinity = 0.9) dissolved Fe(II) was high, ΣH2S was undetectable and the total reduced sulfide concentration was low indicating sulfate limitation. At the last three sites
a low degree of sulfidization and modest total reduced (inorganic) sulfide concentrations appeared to be the result of a limited
supply of metabolizable organic carbon. Fe(II)–S(-II) clusters (FeS(aq)) were undetectable in 10 out of 12 bay sediment profiles where ΣH2S was close to or below detection limits, but was observed in all other porewater profiles. Acid volatile sulfide, but not
total reduced sulfide, was well correlated with total organic carbon and ranged from being undetectable in some cores to representing
a major portion of total reduced sulfide in other cores. Although predicted controls on total reduced sulfide were good for
very low salinity water or sandy sediments, they were only right about half the time for the other sediments. The likely reasons
for the wrong predictions are the poor correlation of total organic carbon with grain size and differing fractions of metabolizable
organic carbon in different sedimentary environments. Differences in sediment accumulation rates may also play a role, but
these are difficult to determine in this region where hurricanes often resuspend and move sediments. This study demonstrates
the need to examine more complex and often difficult to determine parameters in anoxic “normal marine” sediments if we are
to understand what controls the concentration and distribution of sulfides. 相似文献
104.
Takaji Kokusho Ryuichi Motoyama Hiroshi Motoyama 《Soil Dynamics and Earthquake Engineering》2007,27(4):354-366
Seismic wave energy in surface layers is calculated based on vertical array records at four sites during the 1995 Hyogo-ken Nambu earthquake by assuming vertical propagation of SH waves. The upward energy generally tends to decrease as it goes up from the base layer to the ground surface particularly in soft soil sites. Theoretical study on 1D multi-layers model to investigate the basic energy flow mechanism indicates that the energy at the ground surface can be smaller on softer soils due to high soil damping during strong shaking even if resonance effect is considered. A simple calculation for a shear-vibrating structure resting on foundation ground shows that induced strain in the structure is directly related to the energy or the energy flux of surface layers. Hence, a general perception that soft soil sites tend to suffer heavier damage than stiff sites should be explained not by greater incident energy but by other reasons such as degree of resonance. Furthermore, it is recommended that not only acceleration or velocity but also S-wave velocity should be specified at a layer where a design seismic motion is given, so that the seismic wave energy can clearly be quantified in seismic design practice. 相似文献
105.
The time-domain EM induction response of non-magnetic and magnetic targets can be approximated using a conductive permeable prism composed of six faces of conductive plates, each face being composed of a set of conductive ribbons. The effect of magnetic permeability is included by the use of two “apparent flux gathering” coefficients, and two “effective magnetic permeability” coefficients, in the axial and transverse directions. These four magnetic property coefficients are a function of physical properties and geometry of the target, but are independent of prism orientation relative to a transmitter. The approximation algorithm is computationally fast, allowing inversions for target parameters to be achieved in seconds. The model is tested on profiles acquired with a Geonics EM63 time-domain EM metal detector over a non-magnetic copper pipe target, and a steel artillery shell in horizontal and vertical orientations. Results show that this approximation to a permeable prism has a capability of fitting geometric, conductivity and magnetic parameters at both early and late sample times. The magnetic parameters show strong change from early to late times on the EMI decay curve, indicating that the magnetic properties of the target have non-linear characteristics. It is proposed that these magnetic parameters and the nature of their non-linearity may carry additional discrimination information for distinguishing between intact munitions and scrap in UXO studies. 相似文献
106.
J.-F. Girard M. Boucher A. Legchenko J.-M. Baltassat 《Journal of Applied Geophysics》2007,63(3-4):103-116
Karstic conduits play a crucial role for water supply in many parts of the world. However, the imaging of such targets is generally a difficult task for most geophysical methods. Magnetic Resonance Sounding (MRS) is a geophysical method designed for imaging of water bearing structures. Initially, MRS was developed for characterizing horizontally stratified aquifers. However, when applying a 1D MRS measuring setup to the imaging of 2D–3D targets, the size of which may be much smaller than the loop, the accuracy and the lateral resolution may not be sufficient. We have studied the possibility of simultaneously processing several MRS aligned along a profile to perform a Magnetic Resonance Tomography (MRT). This work emphasizes the gain of resolution for 2D–3D imagery of MRT versus the interpolation of 1D inversion results of MRS along the same profile. Numerical modelling results show that the MRT response is sensitive to the size and location of the 2D target in the subsurface. Sensitivity studies reveal that by using the coincident transmitting/receiving (TX/RX) setup and shifting the loop around the anomaly area, the depth, section and position of a single karstic conduit with a size smaller than the MRS loop size can be resolved. The accuracy of the results depends on the noise level and signal level, the latter parameter being linked to the depth and volume of the karstic conduit and the water content in the limestone matrix. It was shown that when applying MRT to the localization of 2D anomalies such as karstic conduits, the inclination of the geomagnetic field, the orientation of the MRT profile and the angle of crossover of the conduit by the MRT profile must be taken into account. Otherwise additional errors in interpretation should be expected. A 2D inversion scheme was developed and tested. Both numerical and experimental results confirm the efficiency of the developed approach. 相似文献
107.
A Least-squares Window Curves Method for Interpretation of Magnetic Anomalies Caused by Dipping Dikes 总被引:1,自引:0,他引:1
E. M. Abdelrahman E. R. Abo-Ezz K. S. Soliman T. M. El-Araby K. S. Essa 《Pure and Applied Geophysics》2007,164(5):1027-1044
We have developed a least-squares method to determine simultaneously the depth and the width of a buried thick dipping dike
from residualized magnetic data using filters of successive window lengths. The method involves using a relationship between
the depth and the half-width of the source and a combination of windowed observations. The relationship represents a family
of curves (window curves). For a fixed window length, the depth is determined for each half-width value by solving one nonlinear
equation of the form f (z) = 0 using the least-squares method. The computed depths are plotted against the width values representing a continuous curve.
The solution for the depth and the width of the buried dike is read at the common intersection of the window curves. The method
involves using a dike model convolved with the same moving average filter as applied to the observed data. As a result, this
method can be applied to residuals as well as to measured magnetic data. Procedures are also formulated to estimate the amplitude
coefficient and the index parameter. The method is applied to theoretical data with and without random errors. The validity
of the method is tested on airborne magnetic data from Canada and on a vertical component magnetic anomaly from Turkey. In
all cases examined, the model parameters obtained are in good agreement with the actual ones and with those given in the published
literature. 相似文献
108.
2001年兰州地区春季沙尘暴天气的对比分析 总被引:1,自引:1,他引:1
2 0 0 1年 4月 ,兰州地区连续出现了两次区域性强沙尘暴天气。文中从天气概况、气候背景、地面和高空环流形势等方面 ,对两次沙尘暴天气进行了分析。结果表明 ,两次沙尘暴天气过程是在同样的大尺度环流背景下产生的 ,都是由冷锋后偏北大风引起的。但由于造成两次沙尘暴天气的冷空气强度、锋区南压程度、冷空气移动路径等不同 ,因此造成两次沙尘暴天气影响范围、强度也有所不同。同时 ,兰州地区 2 0 0 1年冬季气温异常偏高 ,春季降水偏少以及本地区特殊的地理、地形环境 ,加剧了大风、沙尘暴的出现频次和强度。通过分析 ,初步总结出了此类天气的预报思路和要点。 相似文献
109.
110.
分析了影响磁通门磁变仪定向状态函数和经典磁变仪定向状态函数改变的因素,对磁通门磁变仪定向状态函数和经典磁变仪定向状态函数及其稳定性进行了比较,得出了有益的结论。 相似文献