阿联酋东鲁卜哈利盆地白垩系Mishrif组碳酸盐岩储层孔隙特征

上白垩统Mishirif组是阿联酋东鲁卜哈利盆地主要的产油层,目前对Mishrif-1段和Mishrif-3段储层孔隙特征差异的研究较为薄弱.在岩心描述、薄片鉴定、气测、压汞及核磁共振测试的基础上,对Mishrif组储层储集空间、孔隙结构进行了系统研究,明确了储层的相控特征以及Mishrif-1段和Mishrif-3段...     

青藏高原东缘盐源盆地古近纪风成沙丘及其古地理意义*

盐源盆地始新世丽江组沉积时期发育了一套具大型高角度交错层理的红色砂岩,其确切成因对于厘定青藏高原东缘古近纪古地理格局、恢复东亚新生代干旱带与古气候演化过程具有重要意义。文中通过对盐源盆地始新统丽江组红色砂岩的沉积特征进行系统分析,证明该套砂岩的岩性、粒度分布、石英颗粒表面特征与沉积构造等明显不同于水成沉积,而与典型风成沙丘相应特征完全一致,表明其为风成沙丘沉积。结合古近纪研究区的古气候条件、大气环流样式与大地构造背景,笔者进一步推断盐源盆地始新世风成沙丘可能沉积于中国古近纪干旱带内的沙漠环境。根据目前相关研究资料,确认青藏高原东缘存在一个厚度稳定的古近纪风成沙丘富集带。     

Relationship of spatial heterogeneity for vegetation and aeolian sand soil properties on longitudinal dunes in Gurbantunggut Desert, China

On longitudinal dunes in the southern Gurbantunggut Desert, the vegetation was investigated, and the texture, water content, organic matter, total nitrogen, salt content and pH of aeolian sand soil were measured. By means of geostatistical methods, the spatial heterogeneity for vegetation and aeolian sand soil properties was analyzed. The vegetation pattern and aeolian sand soil properties were moderately to strongly spatially heterogeneous as a whole, with a spatially dependent range of 8.8–74.8 m. Because both of them had a nest structure of grading system, their spatial heterogeneity needed to be described by the fractal dimensions at different sampling scales. The autocorrelated spatial range A ₀ and fractal dimensions of the cover of vegetation and the diversity of herberious synusium were similar to these of soil water contents (SM). The coarse grain size (φ1) and sorting (σ) of soil, the diversity of herbaceous synusium and the cover of vegetation had a closer dependent range A₀, being 37.8–57.8 m. The trends of spatial variation for organic matter and total nitrogen contents were very similar to that of vegetation cover. The spatial heterogeneities of soil pH and salt content were mainly restricted by terrain and basically not related to vegetation.     

大型海底、海岸和沙漠沙丘的形态和迁移特征

海底、海岸和沙漠沙丘的迁移与其波高、波长等形态参数有关。对一些代表性大型沙丘的分析表明,海底、海岸和沙漠沙丘的形态特征存在着较大的差异,在相同波长条件下,海底沙丘波高最小,海岸沙丘波高次之,沙漠沙丘波高最大。其原因主要是流体厚度的差异,其次是物质供给条件的不同:浅海地区的水深限制了沙丘向上生长,而陆地气流厚度较大,给沙丘的向上生长提供了较大的空间;沙漠环境的沉积物供给远大于海岸环境,因而导致沙丘高度的差异。沙丘形态参数经常偏离统计的波长 波高曲线,数值实验结果显示,这与推移质输运率有关。推移质输运率的沿程变化可以使形态参数系统性地偏离波长 波高曲线;推移质输运率的沿程突变可使沙丘迁移受阻,造成沉积物的垂向堆积,形成超高的沙丘。由于大型沙丘的迁移特征受控于推移质输运率和沙丘高度,因此可以通过波高设计来计算迁移距离 历时曲线,进而控制沙丘迁移动态。文中给出了一个获取迁移距离 历时曲线的算例。设计波高可通过人工篱笆、隔挡墙、沟渠、表面护层等措施而实现。     

Influence of palaeokarst morphology on the formation of ice-pushed ridges: a case study from Rejowiec, eastern Poland

This article describes the well-exposed landform/sediment assemblage of a Pliocene palaeouvala and Pleistocene (Saalian) ice-pushed ridge in a large quarry in Upper Cretaceous marls near Rejowiec, eastern Poland. The site provides a rare opportunity to study the development of glacial depositional and deformational processes on morphologically and structurally variable bedrock. The internal structures of both chronostratigraphic units which comprise this assemblage provide evidence of two principal stages of deformation associated with an ice advance on a karstified foreland, each stage preceded by stabilization of the ice mass. The first deformational stage was characterized by the development of imbricate structures in outwash sediments (the initial ice-pushed ridge) and listric faults at the contact between the bedrock and palaeouvala fills (caused by an increasing ice load). Shallow subglacial folding of the proximal fan deposits, and a listric thrust which limited the extent of the ice-pushed ridge under development occurred in the second deformational stage. The data assembled indicate that the formation of push moraines (in a general sense) during ice-sheet advance is controlled by the substratum undulations. Closed depressions with loose fills in the foreland of advancing ice sheets can control the deformational style, geometry and extent (both lateral and vertical) of the push moraines.     

Niveo-aeolian sand deposition in subarctic dunes,eastern coast of Hudson Bay,Québec,Canada

Aeolian sand transport during winter and the snow-free season was assessed quantitatively by direct year-round field measurements along transects on the lee side of parabolic dunes in subarctic Québec. In 1987–1988, niveo-aeolian deposition was more important than aeolian sedimentation in three of the four study sites, and contributed > 75% of the total annual accumulation in exposed sites and < 25% in protected forest sites. The maximum depth of interstratified snow and sand deposits (3.5 m) was recorded in March. Semi-permanent snow lenses may persist longer than 2 years in the aeolian sediments. After dissipation of snow, 22 cm of sand (as a maximum) accumulated on the slipface of the most active dunes, whereas only minor sand accumulation occurred in distant areas from active sand erosion. Wind-driven sand was dispersed over 7.4 km² in the Whapmagoostui-Kuujjuarapik area. The acumulation of snow and sand during the snow season, together with spring thaw and collapse of the niveo-aeolian deposit, caused different types of injuries to trees, especially in 1985 and 1987 when a maximum of torn branches was recorded over the last 10 year period.     

Fluid flow characteristics of Bandanna Coal Formation: a case study from the Fairview Field,eastern Australia

Fluid flow characteristics of cleat systems in coalbed methane reservoirs are crucial in reservoir management and field development plans. This paper aims to evaluate the cleat system properties including cleat porosity, permeability, and aperture as well as the impact of permeability growth on production performance in the Bandanna Coal Formation of the Fairview Field, eastern Queensland. Owing to the presence of bad hole conditions and poor core recovery of the coal intervals, the petrophysical well logs and laboratory measurements cannot be used as a source of information for this purpose. Hence, a new approach is employed that utilises early water production data to measure water in place and absolute permeability of the coal. In addition, micro-computed tomography (CT) scan method is used to investigate the cleat system that is preserved in a core sample and results are compared with the ones obtained by analysis of production data. Cleat system evaluation by analysis of production data and micro-CT scan technique provides a comprehensive approach that brings confidence in measurements and helps to obtain cleat properties at the sufficient scale for reservoir engineering purposes. The necessary information including production data and core samples are collected from a dewatering well and the nearby observation well in the study area. Analysis of early water production data (single-phase flow) indicates that coal permeability is 189 mD and the average cleat porosity is approximately 5%. High cleat porosity describes the large volume of water produced over the life of the study well. The 3D model of the fossilised cleat system constructed by the micro-CT scan method reveals that coal is well-cleated and cleat spacing and mean cleat aperture are 4 and 0.136 mm, respectively. The average cleat porosity that is measured by the micro-CT scan method is 5.7%, which is fairly close to the cleat porosity measured by analysis of production data. Production data analysis indicates that effective permeability to gas starts to grow at the midlife of the well and it strongly controls the shape of the production profile. The results of this study help in future field development and infill drilling programs in the Fairview Field and provide important insights into cleat system of Bandanna Coal Formation.     

Developmental characteristics of aeolian dunes and environmental changes in the adjoining region of Puruogangri ice sheet, North Tibetan Plateau

A large area of moraine sediments and cryogenic weathering products, formed by glacial action and a cold environment, are the main source of aeolian sand in the high and cold region of the Qinghai–Tibetan Plateau in China. The evolution of aeolian dunes is closely related to the periglacial environment. Owing to the freezing of dune-land surfaces, the evolution of sand dunes is dominated by expanding dune bases and vertical accretion, thereby forming large barchan dunes. The migration rates of these large barchan dunes are very slow at an average rate of 1.7–0.7 cm·a^–1. The temperature mainly controls the environmental changes in the adjoining region of Puruogangri ice sheet. The ¹⁴C dating of humus layers in the studied area of the sand dune are 10,780±130, 9,549±130, 8,320±110, 7,450±100, 5,970±95, 5,330±90, 4,420±80, 3,460±80, 2,280±70, 980±70 aBP, respectively. The regions high temperature rising up during summer from the southwest monsoon intensity might be an important factor. As long as both water and temperature conditions are suitable, the plants will grow well, sand dunes will be stabilized, forming humus layers. Otherwise, sand dunes are bare and re-activate.     

The morphodynamics of fluvial sand dunes in the River Rhine, near Mainz, Germany. I. Sedimentology and morphology

The dynamics of large isolated sand dunes moving across a gravel lag layer were studied in a supply‐limited reach of the River Rhine, Germany. Bed sediments, dune geometry, bedform migration rates and the internal structure of dunes are considered in this paper. Hydrodynamic and sediment transport data are considered in a companion paper. The pebbles and cobbles (D₅₀ of 10 mm) of the flat lag layer are rarely entrained. Dunes consist of well‐sorted medium to coarse sand (D₅₀ of 0·9 mm). Small pebbles move over the dunes by ‘overpassing’, but there is a degree of size and shape selectivity. Populations of ripples in sand (D₅₀ < 0·6 mm), and small and large dunes are separated by distinct breaks in the bedform length data in the regions of 0·7–1 m and 5–10 m. Ripples and small dunes may have sinuous crestlines but primarily exhibit two‐dimensional planforms. In contrast, large dunes are primarily three‐dimensional barchanoid forms. Ripples on the backs of small dunes rarely develop to maximum steepness. Small dunes may achieve an equilibrium geometry, either on the gravel bed or as secondary dunes within the boundary layer on the stoss side of large dunes. Secondary dunes frequently develop a humpback profile as they migrate across the upper stoss slope of large dunes, diminishing in height but increasing in length as they traverse the crestal region. However, secondary dunes more than 5 m in length are rare. The dearth of equilibrium ripples and long secondary dunes is probably related to the limited excursion length available for bedform development on the parent bedforms. Large dunes with lengths between 20 m and 100 m do not approach an equilibrium geometry. A depth limitation rather than a sediment supply limitation is the primary control on dune height; dunes rarely exceed 1 m high in water depths of ≈4 m. Dune celerity increases as a function of the mean flow velocity squared, but this general relationship obscures more subtle morphodynamics. During rising river stage, dunes tend to grow in height owing to crestal accumulation, which slows downstream progression and steepens the dune form. During steady or falling stage, an extended crestal platform develops in association with a rapid downstream migration of the lee side and a reduction in dune height. These diminishing dunes actually increase in unit volume by a process of increased leeside accumulation fed by secondary dunes moving past a stalled stoss toe. A six‐stage model of dune growth and diminution is proposed to explain variations in observed morphology. The model demonstrates how the development of an internal boundary layer and the interaction of the water surface with the crests of these bedload‐dominated dunes can result in dunes characterized by gentle lee sides with weak flow separation. This finding is significant, as other studies of dunes in large rivers have attributed this morphological response to a predominance of suspended load transport.     

Physical and chemical properties of sound-producing and soundless sand particles from booming sand dunes,northern China

This study here is the result of a comparative study of the geomorphic features, grain size distribution, major mineral components, and micro-textures of sound-producing and soundless sands from three geoparks in north China, and discusses the possible causes of this naturally occurring, physical phenomenon. The sound-producing sand dunes we have investigated are situated along a curvilinear belt of deserts and experience variable precipitation–evaporation rates on a yearly basis. “Singing sands” occur mainly on barchan-type dunes and adjacent to lakes or springs, whereas soundless sands are mainly located in desert areas where there is no nearby surface or groundwater sources. We have analyzed samples from nine sound-producing and two soundless sand dunes using grain size, X-ray diffraction and fluorescence, and SEM analyses. All sand types are composed largely of quartz and feldspar, but sound-producing sands also contain secondary minerals such as kaolinite (3–5%), albite (2–6%), microcline (2–5%), and calcite (5%) that are lacking in the soundless sand samples. Sound-producing sands are generally fine-grained whereas soundless sands are coarse-grained, and all sand types are generally sub-rounded to rounded indicating long transport distance from their provenance. Sphericity values of both sand types are nearly identical with predominantly oblate shapes. Surface pitting is not a unique feature of either sand types, and hence can be ruled out as a major cause of the acoustic properties of sound-producing sands. Densely distributed dissolution features such as scale-like upturned plates and silica scales on grain surfaces contribute significantly to the sound emission of singing sands. Thus, the physical–climatic conditions in deserts such as the presence of surface water and groundwater and precipitation–evaporation rates, which collectively control the formation and distribution of dissolution features on sand surfaces, have a first-order control on the production of sound-producing sands.     

A wind tunnel study of aeolian sand transport on a wetted sand surface using sands from tropical humid coastal southern China

This article reported a wind tunnel test of sediment transport related to surface moisture content and wind velocity using sands from tropical humid coastal area. A 1 mm-thick portion of surface sand was scraped using a self-made sediment sampler, and the gravimetric moisture content was determined. Sand transport was measured via a standard vertical sand trap with a 60 cm height. The result shows that the sand transport profile above the wet surface can be expressed with an exponential equation. In general, the influence of moisture content on sand transport profile mainly focuses on the bottom of the blowing sand cloud. Meanwhile, with moisture content increased, total sand transport dropped, and a relatively larger proportion is transported at greater heights. The vertical movement of particles on higher moisture surface (0.587% < M < 1.448%) is more sensitive to moisture content variation as compared to those on low wet surface (M < 0.587%), total sand transport rate tends to be rather low (0.99 g cm⁻¹ s⁻¹) when M > 1.448%. The total sand transport rate varying with moisture content is divided into three regions of differing gradient at the moisture contents of 0.587 and 1.448%. The gradient of the curve reflected the different influences of the various water forms in surface sediments. The higher moisture surface (M > 1.448%) merely functions as a transport plain for the saltation material. Surface moisture content was the dominant control factor for saltation activity between the moisture contents of 0.587 and 1.448%, wind velocity could resume control saltation after the surface dried to the extent (M < 0.587%).     

北淮阳东段板桥岩体地球化学特征及同位素年代学研究

位于北淮阳东段的板桥岩体为凌家冲杂岩体的重要组成部分,岩石类型为花岗闪长岩.该岩体偏铝质、富碱、高钾、贫钙,属于高钾钙碱性系列岩石;稀土元素含量中等,(La/Yb)N与HREE/LREE值较高,重稀土元素相对亏损,铕弱负异常,属轻稀土元素富集型;大离子亲石元素Rb、Ba、K、La、Nd富集,高场强元素Nb、Ta、Ti、P亏损.通过LA-ICP-MS锆石U-Pb定年,获得板桥岩体206pb/238U年龄为129.0±1.9 Ma,表明该岩体形成于燕山晚期,是早白垩世岩浆活动的产物.板桥花岗闪长岩形成于后碰撞的伸展构造环境.     

A geoelectrical and hydrogeological study for the assessment of groundwater resources in Wadi Al Bih, UAE

Drilling information, historical water table levels, groundwater salinity records of the existing water wells in Wadi Al Bih area, United Arab Emirates, were stored in a geodatabase and used to characterize the geological and hydrogeological settings of this area. A 2D earth resistivity imaging survey was conducted for the first time in the Northern UAE to determine the potential of the Quaternary aquifer and its groundwater quality in the areas where there are no monitoring wells. The results of the chemical analyses of the collected groundwater samples together with the inversion results of the resistivity data were used to draw a total salinity map and determine the spatial variations in groundwater quality. The inversion results of the 2D earth resistivity imaging data indicated that the Quaternary aquifer in the study area is in a good connection with the underlying carbonate aquifer. It also indicated that the carbonate aquifer is of major regional and vertical extension and it contains the fresh water in this area. The data stored in the developed database were used to produce different types of geopotential maps.     

东昆仑吐拉地区地球化学特征及找矿方向探讨

吐拉工作区位于昆仑-柴达木成矿带西段的祁曼塔格岩浆弧,成矿条件有利,也是大调查工作以来新发现的重要成矿带之一.已发现特大型钨锡矿床,区域物化探异常密集分布,具有较好的找矿前景.     

川西北天井山泥盆系平驿铺组油砂储层沉积学研究

通过岩石学、沉积学和储层地质学分析认为天井山平驿铺组主要发育灰白色中-厚层石英砂岩、石英砂岩夹粉砂岩、粉砂质泥岩和泥岩。从平驿铺组油砂储层中识别出临滨亚相,并进一步划分为上临滨、中临滨和下临滨3个微相;得出了平驿铺期龙门山地区持续沉降并接受自西向东方向的古特提斯洋的海侵的初步认识。海侵带来的大量陆源碎屑物质堆积在沉降区,形成了北东向展布、北西—南东分带、北西厚而南东薄的平驿铺组的陆缘碎屑滨岸沉积。储层的物性受沉积相的控制,上临滨微相的储层物性最好,中临滨微相次之,下临滨微相较差。     

The characteristics of aeolian sediment flux profiles in the south‐eastern Tengger Desert

Deserts are one of the most important dust sources in the world. Because dust content changes as a function of height at low levels in the atmosphere, this affects long‐term dust transport. In this paper, field data measured above shifting sands in the south‐eastern Tengger Desert were used to analyse the vertical distribution of sediment fluxes in the near‐surface layer (0 to 48 m). It was possible to express horizontal sediment flux as a power function, but aeolian deposition as a function of height could be expressed as an exponential function. There are two curve types for the particle size distributions in the horizontal sediment flux and aeolian deposition: bimodal and unimodal curves. For the horizontal sediment flux and aeolian deposition, heights of 24 m and 32 m, respectively, were the key heights in the size distribution curve; below these heights, the curve was bimodal, whereas above these heights, it was unimodal. At heights of 4 to 16 m, and especially between 8 m and 12 m, the data were particularly interesting because the sediment size, transport mode, degree of sorting, and the skewness and kurtosis change. For the horizontal sediment flux, wind turbulence moved saltating particles higher than expected.     

A wind tunnel study of the parameters for aeolian sand transport above a wetted sand surface using sands from a tropical humid coastal region of southern China

In this study, wind tunnel tests were performed to determine the relationships between sediment transport, the surface moisture content, and wind velocity using beach sands from a tropical humid coastal area of China. The variation in the properties of the creep proportion, relative decay rate as a function of height, and average saltation height in the flux profile were determined. Sand transport was measured using a standard vertical sand trap. The creep proportion (i.e., the proportion of the particles that move along the surface rather than undergoing saltation) and relative decay rate decreased and more particles were ejected to higher positions as moisture content and wind velocity increased. The creep proportion ranged between 0.12 and 0.33, and averaged 0.22. The creep proportion and relative decay rate decreased abruptly at moisture contents between 0.587 and 1.448%; the latter value was close to 1.591%, the moisture content at a matric potential of ?1.5 MPa. This moisture content limit may indicate a change in the form of soil water from adsorbed films on particle surfaces to capillary forces created by inter-particle water bridges. The surface moisture content therefore appears to decisively determine the degree of the restraint on particle entrainment by the wind. The average heights, below which 25, 50, 75, and 90% of sand transport occurred, increased with increasing moisture content (except at 0.231% moisture content) and wind velocity. The mean saltation height at various wind velocities increased linearly with increasing moisture content.