Search Results (7)

Reservoir evaluation in multi-source systems is challenging because studies generally follow single-source principles. This limitation has substantially hindered the understanding of reservoir and hydrocarbon accumulation processes in source–reservoir systems. This study examines the Dingbian area of the Ordos Basin, China, and investigates the key factors controlling hydrocarbon accumulation in the Chang 9 reservoir of the Triassic Yanchang Formation within a multi-source system. The study area spans approximately 0.9 × 10⁴ km². First, by comparing the biological markers in Chang 9 crude oil with those of potential source rocks, the oil source of the Chang 9 reservoir was identified. The study area was subsequently divided into three provenance zones—northeast, northwest, and central mixed source areas—based on heavy mineral content and the orientation of sedimentary sand bodies. Additionally, well logging data, oil production data, petrographic thin sections, scanning electron microscopy (SEM), and mercury injection porosimetry were used to investigate the reservoir characteristics, oil reservoir features, and crude oil properties across different source areas. The results indicate that the oil source of the Chang 9 reservoir in the Dingbian area is the Upper Chang 7 source rock. The northwest source area exhibits superior reservoir properties compared to the other two zones. In the northwest source area, lithology-structure oil reservoirs are predominant, whereas the central mixed source area is characterized by structural-lithology oil reservoirs, and the northeast source area predominantly features lithology-controlled reservoirs. From the northwest to the central mixed source areas, and finally to the northeast source area, crude oil density and viscosity increase gradually, while the degree of oil–water separation decreases correspondingly. Based on these findings, the study concludes that the distribution of structures, lithology, and source rocks significantly influences the Chang 9 reservoirs in the Dingbian area. The controlling factors of oil reservoirs differ across the various source zones. In multi-source systems, evaluating oil reservoirs based on source zones provides more precise insights into the characteristics of reservoirs in each area. This approach provides more accurate guidance for exploration and development in multi-source regions, as well as for subsequent “reserve enhancement and production increase” strategies. Full article

Surveys show that rivers worldwide transport an annual sediment load of 15 billion tons into the sea, with the Yellow River Basin alone contributing 1.6 billion tons of sand. Therefore, understanding the wind and sand dynamics in the Yellow River Basin is crucial to ensuring the safe development of similar basins across China and the world. This study investigated the midstream wind and sand area of the Xiliugou tributary, a part of the upper Yellow River. Sand transport flux at 0–50 cm height on various underlying surfaces of the basin was measured using a stepped sand collector combined with an anemometer. Then, the amounts of wind and sand entering the Yellow River were estimated using a function model based on the measured factors. The particle size composition of wind-eroded sand was further analyzed to better understand the principles of wind and sand erosion and accumulation in the basin. The results show that the sand transport flux per unit area varies significantly across different underlying surfaces. The vertical change in sand transport rate on the basin’s surface shows that the total sand transport rate is an exponential function of wind speed. Based on this relationship, the total annual average wind and sand entering the Yellow River basin via the Xiliugou tributary was estimated to be approximately 8.09 × 10⁵ t. Controlled by the basin’s unique geography, sand source, and human activities, the particle size composition of wind-eroded sand distinctly differs between the east and west sides of the river channel, exhibiting a “wind-blown mud and water-washed sand” pattern. The Yellow River basin still faces significant ecological security hazards. Understanding the coupling relationship between desert-basin-sand and wind is the foundation for effectively controlling wind and sand flow into the Yellow River Basin. Full article

This study examined the evolution of the beach profile and sedimentary balance in Playa del Coco, Mexico, during one year (September 2013–September 2014) to monitor these conditions at a site with little or no anthropogenic influence. The type of beach profile was determined according to the energy profile of the geomorphology, resulting in three types of profiles: low, medium, and high energy. In addition, sediment volumes were quantified, and erosion or accumulation at each study site was described. The results showed that the medium-energy profile was characteristic of the beach most of the time. High-energy conditions were recorded only once due to the influence of a high-category hurricane (Odile, III) during the hurricane season. The dominant sediment size was medium, moderately well-classified to well-classified, coinciding with the medium-energy profile. Coarse, well-sorted sand was recorded at the end of the study, coinciding with the highest loss of sediment on the beach. Playa del Coco showed a state of quasi-equilibrium before the end of the annual cycle, recovering the characteristics of the beach at the beginning of the study. After that time, there was a great loss of sedimentary material influenced by Hurricane Odile (III), modifying the beach’s state of recovery. Therefore, the stability of this beach could be cyclical and respond to the self-organization principle rather than to seasonal parameters. However, the duration of the cycles that influence Playa del Coco seems to be determined by the hurricane season, especially the combination of two main factors: the proximity to the coast of the hurricane and the amount of rainfall associated with the hurricane. Full article

After the construction of desert highway, the physiognomy changes caused by surface wind erosion and accumulation not only seriously threaten the stability of road structure, but also have a tremendous impact on the safety of the highway operation and the maintenance work on the highway. The purpose of this paper is to explore the change of sand sedimentation and the law of sand transport along the highway in the moving dune areas, and to clarify the change of sand flow and the formation mechanism of sand damage in the moving dune areas. Taking the test section of Wuhai-Maqin Expressway in the hinterland of Tengger Desert as the research object, the on-site observation of sand accumulation and the recording of wind information by small weather stations were adopted, supplemented by CFD numerical simulation method, in order to provide reference for the construction of sand control system in moving dune areas. The study results show that: (1) Dunes not only obstruct wind-drift sand but are also the sediment source condition for forming road sand. The windward dunes near the road are affected by wind and the deposition of sand will quickly bury the road in the strong wind season. (2) Compared with highways with flat terrain, the existence of dunes affects the flow field structure and the distribution of sand sedimentation on the highway, in which, under the influence of the gathering effect, the flow velocity reaches the maximum at the top of the dune and a large low-speed recirculation zone is formed on the lee side of the dune, easily causing sand accumulation. (3) Sediment accumulates at the windward side of the embankment or dune where sandy air current is easy to saturate. However, with the increase of wind speed, in addition to the grit carried by the sandy air current itself, new sand rolled up on the windward side of the dunes also form deposits on the road surface and the amount of sand-accumulation on highway surface and leeward side tends to increase. As a result, for the highway in drifting sand dunes areas, sediment prevention and control measures should be taken actively. It is necessary to remove sediment from the road in time and reduce the moving speed of sand dunes and the deposition range of wind-sand flow, ultimately for the purpose of reducing the damage wind-sand activity causes to the highway in desert. Full article

On the Curonian Spit, the leading conservation issue is an opposition between the two contrasting nature-management principles—anthropocentricity and biocentricity. Land managers still waver between the two options, and the worst-case scenario materializes as a rapid proliferation of vegetation to the accumulative sandplain (palve). It results in the decline of sand drift to the mobile dunes. This article aims to examine how climate change affects the coastal dune landscape and to identify current dune protection and management priorities. The analysis of hydroclimatic changes; succession patterns in forest, herbaceous, and open-sand ecosystems; and phenological-based evaluation (NDVI from MODIS, 2000–2020), influencing possible management directions, were carried out in this study. The results show the significant hydro-climatic changes (air temperature, precipitation, and sea level) occurring over the last thirty years. They influence the prevailing overgrowth trends in recent decades, especially in herbaceous ecosystems. Therefore, if the EU’s priority habitat—open-sand ecosystems—is to be preserved, the main policy recommendation is to apply adequate management tools such as grazing, and to pay more attention to the aesthetic ecosystem services of the mobile dunes parallel to biodiversity conservation. Full article

The Mesozoic Chang 8 Section in the Zhenjing area is a typical low permeability-tight sand reservoir and is regarded as the most important set of paybeds in the study area. Guided by the principles of basic geological theory, the diagenetic evolution process and hydrocarbon accumulation periods of the Chang 8 reservoir in the study area were determined through various techniques. More specifically, core observation, scanning electron microscopy (SEM), X-ray diffraction (XRD), and vitrinite reflectance experiments were performed in combination with systematic studies on rock pyrolysis and the thermal evolutionary history of basins, the illite-dating method, and so on. The Chang 8 reservoir is dominated by feldspar lithic and lithic feldspar sandstones. Quartz, feldspar, and lithic fragments are the major clastic constituents. In clay minerals, the chlorite content is the highest, followed by illite/smectite formation and kaolinite, while the illite content is the lowest. The major diagenesis effect of the Chang 8 reservoir includes compaction, cementation, dissolution, metasomatism, and rupturing. The assumed diagenetic sequence is the following: mechanical composition → early sedimentation of chlorite clay mineral membrane → early cementation of sparry calcite → authigenic kaolinite precipitation → secondary production and amplification of quartz → dissolution of carbonate cement → dissolution of feldspar → late cementation of minerals such as ferrocalcite. Now, the study area is in Stage A in the middle diagenetic period. Through the inclusion of temperature measurements, in conjunction with illite dating and thermal evolutionary history analysis technology in basins, the Chang 8 reservoir of this study was determined as the phase-I continuous accumulation process and the reservoir formation epoch was 105~125 Ma, which was assigned to the Middle Early Cretaceous Epoch. Full article

The sand daffodil (Pancratium maritimum) is a perennial geophyte, widely distributed and grown in a wild stage along the Mediterranean seashores. The aboveground tissues of this geophyte are exposed to harsh, ambient conditions and its large inflorescences of remarkable beauty and fragrance expand during the drought season and carry particular ornamental worth. The ecophysiological principles underlining metabolic processes of this geophyte are poorly understood. The seasonal variation of soluble sugars, starch, and proline was investigated in individuals collected from patches of P. maritimum, therefore, monthly measurements were performed in bulbs, leaves, scapes, and petals during a year. It was found that (a) sugar content showed similar seasonal trends between bulbs and leaves, as well as between petals and scapes, (b) bulbs contained enhanced starch concentrations irrespective of season, (c) proline accumulation exhibited substantial seasonal fluctuations among the considered tissues and pronounced differences were detected between maxima in petals and leaves. A substantial increase in both sugar and proline content was evident in petals during the drought season. In leaves, the accumulation of proline and, to a lesser extent, sugars was negatively correlated to the precipitation of the Mediterranean study site. It seems likely that the astonishing flowering of P. maritimum is supported by large leaf and bulb reserves. Full article