鹿乡断陷C区块双阳组测井岩性识别及储层有效厚度的确定

针对伊通盆地鹿乡断陷五星构造带油藏,提出一种适用于本区块的测井岩性识别模式及确定储层有效厚度的方法。利用包括自然伽马(吉林伽马)、普通电阻率、声波时差和自然电位曲线的综合分析,通过绘制各类曲线交会图,确定各类岩性的有效指标范围,确认出本区可识别的6种岩石类型即泥岩、粉砂岩、细砂岩、中砂岩、粗砂岩和砂砾岩。在测井解释近似的情况下,提出反推排除法,结合区域整体沉积相带分布规律和相邻井之间的测井曲线相互关系,区分细砂岩与含砾砂岩。在测井解释的基础上进行储层有效厚度研究,建立孔隙度、渗透率、含油饱和度模型,总结出岩性下限标准、物性下限标准、电性下限标准,利用建立的模型及解释图版,对本区块的39口井进行油水层校正,编制单砂层有效厚度图和单砂层岩性-微相图。     

粗糙透水床面明渠水流的垂线流速分布

为了进一步揭示粗糙透水床面明渠水流运动特性,针对垂线流速分布研究存在的问题,根据边界层理论,推导了含有摩阻流速、理论床面流速和原点位移等3个参数的修正对数公式;通过水槽试验,运用激光多普勒测速仪,分别对用直径1 cm玻璃珠构成的粗糙不透水和透水床面明渠水流的垂线流速分布进行了测量。结果表明:推导的修正对数公式与实测符合很好;相同水流条件下,透水床面的摩阻流速要大于不透水床面,各自的阻力系数保持基本不变;理论床面流速是主流平均流速的0.35~0.45倍,且床面相对流速随着雷诺数的增大而略有减小。     

High-resolution X-ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

Hybrid event beds form when turbidity currents that transport or locally acquire significant quantities of mud decelerate. The mud dampens turbulence driving flow transformations, allowing both mud and sand to settle into dense, near-bed fluid layers and debris flows. Quantifying details of the mud distribution vertically in what are often complex tiered deposits is critical to reconstructing flow processes and explaining the diverse bed types left by mud-bearing gravity flows. High-resolution X-ray fluorescence core scanning provides continuous vertical compositional profiles that can help to constrain mud distribution at sub-millimetre scale, offering a significant improvement over discrete sampling. The approach is applied here to cores acquired from the Pennsylvanian Ross Sandstone Formation, western Ireland, where a range of hybrid event beds have been identified. Raw X-ray fluorescence counts are calibrated against element concentrations and mineral abundances determined on coincident core plugs, with element and element log-ratios used as proxies to track vertical changes in abundances of quartz, illite (including mica), chlorite and calcite cement. New insights include ‘stepped’ (to higher values) as opposed to ‘saw-tooth’ vertical changes in mud content and the presence of compositional banding that would otherwise be overlooked. Hybrid event beds in basin floor sheets that arrived ahead of the prograding fan system have significantly cleaner sandy components than those in mid-fan lobes. The latter may imply that the heads of the currents emerging from mid-fan channels entrained significant mud immediately before they collapsed. Many of the H3 debrites are bipartite with a sandier H3a division attributed to re-entrainment and mixing of a trailing debris or fluid mud flow (H3b) with sand left by the forward part of the flow. Hybrid event bed structure may thus partly reflect substrate interaction and mixing during deposition, and the texture of the bed divisions may not simply mirror those in the suspensions from which they formed.     

Numerical modelling and analysis of the influence of local variation in the thickness of a coal seam on surrounding stresses: Application to a practical case

One of the factors with the most influence in the carrying out of underground coal mining work is the stress state, especially when such work is carried out at great depths. One of the mining methods in which the influence of stresses becomes most patent is that of sublevel caving. For that reason, a variety of authors have studied many of the causes which condition the stress state of mining work of this kind at a general level.However, diverse types of conditioning factors exist at a local level that may substantially vary recorded pressures in the surroundings of the workings. Using numerical models, this paper analyses the specific case of a coal seam mined by the sublevel caving method at a depth of 1000 m which suffers significant increases in stress and major deformations in certain advance headings as a result of variations in the geometry and dimensions of the load itself, in particular, thinning.The results of the research carried out were validated by measuring the stresses in the area under study. Furthermore, on the basis of a retrospective analysis of what was observed in the mine, another series of predictive models were analyzed to establish the existing relation between the increase in stress due to thinning of the seam and the depth at which such thinning is situated.