Facies and architectural element analysis of a meandering fluvial succession: The Permian Warchha Sandstone, Salt Range, Pakistan

The 30 to 155 m thick Early Permian (Artinskian) Warchha Sandstone of the Salt Range, Pakistan is a conglomerate, sandstone and claystone succession within which seven lithofacies types (Gt, St, Sp, Sr, Sh, Fl and Fm) occur in a predictable order as repeated fining-upward cycles. Common sedimentary structures in the conglomerates and sandstones include planar and trough cross-bedding, planar lamination, soft sediment-deformed bedding, compound cosets of strata with low-angle inclined bounding surfaces and lags of imbricated pebbles. Structures in the finer-grained facies include desiccation cracks, raindrop imprints, caliche nodules and bioturbation. Groups of associated facies are arranged into nine distinct architectural elements (channels, gravel bars, sandy bedforms, downstream and laterally accreting barforms, sand sheets, crevasse splays, levees, floodplain units and shallow lakes), which is consistent with a fluvial origin for the succession. The types of architectural elements present and their relationship to each other demonstrate that the Warchha Sandstone preserves a record of a meandering river system that drained the northern margin of Gondwanaland. The dominance of fine-grained (floodplain) facies over gravel-grade (channel-base) facies and the widespread occurrence of large-scale lateral accretion elements supports the interpretation of a high-sinuosity, meandering fluvial system in which channel bodies accumulated via the lateral accretion of point bars but in which the active channels covered only a small part of a broad floodplain at any time instant. Although the regional and temporal distribution of these deposits is complex, in broad terms the lower part is dominated by stacked, multistorey channel bodies, whereas single-storey channel elements isolated in abundant fine-grained floodplain deposits dominate the middle and upper parts of the formation.     

基于ASCAT风场数据的中国近海风能资源评估

卫星反演海面风场资料能够弥补海上气象测风资料缺乏的不足,对近海风能资源评估具有重要意义。通过ASCAT(Advanced Scatterometer)风速数据与美国及中国近海岸浮标测风资料的对比分析,结果表明,ASCAT风速的均方根误差为1.27 m·s-1。比较利用近海岸浮标逐小时风速及与其相匹配ASCAT瞬时风速计算的各项风能参数,得出ASCAT与浮标的平均风速和风功率密度的残差分别在±0.5 m·s-1和±50 W·m-2以内,该残差占浮标计算结果的比例分别在±8%和±12%以内。使用ASCAT风速资料拟合的Weibull分布函数与浮标的结果较吻合。因此,ASCAT风速资料也能够为海上风能资源评估提供有用的风能参数信息。最后使用ASCAT瞬时风速数据分析了中国近海10 m及70 m高度处的风能资源的空间分布特征,结果表明,台湾海峡平均风速和风功率密度最大。     

Significant load and green water on deck of offshore units/vessels

In this paper the probability of green water occurrence is investigated by taking into account the threshold of the vertical relative motion exceeding the freeboard. The number of wetting of the unit/vessel is predicted using probabilistic method. This paper compares the significant load, due to shipping of green water with the works of other researchers, and the loads are found to be close with the results presented in this paper. There is no direct relation between the velocities in the waves and the water velocity over the deck. The water velocities around the bow are heavily distributed by the presence of the bow. This scenario makes the flow very complex for schematic modelling.     

Exploration prospects of oil and gas in the Northwestern part of the Offshore Indus Basin,Pakistan

Oil and gas resources are short in Pakistan and no commercially viable oil and gas sources have been yet discovered in its offshore areas up to now. In this study, the onshore-offshore stratigraphic correlation and seismic data interpretation were conducted to determine the oil and gas resource potential in the Offshore Indus Basin, Pakistan. Based on the comprehensive analysis of the results and previous data, it is considered that the Cretaceous may widely exist and three sets of source rocks may be developed in the Offshore Indus Basin. The presence of Miocene mudstones has been proven by drilling to be high-quality source rocks, while the Cretaceous and Paleocene–Eocene mudstones are potential source rocks. Tectonic-lithologic traps are developed in the northwestern part of the basin affected by the strike-slip faults along Murray Ridge. Furthermore, the Cretaceous and Paleocene–Eocene source rocks are thick and are slightly affected by volcanic activities. Therefore, it can be inferred that the northwestern part of Offshore Indus Basin enjoys good prospects of oil and gas resources.     

New high-resolution 2D seismic imaging of fluid escape structures in the Makran subduction zone,Arabian Sea

Seabed fluid escape is active in the Makran subduction zone, Arabian Sea. Based on the new high-resolution 2D seismic data, acoustic blanking zones and seafloor mounds are identified. Acoustic blanking zones include three kinds of geometries: Bell-shaped, vertically columnar and tilted zones. The bell-shaped blanking zone is characterized by weak and discontinuous reflections in the interior and up-bending reflections on the top, interpreted as gas chimneys. Vertically columnar blanking zone is interpreted as side-imaged gas chimneys associated with focused fluid flow and topped by a seafloor anomaly expressed as a localized reflection discontinuity, which may together serve as a vent structure. Tilted acoustic blanking zone could be induced by accretionary thrust activity and rapid sedimentation surrounding slope. Seafloor mounds occur at the sites of bell-shaped acoustic blanking zone and may be associated with the material intrusion. Bottom simulating refectors (BSRs) are widely distributed and exhibit a series of characteristics including diminished amplitude, low continuity as well as local shoaling overlapping with these acoustic blanking zones. The large amount of gases dissociated from the gas hydrates migrated upwards and then arrived at the near-seafloor sediments, followed by the formation of the gas hydrates and hence the seafloor mound.     

Environmental management frameworks for offshore mining: the New Zealand approach

The New Zealand region contains untapped natural mineral, oil, and gas resources while also supporting globally unique and diverse faunal communities that need to be managed sustainably. In this paper key information from the international literature is reviewed that can underpin an Environmental Mining Management System which includes elements of Environmental Risk Assessment, Environmental Impact Assessment and Environmental Management Planning. This paper focuses on four developing areas of seafloor mining activities presently being undertaken or planned in the New Zealand region: hydrocarbons (oil and gas), minerals, ironsands and phosphorite nodules. A number of issues with the implementation of environmental management systems are identified including the difficulty of assessing new marine activities or technologies and the need for standardised reporting metrics. Finally, the development of ecosystem-based management and marine spatial planning is discussed which will be required to enhance environmental mining management frameworks in New Zealand.     

Effect of geometric and material discontinuities on the reeling of pipelines

The winding and unwinding of a pipeline onto a large diameter reel as practiced in the reeling installation method, induces bending strains of 1–3% followed by straightening, and reverse bending. The operator must ensure that such plastic deformations are sustained free of local buckling or rupture in the line. Such failures are for example precipitated by pipeline discontinuities in wall thickness and yield stress as they act as stress risers, lead to localized deformations severe enough to result in local buckling. The effect of such discontinuities is studied using a large-scale nonlinear finite element model that simulates the reeling/unreeling of a pipeline. Nonlinear kinematic hardening is used to capture the elasto-plastic behavior of the material imposed by the bending/reverse bending history. Discontinuities in wall thickness and yield stress are shown to result in sharp local changes in curvature that extend over 3–4 pipe diameters accompanied by severe local straining and ovalization. The extent of the disturbance is governed by the bending strain imposed by the ratio of pipe to reel diameter. It can be reduced by an increase in the applied tension but at the expense of additional ovalization of the pipeline. It can also be reduced by increasing the pipe wall thickness but with the consequent increase in costs. A parametric study of the effect of such discontinuities demonstrates that for some combinations of process parameters, the disturbance can lead to local buckling either during winding or unwinding. It is concluded that a modeling framework such as the one presented should be used to generate a design protocol for reel-installed pipelines.     

Recreational use of offshore wind farms: Experiences and opinions of sea anglers in the UK

The expansion of offshore wind farms (OWFs) is likely to increase conflict with other marine users as different sectors compete for space. There may also be positive interactions, as the artificial reef effects from energy infrastructure have the potential to sustain and enhance fishing opportunities. Recreational sea angling is an important sector within the UK but the experiences and opinions of UK sea anglers with respect to OWFs have not been documented. To address this, an online survey was undertaken with recreational anglers around the UK (n=199). Respondents represented a range of socio-demographic and angling characteristics, although male, more frequent and older fishers as well as club members were over-represented compared to a 2012 national survey. One quarter of the respondents had fished around the perimeter of or within an OWF, most on multiple occasions, and 73% of those who had not expressed a willingness to do so in future. Anglers reported both positive and negative effects on catch success when fishing near or within OWFs compared to their experiences of the same site prior to OWF development. Outcomes for individual species were also mixed. Anglers recognised the potential artificial reef effects of OWFs and their role as a “safe haven”, particularly due to the exclusion of commercial fishers. Negative perceptions included restricted access, harm to marine wildlife, and visual impact. There is little evidence that OWFs will have a significant economic impact on recreational fishing, as most anglers are unlikely to change their behaviour in response to future developments.     

Business case for mussel aquaculture in offshore wind farms in the North Sea

The European Blue Growth strategy aims to expand the new maritime sectors of aquaculture, energy, biotechnology, coastal tourism and mineral mining. Growth of these sectors will increases pressure on the seas, particularly on those areas that are densely used by traditional sectors such as fisheries and transport. This has triggered interest in developing multiuse of space and multiuse platforms at sea. This paper assesses the feasibility of offshore mussel production project in wind farms by design and ex-ante evaluation of a mussel aquaculture system in the North Sea. A system for mussel cultivation in the Dutch Borssele offshore wind farm was designed, producing both mussel seed and consumption-sized mussels with semi-submerged longlines. Based on the economic model and the risk assessment, this paper concludes that mussel aquaculture is an appealing commercial model for increased returns in offshore wind farms. The economic models shows that the internal rate of return and net present value are positive and based on the sensitivity analysis, it can be concluded that these results are robust.     

海洋油气开发工程环境影响评价特点浅析

相比陆上油气开发工程和其他海洋工程而言,海洋油气开发工程有其自身的特点,海洋油气开发工程环境影响评价应关注的内容与其他工程有所不同。文章通过分析海洋油气开发工程的特点以及对环境影响的特点,提出海洋油气开发工程环境影响评价要点,即包括施工期悬浮泥沙及钻井液钻屑排放对海洋生态环境的影响、运营期含油生产水排放对海洋生态环境的影响、工程建设对海洋环境敏感目标的影响、溢油事故环境风险分析、污染防治及生态保护措施,并针对目前海洋油气开发工程环境影响评价存在的问题提出改进建议。