Controls on temporal & spatial distribution of organic matter in siliciclastic mudstones: implications for source rock development in Shale Gas plays

这个博士学位是一个令人兴奋的机会，可以为快速扩展的沉积学领域做出贡献，并使用创新的方法来研究影响泥岩变异性的基本物理、化学和生物控制。未来高达60%的碳氢化合物产量可能来自非常规页岩气。该博士学位将有助于了解已知的区块，并检查英国大陆架页岩气区块的潜力。直到最近，地质学家一直认为泥岩演替基本上是均匀的，任何不均匀性都是由沉积时初级生产力的变化和缺氧造成的。最近利用光学和电子光学方法的研究表明，这些岩石比以前假设的要多变得多。连续地层（毫米级和亚毫米级）可能包含由碎屑输入、初级生产力和成岩作用产生的物质比例非常不同。这些研究还表明，变异性是系统性的，可以用不同的碎屑输入、生物生产力和随后的层序地层学原理来解释。因此，了解毫米尺度下支撑岩相变异性的基本控制因素，对于解释保存在这些地层中的气候变化信号以及有效勘探非常规页岩气具有重要意义。这些尺度上的岩相变异性控制着有机质的分布、丰度及其水力压裂性质。这一建议与J. Macquaker博士（曼彻斯特大学）发表的“混合碎屑碳酸盐细粒层序中的岩相变异性：页岩气勘探甜点的识别意义”相关，但又不同。主要目的：研究硅屑泥岩岩相的变异性，以确定细粒层序中沉积和有机质保存的根本控制因素。(1)利用多学科方法（野外测井、光学、电子光学、全岩地球化学方法）描述英格兰北部宾夕法尼亚期硅屑层序泥岩特征的可变性。(2)从基本的物理、化学和生物控制的角度来解释这种可变性，这些控制作用在沉积物和水界面附近。(3)研究地球化学指标作为沉积过程中氧化还原条件的指标，可能与有机质沉积/保存增强相对应。(4)建立综合的高分辨率层序地层模型，以确定在特定环境下可能导致硅石异常富集的时空过程。(1)泥岩岩相方案，突出了富有机质相，可以从泥岩沉积的基本控制因素来解释（目标1和2）。(2)地球化学指标评估，与泥岩岩相联系，及其在解释变化的氧化还原条件和与增强的有机质保存的关联方面的意义（目标3）。(3)一个高分辨率层序地层模型，将盆地填方的所有元素结合在一起；研究了以硅质碎屑为主的浅海环境中富有机质泥岩岩相的时空分布和保存情况。（目标4）培养学生进行沉积学和层序地层学分析；沉积学和古生物学现场和实验室程序；光学和电子显微镜，地球化学制备，分析和解释技术（XRF， XRD和有机碳）。该学生将在公司（Leatherhead和Upstream Research company， Houston）工作3到18个月，并与埃克森美孚的主管进行正式会议。

This PhD is an exciting opportunity to contribute a rapidly expanding area of sedimentology and use innovative approaches to investigate the fundamental physical, chemical and biological controls that act upon mudstone variability. Up to 60% of future hydrocarbon production may derive from unconventional Shale Gas sources. This PhD would aid understanding of known plays and examine the potential for the UKCS Shale Gas plays. Until recently geologists have assumed that mudstone successions were largely homogenous with any inhomogeneties produced by changes in primary productivity and anoxia at the time of deposition. Recent studies utilising optical and electron optical methods reveal that these rocks are much more variable than previously assumed. Successive strata (mm and sub-mm scales) can contain very different proportions of material derived from clastic input, primary productivity and diagenetic processes. These studies also reveal that variability is systematic and can be interpreted in terms of varying detrital inputs, biological productivity and subsequent diagenesis using sequence stratigraphic principles. Therefore understanding the fundamental controls that underpin lithofacies variability at mm scales has significant implications for interpreting climate change signals preserved in these strata and for effectively exploring for unconventional shale gas plays. Lithofacies variability at these scales controls the distribution and abundance of organic matter and their hydrofracturing properties. This proposal is linked to, but distinct from, 'Lithofacies variability in mixed clastic carbonate fine-grained successions: implications for identifying Shale Gas exploration sweet spots' submitted by Dr. J. Macquaker (University of Manchester). Major aim: to investigate the variability of siliciclastic mudstone lithofacies in order to determine the fundamental controls on sedimentation and the preservation of organic matter in fine-grained successions. Key Objectives: (1) Describe the variability in mudstone character from Pennsylvanian siliciclastic successions from northern England using a multidisciplinary approach (field logging, optical, electron optical, whole rock geochemical methods). (2) Interpret this variability in terms of fundamental physical, chemical and biological controls operating at and close to the sediment water interface. (3) Investigate geochemical proxies as indicators of redox conditions during deposition that may correspond with enhanced organic matter deposition/preservation. (4) Generate integrated high-resolution sequence stratigraphic models in order to determine the temporal and spatial processes that might lead to unusual silica enrichment in specific environments. Deliverables (1) A mudstone lithofacies scheme, highlighting organic rich facies, that can be interpreted in terms of fundamental controls on mudstone deposition (Objectives 1 and 2). (2) An assessment of geochemical proxies, links to mudstone lithofacies and their significance in interpreting changing redox conditions and association with enhanced organic matter preservation (Objective 3). (3) A high-resolution sequence stratigraphic model that draws together all elements of the basin fill, and examines the temporal and spatial distribution, and preservation, of organic-rich mudstone lithofacies in a siliciclastic-dominated, shallow-marine setting. (Objective 4) The student will be trained in sedimentological and sequence stratigraphic analysis; sedimentological and palaeontological field and laboratory procedures; optical and electron microscopy, geochemical preparation, analytical and interpretation techniques (XRF, XRD and organic carbon). The student will spend between 3 and 18 months working within the company (Leatherhead and Upstream Research Company, Houston), in addition to formal meetings with ExxonMobil supervisors.