Lithostratigraphy determination and mineralogical variation of subduction input sediments from wireline log data: NanTroSEIZE IODP Expedition 322

根据测井数据确定俯冲输入沉积物的岩石地层学和矿物学变化：NanTroSEIZE IODP Expedition 322

• 批准号: NE/H013636/1
• 负责人: Michael Lovell
• 金额: $ 2.02万
• 依托单位: University of Leicester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH013636%2F1
• 关键词: Lithostratigraphy; determination; mineralogical; variation; subduction

The Integrated Ocean Drilling Programme (IODP) Expedition 322 is part of the Nankai Trough seismogenic zone experiment (NanTroSEIZE). The Nankai Trough is located along the SW margin of Japan, and is part of a subduction zone in the western Pacific where large magnitude earthquakes (>8) have occurred repeatedly. These earthquakes pose a significant threat to people but also allow scientists to study the science of plate tectonics. This experiment is a multi-expedition drilling project, designed to investigate fault mechanics and seismogenesis through direct sampling, in situ measurements, and long-term monitoring in conjunction with laboratory studies and numerical modeling. As part of Stage 2 of NanTroSEIZE IODP Expedition 322 targets the sediments in the Shikoku Basin (Philippine Sea Plate) seaward of the subduction zone. The aim is to characterize the composition, lithology and physical properties of the undeformed sediments which form the input to the subduction system. This will define a reference dataset to track changes during deformation as sediments either enter the subduction zone or are accreted into the accretionary prism. NanTroSEIZE Expedition 322 will drill two wells in the Shikoku Basin with continuous coring and wireline log data through undisturbed sediments; likely to be dominated by hemipelagic mud with volcanic ash layers and sand-silt turbidites. The downhole logs provide continuous measurements from the strata beneath the seafloor and are a 'representative' or a 'proxy' for the rock properties in-situ. We will use standard interpretation techniques, and also develop new interpretation methodologies, to use these data (electrical, nuclear, images of the rocks along the borehole sides) to deduce rock properties, e.g. rock type, sediment character, and fluid type. In particular we will focus on identifying where the rock types change even where actual samples cannot be retrieved, and in identifying different facies as well as changes in porosity (compaction), sediment mineralogy and fluid content. The main aim is to develop a facies scheme by integrating the datasets acquired through observations and measurements on recovered core and downhole logs, to produce a vertical column representing the sediment succession present at the drill site, and allow the characterization of sediments purely from log data. The project will also interpret other characteristics, such as structures produced by sediment transport or post-deposition disturbance. During earthquakes sediments accumulated on a nearby knoll may become unstable and 'fail' resulting in transport by slumps and slides. The resultant deposits will exhibit different sedimentary structures which will be visible on the borehole image logs. Previous (Stage 1) sites drilled through the fault system measured more disturbed (deformed) sedimentary strata. We will compare results from the undisturbed sediments with data from the deformed sedimentary successions to compare lithologies, mineralogies and structures. Stage 2 provides the ideal opportunity to maximise core-log integration and through this integration we will propose an overarching scheme that will group the successions into units with similar data characteristics, identify structural and fluid flow features and enable us to suggest sediment characteristics in the absence of core. Ultimately our results will deliver a predictive capability to allow future recognition and prediction of sediment properties from log data alone. This will be invaluable in interpreting future NanTroSEIZE drilling (Stage 3), where deeper sediments within the prism are targeted but limited core recovery is planned, and will be essential for integrating the results of all 3 NanTroSEIZE Stages. This project is at the interface with applied research: the type of data collected is used by industry in exploration, and its interpretation will become increasingly important in the search for smaller oil and gas fields.

综合大洋钻探计划第322次考察是南海海槽孕震区实验的一部分。南海海槽位于沿着日本西南边缘，是西太平洋俯冲带的一部分，在那里多次发生大地震（>8级）。这些地震对人类构成了重大威胁，但也使科学家能够研究板块构造科学。该实验是一个多勘探钻探项目，旨在通过直接取样、现场测量和长期监测，结合实验室研究和数值模拟，调查断层力学和地震成因。作为NanTroSEIZE IODP第二阶段的一部分，第322次考察的目标是四国盆地（菲律宾海板块）俯冲带向海的沉积物。目的是确定构成俯冲系统输入物的未变形沉积物的成分、岩性和物理性质。这将定义一个参考数据集，以跟踪变形期间的变化，因为沉积物要么进入俯冲带，要么被增生到增生棱柱。NanTroSEIZE Expedition 322将在Shikoku盆地钻两口威尔斯井，通过未受干扰的沉积物进行连续取芯和电缆测井数据;可能主要是半远洋泥浆，含火山灰层和砂-粉砂浊积岩。井下测井提供海底地层的连续测量值，是现场岩石特性的“代表”或“代用品”。我们将使用标准解释技术，并开发新的解释方法，以利用这些数据（电气、核、沿着钻孔两侧的岩石图像）推断岩石性质，例如岩石类型、沉积物特征和流体类型。特别是，我们将专注于识别岩石类型的变化，即使在实际样品无法检索，并在识别不同的相以及孔隙度（压实），沉积物矿物学和流体含量的变化。主要目的是通过整合通过对回收的岩心和井下测井进行观察和测量而获得的数据集来制定相方案，以产生代表钻井现场存在的沉积物序列的垂直柱，并允许纯粹从测井数据表征沉积物。该项目还将解释其他特征，如沉积物迁移或沉积后扰动产生的结构。在地震期间，堆积在附近小山丘上的沉积物可能变得不稳定，并“失败”，导致通过滑塌和滑坡进行运输。由此产生的矿床将显示出不同的沉积结构，这些结构将在井眼成像测井上可见。以前（第1阶段）通过断层系统钻探的地点测量到更多的扰动（变形）沉积地层。我们将比较原状沉积物的结果与变形沉积序列的数据，以比较岩性、矿物学和结构。第2阶段提供了最大限度地提高岩心-测井整合的理想机会，通过这种整合，我们将提出一个总体方案，将序列分组为具有相似数据特征的单元，确定结构和流体流动特征，并使我们能够在没有岩心的情况下提出沉积物特征。最终，我们的研究结果将提供一个预测能力，使未来的识别和预测沉积物的性质，从单独的日志数据。这对于解释未来的NanTroseIZE钻探（第3阶段）将是非常宝贵的，其中目标是棱柱体内更深的沉积物，但计划进行有限的岩心回收，并且对于整合所有3个NanTroseIZE阶段的结果至关重要。该项目与应用研究相结合：工业界在勘探中使用所收集的数据类型，其解释在寻找较小的石油和天然气田方面将变得越来越重要。