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

综合大洋钻探计划(IODP)322考察是南开海槽地震孕育带实验(NantroseIZE)的一部分。南开海槽位于日本西南边缘，是西太平洋俯冲带的一部分，那里曾多次发生大地震(&GT；8)。这些地震对人类构成了重大威胁，但也让科学家能够研究板块构造科学。这项实验是一个多探险钻井项目，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来研究断层力学和地震成因。作为Nantroseize IODP探险第二阶段的一部分，322次IODP探险的目标是俯冲带向海的四国盆地(菲律宾海板块)的沉积物。其目的是描述构成俯冲系统输入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，以跟踪沉积物进入俯冲带或吸积到吸积棱柱中时变形过程中的变化。Nantroseize Expesion322将在四国盆地钻两口井，用连续取心和有线测井数据穿过未受干扰的沉积物；可能主要是带有火山灰层和砂粉浊积层的半洋泥浆。井下测井提供了对海底下地层的连续测量，是现场岩石性质的“代表”或“代理”。我们将使用标准解释技术，并开发新的解释方法，以使用这些数据(电性、核性、井壁岩石的图像)来推断岩石属性，例如岩石类型、沉积物特征和流体类型。特别是，我们将侧重于识别岩石类型的变化，即使在无法提取实际样品的情况下，还将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。其主要目的是通过整合通过对回收的岩心和井下测井记录进行观察和测量而获得的数据集来制定相图，以产生代表钻探现场存在的沉积物序列的垂直柱，并允许纯粹根据测井数据来表征沉积物。该项目还将解释其他特征，如泥沙输送或沉积后扰动产生的结构。在地震期间，堆积在附近丘陵上的沉积物可能会变得不稳定，并“坍塌”，导致塌陷和滑坡。由此产生的沉积物将表现出不同的沉积结构，这将在钻孔图像记录中可见。以前(阶段1)钻过断层系统的场地测量到更多扰动(变形)的沉积层。我们将把未扰动沉积物的结果与变形沉积序列的数据进行比较，以比较岩性、矿物学和构造。第二阶段提供了最大限度地实现岩心-测井整合的理想机会，通过这一整合，我们将提出一个总体方案，将序列划分为具有相似数据特征的单元，识别结构和流体流动特征，并使我们能够在没有岩心的情况下建议沉积物特征。最终，我们的结果将提供一种预测能力，使未来能够仅从测井数据识别和预测沉积物特性。这对于解释未来的NantroSEIZE钻探(第3阶段)将是非常宝贵的，棱镜内更深的沉积物是有目标的，但计划进行有限的岩心回收，这将是整合所有3个NantroSEIZE阶段的结果所必需的。该项目处于应用研究的交界处：收集的数据类型被工业用于勘探，其解释在寻找较小油气田方面将变得越来越重要。

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.