Geophysical downhole logging analysis within the shallow depth ICDP STAR drilling project (Central Italy)

IF 3.2 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Solid Earth Pub Date : 2024-05-13 DOI:10.5194/egusphere-2024-1249

Paola Montone, Simona Pierdominici, Maria Teresa Mariucci, Francesco Mirabella, Marco Urbani, Assel Akimbekova, Lauro Chiaraluce, Wade Johnson, Massimiliano Rinaldo Barchi

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引用次数: 0

Abstract

Abstract. The ICDP STAR drilling project aims to study the seismic and aseismic fault slip behaviour of the active low-angle Alto Tiberina normal Fault (ATF) in the Northern Apennines, Central Italy, drilling and instrumenting six shallow boreholes with seismometers and strainmeters. During the STAR field work, a geophysical downhole logging campaign was carried on defining the optimal target depth for instrument deployment and formation rock characterization. In particular, the main objectives of this study were to define in situ physical properties of the rocks and the tectonic discontinuity geometry along the boreholes. The downhole logging data provide new findings and knowledge especially with regards to the physical properties such as resistivity, gamma ray and wave velocity. The collected parameters were compared to the results of literature data collected in similar lithologies, as well as with the results of logging performed in deeper wells drilled for commercial purposes. The physical properties of the Mesozoic-Early Tertiary calcareous formations show low Gamma Ray values and high compressional (Vp) and shear wave (Vs) velocities (up to 5.3 km/s and 2.9 km/s, respectively), whereas the overlying clay-rich Late Tertiary formations exhibit high Gamma Ray and low resistivity and relatively low Vp and Vs values (up to 3.5 km/s and 2.0 km/s, respectively). The results obtained from the analysis of the orientations of the tectonic structures, measured along the six boreholes, show a good agreement with the orientations of the present-day extensional stress field, NE-SW oriented. Our study allowed to bridge the gap between the physical properties obtained from literature data and those obtained from the deep wells measurements, representing a possible case history for future projects. These new data will contribute to the advancement of knowledge of the physical properties of the rocks at shallow depths, typically overlooked.

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ICDP STAR 钻探项目（意大利中部）浅层井下地球物理测井分析

摘要ICDP STAR 钻探项目旨在研究意大利中部亚平宁半岛北部活跃的低角度 Alto Tiberina 正断层（ATF）的地震和非地震断层滑动行为，该项目使用地震仪和应变仪钻探了六个浅孔并安装了仪器。在 STAR 实地工作期间，进行了一次地球物理井下测井活动，以确定仪器部署和地层岩石特征描述的最佳目标深度。特别是，这项研究的主要目标是确定岩石的现场物理特性和沿钻孔的构造不连续几何形状。井下测井数据提供了新的发现和知识，特别是在电阻率、伽马射线和波速等物理特性方面。收集到的参数与在类似岩性中收集到的文献数据结果以及为商业目的钻探的深井测井结果进行了比较。中生代-早第三纪钙质地层的物理性质显示出较低的伽马射线值以及较高的压缩波（Vp）和剪切波（Vs）速度（分别高达 5.3 千米/秒和 2.9 千米/秒），而上覆富含粘土的晚第三纪地层则显示出较高的伽马射线值和较低的电阻率以及相对较低的 Vp 值和 Vs 值（分别高达 3.5 千米/秒和 2.0 千米/秒）。沿六个钻孔测量的构造结构方向分析结果显示，与当今东北-西南走向的伸展应力场方向十分吻合。我们的研究弥补了从文献数据中获得的物理性质与深井测量获得的物理性质之间的差距，为未来的项目提供了可能的案例。这些新数据将有助于增进人们对通常被忽视的浅层岩石物理性质的了解。

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来源期刊

Solid Earth GEOCHEMISTRY & GEOPHYSICS-

CiteScore

6.90

自引率

8.80%

发文量

审稿时长

4.5 months

期刊介绍： Solid Earth (SE) is a not-for-profit journal that publishes multidisciplinary research on the composition, structure, dynamics of the Earth from the surface to the deep interior at all spatial and temporal scales. The journal invites contributions encompassing observational, experimental, and theoretical investigations in the form of short communications, research articles, method articles, review articles, and discussion and commentaries on all aspects of the solid Earth (for details see manuscript types). Being interdisciplinary in scope, SE covers the following disciplines: geochemistry, mineralogy, petrology, volcanology; geodesy and gravity; geodynamics: numerical and analogue modeling of geoprocesses; geoelectrics and electromagnetics; geomagnetism; geomorphology, morphotectonics, and paleoseismology; rock physics; seismics and seismology; critical zone science (Earth''s permeable near-surface layer); stratigraphy, sedimentology, and palaeontology; rock deformation, structural geology, and tectonics.