Characterization of the Degree of Fracturing and the Nature of Fracture Alteration from MCS Logging Data at Site 395A, 418A and 504B

该项目通过分析海底钻孔的现有声波测井数据，获得高分辨率的速度和衰减估计，从而推断海洋地壳的破裂程度。这一点很重要，因为地壳中的流体流动主要是由裂缝控制的：在年轻的海洋地壳中，数据表明，浅层地壳中含有许多张开的裂缝，这些裂缝构成了一个高渗透率的欠压含水层。随着时间的变化，产品会密封这些裂缝，从而显著降低渗透率和流体流量。通过将改进的速度数据和新的衰减估计与井眼电视和伽马射线测井相结合，可以定位裂缝层，并将其描述为开放或封闭。封闭裂缝中蚀变物质性质的变化将通过速度和衰减数据，结合其他测井数据和岩心地球化学结果来确定。从衰减数据中可以识别出开放裂缝的孔径或渗透率的变化。

This project analyzes existing sonic log data from bore holes in the ocean floor to obtain high resolution velocity and attenuation estimates from which to infer the degree of fracturing in ocean crust. This is important because fluid flow in the crust is controlled primarily by fractures: in young ocean crust data indicate that the shallow crust contains many open fractures which constitute an underpressured aquifer of high permeability. With time alteration products seal these fractures which reduces the permeability and fluid flow dramatically. By integrating improved velocity data and new attenuation estimates with borehole televiewer and gamma ray logs, fractured intervals will be located and characterized as open or sealed. Variations in the nature of the alteration material in the sealed fractures will be indentified from velocity and attenuation data in conjunction with other log data and core geochemical results. Variations in the aperture or permeability of the open fractures will be identified from the attenuation data.