METHOD AND APPARATUS FOR OPTICAL LOGGING

摘要

A method of characterizing underground formations, for example locating in situ hydrocarbons, comprises illuminating the borehole wall with light such as visible, infrared or ultraviolet light or combinations of these, from a source (50) in a tool such as a wireline logging tool or an LWD tool, detecting any light returning to the tool, such as fluorescent radiation, with a detector (68) in the tool and analyzing the fluorescent radiation to characterize the formation. The tool is moved through the borehole while irradiating the formation and detecting light returning through a window (62) in the tool which is pressed against the borehole wall with sufficient force to displace any mudcake. The window (62) is made of a wear resistant material such sapphire or diamond and is conveniently secured in a wear resistant housing (60) which might be made of tungsten carbide or the like.