Downhole depth correlation and computation apparatus and methods for combining multiple borehole measurements

摘要

The current invention is directed toward the use of a downhole computer and downhole storage within a measurement-while-drilling (MWD) downhole subassembly to process data from the response of a plurality of sensors of different classes or one or more sensors of the same class which exhibit different measure points and vertical resolutions. Classes or types of sensors applicable to the invention include, but are not limited to, electromagnetic, acoustic, and nuclear. Sensor measurements are made essentially simultaneously. In combining downhole responses from one or more sensors to obtain parameters of interest, a critical prerequisite is downhole depth correlation and vertical resolution matching of all sensor responses prior to combination. Methods and apparatus are disclosed for performing these critical functions within the limits of telemetry and downhole storage capacities of current MWD systems, Alternate embodiments of the invention include wireline operations in which telemetry band width is limited by components such as single conductor logging cables employed in logging wells under high pressure. <IMAGE>