Method and apparatus for sensing elongated subterranean anomalies

摘要

Various logging-while-drilling (LWD) systems and methods provide resistivity logging coupled with deep detection of elongated anomalies at acute angles, enabling effective geosteering without disrupting drilling operations and without requiring intervention in the operations of the existing well. One LWD system embodiment employs a tool having tilted antennas as the transmitter and the receiver, where at least one of the antennas is placed in the vicinity of the bit, making it possible to detect existing wells at distances of 50-100 feet. In some cases, the detection distance is increased by enhancing the visibility of the existing well using a contrast fluid treatment on target well, either to fill the bore or to surround the well with treated cement or fluids that invade the formation. At least one inversion method separates the inversion of formation parameters from the inversion of parameters specifying distance, direction, and orientation of the existing well.

主权项

1. A geosteering system that comprises:
a electromagnetic logging tool to obtain a multi-component response; a position and orientation tracking module to associate tool position and orientation information with measurements of the logging tool; and a processing system to invert the logging tool measurements to estimate formation parameters and the position and orientation of one or more elongated anomalies, said orientation being expressible in terms of a tilt angle of the elongated anomaly relative to a first line in an X-Y plane of the tool and a cross angle of the elongated anomaly relative to a second line in the X-Y plane perpendicular to the first line.