| US 7,538,555 B2 | ||
| System and method for locating an anomaly ahead of a drill bit | ||
| Erik Banning, Houston, Tex. (US); Teruhiko Hagiwara, Houston, Tex. (US); and Rich Ostermeier, Houston, Tex. (US) | ||
| Assigned to Shell Oil Company, Houston, Tex. (US) | ||
| Filed on Jul. 23, 2004, as Appl. No. 10/897,585. | ||
| Application 10/897585 is a continuation in part of application No. 10/701735, filed on Nov. 05, 2003. | ||
| Prior Publication US 2005/0092487 A1, May 05, 2005 | ||
| This patent is subject to a terminal disclaimer. | ||
| Int. Cl. G01V 3/18 (2006.01) | ||
| U.S. Cl. 324—338 | 22 Claims |
| 1. A method for determining a distance to an anomaly in a formation ahead of a wellbore using a device comprising a transmitter
for transmitting electromagnetic signals through the formation and a receiver for detecting responses, the method comprising:
calculating one of apparent conductivity and apparent resistivity based on a detected response;
monitoring the one of apparent conductivity and apparent resistivity over time;
determining the distance to the anomaly when the one of apparent conductivity and apparent resistivity reaches an asymptotic
value; and
outputting the determined distance.
|