Patent ID: 9664027
Date: 2017-05-30
CPC Classifications: E21B,G01V

Claim:
1. A method for use in conjunction with a horizontal directional drilling system that includes a drill string that extends from a drill rig to an inground tool such that extension and retraction of the drill string generally produces corresponding movements of the inground tool during an inground operation, said drill string defining a through passage for carrying a pressurized flow of drilling mud from the drill rig to the inground tool for emission from the inground tool, said method comprising: during the inground operation, monitoring an annular mud pressure in the ground surrounding the inground tool; detecting a decrease in the annular mud pressure; continuing to monitor the annular mud pressure subsequent to detecting said decrease for a recovery in the annular mud pressure such that a negative going pulse is defined in the annular mud pressure; and initiating a response as being indicative of a potential cross-bore.