US 12,078,053 B2
Null point depth calibration
Scott B. Cole, Edmond, OK (US)
Assigned to The Charles Machine Works, Inc., Perry, OK (US)
Filed by The Charles Machine Works, Inc., Perry, OK (US)
Filed on Aug. 5, 2022, as Appl. No. 17/881,804.
Claims priority of provisional application 63/231,055, filed on Aug. 9, 2021.
Prior Publication US 2023/0056853 A1, Feb. 23, 2023
Int. Cl. E21B 47/092 (2012.01); E21B 7/04 (2006.01); G01V 3/08 (2006.01); G01V 3/38 (2006.01)
CPC E21B 47/092 (2020.05) [E21B 7/046 (2013.01); G01V 3/081 (2013.01); G01V 3/38 (2013.01)] 22 Claims
OG exemplary drawing
 
1. A method, comprising:
advancing a drill string carrying a beacon to a first underground location;
emitting an electromagnetic signal from the beacon;
performing a calibration procedure comprising:
at an above ground location, detecting a first null point and a second null point with a receiving antenna;
determining a distance between the first null point and the second null point and storing the distance in a memory;
receiving a signal indicative of a pitch of the beacon;
determining a signal strength at the selected one of the first null point and the second null point;
using the pitch and the signal strength to determine a calibration constant; and
storing the calibration constant in a memory.