Downhole markers

Abstract

The present disclosure relates to one or more methods and apparatus to dispose one or more markers within a subterranean formation. The method includes positioning a drill probe assembly in a borehole extending into the subterranean formation, drilling a hole through a sidewall of the borehole with a flexible shaft of the drill probe assembly, the hole penetrating the subterranean formation, and disposing a marker in the hole.

1 . A method, comprising:
 positioning a drill probe assembly in a borehole extending into a subterranean formation;   drilling a hole through a sidewall of the borehole with a flexible shaft of the drill probe assembly, the hole penetrating the subterranean formation; and   disposing a marker in the hole.   
     
     
         2 . The method of  claim 1  wherein disposing the marking in the hole comprises using a plugging piston of the drill probe assembly to dispose the marker, at least partially, in the hole. 
     
     
         3 . The method of  claim 1  further comprising pushing the marker in the hole with the flexible shaft. 
     
     
         4 . The method of  claim 1  further comprising:
 drilling a through hole into a casing disposed within the borehole with the flexible shaft; and 
 disposing a casing plug in the through hole formed in the casing. 
 
     
     
         5 . The method of  claim 1  wherein the hole is a first hole, and wherein the marker is a first marker, the method further comprising:
 re-positioning the drill probe assembly in the borehole; 
 drilling a second hole through a sidewall of the borehole with the flexible shaft, the second hole penetrating the subterranean formation; and 
 inserting a second marker into the second hole. 
 
     
     
         6 . The method of  claim 1  wherein casing is disposed within the borehole and cement is disposed, at least partially, within an annulus formed between the casing and the borehole. 
     
     
         7 . The method of  claim 1  wherein the marker comprises a radioactive material. 
     
     
         8 . The method of  claim 1  further comprising measuring a distance between the marker and a reference location. 
     
     
         9 . The method of  claim 8  wherein measuring the distance between the marker and the reference location comprises disposing a measurement tool within the borehole. 
     
     
         10 . The method of  claim 9  wherein the marker comprises a radioactive material and the measurement tool comprises a gamma radiation detector. 
     
     
         11 . The method of  claim 8  wherein the hole is a first hole, wherein the marker is a first marker, and wherein the reference location comprises a second marker disposed in a second hole, the second hole penetrating the subterranean formation. 
     
     
         12 . The method of  claim 8  wherein the distance is a first distance, the method further comprising:
 measuring a second distance between the marker and the reference location; and 
 comparing the first distance and the second distance to each other. 
 
     
     
         13 . An apparatus, comprising:
 a drill probe assembly configured to be disposed within a borehole extending into a subterranean formation, the drill probe assembly comprising a flexible shaft and a marker;   wherein the flexible shaft is configured to drill a hole through a sidewall of the borehole, the hole penetrating the subterranean formation; and   wherein the drill probe assembly is configured to dispose the marker within the hole.   
     
     
         14 . The apparatus of  claim 13  wherein the flexible shaft is configured to dispose the marker, at least partially, within the hole. 
     
     
         15 . The apparatus of  claim 13  wherein the drill probe assembly further comprises a plugging piston and a casing plug, wherein the plugging piston is configured to dispose the plug within a through hole formed within casing. 
     
     
         16 . The apparatus of  claim 15  wherein the plugging piston is configured to dispose the marker, at least partially, within the hole. 
     
     
         17 . The apparatus of  claim 15  wherein the drill probe assembly further comprises a moveable carriage configured to move with respect to the subterranean formation. 
     
     
         18 . The apparatus of  claim 17  wherein the flexible shaft and the plugging piston translate in unison with the movable carriage and are configured to extend from the moveable carriage. 
     
     
         19 . The apparatus of  claim 15  wherein the drill probe assembly further comprises a holder in which the plug and the marker are disposed. 
     
     
         20 . The apparatus of  claim 13  wherein the marker comprises a radioactive material.