Systems and Methods for Placing Markers in a Formation

Abstract

A marker placement device, such as a modified coring gun, is used to place one or more markers into the formation. The marker placement device uses explosive charges to fire one or more marker assemblies into a borehole wall. A marker assembly includes a driver assembly which is adapted to be fired from the placement device and a marker which is releasably secured to the driver with frangible shear members.

1 . A marker assembly to be fired from a marker placement tool to place a marker in a formation surrounding a wellbore, the marker assembly comprising:
 a marker to be disposed within the formation;   a driver assembly that is shaped and sized to be fired from a marker placement tool; and   the driver assembly being releasably secured to the marker.   
     
     
         2 . The marker assembly of  claim 1  wherein the marker further comprises:
 an outer housing defining an interior chamber; 
 a magnetic insert retained within the chamber. 
 
     
     
         3 . The marker assembly of  claim 1  wherein the marker further comprises an RF marker. 
     
     
         4 . The marker assembly of  claim 1  further comprising a cushion within the chamber to protect the magnetic insert from breakage. 
     
     
         5 . The marker assembly of  claim 1  wherein the driver assembly is releasably secured to the marker by a frangible shear member. 
     
     
         6 . The marker assembly of  claim 5  wherein the frangible shear member comprises a shear screw formed of polymer. 
     
     
         7 . The marker assembly of  claim 2  wherein the housing is non-magnetic. 
     
     
         8 . The marker assembly of  claim 1  further comprising a retrieval cable affixed to the driver assembly for retrieving the driver assembly. 
     
     
         9 . A system for placing markers within a formation surrounding a wellbore, the system comprising:
 a marker placement tool for firing a marker assembly into the formation;   a marker assembly comprising:
 a marker to be disposed within the formation; 
 a driver assembly that is shaped and sized to be fired from a marker placement tool; and 
 the driver assembly being releasably secured to the marker. 
   
     
     
         10 . The system of  claim 9  wherein the marker placement tool comprises a sidewall coring gun. 
     
     
         11 . The system of  claim 9  wherein the marker further comprises:
 an outer housing defining an interior chamber; 
 a magnetic insert retained within the chamber. 
 
     
     
         12 . The system of  claim 11  further comprising a cushion within the chamber to protect the magnetic insert from breakage. 
     
     
         13 . The system of  claim 9  wherein the driver assembly is releasably secured to the marker by a frangible shear member. 
     
     
         14 . The system of  claim 13  wherein the frangible shear member comprises a shear screw formed of polymer. 
     
     
         15 . The system of  claim 11  wherein the housing is non-magnetic. 
     
     
         16 . The system of  claim 9  further comprising a retrieval cable extending between the driver assembly and the marker placement tool for retrieval of the driver assembly. 
     
     
         17 . A method of placing markers within a formation surrounding a wellbore having a wellbore wall, the method comprising the steps of:
 a) disposing a marker placement tool within a wellbore;   b) firing a marker assembly from the marker placement tool into the wellbore wall, the marker assembly having a marker to be disposed within the formation and a driver assembly that is shaped and sized to be fired from the marker placement tool;   c) lodging the driver assembly in the wellbore wall; and   d) separating the marker from the driver assembly, allowing the marker to penetrate into the formation beyond the wellbore wall.   
     
     
         18 . The method of  claim 17  wherein the step of separating the marker from the driver assembly further comprises shearing a frangible shear member. 
     
     
         19 . The method of  claim 17  further comprising the step of retrieving the driver assembly from the wellbore wall. 
     
     
         20 . The method of  claim 19  wherein the driver assembly is retrieved from the wellbore wall by a retrieval cable that interconnects the driver assembly with the marker placement tool.