Through Casing Coring

Abstract

Devices and methods for obtaining core samples from a formation that surrounds a cased wellbore. A coring tool includes a casing cutter for cutting an opening in the casing and a coring device for obtaining a core sample from the formation.

What is claimed is: 
     
         1 . A coring tool for obtaining a core sample from a formation surrounding a cased wellbore, the coring tool comprising:
 a casing cutter for cutting an opening in casing lining the wellbore; and   a coring device for obtaining a core sample from the formation.   
     
     
         2 . The coring tool of  claim 1  further comprising a hole plugging subassembly to close off said opening in the casing lining the wellbore. 
     
     
         3 . The coring tool of  claim 1  wherein:
 the coring tool has an outer housing having an opening therein; and 
 the casing cutter and the coring device are retained within a carrier that is moveable within the outer housing between a first operational position wherein the casing cutter is aligned with the opening in the coring tool housing and a second operational position wherein the coring device is aligned with the opening in the coring tool housing. 
 
     
     
         4 . The coring tool of  claim 3  wherein the carrier is rotatable within the casing tool housing. 
     
     
         5 . The coring tool of  claim 1  wherein the casing cutter comprises a casing cutting mill bit that is mounted upon a rotary cutting device. 
     
     
         6 . The coring tool of  claim 1  wherein the coring device comprises a coring bit that is mounted upon a rotary cutting device. 
     
     
         7 . The coring tool of  claim 1  wherein:
 the coring tool is positioned by wireline manipulation to align the casing cutter with a target position within the wellbore from which it is desired to obtain a core sample; and 
 the coring tool is then repositioned by wireline manipulation to align the coring device with the target position to obtain a coring sample from the target position. 
 
     
     
         8 . A coring tool for obtaining a core sample from a formation surrounding a cased wellbore, the coring tool comprising:
 a casing cutter for cutting an opening in casing lining the wellbore;   a coring device for obtaining a core sample from the formation; and   a hole plugging subassembly to close off said opening in the casing lining the wellbore.   
     
     
         9 . The coring tool of  claim 8  wherein:
 the coring tool has an outer housing having an opening therein; and 
 the casing cutter and the coring device are retained within a carrier that is moveable within the outer housing between a first operational position wherein the casing cutter is aligned with the opening in the coring tool housing and a second operational position wherein the coring device is aligned with the opening in the coring tool housing. 
 
     
     
         10 . The coring tool of  claim 9  wherein the carrier is rotatable within the casing tool housing. 
     
     
         11 . The coring tool of  claim 8  wherein the casing cutter comprises a casing cutting mill bit that is mounted upon a rotary cutting device. 
     
     
         12 . The coring tool of  claim 8  wherein the coring device comprises a coring bit that is mounted upon a rotary cutting device. 
     
     
         13 . A method of obtaining a core sample from a formation surrounding a cased wellbore, the method comprising the steps of:
 forming an opening in casing lining the wellbore; and   obtaining a core sample from the formation.   
     
     
         14 . The method of  claim 13  further comprising the step of closing o the opening in the casing. 
     
     
         15 . The method of  claim 14  wherein the step of closing off the opening in the casing further comprises actuating a hole plugging subassembly to emplace a plug in the opening. 
     
     
         16 . The method of  claim 13  further comprising disposing the core sample in a core sample receptacle within the coring tool. 
     
     
         17 . The method of  claim 13  wherein the step of forming an opening in the casing comprises rotating a casing cutting bit to form a circular cut within the casing. 
     
     
         18 . The method of  claim 13  wherein the step of obtaining a core sample comprises rotating a coring bit to form a cylindrical core sample and separating the core sample from the formation. 
     
     
         19 . The method of  claim 13  wherein:
 the step of forming an opening in casing lining the wellbore further comprises locating the casing cutter to be aligned with a target position from which it is desired to obtain a core sample and actuating the casing cutter to cut an opening in the casing; and 
 the step of obtaining a core sample from the formation further comprises locating the coring device to be aligned with the target position and actuating the coring device to obtain a core sample from the target position. 
 
     
     
         20 . The method of  claim 19  wherein the coring device is located to be aligned with the target position by moving a bit box carriage within an outer housing of the coring tool. 
     
     
         21 . The method of  claim 19  wherein the coring device is located to be aligned with the target position by moving an outer housing containing the coring device within the wellbore.