Method and apparatus for a downhole excavation in a wellbore

Abstract

The method and apparatus can create excavation cavities suitable for drilling multilateral wellbores through the excavation using a kick-off. One embodiment of the method comprises isolating a wellbore at a determined location, excavating a downhole cavity in a wellbore above the determined location, and removing the apparatus for isolating the wellbore and the apparatus for excavating the downhole cavity from the wellbore to provide full access to the wellbore and the excavation cavity.

1 ) An apparatus for excavating in a wellbore comprising,
 (a) means for isolating a wellbore at a determined location;   (b) means for excavating a downhole cavity around the entire circumference of a portion of the wellbore; wherein the means for excavating is adapted to provide a downhole cavity having at least one configuration selected from the group comprising: a cavity having radial clearance to enable lateral kick-off without concrete plugs; a cavity sized to accommodate kick-off of multiple laterals from the cavity; and   (c) means for removing the means for isolating the wellbore and means for excavating a downhole cavity in a wellbore thereby providing full access to the wellbore and the excavated cavity.   
   
   
       2 ) The apparatus of  claim 1  further comprising means for drilling a lateral bore through the excavated cavity. 
   
   
       3 ) The apparatus of  claim 1  wherein the downhole cavity is substantially concentric with respect to the wellbore. 
   
   
       4 ) The apparatus of  claim 1  wherein the means for excavating the downhole cavity removes a section of casing from the wellbore. 
   
   
       5 ) The apparatus of  claim 1  further comprising drilling at least two lateral bores through the excavated cavity. 
   
   
       6 ) A method for excavating a wellbore comprising,
 (a) providing means to isolate a wellbore;   (b) isolating a wellbore at a determined location;   (c) providing means to excavate a downhole cavity in the wellbore; and   (d) excavating a downhole cavity around the entire circumference of a section of the wellbore.   
   
   
       7 ) The method of  claim 6  further comprising removing the means for excavating the downhole cavity from the wellbore and removing the means for isolating the wellbore thereby providing full access to the wellbore and the excavated cavity. 
   
   
       8 ) The method of  claim 6  further comprising drilling a lateral bore through the excavated cavity. 
   
   
       9 ) The method of  claim 6  wherein the downhole cavity is substantially concentric with respect to the wellbore. 
   
   
       10 ) The method of  claim 6  wherein the means for excavating the downhole cavity removes a section of casing from the wellbore. 
   
   
       11 ) The method of  claim 7  further comprising drilling a plurality of lateral bores through the excavated cavity. 
   
   
       12 ) A method for excavating a wellbore comprising,
 (a) installing a packer in a wellbore at a desired orientation;   (b) attaching a drillpipe stinger on top of the packer, the drillpipe stinger comprising a tapered top adapted to attach an overshot section milling on top of the drillpipe stinger and a hollow ported-stub, means for the drillpipe stinger ports to direct flow of drilling fluids to the annulus between the drillstring and casing wherein the circulation of drilling fluids removes drill cuttings;   (c) attaching an overshot section milling assembly to the tapered top on the drillpipe stinger;   (d) initiating the drillstring rotation to extend the section-mill retractable arm to cut a cavity in the casing; and   (e) initiating pumping operations to lift the cutting debris out of the well.   
   
   
       13 ) The method of  claim 12  further comprising removing the overshot section milling assembly from the wellbore. 
   
   
       14 ) The method of  claim 13  further comprising removing the drillpipe stinger and packer thereby providing full access to the wellbore and the excavated cavity. 
   
   
       15 ) The method of  claim 12  wherein the tapered drillpipe stinger top is adapted to attach an overshot whipstock assembly and further comprising;
 (a) providing an overshot whipstock assembly on a drillstring and attaching the overshot whipstock assembly on the tapered top of the drillpipe stinger;   (b) releasing the drillpipe stinger from the overshot whipstock assembly and pulling the drillstring out of the wellbore; and   (c) running a drilling assembly to drill a lateral bore.   
   
   
       16 ) The method of  claim 15  further comprising removing the overshot whipstock assembly, drillpipe stinger and packer, thereby providing full access to the wellbore and the cavity. 
   
   
       17 ) The method of  claim 15  further comprising cementing a lateral liner in the lateral bore. 
   
   
       18 ) The method of  claim 17  further comprising a washover procedure wherein the washover procedure retrieves the liner stub protruding from the lateral bore, the overshot whipstock assembly and the drillpipe stinger assembly. 
   
   
       19 ) A multilateral wellbore comprising a lateral bore drilled according to the method of  claim 15 .