Plug and Gun Apparatus and Method for Cementing and Perforating Casing

Abstract

An apparatus is used in cementing and perforating casing in a borehole. A cement head disposed on the casing has first and second containers. A first plug positioned in the first container deploys from the cement head in the casing in advance of cement slurry. An assembly positioned in the second container deploys from the cement head in the casing after the cement slurry. The first plug lands on a float collar on the casing, and a breachable passage in the first plug opens and allows the cement slurry to pass into the borehole annulus. The assembly has a wiper and has one or more charges. The wiper wipes the casing as the assembly is displaced down the casing with displacing fluid. Eventually, the assembly lands at the first plug, and hydraulic pressure applied in the casing activates the one or more charges to perforate the casing.

What is claimed is: 
     
         1 . A method of cementing and perforating casing in a borehole, comprising:
 pumping cement slurry down the casing and into an annulus of the borehole;   pumping an assembly having a wiper and at least one charge down the casing behind the cement slurry;   landing the assembly in the casing;   applying hydraulic pressure in the casing; and   perforating the casing by activating the at least one charge of the assembly with the hydraulic pressure applied in the casing.   
     
     
         2 . The method of  claim 1 , wherein pumping the cement slurry down the casing and into the annulus of the borehole comprises:
 pumping a plug down the casing in advance of the cement slurry;   landing the plug in the casing; and   opening fluid communication through the plug for passage of the cement slurry.   
     
     
         3 . The method of  claim 2 , wherein landing the plug in the casing comprises landing the plug adjacent a float collar disposed on the casing. 
     
     
         4 . The method of  claim 2 , wherein pumping the plug down the casing in advance of the cement slurry comprises pumping a spacer in the casing between the plug and the cement slurry. 
     
     
         5 . The method of  claim 1 , wherein pumping the assembly down the casing behind the cement slurry comprises pumping a displacing fluid down the casing after the assembly. 
     
     
         6 . The method of  claim 1 , wherein perforating the casing comprises first permitting the cement slurry in the annulus to cure before perforating at least the casing. 
     
     
         7 . The method of  claim 1 , wherein applying the hydraulic pressure in the casing comprises applying at least one coded signal with the hydraulic pressure in the casing. 
     
     
         8 . The method of  claim 7 , wherein activating the at least one charge of the assembly with the hydraulic pressure applied in the casing comprises detecting the at least one coded signal and at least initiating activation of the at least one charge for detonation in response thereto. 
     
     
         9 . The method of  claim 7 , wherein activating the at least one charge of the assembly with the hydraulic pressure applied in the casing comprises detecting the at least one coded signal and detonating the at least one charge in response thereto. 
     
     
         10 . The method of  claim 1 , wherein applying the hydraulic pressure in the casing comprises applying the hydraulic pressure at a first pressure level at least higher than a second pressure level for testing integrity of the casing. 
     
     
         11 . The method of  claim 1 , wherein applying the hydraulic pressure in the casing comprises applying the hydraulic pressure at a first pressure level at least higher than a second pressure level for fracturing. 
     
     
         12 . The method of  claim 1 , wherein activating the at least one charge with the hydraulic pressure applied in the casing comprises activating a firing head of the assembly with the applied hydraulic pressure. 
     
     
         13 . The method of  claim 12 , wherein activating the firing head of the assembly with the applied hydraulic pressure comprises breaking at least one first temporary retainer in the assembly separating the applied hydraulic pressure from the firing head. 
     
     
         14 . The method of  claim 13 , wherein activating the firing head of the assembly with the applied hydraulic pressure comprises breaking at least one second temporary retainer of the firing head with the applied hydraulic pressure after breaking the at least one first temporary retainer. 
     
     
         15 . The method of  claim 14 , wherein breaking the at least one second temporary retainer of the firing head with the applied hydraulic pressure after breaking the at least one first temporary retainer comprises breaking the at least one second temporary retainer with a higher level of the applied hydraulic pressure than used to break the at least one first temporary retainer. 
     
     
         16 . The method of  claim 1 , wherein pumping the assembly down the casing behind the cement slurry comprises deploying the assembly from a cement head at surface. 
     
     
         17 . The method of  claim 1 , further comprising retrieving at least a portion of the assembly from the casing after perforating the casing. 
     
     
         18 . The method of  claim 1 , further comprising:
 deploying a bridge plug in the casing uphole of the perforation; and   perforating the casing further uphole using another perforating gun.   
     
     
         19 . The method of  claim 1 , wherein landing the assembly in the casing comprises testing integrity of the casing by applying intermediate hydraulic pressure in the casing behind the assembly. 
     
     
         20 . The method of  claim 19 , further comprising delaying activation of the at least one charge should the intermediate hydraulic pressure activate the at least one charge. 
     
     
         21 . An apparatus used in cementing and perforating casing in a borehole, the apparatus comprising:
 a plug;   a perforating gun attached to the plug and having one or more charges; and   a firing mechanism disposed on the perforating gun and coupled to the one or more charges, the firing mechanism in fluid communication with the casing and being activated hydraulically to detonate the one or more charges.   
     
     
         22 . The apparatus of  claim 21 , further comprising a bottom plug independent of the plug and deploying in the casing in advance of the plug, the bottom plug having a breachable passage therethrough. 
     
     
         23 . The apparatus of  claim 21 , further comprising a fishing neck disposed on a proximal end of the perforating gun. 
     
     
         24 . The apparatus of  claim 21 , further comprising a cement head having launchers, at least one of the launchers accommodating the perforating gun attached to the plug. 
     
     
         25 . The apparatus of  claim 24 , wherein the firing mechanism is hydraulically activated in response to at least one coded signal applied with hydraulic pressure in the casing. 
     
     
         26 . The apparatus of  claim 25 , wherein the firing mechanism at least initiates activation of the one or more changes for detonation in response to the at least one coded signal. 
     
     
         27 . The apparatus of  claim 25 , wherein the firing mechanism detonates the one or more charges in response to the at least one coded signal. 
     
     
         28 . The apparatus of  claim 21 , wherein the firing mechanism comprises:
 a detonator connected to the one or more charges;   a pin exposed to a chamber and movable toward the detonator; and   at least one first temporary retainer separating the chamber from external pressure in the casing.   
     
     
         29 . The apparatus of  claim 28 , wherein the pin comprises at least one second temporary retainer holding the pin away from the detonator. 
     
     
         30 . The apparatus of  claim 29 , wherein the at least one second temporary retainer releases the pin at a higher level hydraulic pressure than used to break the at least one first temporary retainer. 
     
     
         31 . The apparatus of  claim 29 , wherein the at least one second temporary retainer comprises at least one shear pin, and wherein the at least one first temporary retainer comprises at least one rupture disc. 
     
     
         32 . The apparatus of  claim 21 , wherein a distal end of the perforating gun threads to a top of the plug. 
     
     
         33 . The apparatus of  claim 21 , wherein the plug and the perforating gun are formed integrally together. 
     
     
         34 . An apparatus used in cementing and perforating casing in a borehole, the apparatus comprising:
 a cement head disposed on the casing and having first and second launchers;   a bottom plug positioning in the first launcher and deploying from the cement head in the casing in advance of cement slurry;   an assembly positioning in the second launcher and deploying from the cement head in the casing after the cement slurry, the assembly having a wiper and having one or more charges, the wiper wiping the casing, the one or more charges being activated hydraulically with pressure in the casing to perforate the casing.