Pressure regulated downhole equipment

Abstract

Methods and apparatus are provided for regulating a pressure in a wellbore by including multiple stages of pressure regulation in a casing to gradually change the pressure in the casing. For example, a method of regulating a pressure of a fluid in a wellbore includes positioning a tubular equipped with a first float assembly having a first unidirectional valve and a second float assembly having a second unidirectional valve, wherein each of the first and second unidirectional valves include an inlet and an outlet; and reducing a pressure differential across the first unidirectional valve when a pressure at the outlet is higher than a pressure at the inlet by a predetermined amount.

We claim: 
     
         1 . A method of regulating a pressure of a fluid in a wellbore, comprising:
 positioning a tubular equipped with a first float assembly and a second float assembly, wherein each float assembly includes a unidirectional valve with an inlet and an outlet;   reaching a pressure differential between an upstream pressure and a downstream pressure of the unidirectional valve of the first float assembly; and   reducing the pressure differential across the unidirectional valve of the first float assembly when the downstream pressure is higher than the upstream pressure by a predetermined amount.   
     
     
         2 . The method of  claim 1 , wherein reducing the pressure differential across the first unidirectional valve includes opening a relief valve to allow fluid to move across the first float assembly. 
     
     
         3 . The method of  claim 2 , wherein the fluid flowing through the first float assembly pressurizes an area between the first and second float assemblies. 
     
     
         4 . The method of  claim 3 , further comprising reducing a pressure differential across the second unidirectional valve when the pressure differential across the second unidirectional valve reaches a second predetermined pressure differential. 
     
     
         5 . The method of  claim 2 , wherein the relief valve closes when the pressure differential is at or below the predetermined amount. 
     
     
         6 . The method of  claim 2 , wherein the relief valve closes when the pressure differential is below the predetermined amount of pressure differential. 
     
     
         7 . The method of  claim 2 , wherein the relief valve remains open until the pressure differential is less than 80% of the predetermined amount of pressure differential. 
     
     
         8 . The method of  claim 1 , wherein reducing the pressure differential across the first unidirectional valve pressurizes an area between the first and second float assemblies. 
     
     
         9 . The method of  claim 8 , further comprising reducing a pressure differential across the second unidirectional valve when the pressure differential across the second unidirectional valve reaches a second predetermined pressure differential. 
     
     
         10 . The method of  claim 1 , wherein reducing the pressure differential across the first unidirectional valve includes moving the first float assembly toward the second float assembly. 
     
     
         11 . The method of  claim 10 , wherein moving the first float assembly pressurizes an area between the first and second float assemblies. 
     
     
         12 . The method of  claim 11 , further comprising reducing a pressure differential across the second unidirectional valve when the pressure differential across the second unidirectional valve reaches a second predetermined pressure differential. 
     
     
         13 . A system for regulating a pressure of a fluid in a wellbore, comprising:
 a tubular;   a first float assembly disposed in the tubular, wherein the first float assembly includes a first unidirectional valve for allowing fluid to flow in a first direction;   a second float assembly disposed in the tubular, wherein the second float assembly includes a second unidirectional valve for allowing fluid to flow in the first direction;   wherein the first float assembly is equipped with a pressure regulating device configured to actuate when a predetermined pressure differential is reached.   
     
     
         14 . The system of  claim 13 , wherein the pressure regulating device includes a relief valve for allowing fluid to flow in a second direction. 
     
     
         15 . The system of  claim 13 , wherein the pressure regulating device includes a movable first float assembly. 
     
     
         16 . The system of  claim 13 , further comprising a first plug and a second plug, wherein the first plug includes a removable seal. 
     
     
         17 . The system of  claim 16 , wherein the removable seal includes a rupture disc. 
     
     
         18 . A method of regulating a pressure of a fluid in a wellbore, comprising:
 positioning a tubular equipped with a first float assembly having a first unidirectional valve and a second float assembly having a second unidirectional valve in a wellbore, wherein each of the first and second unidirectional valves include an inlet and an outlet; and   reducing a pressure differential across the first unidirectional valve when a pressure at the outlet of the first unidirectional valve is higher than a pressure at the inlet of the second unidirectional valve by a predetermined amount.   
     
     
         19 . The method of  claim 18 , wherein reducing the pressure differential across the first unidirectional valve includes opening a relief valve to allow fluid to move across the first float assembly. 
     
     
         20 . The method of  claim 19 , further comprising reducing a pressure differential across the second unidirectional valve when a pressure at the outlet is higher than a pressure at the inlet by a predetermined second amount. 
     
     
         21 . The method of  claim 18 , wherein reducing the pressure differential across the first unidirectional valve pressurizes an area between the first and second float assemblies. 
     
     
         22 . The method of  claim 21 , further comprising reducing a pressure differential across the second unidirectional valve when a pressure at the outlet of the second unidirectional valve is higher than a pressure at the inlet of the second unidirectional valve by a predetermined second amount. 
     
     
         23 . The method of  claim 18 , wherein reducing the pressure differential across the first unidirectional valve includes moving the first float assembly toward the second float assembly. 
     
     
         24 . The method of  claim 23 , wherein moving the first float assembly pressurizes an area between the first and second float assemblies. 
     
     
         25 . The method of  claim 24 , further comprising reducing a pressure differential across the second unidirectional valve when a pressure at the outlet of the second unidirectional valve is higher than a pressure at the inlet of the second unidirectional valve by a predetermined second amount.