Apparatus and Method for Underbalanced Drilling and Completion of a Hydrocarbon Reservoir

Abstract

A system and method for underbalanced drilling and completion of a hydrocarbon reservoir is disclosed. The system prevents formation damage by using a solids-free, non-wetting phase drilling fluid while maintaining underbalanced conditions throughout the entire drilling and completion phase of the operation. By preventing formation damage, this system provides an alternative or supplement to hydraulic fracking.

What is claimed is: 
     
         1 . An advanced method of drilling a hydrocarbon wellbore, comprising:
 using at least one of an overbalanced and an underbalanced fluid column to drill a wellbore to an upper portion of a hydrocarbon reservoir;   installing and cementing a casing string inside the wellbore to the upper portion of the hydrocarbon reservoir;   providing a mechanical fluid control valve in the casing string segment above a predetermined target producing zone;   using an underbalanced fluid column, drilling and completing the targeted producing zone using a solids-free and non-wetting phase drilling fluid maintained below the pressure of the hydrocarbon reservoir;   injecting nitrogen into the drilling fluid as needed to reduce the hydrostatic head of the drilling fluid and enable the underbalanced drilling to be maintained; and   circulating the drilling fluid and nitrogen, and any produced fluids and rock cuttings, through a series of surface process equipment designed to separate oil, gas, water and rock cuttings under pressure.   
     
     
         2 . The method of  claim 1 , wherein the solids-free and non-wetting phase fluid comprises a crude oil, a pure mineral oil and an LVT drilling fluid for a water wet reservoir. 
     
     
         3 . The method of  claim 1 , wherein the nitrogen is injected into the hydrocarbon wellbore by at least one of the drill string and through an annulus formed with a casing string. 
     
     
         4 . The method of  claim 3 , wherein the solids-free and non-wetting phase fluid comprises water for an oil wet reservoir. 
     
     
         5 . The method of  claim 1 , wherein a rotating pressure control device is positioned at a surface location in communication with the drill string, and the mechanical fluid control valve is positioned at a subsurface location above the producing formation. 
     
     
         6 . The method of  claim 1 , wherein nitrogen is circulated downhole between two strings of casing. 
     
     
         7 . The method of  claim 1 , wherein no drilling or completion fluid which is overbalanced with respect to the hydrocarbon formation pressure comes in contact with the hydrocarbon formation. 
     
     
         8 . The method of  claim 1 , wherein the underbalanced fluid column is maintained throughout the entire drilling and completion operations. 
     
     
         9 . The method of  claim 5 , wherein the downhole deployment valve is interconnected to the lowermost portion of casing string. 
     
     
         10 . The method of  claim 9 , wherein formation cuttings, nitrogen and any wellbore fluid is produced under pressure in the annulus between the drill string and production casing. 
     
     
         11 . A method of drilling for recovery of hydrocarbons comprising oil and natural gas from a hydrocarbon reservoir, comprising:
 using an overbalanced or underbalanced fluid column to drill a hydrocarbon wellbore to an upper portion of a hydrocarbon reservoir;   installing and cementing a casing string inside the wellbore;   providing a downhole deployment valve in a lowermost casing string segment and above a projected hydrocarbon producing zone;   using an underbalanced fluid column, drilling and completing the targeted producing zone using a solids-free and non-wetting phase drilling fluid maintained below the pressure of the hydrocarbon reservoir;   providing nitrogen as needed in the drilling fluid to reduce the hydrostatic head of the drilling fluid;   circulating the nitrogen through an annulus formed by a second casing;   circulating the drilling fluid and nitrogen, and any produced fluids and rock cuttings, through surface process equipment designed to separate oil, gas, water and rock cuttings under pressure.   
     
     
         12 . The method of  claim 11 , wherein the wellbore is configured such that underbalanced conditions are maintained throughout the entire drilling and completion operations. 
     
     
         13 . A system for drilling for recovery of hydrocarbons comprising oil and natural gas from a hydrocarbon reservoir, comprising:
 a wellbore extending at least to an upper portion of a hydrocarbon reservoir;   a casing string disposed inside the wellbore;   a mechanical fluid control valve disposed in the casing string segment and above a target producing zone;   utilizing a solids-free and non-wetting phase drilling fluid maintained below the pressure of the hydrocarbon reservoir; and   wherein the drilling fluid is maintained below the pressure of the hydrocarbon reservoir to enable underbalanced drilling;   wherein nitrogen is injected into the drilling fluid as needed to reduce the hydrostatic head of the drilling fluid and enable the underbalanced drilling to be maintained; and   wherein nitrogen, hydrocarbons, and drilling fluid are produced and treated under pressure with surface process equipment.   
     
     
         14 . The system of  claim 13 , wherein the solids-free and non-wetting phase fluid comprises: (a) crude oil, pure mineral oil and LVT drilling fluid for water wet and partially water wet reservoirs, and (b) water for oil wet reservoirs. 
     
     
         15 . The system of  claim 14 , wherein the nitrogen is injected into the wellbore through at least one of a drill string and an annulus in the casing. 
     
     
         16 . The system of  claim 15 , wherein the rotating pressure control device is positioned at a surface location, and the mechanical fluid control valve is deployed subsurface above the hydrocarbon formation. 
     
     
         17 . The system of  claim 16 , wherein the downhole deployment valve is interconnected to the lowermost joint of casing. 
     
     
         18 . The system of  claim 13 , wherein the solids-free and non-wetting phase fluid comprises a crude oil, a pure mineral oil and an LVT drilling fluid for a water wet or partially water wet reservoir. 
     
     
         19 . The system of  claim 13 , wherein no drilling or completion fluid which is overbalanced with respect to the hydrocarbon formation pressure comes in contact with the hydrocarbon formation. 
     
     
         20 . The system of  claim 13 , wherein produced hydrocarbons, drilling fluid, water, nitrogen, wellbore cuttings and gas are treated in a pressurized four phase separator at a surface location.