Downhole shutoff tool

Abstract

A downhole drilling valve tool, positioned above the drill bit, which utilizes a ball valve having a through bore for normal flow. The ball valve is operated bidirectionally by a piston driven mechanism between an open position and a closed position. The piston mechanism is responsive to a reference accumulator pressure on a first side and the pressure in the apparatus bore above the ball valve on a second side. Whenever the valve apparatus is lowered at least a minimum distance into the well bore, a pressure relief valve is used to maintain a fixed margin between the flowing bore pressure and the accumulator pressure. Closure of the ball valve occurs when the accumulator pressure exceeds the bore pressure during pump stoppages. The downhole drilling valve tool offers a more wear resistant sealing means, as well as higher pressure operability than conventional downhole check valves.

What is claimed is: 
     
         1 . A downhole shutoff valve for operation in a drillstring, including:
 a) a housing having a through bore;   b) an accumulator positioned within the housing, wherein a gas chamber within the accumulator is selectably chargeable with a gas to create an accumulator pressure, and wherein the accumulator is in fluid communication with a bore pressure present in the bore through a pressure relief valve;   c) a ball valve rotatable between a closed position and an open position;   d) an axially reciprocable piston exposed to the accumulator pressure on a first side and the bore pressure on a second side; and   e) a valve rotational mechanism connected to and operable by the piston, wherein the ball valve is closed by the valve rotational mechanism when the accumulator pressure exceeds the bore pressure and wherein the ball valve is opened by the valve rotational mechanism when the bore pressure exceeds the accumulator pressure.   
     
     
         2 . The downhole shutoff valve of  claim 1 , wherein whenever the accumulator pressure is greater than a pressure exterior to the downhole shutoff valve by a predetermined margin, a pop off valve opens and releases to the tool exterior an excess of the accumulator pressure over the pressure external to the downhole shutoff tool. 
     
     
         3 . The downhole shutoff valve of  claim 2 , wherein the pop off valve consists of a carrier and a poppet closed with a shear pin and opened by shearing the shear pin. 
     
     
         4 . The downhole shutoff valve of  claim 1 , wherein the through bore has a latch groove. 
     
     
         5 . The downhole shutoff valve of  claim 4 , further including a lockopen tool that selectably interacts with the latch groove to position the lockopen tool in the through bore to prevent opening or closing of the valve. 
     
     
         6 . A downhole shutoff valve for use in a drillstring including:
 a) a housing having a through bore;   b) a pressure relief valve in fluid communication with the through bore;   c) an accumulator positioned within the housing having
 (i) an accumulator bore, 
 (ii) an accumulator charging port that provides selectable fluid communication between an exterior of the accumulator and a gas chamber to create an accumulator pressure, 
 (iii) a mud chamber in fluid communication with the through bore through a pressure relief valve, and 
 (iv) a separator piston having the mud chamber on a first side and the gas chamber on a second side; 
   d) a ball valve rotatable between a closed position and an open position;   e) an axially reciprocable piston movable between a first position and a second position, the reciprocable piston having the gas chamber positioned on a first piston side and a through bore chamber in fluid communication with the through bore positioned on a second piston side; and   f) a valve rotational mechanism interconnecting the valve and the piston, wherein when the piston is in the first position the ball valve is in the closed position and when the piston is in the second position the ball valve is in the open position.   
     
     
         7 . The downhole shutoff valve of  claim 6 , wherein the reciprocable piston is exposed to the accumulator pressure on the first piston side and a through bore fluid pressure on the second piston side. 
     
     
         8 . The downhole shutoff valve of  claim 7 , wherein the reciprocable piston is the first position when the accumulator pressure exceeds the through bore fluid pressure and wherein the reciprocable piston is in the second position when the through bore fluid pressure exceeds the accumulator pressure. 
     
     
         9 . The downhole shutoff valve of  claim 6 , wherein whenever the accumulator pressure is greater than a pressure exterior to the downhole shutoff valve by a predetermined margin, a pop off valve opens and releases to the tool exterior an excess of the accumulator pressure over the pressure external to the downhole shutoff tool. 
     
     
         10 . The downhole shutoff valve of  claim 6 , further including a lockopen tool that selectably interacts with a latch groove in the through bore to position the lockopen tool in the through bore to prevent opening or closing of the valve. 
     
     
         11 . A downhole shutoff valve for use in a drillstring including:
 a) a first module having
 (i) a first body having a first end, a second end, and a first through bore, 
 (ii) a flow port extending into the first body, wherein the flow port is parallel to and offset from the first through bore, and 
 (iii) a pressure relief valve in fluid communication with the first through bore and the flow port, wherein the pressure relief valve opens when a pressure in the first through bore exceeds a pressure in the flow port by a predetermined amount; 
   b) an accumulator module having
 (i) a second body having a first module end, a second module end, and a second through bore, wherein the first module end is attached to the first module, 
 (ii) a bore extension tube connected to the first through bore at the second end of the first module and extending into the second through bore, wherein the bore extension tube has a smaller outer diameter than a diameter of the second through bore, 
 (iii) an axially reciprocable separator piston having a first side facing the first module, the separator piston encircling the bore extension tube between an exterior surface of the bore extension tube and an interior surface of the second through bore, 
 (iv) an accumulator charging port providing selectable communication between an exterior of the accumulator module and a gas chamber located between the second through bore and the exterior surface of the bore extension tube on a second side of the separator piston, and 
 (v) a mud chamber in fluid communication with the flow port, the mud chamber located between the second through bore and the exterior surface of the bore extension tube on a second side of the separator piston; and 
   c) a third module having
 (i) a housing attached to the accumulator module, 
 (ii) a ball valve rotatable between a closed position and an open position, 
 (iii) a third through bore, wherein the third through bore is coaxially aligned and in fluid communication with the first through bore and a bore of the bore extension tube, 
 (iv) a tool bore pressure chamber in fluid communication with the third through bore, 
 (v) an axially reciprocable piston movable between a first position and a second position, the reciprocable piston having the gas chamber positioned on a first piston side and the through bore chamber positioned on a second piston side, and 
 (vi) a valve rotational mechanism interconnecting the valve and the reciprocable piston, wherein when the piston is in the first position the ball valve is in the closed position and when the piston is in the second position the ball valve is in the open position. 
   
     
     
         12 . The downhole shutoff valve of  claim 11 , wherein the gas chamber is precharged with nitrogen to create an accumulator pressure. 
     
     
         13 . The downhole shutoff valve of  claim 12 , wherein the reciprocable piston is exposed to the accumulator pressure on the first piston side and a through bore fluid pressure on the second piston side. 
     
     
         14 . The downhole shutoff valve of  claim 11 , wherein the reciprocable piston is in the first position when the accumulator pressure exceeds the through bore fluid pressure and wherein the reciprocable piston is in the second position when the through bore fluid pressure exceeds the accumulator pressure. 
     
     
         15 . The downhole shutoff valve of  claim 11 , wherein the first module further includes a pop off valve in fluid communication with the flow port. 
     
     
         16 . The downhole shutoff valve of  claim 12 , wherein whenever the accumulator pressure is greater than a pressure exterior to the downhole shutoff valve by a predetermined amount, the pop off valve opens and releases to the tool exterior an excess of the accumulator pressure over the pressure external to the downhole shutoff tool. 
     
     
         17 . The downhole shutoff valve of  claim 11 , wherein the pop off valve consists of a carrier and a poppet closed with a shear pin and opened by shearing the shear pin. 
     
     
         18 . The downhole shutoff valve of  claim 11 , wherein the first module further includes a latch groove. 
     
     
         19 . The downhole shutoff valve of  claim 18 , wherein a lockopen tool is selectably latched into the latch groove and positioned to pass through a through hole in the ball valve, thereby preventing the ball valve from rotating into the closed position. 
     
     
         20 . The downhole shutoff valve of  claim 19 , wherein the lockopen tool is selectably removable from the downhole shutoff valve to permit the ball valve to rotate between the closed position and the open position. 
     
     
         21 . The downhole shutoff valve of  claim 11 , wherein the pressure relief valve has an opening pressure less than an estimated maximum flow-induced pressure produced in the first tool bore.