Surface controlled formation isolation valve adapted for deployment of a desired length of a tool string in a wellbore

A method and apparatus is disclosed for building a tool string uphole of any desired length prior to lowering that tool string downhole into a wellbore for the purpose of performing wellbore operations downhole during a single trip into the wellbore. The apparatus includes a valve disposed between an upper section and a lower section of the wellbore and adapted to open and to close, the upper section of the wellbore being isolated from the lower section of the wellbore when the valve is closed. The tool string of any desired length is built in the upper section of the wellbore when the valve is closed and the upper section of the wellbore is isolated from the lower section of the wellbore. The apparatus also includes a mandrel and piston, the valve being initially disposed in an open position and adapted to be changed from the open position to a closed position when the mandrel is shifted from one position to another position. An upper chamber communicates with a gas reservoir and a valve manifold at the surface. The manifold includes a slow bleed valve and a fast bleed valve disposed at the wellbore surface. A gas metering orifice separates the upper chamber from a lower chamber. The mandrel is shifted in one direction and the valve changes position when a gas is delivered from the surface of the wellbore to the upper chamber thereby moving the piston and the mandrel, the mandrel shifting in an opposite direction and the valve changing position again when the gas in the upper chamber leaks from the upper chamber to the fast bleed valve at the surface. The mandrel shifts in the one direction and the valve changes position again when the gas from the surface is delivered to the upper chamber. However, the mandrel does not shift in the opposite direction and the valve does not change position again when the gas in the upper chamber leaks from the upper chamber to the slow bleed valve at the surface.

BACKGROUND OF THE INVENTION 
The subject matter of the present invention relates to a method and 
apparatus for isolating a first section of a wellbore from a second 
section of the wellbore, the second section being disposed below the first 
section in the wellbore and adjacent a formation, in order that a wellbore 
tool string of any desired length may be made up in the first section 
prior to opening a ball valve and lowering the tool string downhole into 
the second section of the wellbore for performing one or more wellbore 
operations downhole in the second section. 
A prior pending application, filed by the same applicant (Dinesh R. Patel) 
and owned by the same assignee as that of the present invention, relates 
to the same field of the invention as that recited above. The prior 
pending application corresponds to attorney docket number 22.1185, was 
filed on May 10, 1996, and is entitled "Formation Isolation Valve Adapted 
for Building a Tool String of Any Desired Length Prior to Lowering the 
Tool String Downhole for Performing a Wellbore Operation". In the prior 
pending application to Patel, a valve is disposed in a tubing string in a 
similar manner as shown in FIG. 1 of the drawings of this application. The 
valve is responsive to the running of a shifting tool through a full bore 
of the valve for opening and closing the valve. When the valve is closed 
in response to the running of the shifting tool through the valve, a tool 
string of any desired length is built in a first section of the wellbore 
above the valve. When the tool string is built, the valve is opened in 
response to a pressure applied to a wellbore fluid in the first section, 
and the tool string is run downhole through the open valve for performing 
wellbore operations. 
When performing wellbore operations downhole, it is necessary to first make 
up a tool string at the surface of the wellbore prior to lowering that 
tool string downhole for performing the wellbore operations. In the past, 
the length of the tool string was limited by the maximum height of surface 
equipment and a longer tool string length was often desired. Therefore, 
when the tool string performed the wellbore operations downhole, that tool 
string was raised uphole and another, second tool string was made up at 
the surface of the wellbore. The second tool string was lowered downhole 
for performing additional wellbore operations. However, it is time 
consuming and expensive to continually make up additional tool strings at 
the wellbore surface, following the performance of the initial wellbore 
operation by the first tool string, and sequentially lower those 
additional tool strings downhole for performing additional wellbore 
operations. It would be desirable to make up one tool string having the 
desired length at the wellbore surface and to lower that desired tool 
string downhole for performing a wellbore operation during one trip into 
the wellbore. For example, when the tool strings include perforating guns, 
in the past, it was necessary to implement the following perforating 
procedure when perforating long length intervals of a wellbore: perforate 
the long length interval during multiple trips into the wellbore by making 
up, at the wellbore surface, a first perforating gun having a limited 
first length, lowering the first perforating gun downhole, perforating a 
formation penetrated by the wellbore, raising the first perforating gun 
uphole (or dropping that perforating gun to the bottom of the wellbore), 
making up a second perforating gun having another second limited length at 
the wellbore surface, lowering the second perforating gun downhole, 
perforating another section of the formation, raising the second 
perforating gun uphole (or dropping it to a bottom of the wellbore), etc. 
The above referenced perforating procedure is time consuming and costly. 
As a result, it became necessary to design a method and apparatus for 
creating a tool string, of any desired length, uphole at the surface of 
the wellbore, so that the tool string may be lowered downhole and wellbore 
operations performed downhole during only one trip into the wellbore. 
U.S. Pat. No. 5,509,481 to Huber et al discussed one method for perforating 
long length intervals of a formation during a single run into the 
wellbore. The Huber apparatus disclosed an automatic release apparatus 
which would disconnect one part of a long gun string from a second part of 
the gun string just before the perforating guns of that gun string would 
detonate. 
Another prior pending application also discloses a method and apparatus for 
making up, at the wellbore surface, a tool string of any desired length 
prior to lowering that tool string downhole for performing a wellbore 
operation in the wellbore during one trip into the wellbore. In a prior 
pending application entitled "Completions Insertion and Retrieval Under 
Pressure (CIRP) Apparatus including the Snaplock Connector", having a Ser. 
No. 08/638,001 and filed on Apr. 25, 1996 and corresponding to attorney 
docket number 22.1183 and corresponding to a prior filed provisional 
application number 60/010,500 filed Jan. 24, 1996 (hereinafter, the "CIRP 
application"), a tool string of any desired length is built uphole prior 
to lowering that tool string downhole by first holding a first tool, 
having a first and a second section of a snaplock connector connected 
thereto, in a deployment BOP or snaplock operator while suspending a 
second tool, also having a third section of the snaplock connector 
connected thereto, by wireline in a lubricator. The second tool is lowered 
down through the lubricator and through a master valve by operating a 
winch until the third section of the snaplock connector on the second tool 
connects to the second section of the snaplock connector on the first tool 
thereby forming a first tool string having a length which corresponds to 
the first tool and the second tool. The hold by the deployment BOP is 
released from the first tool, the first tool string is lowered, and the 
deployment BOP grips the second tool. The second tool also includes 
another first, second, and third section of a snaplock connector connected 
to its opposite side, the third section (called a deployment stinger) 
being connected to the wireline. The deployment stinger is raised uphole 
by operating the winch, and it is replaced by a third tool, such as a 
firing head, which also includes a third section of a snaplock connector. 
The third tool suspends by the wireline in the lubricator and it is 
lowered downhole and attached to the second tool being held by the 
deployment BOP. The hold by the deployment BOP on the second tool is 
released, and a resultant tool string of the desired length, consisting of 
the first tool, the second tool, and the third tool, is lowered downhole 
for the purpose of performing wellbore operations downhole during one trip 
into the wellbore. 
However, another alternate apparatus, and corresponding method, is needed 
for isolating the formation downhole by means of closing a valve so that 
wellhead pressure can be bled off for building a long tool string uphole 
of any desired length and lowering that tool string downhole without a 
need for snubbing under wellhead pressure for the purpose of performing 
wellbore operations downhole during a single trip into the wellbore. 
SUMMARY OF THE INVENTION 
Accordingly, it is a primary object of the present invention to provide 
another alternate method and apparatus for building a tool string uphole 
of any desired length prior to lowering that tool string downhole for the 
purpose of performing wellbore operations downhole during a single trip 
into the wellbore. 
It is a further object of the present invention to provide another 
alternate method and apparatus for building a tool string uphole of any 
desired length prior to lowering that tool string downhole for the purpose 
of performing wellbore operations downhole during a single trip into the 
wellbore, the alternate apparatus including a valve disposed between an 
upper section and a lower section of the wellbore and adapted to open and 
to close, the upper section of the wellbore being isolated from the lower 
section of the wellbore when the valve is closed, the tool string of any 
desired length being built in the upper section of the wellbore when the 
valve is closed and the upper section of the wellbore is isolated from the 
lower section of the wellbore. 
It is a further object of the present invention to provide another 
alternate method and apparatus for building a tool string uphole of any 
desired length prior to lowering that tool string downhole into a wellbore 
for the purpose of performing wellbore operations downhole during a single 
trip into the wellbore, the alternate apparatus including a valve disposed 
between an upper section and a lower section of the wellbore and adapted 
to open and to close, the upper section of the wellbore being isolated 
from the lower section of the wellbore when the valve is closed, the tool 
string of any desired length being built in the upper section of the 
wellbore when the valve is closed and the upper section of the wellbore is 
isolated from the lower section of the wellbore, the alterate apparatus 
further including a mandrel and piston, the valve, such as a ball valve, 
initially disposed in an open position adapted to be changed from the open 
position to a closed position when the mandrel is shifted from one 
position to another position, an upper chamber communicating with a gas 
reservoir and a valve manifold including a slow bleed valve and a fast 
bleed valve disposed at the wellbore surface, a lower chamber, and a gas 
metering orifice separating the upper chamber from the lower chamber, the 
mandrel being shifted in one direction and the valve changing position 
when a gas is delivered from the surface of the wellbore to the upper 
chamber thereby moving the piston and the mandrel, the mandrel shifting in 
an opposite direction and the valve changing position again when the gas 
in the upper chamber leaks from the upper chamber to the fast bleed valve 
at the surface, the mandrel shifting in the one direction and the valve 
changing position again when the gas from the surface is delivered to the 
upper chamber, and the mandrel not shifting in the opposite direction and 
the valve not changing position again when the gas in the upper chamber 
leaks from the upper chamber to the slow bleed valve at the surface. 
In accordance with these and other objects of the present invention, an 
apparatus adapted to be disposed in a wellbore allows an operator at the 
wellbore surface to build a tool string uphole of any desired length prior 
to lowering that tool string downhole into a wellbore for the purpose of 
performing wellbore operations during a single trip into the wellbore. The 
apparatus includes a valve disposed between an upper section and a lower 
section of the wellbore which is adapted to open and to close. The upper 
section of the wellbore is isolated from the lower section of the wellbore 
when the valve is closed. The tool string of any desired length is built 
in the upper section of the wellbore when the valve is closed and the 
upper section of the wellbore is isolated from the lower section of the 
wellbore. The apparatus further includes a mandrel and a piston, the 
valve, such as a ball valve, which is initially disposed in an open 
position and is adapted to be changed from the open position to a closed 
position when the mandrel is shifted from one position to another 
position, an upper chamber communicating with a gas reservoir and a valve 
manifold (including a slow bleed valve and a fast bleed valve) disposed at 
the wellbore surface, a lower chamber, and a gas metering orifice 
separating the upper chamber from the lower chamber. The mandrel is 
shifted in one direction and the valve changes position when a gas is 
delivered from the surface of the wellbore to the upper chamber thereby 
moving the piston and the mandrel. The mandrel shifts in an opposite 
direction and the valve changes position again when the gas in the upper 
chamber leaks from the upper chamber to the fast bleed valve at the 
surface. The mandrel shifts in the one direction and the valve changes 
position again when the gas from the surface is delivered to the upper 
chamber. However, the mandrel does not shift in the opposite direction and 
the valve does not change position again when the gas in the upper chamber 
leaks from the upper chamber to the slow bleed valve at the surface. The 
mandrel does not shift in the opposite direction because the flow rate at 
which the gas in the upper chamber flows through the slow bleed valve at 
the surface is less than the rate at which the gas in the lower chamber 
meters into the upper chamber via the gas metering orifice. Therefore, the 
gas pressure in the upper and lower chambers remain approximately equal 
despite the fact that the gas in the upper chamber flows upwardly through 
the slow bleed valve at the surface. As a result, the mandrel and piston 
fail to shift in either direction. 
Further scope of applicability of the present invention will become 
apparent from the detailed description presented hereinafter. It should be 
understood, however, that the detailed description and the specific 
examples, while representing a preferred embodiment of the present 
invention, are given by way of illustration only, since various changes 
and modifications within the spirit and scope of the invention will become 
obvious to one skilled in the art from a reading of the following detailed 
description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a tubing string 12 having a full bore is disposed in a 
partially deviated wellbore consisting of a vertical wellbore 13 and a 
deviated wellbore 15. The tubing string 12 includes a valve 18 which is 
disposed in the vertical wellbore 13 portion of the partially deviated 
wellbore. The valve 18 includes a ball valve 18a which is rotatable 
between a closed position, for closing off the full bore of the tubing 
string 12 thereby preventing fluid communication within the tubing string 
12 between the vertical wellbore 13 and the deviated wellbore 15, and an 
open position for opening and allowing fluid communication within the 
tubing string 12 between the vertical wellbore 13 and the deviated 
wellbore 15. In FIG. 1, a tubing 14, such as coiled tubing 14, having a 
perforating gun 10 suspending from the lower end of the coiled tubing 14, 
is disposed within the tubing string 12 and within both the vertical 
wellbore 13 and the deviated wellbore 15 of the partially deviated 
wellbore when the ball valve 18a is disposed in the open position. When 
the coiled tubing 14 is disposed within the tubing string 12 as shown in 
FIG. 1, an annulus space 22 located above the ball valve 18a is defined 
between the coiled tubing 14 and the tubing string 12. However, when the 
coiled tubing 14 is not disposed within the tubing sring 12 as shown in 
FIG. 1, a full bore space 22 is located above the ball valve 18a within 
the tubing string 12. As mentioned later, when the ball valve 18a is 
closed, this full bore space 22 can be used to build a new tool string 
uphole of any desired length. In the vertical wellbore 13 of FIG. 1, the 
tubing string 12 does not form part of the casing of the wellbore; 
however, in the deviated wellbore 15 of FIG. 1, the tubing string 12 forms 
the casing in the deviated wellbore. 
In FIG. 1, the valve 18, which is situated downhole, is connected to a gas 
reservoir 24 (a nitrogen bottle 24) and a valve manifold 26, each of which 
are separately situated at the surface of the wellbore. A gas is stored in 
the gas reservoir 24, the gas flowing between the gas reservoir 24/valve 
manifold 26 at the wellbore surface and the valve 18 located downhole in 
the wellbore via a flowline 17. The flowline 17 is a one-quarter inch 
(1/4") pipe situated between the tubing string 12 and a casing 19 in the 
vertical wellbore 13 and connected between a control line 18c of the valve 
18 (see FIG. 3) and the gas reservoir 24/valve manifold 26 situated at the 
surface of the wellbore. The gas reservoir 24 is really a nitrogen bottle 
which stores a gas, such as nitrogen, and the valve manifold 26 includes a 
pair of bleed valves (a slow bleed valve and a fast bleed valve) which are 
more particularly shown in FIG. 2. The gas in the gas reservoir 24 uphole 
communicates with the valve 18 downhole. When the gas in the gas reservoir 
24 has been communicated to the valve 18, that same gas in the valve 18 
can then be re-communicated back to the bleed valves of the valve manifold 
26, a process which will be described in more detail below in this 
specification. 
Referring to FIG. 2, the valve manifold 26 includes a slow bleed valve 26a 
and a fast bleed valve 26b. As the names imply, the slow bleed valve 26 
will allow a gas to pass (bleed) very slowly therethrough, whereas the 
fast bleed valve 26b will allow a gas to pass (bleed) very rapidly 
therethrough. The function of these bleed valves 26a, 26b will be set 
forth below in the functional description of the operation of the present 
invention. 
In operation, referring to FIG. 1, the ball valve 18a is open and the 
perforating gun 10 with associated coiled tubing 14 is situated in the 
wellbore as shown in FIG. 1, the perforating gun 10 perforating the 
formation penetrated by the deviated wellbore 15 thereby forming a 
plurality of perforations 20 in the deviated wellbore 15. When the 
perforating gun 10 has perforated the deviated wellbore 15, the coiled 
tubing 14 and the perforating gun 10 are raised uphole until the 
perforating gun 10 passes through the ball valve 18a of the valve 18, at 
which point, the perforating gun 10 and associated coiled tubing 14 are 
located above the valve 18 within the tubing string 12 in the vertical 
wellbore 13. The ball valve 18a is then closed. When the ball valve 18a is 
closed, the perforating gun 10 is raised uphole to a surface of the 
wellbore, leaving empty the full bore space 22 which is located above the 
closed ball valve 18a within the tubing string 12. A new tool string of 
any desired length (the length of the new tool string being limited only 
by the distance between the ball valve 18a and the wellbore surface) may 
then be built within the full bore space 22. When the new tool string is 
built within the full bore space 22, the ball valve 18a is reopened, and 
the new tool string is lowered downhole for the purpose of performing 
other wellbore operations downhole. 
Referring to FIGS. 3 and 4, a detailed construction of the valve 18 of the 
present invention is illustrated. 
In FIGS. 3 and 4, the valve 18 of the present invention, adapted for 
deploying a desired length of a tool string in a wellbore, includes an 
outer housing 18b. The outer housing 18b further includes an open port 
18c, otherwise known as a control line 18c, which is connected to the 
flowline 17, the one-quarter inch pipe 17 that is connected to the gas 
reservoir 24 and the valve manifold 26 at the surface of the wellbore. The 
gas in the gas reservoir 24 can communicate with the control line 18c of 
the valve 18 via the flowline pipe 17, and the gas in the valve 18 can 
communicate with the bleed valves 26a, 26b of the valve manifold 26 via 
the control line 18c of the valve 18 and the flowline pipe 17. 
The valve 18 of FIGS. 3 and 4 further include a mandrel 18d connected to 
the ball valve 18a and enclosed by the outer housing 18b. The mandrel 18d 
is further connected to a piston 18e, and the piston 18e separates an 
upper gas chamber 18f from a lower gas chamber 18g. The upper gas chamber 
18f is defined by the mandrel 18d, an upper part of the piston 18e and the 
outer housing 18b, whereas the lower gas chamber 18g is defined by the 
mandrel 18d, a lower part of the piston 18e, and the outer housing 18b. 
The piston 18e includes a gas metering orifice 18e1 disposed through the 
axial center of the piston 18e. The gas metering orifice 18e1 allows a 
gas, such as nitrogen, from the gas reservoir 24, to be metered slowly 
between the upper gas chamber 18f and the lower gas chamber 18g, for 
reasons which will be described later in this specification. A spring 
biased ratchet 18h is biased inwardly by a spring, as shown in FIGS. 3 and 
4, the ratchet 18h adapted to be received in one of two detents 18d1 and 
18d2 in the mandrel 18d, the detents 18d1, 18d2 each being a groove which 
is carved into the mandrel 18d and which is adapted to receive the ratchet 
18h. 
A functional description of the operation of the surface controlled 
formation isolation valve of the present invention, adapted for deploying 
a desired length of a tool string in a wellbore, will be set forth in the 
following paragraphs with reference to FIGS. 1 through 4 of the drawings. 
The perforating gun 10 of FIG. 1 perforates the formation 15 and produces a 
plurality of perforations 20 in the formation 15. An operator at the 
wellbore surface of FIG. 1 raises the coiled tubing 14 uphole. Since the 
perforating gun 10 is connected to the coiled tubing 14, the perforating 
gun 10 also is raised uphole in FIG. 1. Since the ball valve 18a of the 
valve 18 is open, the perforating gun 10 will pass through the full bore 
center of the valve 18. When the perforating gun 10 is removed from the 
full bore space 22 of the vertical wellbore 13, the valve 18 must now be 
closed so that a tool string of desired length may be built inside the 
full bore space 22 which is situated above the closed ball valve 18a in 
the vertical wellbore 13. 
In order to close the ball valve 18a, referring to FIGS. 1, 2, and 3, 
assume that the gas pressure within the upper gas chamber 18f is equal to 
the gas pressure within the lower gas chamber 18g. The gas present in the 
upper gas chamber 18f is allowed to flow through the control line 18c, 
through the flowline pipe 17, and into the valve manifold 26 of FIG. 1 for 
the purpose of closing the ball valve 18a. In the valve manifold 26, the 
gas flows into the fast bleed valve 26b of FIG. 2. As a result, the gas 
will flow from the upper gas chamber 18f, through flowline 17, and through 
the fast bleed valve 26b at a rate which is faster than the rate at which 
the gas in the lower gas chamber 18g can meter through the gas metering 
orifice 18e1 into the upper gas chamber 18f. Therefore, the gas pressure 
inside the upper gas chamber 18f will be less than the gas pressure inside 
the lower gas chamber 18g and, as a result, the piston 18e and the mandrel 
18d move upwardly in FIG. 3. The ball valve 18a closes. Eventually, the 
gas pressure inside the upper gas chamber 18f and the lower gas chamber 
18g falls to a value which is approximately equal to zero. The closed ball 
valve 18a is shown in FIG. 4. 
With the ball valve 18a closed, another, new tool string of desired length 
is built inside the full bore space 22 located above the closed ball valve 
18a in FIG. 1. 
When the new tool string is built in the full bore space 22, the ball valve 
18a must now be re-opened so that the new tool string can be lowered 
downhole, from its current location in the full bore space 22, for the 
purpose of performing a new wellbore operation downhole. 
The ball valve 18a is re-opened in the following manner: referring to FIGS. 
1 and 4, a gas, such as Nitrogen, from the gas reservoir 24, is forced to 
flow from the reservoir 24, through the flowline pipe 17, through the 
control line 18c in FIG. 3, and into the upper gas chamber 18f. The gas is 
exerted against the piston 18e, and it begins to meter slowly through the 
gas metering orifice 18e1 into the lower gas chamber 18g. However, since 
there is no gas within the lower gas chamber 18g, the piston 18e moves 
downwardly in FIG. 4 which, in turn, moves the mandrel 18d downwardly and 
which re-opens the ball valve 18a, as shown in FIG. 3. Eventually, the gas 
in the upper gas chamber 18f flows through the metering orifice 18e1 into 
the lower gas chamber 18g. As a result, when the ball valve 18a is 
re-opened, the gas pressure in the upper gas chamber 18f equals the gas 
pressure in the lower gas chamber 18g. 
At this point, now that the ball valve 18a is reopened, the new tool string 
can be lowered downhole, from its current location in the full bore space 
22, and through the ball valve 18a, for the ultimate purpose of performing 
a new wellbore operation downhole. 
In FIGS. 1, 2 and 3, the gas in the lower gas chamber 18g of FIG. 3 can 
flow into the upper gas chamber 18f, and the gas in the upper gas chamber 
18f in FIG. 3 can flow through the flow line pipe 17 and into valve 
manifold 26 without reclosing the ball valve 18a as previously recited. To 
accomplish this without reclosing the ball valve 18a, in FIG. 3, the gas 
in the upper gas chamber 18f will flow into the flowline pipe 17, and into 
the slow bleed valve 26a of the valve manifold 26 of FIG. 2 (the gas does 
not flow into the fast bleed valve 26b). As a result, since the gas flows 
into the slow bleed valve 26a, the rate at which the gas flows from the 
upper gas chamber 18f and through the slow bleed valve 26a is lower than 
the rate at which the gas in the lower gas chamber 18g flows through the 
gas metering orifice 18e1 and into the upper gas chamber 18f. 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the invention, and all such modifications as 
would be obvious to one skilled in the art are intended to be included 
within the scope of the following claims.