U.S. patent application number 12/976727 was filed with the patent office on 2012-06-14 for system and method for operating multiple valves.
This patent application is currently assigned to I-TEC AS. Invention is credited to Roger Antonsen, Kristoffer Braekke, Geir Lunde.
Application Number | 20120145382 12/976727 |
Document ID | / |
Family ID | 45094471 |
Filed Date | 2012-06-14 |
United States Patent
Application |
20120145382 |
Kind Code |
A1 |
Braekke; Kristoffer ; et
al. |
June 14, 2012 |
System and Method for Operating Multiple Valves
Abstract
A valve system for providing fluid flow through radial openings
disposed along an axial length of a tubular. The tubular comprises
at least one valve group containing at least two valves operable by
one drop ball. An inset 302 e.g. of standard grade steel provided
in a harder liner 301 in the opening provides an intermediate small
opening for at least the time required to open all the remaining
valves in the group. The small opening limits the pressure drop
over the valve. When all valves are open, the insets 302 are eroded
away by an abrasive material, e.g. a slurry used for hydraulic
fracturing, and permanent full openings are created.
Inventors: |
Braekke; Kristoffer;
(Stavanger, NO) ; Lunde; Geir; (Sandnes, NO)
; Antonsen; Roger; (Randaberg, NO) |
Assignee: |
I-TEC AS
Royneberg
NO
|
Family ID: |
45094471 |
Appl. No.: |
12/976727 |
Filed: |
December 22, 2010 |
Current U.S.
Class: |
166/250.01 ;
166/318; 166/373 |
Current CPC
Class: |
E21B 33/124 20130101;
E21B 43/14 20130101; E21B 34/14 20130101 |
Class at
Publication: |
166/250.01 ;
166/318; 166/373 |
International
Class: |
E21B 34/06 20060101
E21B034/06; E21B 47/00 20060101 E21B047/00; E21B 34/10 20060101
E21B034/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2010 |
NO |
20101748 |
Claims
1. A valve system for providing fluid flow through radial openings
disposed along an axial length of a tubular, comprising at least
one valve group containing at least two valves operable by one drop
ball, each valve having a closed state, an intermediate state
providing an intermediate opening for at least the time required to
open all the remaining valves in the group, and an open state
providing a full radial opening larger than the intermediate
opening.
2. The valve system of claim 1, further comprising at least one
valve operable to close fluid flow through the tubular.
3. The valve system of claim 1, wherein each valve in a valve group
comprises an expandable ball seat having a seat diameter adapted to
the drop ball.
4. The valve system of claim 1, wherein the intermediate opening is
provided by an inset fit into the full radial opening.
5. The valve system of claim 4, wherein the full radial opening is
lined with a material that is harder than the inset.
6. A method for providing fluid flow through radial openings
disposed along an axial length of a tubular, comprising disposing
at least one valve group associated with a section of the tubular,
the valve group containing at least two valves operable by one drop
ball in the tubular, each valve having a closed state, an
intermediate state providing an intermediate opening for at least
the time required to open all the remaining valves in the group,
and an open state providing a full radial opening larger than the
intermediate opening, altering the state of each valve from the
closed state to the intermediate state in turn using the drop ball,
and altering the state of each valve from the intermediate to the
open state.
7. The method of claim 6, wherein altering the state of each valve
from the intermediate to the open state involves pumping an
abrasive material through the openings.
8. The method of claim 6, wherein more than one drop ball are used,
each altering the valves in the valve group from their closed to
their intermediate states.
9. The method of claim 6, further comprising monitoring the fluid
flowing through each valve section, and closing the section of
tubular associated with a valve section when the fluid flowing
through it no longer satisfies predetermined criteria.
10. The valve system of claim 2, wherein each valve in a valve
group comprises an expandable ball seat having a seat diameter
adapted to the drop ball.
11. The method of claim 7, wherein more than one drop ball are
used, each altering the valves in the valve group from their closed
to their intermediate states.
12. The method of claim 7, further comprising monitoring the fluid
flowing through each valve section, and closing the section of
tubular associated with a valve section when the fluid flowing
through it no longer satisfies predetermined criteria.
13. The method of claim 8, further comprising monitoring the fluid
flowing through each valve section, and closing the section of
tubular associated with a valve section when the fluid flowing
through it no longer satisfies predetermined criteria.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a valve system and method
for providing fluid flow between the interior and exterior of a
tubular through several radial openings disposed along an axial
length of the tubular. It allows opening multiple valves by one
drop ball, and it may find applications in recovery of hydrocarbons
from subterranean formations.
[0003] 2. Prior and Related Art
[0004] A subterranean formation containing hydrocarbons consists of
at least one layer of soft or fractured rock to contain the
hydrocarbons, in the following called a production layer. Each
production layer must be covered by a layer of impermeable rock
preventing the hydrocarbons from escaping. The production layers in
an oil or gas field are collectively known as the reservoir. A
production well extending through the reservoir is conventionally
divided into production zones, one or more production zones per
production layer. A production well may extend several thousand
meters vertically through the formation, and be connected to
horizontal branches extending up to several kilometres through a
production layer. One or more injection wells may be provided at a
distance from the production well(s) in a field. The injection
wells can be used to pump water, brine or gas into the formation in
order to increase the pressure. Additives such as acid, solvents or
surfactants may be added to the fluid in order to enhance
production of hydrocarbons in processes known as "stimulating a
zone."
[0005] The production and injection wells and horizontal branches
are typically lined with a steel pipe cemented to the formation and
penetrated at the production layer(s). As known in the art, this
pipe consists of sections having a decreasing diameter as the
distance from the surface increases. In this disclosure, no
distinction is made between a liner and a casing. That is, all
steel pipes lining a borehole are denoted "casing" in the
following. A smaller diameter production pipe or riser is provided
within the casing of a production well, and used for conveying
formation fluid typically consisting of a mixture of oil, water and
gas, to the surface. Steel pipes of different diameters used for
casing, production pipes or risers are collectively known as
"tubulars."
[0006] Production zones may be separated by packers sealing the
annulus formed by the outer surface of a production pipe and the
inner surface of a casing. The annulus formed by the borehole walls
and outer circumference of a casing is usually sealed by cement and
sometimes by open hole packers.
[0007] Hydraulic fracturing is a technique to enhance the flow of
fluid from the formation, where the hydraulic pressure in a
production zone is increased until fractures or cracks in the
formation are enlarged. A slurry containing fracturing material,
e.g. sand, ceramic balls or similar particles, is pumped into the
cracks. When the fracturing pressure is removed, the fracturing
material remains in the cracks, keeping them open. For the present
invention, it is noted that the slurry containing fracturing
material, e.g. sand, ceramic balls, or similar particles, used for
hydraulic fracturing is highly abrasive, especially where the flow
of slurry changes direction from an axial direction through a pipe
to a radial movement through openings in a valve. Hence, the radial
openings of a valve used for hydraulic fracturing may be lined with
a hard material, e.g. tungsten carbide (WC). It is further noted
that pumps and other equipment for handling the abrasive slurry and
pressures involved in hydraulic fracturing are readily
available.
[0008] Valves are used to control the flow of formation fluid from
a production zone into the production pipe through the casing,
possibly through a horizontal branch. Valves are also used for
controlling an injection fluid from an injection well into a zone
of the formation to be stimulated. When the formation fluid from a
production zone contains too much water to be economically
sustainable, the production zone is shut down, typically by means
of one or more valves. The valves are operated between open and
closed, and possibly choked, positions using a variety if
techniques, including the use of wireline tools, strings of pipes,
coiled tubing, self-propagating tools known as well tractors, and
drop balls. Some valves may be operated using separate hydraulic
control lines. However, the space and cost required for providing
separate hydraulic control lines and relatively expensive hydraulic
valves quickly make hydraulically operated valves impractical for
use in a tubular with many valves. This is especially true if the
valves are to be opened once, and then left open.
[0009] A drop ball may be dropped or pumped into a tubular. Once it
lands on a seat of a device, it prevents further fluid flow through
the tubular, and hydraulic pressure builds up behind it. This
hydraulic pressure may be used to operate the device, e.g. to open
a valve. Thus, a drop ball may provide a simple, inexpensive and
convenient way to open a valve. It does not require expensive
equipment like a string of pipes, coiled tubing or a well tractor,
and it can be delivered to a device in less time than it takes to
make up a string, insert coiled tubing or for a well tractor to
crawl to the device. However, conventional drop ball systems uses
one drop ball per device, such that a drop ball passes through all
bigger seats in the system until it lands on the seat intended for
it. To prevent a drop ball from getting stuck on a seat not
intended for it, there is a certain minimum size difference in the
drop balls of the system. Hence, the number of drop balls, and
consequently the number of drop ball operated devices, has been
limited to about 20 per system.
[0010] In a reservoir as the one discussed above, fluid, e.g.
seawater or CO.sub.2, may be pumped into a production layer from an
injection well. The injected fluid ideally forces the hydrocarbons
in front of it into a production pipe, e.g. a horizontal branch or
a sealed off production zone of a production zone, and further
through a riser to the surface. In reality, the flow of injected
fluid will follow the easiest path to the nearest exit through a
valve in a horizontal or vertical tubular, possibly leaving a
substantial amount of desirable hydrocarbons in dead zones passed
over by the easy path. Devices monitoring the formation fluid from
this zone would correctly detect a breakthrough of injected fluid.
A breakthrough of injected fluid may cause a decision to shut down
the production zone, i.e. preventing more formation fluid flowing
from the zone from entering the production pipe or riser, thus
leaving valuable hydrocarbons in the dead zone in the formation
permanently.
[0011] As discussed above, twenty or less ball operated valves
would be possible along a length of tubular using a conventional
drop ball system. As modern wellbores may extend more than 2000
meters vertically and/or horizontally, the average distance between
ball operated valves would then exceed 100 meters, which could
still constitute quite large dead zones.
[0012] U.S. patent application Ser. No. 12/705,428 "Expandable ball
seat" assigned to i-Tec AS, discloses a system for operating
multiple devices using one drop ball. This system thus may permit
the use of a larger number of ball operated valves in the various
wellbores or tubulars as compared to conventional systems. However,
unlike other ball operated devices in a well, a valve providing
fluid flow between the formation and a central bore of a tubular
reduces the hydraulic pressure in the bore once it opens and fluid
starts flowing from the bore through radial openings to the
formation. However, this hydraulic pressure is required to open the
next valve, and the pressure drop must be compensated in order to
open the next valve using a drop ball. When two valves are open, an
even larger pressure drop must be compensated to open the third
valve, etc. In a system designed for providing a good flow of
formation fluids into a tubular, the valves should preferably have
large radial openings, or nozzles, such that each valve tends to
contribute a correspondingly large pressure drop as it is opened.
This, in turn, may limit the number of valves operable by a drop
ball in a tubular.
[0013] Hence, a main objective of the present invention is to
provide a tubular with a large number of valves while avoiding
expensive valves, hydraulic control lines and/or expensive
production time spent for operating the valves by means of wireline
tools, strings, well tractors etc. A further objective is to handle
the pressure drop associated with opening a valve, thereby reducing
the hydraulic pressure available for opening the next valve by
means of a drop ball.
SUMMARY OF THE INVENTION
[0014] This is achieved according to the present invention by
providing a valve system for providing fluid flow through radial
openings disposed along an axial length of a tubular, wherein at
least one valve group comprises at least two valves operable by one
drop ball, each valve having a closed state, an intermediate state
providing an intermediate opening for at least the time required to
open all the remaining valves in the valve group, and an open state
providing a full radial opening larger than the intermediate
opening.
[0015] In another aspect, the present invention provides a method
for providing fluid flow through radial openings disposed along an
axial length of a tubular, comprising the steps of: disposing at
least one valve group associated with a section of the tubular, the
valve group containing at least two valves operable by one drop
ball in the tubular, each valve having a closed state, an
intermediate state providing an intermediate opening for at least
the time required to open all the remaining valves in the group,
and an open state providing a full radial opening larger than the
intermediate opening; altering the state of each valve from the
closed state to the intermediate state in turn using the drop ball,
and altering the state of each valve from the intermediate to the
open state.
[0016] In a preferred embodiment, the intermediate state is
provided by an inset made of standard steel having a small opening
and set into a harder lining, and altering from the intermediate to
the open state involves pumping abrasive material through the inset
until it is eroded away. Then, the harder lining provides a full
radial opening. The abrasive material can be a slurry containing
material otherwise used for hydraulic fracturing.
[0017] The valve system may comprise one or more additional valves
to shut down fluid flow from a group of valves when the
concentration of hydrocarbons in the formation fluid flowing from
the group falls below a predetermined level.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The invention will be fully explained in the following
detailed description with reference to the accompanying drawings in
which similar numbers references similar or equivalent parts, and
in which:
[0019] FIG. 1 is a schematic view of a well comprising several
zones and branches;
[0020] FIG. 2 is a schematic view of a valve system according to
the invention; and
[0021] FIG. 3 is a schematic view of a nozzle for use in a drop
ball activated valve according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0022] FIG. 1 is a schematic cross sectional view of a well system
used in production of hydrocarbons, i.e. oil and/or gas, from a
subterranean reservoir. A hole or wellbore 101 is drilled through
several layers of rock in the formation. In FIG. 1, two production
layers 100 and 200 are shown. The wellbore is lined with a steel
casing 102, which is cemented to the formation. In FIG. 1, the
production layers 100 and 200 contain hydrocarbons, and they are
separated by rock layers that do not contain hydrocarbons. The
casing 102 may be penetrated at depths corresponding to the
productive layers 100 and 200, and hydraulic fracturing may be used
to create and open cracks in the formation to facilitate fluid flow
from the formation into the production well. Horizontal wells 100',
100'' and 200' may branch out from a vertical production well, and
extend several kilometres through a production layer 100, 200
containing hydrocarbons.
[0023] A production pipe 103 is provided within the casing 102, and
the completed well can be divided into several production zones by
using packers (not shown) to seal off the annular space formed by
the outer surface of production pipe 103 and the inner surface of
casing 102. The valves 110A-C, 210A-C, . . . in FIG. 1 control
fluid flow from a formation 100, 200 into the segment of production
pipe corresponding to the production zone. The valves will
generally be of different design or types, e.g. sliding sleeve
valves, butterfly valves and ball valves of different sizes and
designs used for different purposes as known in the art. In
operation, fluid flowing from several zones (shown by arrows 120)
at different rates can be mixed and conveyed up the production pipe
to the surface 10.
[0024] In order to increase the amount and/or rate at which
hydrocarbons are produced from a zone, one or more injection wells
300 may be provided at a distance from the production well. An
injection well injects fluid into one or more zones, e.g. to
increase the pressure in the reservoir or to provide some chemical
composition, and can be made in a similar manner as the production
well. A typical oil or gas field can comprise one or more
production wells and zero or more injection wells.
[0025] As discussed above, various devices like sliding sleeve
valves, butterfly valves and ball valves of different sizes and
designs, can be used to control fluid flow and for other purposes.
For convenience, the term "ball operated device" is intended to
include these and other devices when hydraulically operated using a
drop ball, dart or similar device. All such ball operated devices
comprises a seat on which the ball, dart or similar device can
land. Obviously, drop balls of different sizes may be provided as
in a conventional drop ball system. The difference is that a drop
ball will pass groups of seats having similar sizes until it
operates a group of valves rather than the single devices passed
and operated on by conventional drop ball systems.
[0026] FIG. 2 shows a tubular 110 with a group of valves 110A-C all
of which are provided with an expandable ball seat, for example as
disclosed in U.S. patent application Ser. No. 12/705,428, and thus
can be opened one after the other using one and only one drop ball.
The valve 110A is closest to the surface, and hence opened first by
the drop ball. An inset in the valve nozzle (FIG. 3) provides a
small hole from the interior of tubular 110 to the surrounding
formation. Since the hole is small, it limits the amount of fluid
flowing through it, and hence causes a relatively small pressure
drop in the central bore of the tubular. A minor pressure drop may
easily be compensated, so that the hydraulic pressure remains
sufficiently large to open valve 110B. Valve 110B has an inset
similar to the one in valve 110A, thus creating a new, small
pressure drop. These pressure drops are made sufficiently small
that they can be compensated in a relatively simple manner.
[0027] When all the valves are opened, an abrasive material is
passed through the opening. The abrasive material can e.g. be a
slurry with about 5% ceramic balls or sand, such as the medium used
for hydraulic fracturing. In this case the slurry flows
comparatively slowly in the central bore. When it reaches a hole,
the speed increases. Hence the abrasion is much larger at the ports
than in the central bore. In a preferred setup, the ports are lined
with a hard material, e.g. tungsten carbide (WC), providing the
final openings. Ordinary steel are set within the hard inner
surface. For example, the hard liner can be a cylinder, and the
erodible steel inset can be shaped as a concentric ring having an
outer circumference engaging the inner hard surface of the liner.
Tests have shown that normal grade steel is removed from the liner
within 1-2 hours using material otherwise used for hydraulic
fracturing.
[0028] It is noted that softer material may be provided within the
liners. Further, the liners need not be cylindrical, and the insets
do not need to be annular, but can be elliptical or have another
shape.
* * * * *