U.S. patent application number 13/908869 was filed with the patent office on 2014-12-04 for multi-well simultaneous fracturing system.
The applicant listed for this patent is Cameron International Corporation. Invention is credited to Edward L. Ganzinotti, III, Jay P. Painter, Jason L. Pitcher.
Application Number | 20140352968 13/908869 |
Document ID | / |
Family ID | 51983825 |
Filed Date | 2014-12-04 |
United States Patent
Application |
20140352968 |
Kind Code |
A1 |
Pitcher; Jason L. ; et
al. |
December 4, 2014 |
MULTI-WELL SIMULTANEOUS FRACTURING SYSTEM
Abstract
A system for simultaneously fracturing multiple wells is
provided. In one embodiment, the system includes fracturing trees
installed at multiple wells. A fracturing manifold is connected to
the fracturing trees and includes output valves to independently
control flow of fracturing fluid from the manifold to each of
multiple wells. The system may also include a controller connected
to the output valves so that the controller can remotely operate
the output valves to simultaneously fracture the multiple wells and
independently control the volume of fracturing fluid entering each
of the wells from the fracturing manifold. Additional systems,
devices, and methods are also disclosed.
Inventors: |
Pitcher; Jason L.; (The
Woodlands, TX) ; Ganzinotti, III; Edward L.;
(Houston, TX) ; Painter; Jay P.; (Webster,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cameron International Corporation |
Houston |
TX |
US |
|
|
Family ID: |
51983825 |
Appl. No.: |
13/908869 |
Filed: |
June 3, 2013 |
Current U.S.
Class: |
166/308.1 ;
166/67 |
Current CPC
Class: |
E21B 43/26 20130101 |
Class at
Publication: |
166/308.1 ;
166/67 |
International
Class: |
E21B 43/12 20060101
E21B043/12 |
Claims
1. A system comprising: a first fracturing tree installed at a
first well; a second fracturing tree installed at a second well; a
fracturing manifold connected to the first fracturing tree and the
second fracturing tree, the fracturing manifold including output
valves to independently control flow of fracturing fluid from the
fracturing manifold to the first fracturing tree and from the
fracturing manifold to the second fracturing tree; and a controller
connected to the output valves of the fracturing manifold to enable
the controller to remotely operate the output valves to
simultaneously fracture both the first well and the second well by
routing fracturing fluid into each of the first and second wells
via its respective fracturing tree and to independently control the
volume of fracturing fluid entering the first well and the volume
of fracturing fluid entering the second well from the fracturing
manifold.
2. The system of claim 1, comprising at least one ball launcher
connected to one or both of the first fracturing tree and the
second fracturing tree.
3. The system of claim 2, wherein each of the first and second
wells include sliding sleeves for isolating different fracturing
zones in the first and second wells.
4. The system of claim 3, wherein the sliding sleeves are
ball-actuated sliding sleeves and the controller is connected to
the at least one ball launcher so as to allow the controller to
remotely operate the at least one ball launcher to release balls
into the fracturing fluid to be conveyed to the ball-actuated
sliding sleeves of the first and second wells.
5. The system of claim 1, comprising a fracturing supply system
connected to the fracturing manifold, the fracturing supply system
including pumps connected to a blender.
6. The system of claim 5, wherein the fracturing supply system
includes an additional blender and the fracturing manifold includes
input valves connected to the blender and to the additional blender
to control flow of fracturing fluid from the blender and from the
additional blender into the fracturing manifold.
7. The system of claim 6, wherein the controller is connected to
the input valves to enable remote operation of the input valves by
the controller.
8. The system of claim 1, comprising sensors coupled between the
output valves of the fracturing manifold and the first and second
wells, wherein the controller is configured to receive input from
the sensors and use the received input to vary operation of the
output valves of the fracturing manifold.
9. A system comprising: a fracturing manifold including: an input
valve; at least two output valves connected in fluid communication
with the input valve; and one or more ball launchers integrated as
part of the fracturing manifold.
10. The system of claim 9, wherein the one or more ball launchers
are integrated into the fracturing manifold between the input valve
and the at least two output valves.
11. The system of claim 9, wherein the one or more ball launchers
include a first ball launcher connected at, and downstream of, one
of the output valves and a second ball launcher connected at, and
downstream of, another of the output valves.
12. A method comprising: receiving fracturing fluid into a
manifold; routing the fracturing fluid from the manifold into
multiple wells simultaneously; measuring flow characteristics of
the fracturing fluid output from the manifold with sensors
downstream from the manifold; providing input based on the measured
flow characteristics to a controller; and actuating valves
connected to the multiple wells with the controller to control the
amount of fracturing fluid routed into each of the multiple
wells.
13. The method of claim 12, wherein measuring flow characteristics
of the fracturing fluid output from the manifold includes measuring
volumetric flow rate from the manifold to each of the multiple
wells.
14. The method of claim 13, comprising calculating a duration for
pumping fracturing fluid from the manifold into a first well of the
multiple wells to stimulate a fracturing zone of the first
well.
15. The method of claim 14, comprising determining, based on the
calculated duration for the first well, a desired volumetric flow
rate for fracturing fluid into a second well via the manifold.
16. The method of claim 12, wherein actuating valves connected to
the multiple wells includes operating at least one of the valves to
balance volumes of fracturing fluids routed into each of the
multiple wells.
17. The method of claim 12, wherein actuating valves connected to
the multiple wells includes actuating valves of the manifold.
18. The method of claim 12, comprising selecting between different
fracturing fluids for pumping into the manifold by actuating one or
more input valves of the manifold.
19. A method comprising: connecting a fracturing manifold to a
plurality of wells; stimulating at least two wells of the plurality
of wells to increase productivity of the at least two wells,
wherein stimulating the at least two wells includes simultaneously
fracturing the at least two wells with fracturing fluid routed into
each of the at least two wells via the fracturing manifold.
20. The method of claim 19, comprising simultaneously pumping
fracturing fluid from the fracturing manifold into a first well and
into a second well of the at least two wells at different flow
rates.
21. The method of claim 20, comprising controlling at least one
valve to cause the flow rates of fracturing fluid from the
fracturing manifold into the first and second wells to differ.
22. The method of claim 21, wherein controlling the at least one
valve includes controlling at least one valve of the fracturing
manifold.
23. The method of claim 21, wherein controlling the at least one
valve includes automatically controlling the at least one valve
remotely with a programmed controller.
24. The method of claim 19, comprising producing formation fluids
from the at least two wells.
Description
BACKGROUND
[0001] This section is intended to introduce the reader to various
aspects of art that may be related to various aspects of the
presently described embodiments. This discussion is believed to be
helpful in providing the reader with background information to
facilitate a better understanding of the various aspects of the
present embodiments. Accordingly, it should be understood that
these statements are to be read in this light, and not as
admissions of prior art.
[0002] In order to meet consumer and industrial demand for natural
resources, companies often invest significant amounts of time and
money in finding and extracting oil, natural gas, and other
subterranean resources. Particularly, once a desired subterranean
resource is discovered, drilling and production systems are often
employed to access and extract the resource. These systems may be
located onshore or offshore depending on the location of a desired
resource. Further, such systems generally include a wellhead
assembly through which the resource is extracted. These wellhead
assemblies may include a wide variety of components, such as
various casings, valves, fluid conduits, and the like, that control
drilling or extraction operations.
[0003] Additionally, such wellhead assemblies may use a fracturing
tree and other components to facilitate a fracturing process and
stimulate production from a well. As will be appreciated, resources
such as oil and natural gas are generally extracted from fissures
or other cavities formed in various subterranean rock formations or
strata. To facilitate extraction of such resources, a well may be
subjected to a fracturing process that creates one or more man-made
fractures in a rock formation. This facilitates, for example,
coupling of pre-existing fissures and cavities, allowing oil, gas,
or the like to flow into the wellbore. Such fracturing processes
typically include injecting a fracturing fluid--often a mixture or
slurry including sand and water--into the well to increase the
well's pressure and form the man-made fractures.
SUMMARY
[0004] Certain aspects of some embodiments disclosed herein are set
forth below. It should be understood that these aspects are
presented merely to provide the reader with a brief summary of
certain forms the invention might take and that these aspects are
not intended to limit the scope of the invention. Indeed, the
invention may encompass a variety of aspects that may not be set
forth below.
[0005] Embodiments of the present disclosure generally relate to
simultaneous fracturing of multiple wells. In at least some
instances, pumping fluid into two or more wells simultaneously to
fracture those wells reduces total pumping time for fracturing
wells at a pad site. In one embodiment, a fracturing system
includes a manifold having valves to independently control flow
rates of fracturing fluid to multiple wells. Fracturing fluid can
be pumped through the manifold and into the multiple wells
simultaneously, and the valves can be operated to balance the
volume of fluid pumped into each well. A controller can also be
used with the system to remotely actuate the manifold valves and
control flow rates based on measured parameters and stored
data.
[0006] Various refinements of the features noted above may exist in
relation to various aspects of the present embodiments. Further
features may also be incorporated in these various aspects as well.
These refinements and additional features may exist individually or
in any combination. For instance, various features discussed below
in relation to one or more of the illustrated embodiments may be
incorporated into any of the above-described aspects of the present
disclosure alone or in any combination. Again, the brief summary
presented above is intended only to familiarize the reader with
certain aspects and contexts of some embodiments without limitation
to the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features, aspects, and advantages of certain
embodiments will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0008] FIG. 1 generally depicts a fracturing system for
simultaneously fracturing multiple wells in accordance with one
embodiment of the present disclosure;
[0009] FIG. 2 is a block diagram of various components of the
fracturing system of FIG. 1 in accordance with one embodiment;
[0010] FIGS. 3 and 4 are flow charts representative of methods for
simultaneously fracturing multiple wells in accordance with certain
embodiments of the present disclosure;
[0011] FIG. 5 generally depicts two horizontal wells having
fracturing zones in accordance with one embodiment;
[0012] FIG. 6 is a block diagram of a programmable controller for
operating the fracturing system of FIGS. 1 and 2 in accordance with
one embodiment; and
[0013] FIGS. 7-10 depict various fracturing manifolds in accordance
with certain embodiments of the present disclosure.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0014] One or more specific embodiments of the present disclosure
will be described below. In an effort to provide a concise
description of these embodiments, all features of an actual
implementation may not be described in the specification. It should
be appreciated that in the development of any such actual
implementation, as in any engineering or design project, numerous
implementation-specific decisions must be made to achieve the
developers' specific goals, such as compliance with system-related
and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that
such a development effort might be complex and time consuming, but
would nevertheless be a routine undertaking of design, fabrication,
and manufacture for those of ordinary skill having the benefit of
this disclosure.
[0015] When introducing elements of various embodiments, the
articles "a," "an," "the," and "said" are intended to mean that
there are one or more of the elements. The terms "comprising,"
"including," and "having" are intended to be inclusive and mean
that there may be additional elements other than the listed
elements. Moreover, any use of "top," "bottom," "above," "below,"
other directional terms, and variations of these terms is made for
convenience, but does not require any particular orientation of the
components.
[0016] Turning now to the present figures, an example of a
fracturing system 10 is provided in FIG. 1 in accordance with one
embodiment. The fracturing system 10 facilitates extraction of
natural resources (e.g., oil or natural gas) from wells 12 and 14.
Particularly, by injecting a fracturing fluid into the wells 12 and
14, the fracturing system 10 increases the number or size of
fractures in a formation 16 to enhance recovery of natural
resources present in the formation 16.
[0017] The fracturing fluid may, for example, include water (or
another liquid) mixed with sand or some other proppants. The
fracturing fluid is pumped into the formation 16 to extend
fractures and fill them with the proppants, which operate to hold
open the fractures after pumping has stopped to allow formation
fluids to be more easily produced via the wells 12 and 14. In at
least some embodiments, fracturing fluids used in the wells 12 and
14 also include other additives. For example, the fracturing fluid
can include polymers or other agents to increase the viscosity of
the fracturing fluid (which aids in carrying the proppants down the
wells). And in some instances, the fracturing fluid includes acid
(e.g., hydrochloric acid) that initiates fissures in the formation
16.
[0018] Although generally depicted as horizontal wells extending
through the formation 16, the wells 12 and 14 could take other
forms (e.g., vertical wells). In the presently illustrated
embodiment, the wells 12 and 14 are surface wells formed at a
common pad 20 and accessed through wellhead assemblies 18 installed
at the wells. It will, of course, be appreciated that natural
resources can be extracted from other types of wells, such as
platform or subsea wells.
[0019] The fracturing system 10 also includes a fracturing supply
system 22 coupled to the wellhead assemblies 18 by conduits 24 and
26 so as to provide fracturing fluid to the wells 12 and 14 via the
conduits. In one embodiment, the fracturing supply system 22
includes various components depicted in block diagram 30 of FIG. 2.
As here illustrated, each of the wells 12 and 14 has a fracturing
tree 32 (part of the wellhead assembly 18 of FIG. 1) installed on a
wellhead 34. The fracturing trees 32 include valves to control flow
of fracturing fluids through the wellheads 34 and into their
respective wells. The wells 12 and 14 include sliding sleeves 38,
which can be run into or as part of casing strings in the wells.
When actuated, the sliding sleeves 38 move to expose ports in the
casing strings, allowing fracturing fluid pumped down the wells 12
and 14 to reach the formation 16 via the ports. The wells 12 and 14
can be divided into multiple fracturing zones (also referred to as
fracturing stages) and sliding sleeves 38 can be used to isolate
the fracturing zones to allow sequential fracturing of each
zone.
[0020] In at least some embodiments, such as that depicted in FIG.
2, the sliding sleeves 38 are ball-actuated sliding sleeves and the
fracturing system includes one or more ball launchers 40 to drop
balls 42 (which may also be referred to as packer balls or frac
balls) into the wells 12 and 14. For instance, at least some of the
sliding sleeves 38 are constructed with seats or baffles for
receiving packer balls 42. When the packer ball engages the seat,
the ball inhibits flow through the seat and fluid pressure (e.g.,
from the pumping of fluid down a well behind the ball) increases
and causes the ball to push the sliding sleeve 38 open. The sliding
sleeve 38 can be retained in place by a shear pin or some other
device so the ball does not move the sleeve 38 until the pressure
on the ball exceeds a threshold amount.
[0021] The various sliding sleeves 38 of each well can be
constructed for actuation by differently sized packer balls 42 and
generally have seats with apertures that allow smaller balls 42 to
pass through without actuating the sleeve. More specifically, the
sliding sleeves 38 can be arranged in the wells in sequence by the
size of the balls 42 used to actuate the sleeves, with the sleeves
operated by the smallest balls provided furthest from the surface
and the sleeves operated by the largest balls provided closest to
the surface. In this arrangement, the smallest ball can dropped
into a well and pass through the apertures in other sleeves before
reaching (and actuating) the sleeve furthest from the surface.
Balls of increasing size can then be sequentially dropped to
actuate additional sleeves in the well, with the largest ball being
the last dropped in order to actuate the sleeve closest to the
surface. The sliding sleeves 38 can be placed between adjacent
fracturing zones in the wells so that, as each ball 42 engages the
seat of a corresponding sliding sleeve 38, the ball inhibits flow
through the seat and isolates the fracturing zone associated with
that actuated sleeve from other fracturing zones further down the
well. To facilitate the sequential actuation of the sleeves 38, the
conduits (e.g., conduits 24 and 26) connecting the ball launchers
40 to the wells 12 and 14 can be provided as single high-pressure
lines (one to each well) having bores of sufficient size to allow
the largest packer balls 42 to pass from the ball launchers 40 to
the wells.
[0022] The system depicted in FIG. 2 also includes a fracturing
manifold 44 for controlling the flow of fracturing fluids to both
well 12 and well 14. Fluid conduits 24 and 26 (FIG. 1) generally
connect the fracturing manifold 44 to the wells 12 and 14. This
allows fluid to be routed from the manifold to either or both of
the wells 12 and 14 via one or more manifold output valves 48. The
output valves 48 can include any suitable valves (e.g., chokes or
gate valves) that facilitate separate and independent control of
the flow of fluid from the fracturing manifold 44 to each of the
wells 12 and 14. In some embodiments the ball launchers 40 are
provided separately from the fracturing manifold 44 (as depicted in
FIG. 2), while in others the ball launchers 40 are integrated into
the manifold 44 (see, e.g., FIGS. 7-10).
[0023] Various components, collectively denoted with reference
numeral 46 in FIG. 2, cooperate to provide fracturing fluid to the
manifold 44. In the depicted embodiment, such components include
pumps 50, fluid tanks 52, and blenders 54. The pumps 50 can be
provided by pumping trucks or in some other manner, and these pumps
are used to route fluid from the fluid tanks 52 to the manifold 44
and, ultimately, to the wells. Though often water-based, any
suitable fracturing fluids can be stored in the fluid tanks 52. In
at least some embodiments, the fracturing fluid stored in the fluid
tanks is gelled or crosslinked for increased viscosity, thereby
enhancing the ability of the fluid to transport proppants to the
formation.
[0024] One or more blenders 54 are used to mix additives 58 into
the fracturing fluid. While some other embodiments include a single
blender 54, the system depicted in FIG. 2 includes two blenders.
One of the blenders 54 can be used to mix an additive 58 of sand or
some other proppant into the fracturing fluid routed from the fluid
tanks 52 so that the proppants can be injected into the formation
16 to maintain fissures created or extended during fracturing. The
other blender 54 can be used to mix an additive 58 of acid that
initiates the creation of new fissures or the extension of old
fissures in the formation 16. In some instances, the fracturing
fluid with acid is provided for an initial period to promote
fissures and then followed with proppant-laden fracturing fluid to
inhibit closing of these fissures once fracturing is completed.
Given its role in initiating fissures in the formation 16, the mix
of fracturing fluid and acid can be referred to as a "fracturing
spear." As noted above, a single blender 54 could instead be used
for mixing additives into the fracturing fluid. For example, a
single blender 54 could add acid to the fracturing fluid for a
given period, after which the blender 54 could be converted to then
add a proppant to the fracturing fluid for another time period. But
having two blenders 54 may be more efficient in some instances by
avoiding conversion of a single blender to mix different additives
into the fracturing fluid at different times. And while two
blenders 54 are presently depicted, it is noted that additional
blenders 54 could also be provided.
[0025] In those embodiments having multiple blenders 54, and as
illustrated in FIG. 2 by way of example, the manifold 44 can
include input valves 56 for controlling which fracturing fluid is
routed to the output valves 48 at a given time. For instance, one
of the input valves 56 can be opened to allow the fracturing spear
into the manifold 44 (that is, the fracturing fluid mixed with acid
by one of the blenders), while another of the input valves 56 is
closed to inhibit flow of proppant-laden fracturing fluid (mixed by
a different blender) into the manifold 44. Once a desired amount of
spear fluid is received by the manifold 44 (which can be routed to
one or both wells 12 and 14), the input valves 56 can be operated
to stop flow of the spear fluid into the manifold 44 and to allow
the fracturing fluid with proppants to enter the manifold 44 and
pass to the wells 12 and 14. Like the output valves 48, the input
valves 56 can include chokes, gate valves, or any other suitable
valves.
[0026] Although any or all of the ball launchers 40, the output
manifold valves 48, and the input manifold valves 56 could be
actuated manually, in at least some embodiments these components
are operated remotely by a controller. In FIG. 2, for example, a
controller 60 is connected to the ball launchers 40, the valves 48,
and the valves 56 to control fracturing of the wells 12 and 14.
More specifically, the controller 60 can operate the valves 48 to
independently control the flow of fracturing fluid to each of the
wells 12 and 14 (e.g., with a separate valve 48 for each of the
wells). One or more sensors 62 (e.g., flow meters, pressure gauges,
and densimeters) are connected downstream from the output valves 48
to measure operational parameters (e.g., flow rate and pressure).
And as discussed in greater detail below, these measured parameters
can then be provided as input to the controller 60 to facilitate
operation of the fracturing system. The controller 60 can also
operate the valves 56 to select a fracturing fluid to be provided
to the wells (e.g., one with a high acid concentration or one
carrying proppants) and operate the ball launchers 40 to drop balls
into the wells 12 and 14 (e.g., to engage sliding sleeves 38 and
select fracturing zones). Still further, the controller 60 of some
embodiments can also control operation of other devices, such as
the blenders 54 and the pumps 50.
[0027] To reduce the amount of time needed to fracture wells on a
shared pad, at least some embodiments of the present technique
enable multiple wells to be fractured simultaneously. That is,
fracturing fluid may be pumped into two or more wells at the same
time to fracture rock surrounding the wells and stimulate well
productivity. This is in contrast to other techniques, such as
sequential fracturing of each well or other fracturing processes
(e.g., zipper fracturing) in which two wells alternate between
being prepared for fracturing and actually being fractured. The
simultaneous fracturing techniques disclosed herein can be used to
reduce, in some instances significantly, the amount of pumping time
and associated costs for injecting fluid to fracture multiple wells
compared to some previous approaches.
[0028] With this in mind, two processes for fracturing multiple
wells (e.g., wells 12 and 14) are generally represented by flow
charts 70 and 90 in FIGS. 3 and 4 in accordance with certain
embodiments. These processes are described below in the context of
the fracturing system and various components described above with
respect to FIGS. 1 and 2, but it will be appreciated that the
methods could be readily applied to other systems.
[0029] In the embodiment generally represented in FIG. 3, the wells
12 and 14 are connected to the fracturing manifold 44 (block 72).
The wells 12 and 14 can be connected in any suitable manner, but in
at least some instances each of the wells 12 and 14 are connected
to the manifold 44 via a conduit with a bore diameter sufficient to
pass any packer balls 42 to be dropped within the well (e.g., a
conduit with a four-inch bore in one embodiment). Once the wells 12
and 14 are connected to the fracturing manifold, fracturing fluid
can be pumped into the manifold (block 74) and then routed out of
the manifold (block 76) into the wells 12 and 14 such that they
receive fracturing fluid concurrently. Pumping of the fracturing
fluid into each of the wells continues so that the wells 12 and 14
can be fractured simultaneously (block 78) to stimulate
productivity of the wells. Post-fracturing production can commence
(block 80) at any desired time after fracturing is complete (e.g.,
soon after flowback testing or after a prolonged shut-in
period).
[0030] Fracturing multiple wells simultaneously reduces the amount
of pumping time (and expense) needed to complete fracturing of
wells at a pad. In at least some instances, operation of the
fracturing system can be improved by controlling the individual
flows of fracturing fluid to each well from the fracturing manifold
44. By way of example, the process generally represented in FIG. 4
includes pumping fracturing fluid into multiple wells
simultaneously (block 92) and monitoring one or more fluid
parameters for each well (block 94). Examples of the monitored
fluid parameters include flow rate, flow volume, density, and
pressure, and these parameters can be measured via any suitable
devices (e.g., sensors 62) downstream from the output valves 48.
The method also includes operating valves of the fracturing
manifold 44 (e.g., output valves 46 and input valves 56) to control
the fracturing fluid entering each of the wells connected to the
manifold (block 96) based on fluid parameters monitored for each
well. Additionally, in this embodiment the method includes dropping
balls (block 98) in the wells 12 and 14 to actuate sliding sleeves
38 and isolate a selected fracturing stage from preceding stages
deeper in the wells.
[0031] The operating of the valves and dropping of balls
represented by blocks 96 and 98 may be better understood with
reference to FIG. 5. As here depicted, the wells 12 and 14 have
lateral (here horizontal) portions extending through the formation
16. The lateral portions of these wells can have lengths 102 and
112 of thousands of feet measured heel to toe, and these lengths
may be equal to or different from one another. The lateral portions
of the wells 12 and 14 can be divided into multiple fracturing
zones. In FIG. 5, the well 12 includes fracturing zones or stages
104, 106, 108, and 110, and the well 14 includes fracturing zones
or stages 114, 116, 118, and 120. Although only a handful of
fracturing zones are depicted herein for the sake of explanation,
it is noted that the wells 12 and 14 could include any number of
desired fracturing zones. Further, each well could be divided into
fracturing zones of equal size or of different size, and the zones
of the different wells could also be sized similarly or differently
compared to one another. The fracturing zones in some embodiments
are divided by sliding sleeves 38 to facilitate sequential
isolation and fracturing of these zones.
[0032] In at least some embodiments, including the process
represented in FIG. 4, the fluid distribution between the
simultaneously fractured wells is controlled to reduce total
pumping time for fracturing the wells. The amount of fracturing
fluid used for each well (and for each fracturing zone in the well)
can vary depending on the characteristics of the well (e.g., length
of well or porosity of the formation). But absent leaks in the
system, fluid distribution from the fracturing manifold 44 can be
described by:
V out = i = 1 n V i , ##EQU00001##
[0033] in which V.sub.out is the volume of fracturing fluid output
from the fracturing manifold 44, n is the number of wells being
simultaneously fractured (two in the presently described
embodiment, although a different number of wells may be
simultaneously fractured in other embodiments), and V is the volume
of fracturing fluid pumped into an individual well i. Given the
relationship of flow volume to flow rate, the fluid distribution
from the manifold 44 is also described by:
V out = i = 1 n .intg. Q i t , ##EQU00002##
wherein Q.sub.i is the volumetric flow rate for well i.
[0034] In a simple case in which the wells 12 and 14 are identical
in length, number of fracturing zones, and wellbore length of the
fracturing zones, and also in which each fracturing zone is to
receive the same amount of fracturing fluid, the fracturing fluid
in the manifold 44 could be divided evenly by the output valves 48
so that each well 12 and 14 receives fracturing fluid at the same
rate, such as twenty-five barrels (approximately 2980 liters) per
minute, for an identical amount of time. More specifically, a
desired amount of fracturing spear fluid (e.g., fifty barrels) can
be provided to each well 12 and 14 simultaneously, such as by
opening an input valve 56 to allow the spear fluid to enter the
manifold 44 and opening output valves 48 such that equal amounts of
the spear fluid enters each well. The input valves 56 can then be
operated to stop flow of the spear fluid into the manifold and to
permit flow of a proppant-laden fracturing fluid into the wells 12
and 14 in equal amounts. Once a given zone has been fractured, the
next fracturing zone can be selected by dropping balls 42 into each
of the wells to activate sliding sleeves 38 and the spear fluid and
the proppant-laden fluid can be routed in the same way to the next
fracturing zone. This may be repeated until all of the fracturing
zones have been fractured.
[0035] But in practice there will typically be variation in one or
more well or fracturing parameters (e.g., wells of different
lengths or differences in fracturing zones). In such instances,
fluid flow to the individual wells from the fracturing manifold 44
can be controlled through operation of the output valves 48. For
example, if the well 12 were longer than the well 14, pumping
fracturing fluid at the same rate into each well to fracture the
lowest zones in each well (i.e., zones 104 and 114) and then
dropping balls 42 into each well at the same time to select the
next fracturing zones (i.e., zones 106 and 116) for each well would
cause a greater volume of fracturing fluid to be pumped into the
fracturing zone 104 than into the fracturing zone 114 (due to the
increased volume of fracturing fluid in the well 12 compared to
that in well 14 when the balls 42 are dropped).
[0036] In some embodiments, however, the volumes of fracturing
fluid pumped into zones 104 and 114 are balanced by operating the
output valves 48 to independently control flow to the wells and
change the comparative flow rates of fracturing fluid into the
wells 12 and 14. As noted above, the volume of fracturing fluid
pumped into each well is equal to the product of the volumetric
flow rate and the amount of time the fluid flows at that rate.
Thus, the volume of fracturing fluid pumped into each well can be
controlled by adjusting either the flow rate or the amount of time
that the fluid is pumped. The greater volume of the well 12 (due to
its increased length) can be accounted for as an offset to the
amount of fluid that is to be pumped into well 12 from the manifold
44 to fracture zone 104 before dropping a ball 42 to select the
next fracturing zone. For instance, if a casing string of the well
12 receiving the fracturing fluid has a volume that is greater than
that of a similar casing string of well 14, the manifold output
valves 48 can be operated to slow the flow (and reduce the volume)
to the well 12 from the manifold 44 compared to the flow (and
volume) to the well 14. Further, full flow (e.g., twenty-five
barrels per minute) can be provided to the well 14 and a desired
fracturing time for a given zone can be calculated based on:
V.sub.frac=Qt+V.sub.p,
where V.sub.frac the volume of fracturing fluid to pump into the
fracturing zone, Q is the volumetric flow rate at which fluid is
pumped into the well 14 from the fracturing manifold 44, t is the
desired fracturing time for the zone, and V.sub.p is the volume of
the passageway (i.e., fluid conduit) from the ball launcher 40 (of
the well 14) to the far end of the zone being fractured.
[0037] Accordingly, in one embodiment a manifold valve 48 is opened
to allow full flow of fracturing fluid, and the volumetric flow
rate is measured via a sensor 62 (e.g., a flow meter) and input to
the controller 60. The desired fracturing volume is provided to the
controller 60 as initial data, and the volume of the passageway can
also be provided as (or calculated from) initial data to the
controller 60. Once the desired fracturing time is determined for
zone 114, that time can be input into the same formula to calculate
the appropriate flow rate (the only remaining variable) from the
manifold 44 to the well 12 while fracturing the zone 104. (It is
noted that the fracturing and passageway volumes for zone 104 can
also be determined from initial data provided to the controller 60,
but may differ from those for zone 114.) The manifold valve 48 that
controls flow to the well 12 can then be adjusted to set the flow
rate (which can be measured by a sensor 62) to the calculated
amount. Once the desired fracturing time has elapsed, the ball
launchers 40 may be activated to drop balls 42 into the wells 12
and 14 to isolate the next fracturing stages for stimulation. Each
fracturing stage of corresponding pairs of stages (e.g., zones 106
and 116, zones 108 and 118, and zones 110 and 120) can be fractured
at the same rate and for the same duration if desired, although the
rates and durations could also be varied (e.g., if it is intended
that the zones are to receive different volumes of fracturing
fluid).
[0038] Although the above example describes balancing fluid
distribution by slowing the flow rate into one well compared to
another, in other embodiments the flow rates of both wells may be
kept the same while the fracturing time is varied. For example,
rather than slowing the flow rate of fluid from the manifold 44 to
the well 12 for fracturing zone 104, the fracturing time could be
reduced. That is, a valve 48 of the manifold could be closed once a
desired volume of fracturing fluid has been pumped into the well 12
while additional fracturing fluid is pumped into well 14.
[0039] Various functionality described above (including, for
example, determining desired flow rates and times for multiple
wells and fracturing zones, operating the valves of the manifold to
supply desired fluids at desired rates, and dropping balls into the
wells to isolate fracturing zones) can be implemented with the
controller 60 or with any other suitable controller. In at least
some embodiments, such a controller is provided in the form of a
processor-based system, an example of which is provided in FIG. 6
and generally denoted by reference numeral 130. In this depicted
embodiment, the system 130 includes a processor 132 connected by a
bus 134 to a memory device 136. It will be appreciated that the
system 130 could also include multiple processors or memory
devices, and that such memory devices can include volatile memory
(e.g., random-access memory) or non-volatile memory (e.g., flash
memory and a read-only memory). The one or more memory devices 136
are encoded with application instructions 138 (e.g., software
executable by the processor 132 to perform the control and analysis
functionality described herein), as well as with data 140 (e.g.,
volumes of fracturing fluid to be provided to the fracturing zones
of the wells). In one embodiment, the application instructions 138
are stored in a read-only memory and the data 140 is stored in a
writeable non-volatile memory (e.g., a flash memory). The
application instructions 138 and the data 140 can be copied into a
faster volatile memory (such as a random-access memory or a local
memory of the processor) for execution by the processor. This
generally serves to reduce latency and increase operating
efficiency of the system 130.
[0040] The system 130 also includes an interface 142 that enables
communication between the processor 132 and various input or output
devices 144. The interface 142 can include any suitable device that
enables such communication, such as a modem or a serial port. The
input and output devices 144 can include any number of suitable
devices. For example, in one embodiment the devices 144 include the
sensors 62 (FIG. 2) for providing input of measured parameters
(e.g., flow volume, flow rate, density, and pressure) to the system
130, a keyboard to allow user-input to the system 130, and a
display or printer to output information from the system 130 to a
user. Of course, some devices may allow both input and output, such
as a touchscreen display. The input and output devices 144 can be
provided as part of the system 130, although in other embodiments
such devices may be separately provided.
[0041] As previously noted, the fracturing manifold 44 facilitates
control of fracturing fluid to multiple wells simultaneously. The
fracturing manifold 44 can be provided in any suitable form, and
examples of forms the manifold 44 could take are generally depicted
in FIGS. 7-10. Beginning with FIG. 7, a manifold 150 is shown as
installed to route fluid received from an intake conduit 152 (e.g.,
from pumps 50) to output conduits 154 and 156 (e.g., to wells 12
and 14). An input valve 158 is provided upstream from a ball drop
device 160 (e.g., a ball launcher 40 or a connection block for
receiving a ball from such a launcher) having an access port 162
for receiving a ball 42. The manifold 150 also includes output
valves 164 and 166 (which may function like the output valves 48
described above) for controlling flow of fracturing fluid from the
manifold to connected wells. The valves 158, 164, and 166 can be
actuated in any desired manner (e.g., hydraulically or manually).
Additionally, in at least some embodiments these valves are
hydraulic valves that are actuated remotely in an automated manner
via the controller 60.
[0042] Activation of a ball launcher (whether provided as, or
connected to, the ball drop device 160) to drop balls 42 is also
controlled by the controller 60 in some embodiments. To drop balls
simultaneously into multiple wells, the valves 164 and 166 can be
initially closed. A first ball can be dropped into the manifold 150
and one of the valves 164 and 166 can be briefly opened to advance
the first ball a short distance downstream from the opened valve.
Once that valve is closed, a second ball can be dropped into the
manifold 150 and the other valve can be opened to advance the
second ball downstream from that valve. Both valves 164 and 166 can
then be opened to flow the balls into their respective wells (via
conduits 154 and 156).
[0043] The manifolds of FIGS. 8-10 also include valves 158, 164,
and 166 that can be operated in the same manner as described above
with respect to FIG. 7. Further, in FIG. 8 a manifold 168 includes
a ball drop device 170 with two access ports 172 and 174 for
receiving balls 42. The device 170 includes an internal divider 176
so that balls entering the manifold through the access port 172 are
routed through valve 164 into conduit 154 and balls entering
through the access port 174 are routed through valve 166 into
conduit 156.
[0044] In FIG. 9, a manifold 178 includes a ball drop device 180.
The device 180 includes access ports 182 and 184 for receiving
balls 42, and also includes an internal divider 186 that operates
like the divider 176 to guide balls in desired directions. The
manifold 178 also includes a cap 188 that can be removed to provide
wash-out access to the interior of the manifold. FIG. 10 depicts a
manifold 190 having a connection block 192 (including a cap 194
that provides wash-out access to the manifold) for joining the
valves 158, 164, and 166. But unlike the manifolds of FIGS. 7-9 (in
which the ball drop devices are provided between the input valve
158 and the output valves 164 and 166), the manifold 190 is
arranged so that balls can be dropped into the system downstream
from the valves 164 and 166. Particularly, a ball drop device 196
with access port 198 allows balls to be routed through the conduit
154 to one well, and a ball drop device 200 with access port 202
functions similarly to allow balls to be routed through the conduit
156 to another well. The ball drop devices 196 and 200 (like those
shown in FIGS. 7-9) can be ball launchers or connection blocks
constructed to receive balls from such launchers.
[0045] While the aspects of the present disclosure may be
susceptible to various modifications and alternative forms,
specific embodiments have been shown by way of example in the
drawings and have been described in detail herein. But it should be
understood that the invention is not intended to be limited to the
particular forms disclosed. Rather, the invention is to cover all
modifications, equivalents, and alternatives falling within the
spirit and scope of the invention as defined by the following
appended claims.
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