U.S. patent application number 12/794587 was filed with the patent office on 2011-12-08 for injection-point flow control of undamaged polymer.
Invention is credited to Steven Peter Dyck.
Application Number | 20110297399 12/794587 |
Document ID | / |
Family ID | 45063578 |
Filed Date | 2011-12-08 |
United States Patent
Application |
20110297399 |
Kind Code |
A1 |
Dyck; Steven Peter |
December 8, 2011 |
INJECTION-POINT FLOW CONTROL OF UNDAMAGED POLYMER
Abstract
A device that allows gradually regulation, i.e.,
non-destructively controlling the flow of injected polymer flooding
enhanced oil recovery fluids at each point of injection, using: at
least one conduit providing a variable length flow path combined
with the centrifugal and other retarding or decelerative forces
accessible to a formation engineer by configuring and otherwise
arranging the spatial orientation and relative position of each
section of such conduit, so as to achieve a never before attained
degree of non-damaging flow control density within a compact
space.
Inventors: |
Dyck; Steven Peter; (Slave
Lake, CA) |
Family ID: |
45063578 |
Appl. No.: |
12/794587 |
Filed: |
June 4, 2010 |
Current U.S.
Class: |
166/386 ;
166/90.1 |
Current CPC
Class: |
E21B 21/106 20130101;
E21B 43/16 20130101 |
Class at
Publication: |
166/386 ;
166/90.1 |
International
Class: |
E21B 33/12 20060101
E21B033/12; E21B 19/00 20060101 E21B019/00 |
Claims
1.-15. (canceled)
16. A flow control apparatus to selectively control a flow of a
stream of a polymer fluid during injection at an injection point to
enhance recovery of oil from a production well, comprising: an
inlet fluidly coupled to a source of the polymer fluid under
pressure to receive the polymer fluid; an outlet fluidly coupleable
to the injection point; and at least one conduit that provides a
selectively variable length flow path fluidly coupled between the
inlet and the outlet, the at least one conduit having an associated
internal friction that creates a drag on the stream of polymer
fluid that passes therethrough wherein the selectively variable
length flow path of the at least one conduit controllably
decelerates a rate of flow of the stream of polymer fluid through
at least a portion of the at least one conduit, the at least one
conduit including at least one valve fluidly coupled between the
inlet and the outlet, the at least one valve operable to
selectively control the length of the flow path through which the
stream of polymer fluid pass between the inlet and the outlet, a
first tube fluidly coupled between the inlet and the at least one
valve; and a second tube fluidly coupleable between the first tube
and the outlet by the at least one valve, wherein the at least one
valve is operable to selectively fluidly couple the second tube
into and out of the flow path between the inlet and the outlet to
control the length of the flow path through which the stream of
polymer fluid passes between the inlet and the outlet, wherein the
improvement comprises the first tube and the second tube each
comprises a respective helical coil.
17. The apparatus of claim 16 wherein the first tube and the second
tube are each sections of round tubing.
18. The apparatus of claim 16 wherein the first and the second
tubes are concentrically arranged with respect to one another.
19. The apparatus of claim 16 wherein the first and the second
tubes each include a respective a number of joint-less welded
tubes.
20. A method of operating a flow control apparatus to selectively
control a flow of a stream of a polymer fluid during injection at
an injection point to enhance recovery of oil from a production
well, comprising: providing a source of the polymer fluid under
pressure at an inlet fluidly coupled to receive the polymer fluid;
and selectively varying a length of a flow path provided by at
least one conduit fluidly coupled between the inlet and an outlet,
the at least one conduit having an associated internal friction
that creates a drag on the stream of polymer fluid that passes
therethrough wherein the selectively variable length flow path of
the conduit controllably decelerates a rate of flow of the stream
of polymer fluid through at least a portion of the conduit, wherein
the improvement comprises operating a valve to selectively fluidly
couple a second helical coil tube into and out of the flow path
with a concentrically arranged first helical coil tube between the
inlet and the outlet to control the length of the flow path through
which the stream of polymer fluid passes between the inlet and the
outlet.
21. A flow control apparatus to selectively control a flow of a
stream of a polymer fluid during injection at an injection point to
enhance recovery of oil from a production well, the flow control
apparatus comprising: an inlet fluidly coupled to a source of the
polymer fluid under pressure to receive the polymer fluid; an
outlet fluidly coupleable to the injection point; at least one
valve or diverter selectively operable to vary a length of a flow
path between the inlet and the outlet, wherein the improvement
comprises at least one conduit including a first helical section
and a second helical section that provides the selectively variable
length flow path fluidly coupled between the inlet and the
outlet.
22. The flow control apparatus of claim 21 wherein the at least one
valve or diverter is selectively operable to couple the second
helical section into and out of the flow path with the first
helical section to vary the length of the flow path between the
inlet and the outlet.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] This application relates generally to controlling a flow of
a polymer fluid injected for the purpose of enhancing oil recovery,
and in particular to an apparatus and methods for doing so that
delivers a sufficient quantity and quality of polymer fluid
(including any gelled form thereof) without "shearing" or other
degradation thereof.
[0003] 2. Description of the Related Art
[0004] Traditional oil production methods result in only 20% to 30%
of the original oil in place (OOIP) produced up the well hole.
Polymer flooding, according to which a viscous body or "plug" of
polymer sweeps oil through a formation in a desired direction, is
one Enhanced Oil Recovery ("EOR") technique allowing producers to
recover an additional 15% to 20% of the OOIP. The conventional
polymer flooding system consists of a source of polymer that is
pumped under pressure to at least one injection well (or "point")
adjacent a production well toward which such plugs of flooding
polymer form wave fronts that sweep oil through the formation. As
explained in more detail below, the objective of sweeping oil
toward a production well is complicated by the need to
simultaneously control the velocity and volume of multiple wave
fronts, flowing from different directions, and ostensibly through
zones having different characteristics. Somewhat like an air
traffic controller, with less detailed information, the formation
engineer must apply best judgment respecting what is taking place
sub-surface and coordinate the arrival of multiple polymer wave
fronts on a common production point.
[0005] To further complicate matters, when EOR polymers are mixed,
static shear mixers hydrate or activate the polymer. Once
activated, the polymer fluid is pumped through a pipeline,
typically to multiple injection points. To feed these injection
points a supply "line" (typically a network of pipes) delivers the
activated polymer to each well with a sufficiently elevated
pressure to ensure the required flow to every point. The flow into
each injection point is traditionally restricted in order to
control the flow and deliver the correct volume flow into each
well. A number of problems result if the composition and flow of
the sweeping polymer is not carefully controlled, and each
restriction risks damage to the already activated polymer due to
abrupt changes in energy level during the transition from high to
lower pressure. This is because a polymer is a large molecule
formed by joining simple molecules known as monomers, and
polymerization is the chemical reaction that joins monomers
creating a polymer molecule. Effective liquid polymer activation
depends on the application of high, but non-damaging, mixing energy
to the neat, concentrated polymer. High mixing energy enhances the
performance of emulsion polymer. However, re-exposing emulsion
polymer to such high energy after the polymer is already fully
hydrated or activated can damage the large molecules by "shearing"
their attachment points that bond the water or carrier molecules.
The flooding performance of a plug of polymer fluid depends on
maintaining the bonds formed during activation, so the polymer's
utility can be severely limited when overexposed to anything such
as restrictions or impellers that can apply excessive mixing
energy. Since the traditional flow controlling restriction is
implemented using an orifice such as a choke, turbulence is
introduced that causes shear and damages the polymer. Turbulence
involves the collision of molecules such that bonding points are
re-exposed and may be damaged. Consequently, traditional flow
control devices such as chokes tend to breakdown the polymer
fluid--reducing its viscosity below a useful level. The vast
majority of prior art in the EOR polymer flooding industry has
concentrated on teaching variations of flow control based on the
orifice and similar restrictive devices.
[0006] In a given oilfield of injection wells, driving polymer
towards a specified production well, the formation engineer needs
to be able to apply the available polymer and injection resources
in an efficient manner so as to optimize the sweeping effect and
related production result within those limitations. Accordingly, it
is also desirable to individually adjust the rate of flow of an
undamaged polymer plug at each injection point, in order to
accommodate the unique characteristics of the formation at each
injection point. Whereas at a given injection point the resistance
to flow may be very low and another point (within the same field)
resistance very high, from a production perspective it would be
ineffective to apply the same pressure of polymer fluid supply to
both injection points because the fluid will follow the path of
least resistance such that the low resistance injection point will
consume the majority of the polymer resources leaving less to
inject at the high resistance injection point. Accordingly, it is
necessary to, in some manner, restrict the flow into the low
resistance injection point while also maintaining a specified flow
into the high resistance injection point, despite both being
supplied from a common source of polymer and pressure. The
traditional means of restricting flow to the low resistance
injection point is to "choke" off the flow of polymer at the
injection point, however that results in a sudden change that
causes turbulence that is harmful to the polymer. It is therefore
desirable to have means to individually control the rate of flow of
the polymer fluid at each injection point, but without damaging the
condition of that polymer.
[0007] One method for reducing shear degradation while maintaining
pressure and flow control, is described in U.S. Pat. No. 4,204,574
respecting the insertion of shear degradable aqueous polymer
solutions into a polymer thickened flood wherein a series of pumps
are used in a multi-branch system. This method purports to address
the problem of shear being induced by individual control over a
common polymer source, but disadvantageously relies on a number of
expensive hydraulic drivers and pumps to maintain the unique rate
of injection required at injection point receiving fluid from a
fluctuating common master branch.
[0008] More recently the internal "friction" (or adhesion to the
inside) of pipes has been recognized as a prospective means of
controlling flow. One example of such may be found at link:
http://www.fabtechinc.net/rexasp.aspx. It is believed that the use
of long lengths of small diameter hydraulic hose have also been
applied to control polymer flow. These recent systems appear to
rely on the long known but inadequately applied principle of drag
induced by the relative motion of a viscose fluid inside a conduit.
Disadvantageously, the linear array or cage of pipes comprising
even this most relevant of the known prior attempts is bulky and
inefficient making use of simple lengths of pipe threaded together,
which are not suitable for sour water leak exposure applications.
Within the large physical space required (resulting in a "low
density" of flow control) to operate these rudimentary devices the
amount of drag that may be induced using their linear form of flow
controller is limited to that achieved by taking into account the
Reynolds Number of the flow and the internal roughness of the
selected pipe together with that resulting from mismatched fittings
(both couplings and valves)--that collectively create the risk
(above a characteristically relatively low flow rate) of the
creation of polymer damaging turbulence such that the volume of
flow through their conduit is limited, thereby in turn limiting the
maximum flow to at least some of the injection points. All such
restrictions of flow lead to a "weakest link" problem being imposed
on the injection plan that the formation engineer would prefer to
implement, such that the pace of combined sweep of the polymer wave
fronts is also reduced thereby directly reducing the potential
production rate of the entire injection site, because the available
polymer and injection resources are applied in a less than optimal
manner. Oilfield resources are expensive, such that it is desirable
to identify every practical improvement to polymer injection
flooding control equipment, which improvements would result in more
oil being produced per unit time, in turn permitting those
resources to be taken out of service or moved to a new location
sooner. A more sophisticated and reliably predictable apparatus is
desirable to give the EOR formation engineer the degree and
flexibility of flow control required for optimal production.
BRIEF SUMMARY OF THE INVENTION
[0009] Embodiments of the present invention may, for example,
include a device for non-destructively controlling the flow of
polymer flooding EOR fluids at each point of injection at a
well-site using a conduit providing a variable length flow path
combined with the centrifugal and other retarding or decelerative
forces accessible to a formation engineer by configuring and
otherwise arranging the spatial orientation and relative position
of each section of such conduit, so as to achieve a never before
attained degree of non-damaging flow control density within a
compact space.
[0010] Advantageously, such may provide for synchronized
multi-point flow control over a polymer flood so as to coordinate
multiple polymer wave fronts from different directions to arrive in
a timely manner acting on a common production point, thereby
implementing a site flooding plan in an efficient manner to make
the optimal use of polymer possible. Further, such may allow use of
a compact apparatus which employs tightly configured seamless
conduit and smoothly joined elements that avoid inducing turbulence
despite the continuous deceleration caused by passing the polymer
fluid through coils of pipework densely assembled in close
proximity and using carefully matched internally machined fittings
wherever required.
[0011] According to one aspect, an apparatus may enable a formation
engineer to relatively finely tune the flow of polymer fluid
required to an injection point sweeping oil towards a defined
production well, and then permit a relatively less experienced
operator to implement a substantially optimal injection plan, based
on installing and operating one such apparatus per injection point.
Such may advantageously allow the formation engineer and operators
of an injection well-site to refine and/or customize the flow
pattern of the site so as to supply a sufficient volume of polymer
fluid to each high resistance injection point while simultaneously
limiting the volume of polymer flowing into each low resistance
injection point, without introducing harmful turbulence at any
injection point. When the polymer fluid is delivered to all
injection points without degradation, the polymer fluid is better
able to sweep oil through the reservoir. If appropriate volumes of
polymer fluid synchronously travel through their respective flow
controllers and then their respective portions of the formation so
as to arrive at their designated locations in a timely manner. The
combined sweeping effect of the compressive plugs of polymer fluid
may move the oil through the reservoir toward a common production
point in a more efficient (i.e., no fingering or breakthrough)
fashion than otherwise possible. With the many factors that a
formation engineer must accommodate and control in order to
optimize production at each injection site, it may be advantageous
to install the apparatus at each injection point to provide
individually adjustable means for controlling flow without
introducing turbulence. The apparatus may permit operators to
control the volume of laminar flow of polymer fluid to a particular
injection point by varying the effective length and spatial
orientation of the drag inducing conduit through which the polymer
fluid is required to pass for delivery to that injection point.
Much like the "cars" on a roller coaster, the stream of activated
polymer fluid moving inside a conduit is subjected not only to the
frictional drag between the "wheels and tracks", corresponding to
the tendency for a viscous fluid to adhere to the inner walls of
the conduit, but also to the decelerative forces that absorb energy
from the stream of polymer fluid as the stream changes direction
passing around each curve. Such may be particularly enhanced by use
of a helical structure formed by the tubular coils. By this novel
means of using the combination of friction and decelerating coils
or other loops to restrict the flow of EOR flooding polymer
fluid--excess energy is gradually dissipated to avoid turbulence
such that the attachment points of the polymer molecules are not
exposed to sudden change and thereby sheared. Advantageously, the
low resistance injection points are supplied by longer and/or more
frequent and tightly looped paths of fluid delivery conduit that
delay the arrival of the required volume of polymer fluid into the
formation so as to permit an operator to better coordinate delivery
with slower moving polymer traveling through high resistance
points.
[0012] Accordingly, there may be provided a compact device for
reliably adjusting and controlling flow rate at the point of
injection by allowing the operator to introduce or omit different
series of coils of differing lengths simply by turning any one or
all of the bypass valves in the fluid circuit. Not only does such
an apparatus permit operators to accommodate the fluid flow factors
of: viscosity, density, velocity, active conduit length, inner
diameter of available conduit, internal roughness of conduit,
transient changes in temperature, and the relative position of
supply and discharge manifolds and lines, but it also takes into
account and makes use of the centrifugal forces and other naturally
decelerative effects of the combinations of possible spatial
orientation that are available to the creative engineer within the
efficiently limited volume of space. Thus the apparatus may
accordingly be constructed, transported, and housed less
expensively than otherwise possible.
[0013] In order to overcome the many efficiency disadvantages of
the prior art it is necessary to expedite and coordinate delivery
of polymer fluid to each injection point in sufficient quantity
without shearing. According to at least one embodiment, there is
provided a novel method for using conduit so that rather than
restrict polymer flow instantaneously, the required pressure
reduction is introduced without the attachment points of polymer
molecules being exposed to sudden change and sheared. In at least
one embodiment, an apparatus introduces resistance to flow thereby
gradually reducing velocity (and thus the force of collisions at
the molecular level) by adjusting the number of loops of pipe that
increase back pressure (or drag) as the polymer flows through the
loops. Several loops may be connected in series with bypass valves
permitting each coil of tubing to be used alone. The back pressure
of each loop or coil is caused primarily by the viscosity of the
polymer fluid as the polymer fluid resists flow, since when fluid
flows through a tube, the fluid typically flows fastest at the
middle of the tubing and slowest at the outer edge where the fluid
makes contact with the walls of the tubing. A boundary layer
typically forms in the fluid proximate or at the wall of the tubing
in which the flow may be negligible. Thus, the only movement of the
fluid proximate the wall may be when molecules hop over each other.
Faster flowing fluid towards the middle of the tubing next to
slower moving fluid at the edge of the tubing may cause a rolling
of the fluid molecules. The energy required to move the fluid as it
changes direction (accelerating around each coil) also causes
pressure loss as the fluid flows along the tubing. The losses
resulting from each bundle of coil may be calculated and reliably
predicted once all the variables influencing flow are defined. The
configuration of a flow path defined by the apparatus may be either
adjusted to accommodate local conditions, or a custom compact
embodiment of the apparatus may be assembled to address the
specific conditions present at a given well-site where a particular
injection plan is to be implemented.
[0014] According to at least one aspect, there is further provided
a method of manufacturing such an apparatus incorporating the use
of joint-less welded tubes to prevent deadly leaks of sour water.
The present method of manufacturing and the present apparatus may
further include a heater that protects aqueous polymer against
freezing, and a housing that facilitates leak detection and
protection against mechanical damage during transportation and
operation.
[0015] According to one aspect there is provided a flow control
apparatus to control a flow of a stream of moving polymer fluid
during injection to be used in a well to enhance the recovery of
oil from a production well. The apparatus may be summarized as
including: an inlet fluidly coupled to a source of polymer fluid
under pressure to receive the polymer fluid; an outlet fluidly
coupleable to an injection point; and at least one conduit that
provides a selectively variable length flow path fluidly coupled
between the inlet and the outlet, having internal friction creating
drag between the conduit and moving polymer fluid, to controllably
decelerate the rate of flow of the stream of polymer fluid. The
apparatus optionally further includes at least one valve means
fluidly coupled to the conduit, to control the (portion of the)
length of the conduit through which the stream of moving polymer
fluid pass before reaching the outlet. The conduit may include: a
first tube fluidly coupled to the inlet and a second tube
selectively fluidly coupleable between the first tube and the
outlet. The conduit or apparatus may include at least one valve
operable to selectively fluidly coupled the second tube into and
out of the flow path through which the stream of polymer fluid
passes between the inlet and outlet, thereby controlling the length
of the fluid flow path defined by the conduit. The conduit or
apparatus may include a bypass mechanism operable to divert the
flow of the polymer fluid to the outlet. The first and second tubes
may each optionally comprise a helical coil of round tubing or
connected lengths of pipe, to enhance the deceleration of the
polymer fluid within a more compact space. The helical coils or
pipes may be concentrically arranged with respect to one another.
The apparatus may optionally further include: a heater and a
housing, for permitting aqueous streams of polymer fluid to be
injected during cold weather.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0016] In the drawings, identical reference numbers identify
similar elements or acts. The sizes and relative positions of
elements in the drawings are not necessarily drawn to scale. For
example, the shapes of various elements and angles are not drawn to
scale, and some of these elements are arbitrarily enlarged and
positioned to improve drawing legibility. Further, the particular
shapes of the elements as drawn, are not intended to convey any
information regarding the actual shape of the particular elements,
and have been solely selected for ease of recognition in the
drawings.
[0017] Various embodiments, in order to be easily understood and
practiced, are set out in the following non-limiting examples shown
in the accompanying drawings.
[0018] FIG. 1 is an end isometric view of a compact apparatus for
controlling the flow of a stream of polymer (fluid or gel)
comprising four coils of tubing that form a conduit providing a
variable length flow path, according to one illustrated
embodiment.
[0019] FIG. 2 is an end isometric view of the apparatus of FIG. 1,
suitable for cold weather operation further comprising heating and
an insulated housing, according to one illustrated embodiment.
DETAILED DESCRIPTION
[0020] In the following description, certain specific details are
set forth in order to provide a thorough understanding of various
disclosed embodiments. However, one skilled in the relevant art
will recognize that embodiments may be practiced without one or
more of these specific details, or with other methods, components,
materials, etc. In other instances, well-known formulations,
process steps, and structures associated with polymer flooding EOR
have not been shown or described in detail to avoid unnecessarily
obscuring descriptions of the embodiments. It is to be understood
that all joints, fittings, valves, tees and couplers employed are
preferably of a similar internal diameter (ID) to the selected
conduit for smooth transitions, or during fabrication one will
radius the corners and internal diameter to match and avoid
turbulence. Similarly, the conduit material may in theory be
anything since internal diameter and roughness are variables taken
into account in unit design calculations that make an operational
custom built flow controller possible. It is a matter of
determining how much energy must be extracted from the flow of
polymer to achieve the required rate of injection at the injection
well head. However, in practice it is the local regulations that
may dictate the selection of materials, not the physics. The
materials actually used in the field are determined by the
composition of the substance flowing through them. For example,
using sour water to hydrate the polymer makes stainless steels a
good choice to meet environmental protection requirements. However,
when the water polymer mix is non-toxic and non-polluting, then
even if it leaked one could safely use a suitable form of plastic
pipe as the drag inducing conduit.
[0021] Unless the context requires otherwise, throughout the
specification and claims which follow, the word "comprise" and
variations thereof, such as, "comprises" and "comprising" are to be
construed in an open, inclusive sense, which is as "including, but
not limited to."
[0022] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure or
characteristic described in connection with the embodiment is
included in at least one embodiment. Thus, the appearances of the
phrases "in one embodiment" or "in an embodiment" in various places
throughout this specification are not necessarily all referring to
the same embodiment. Furthermore, the particular features,
structures, or characteristics may be combined in any suitable
manner in one or more embodiments. Reference is to be had to FIGS.
1 and 2 in which identical reference numbers identify similar
components.
[0023] As used in this specification and the appended claims, the
singular forms "a," "an," and "the" include plural referents unless
the content clearly dictates otherwise. It should also be noted
that the term "or" is generally employed in its sense including
"and/or" unless the content clearly dictates otherwise. The
headings and Abstract of the Disclosure provided herein are for
convenience only and do not interpret the scope or meaning of the
embodiments.
[0024] It is to be understood that in accordance with Newton's
second Law, centrifugal force is an outward force associated with
motion along a curved path, which incorporates rotation about some
(possibly non-stationary) center. Centrifugal force is one of the
so-called pseudo-forces (also known as inertial forces), so named
because, unlike fundamental forces, they do not originate in
interactions with other bodies situated in the environment of the
element upon which they act. Instead, centrifugal force originates
in the curved motion of the frame of reference within which
observations are made. As it passes through the conduit(s), a plug
of fluid flowing along the curved path of a helical coil of tube as
the fluid's "rotating" frame of reference experiences various
inertial forces. Consequently, according to the embodiments
described herein which may be implemented using pipes as the
conduit element, the rate of flow of polymer is affected by all of:
the viscosity, density, and velocity of the polymer fluid; the
implementation of a pipe layout that includes looping rises and/or
falls; the location of supply and discharge containers relative to
the pump position; the length, inner diameter, and internal
roughness of each element of pipe deployed as the operational
pipework; and any weather or location related changes in polymer
fluid temperature that influence the viscosity and/or density of
the polymer fluid at the location where the apparatus is operated.
Fluids in motion are subjected to various resistances that are due
to friction. Within the conduit's contemplated curved frame of
reference, friction will occur between the fluid and the pipework,
but friction also occurs within the fluid as sliding between
adjacent layers of fluid takes place. The friction within a fluid
is due to the viscosity of the fluid. When fluids have a high
viscosity, the speed of flow tends to be low and resistance to flow
becomes almost totally dependent on the viscosity of the fluid,
which condition is known as `laminar flow`. These are all factors
that the design and formation engineers takes into account to
control flow.
[0025] It is further to be understood that polymer fluid head
resistance may be calculated using the equation:
h=f(L/d).times.(v.sup.2/2 g) where: h=head loss (m); f=friction
factor; L=length of pipe work (m); d=inner diameter of pipe work
(m); v=velocity of polymer fluid (m/s); and g=acceleration due to
gravity (m/s.sup.2).
[0026] Referring to FIG. 1 there is illustrated a flow control
apparatus, denoted generally as 100, for use with a stream of
polymer fluid moving in the laminar flow range up to 25 centipoise
viscosity, and applied during injection to enhance the recovery of
oil from a production well. According to at least one embodiment of
the apparatus, a lower tube coil 110 of coiled tubing is fluidly
coupled to a bank of upper tube coils 120, 130, 140 of tubing of
varying lengths here connected in series. For example, in the
embodiment illustrated the coils total 300 feet in length with tube
coil 110 being 160 feet long, tube coil 120 being 80 feet long,
tube coil 130 being 40 feet long, and tube coil 140 being 20 feet
long. Lower tube coil 110 is coupled to said upper tube coils
through header 150 that has any suitable inlet 160 and outlet 200.
The tubing may be mounted on any suitable frame.
[0027] Header 150 receives a stream of polymer fluid (not shown)
via inlet 160 and such flow through drag inducing apparatus 100 is
initiated or terminated via any suitable isolation valve or valves
(not shown) that permit said stream of polymer fluid to fluidly
couple to an injection point (not shown) through outlet 200. It is
to be understood that isolation valves may be, but are not
necessarily, installed on the apparatus side of either or both of
inlet 160 and outlet 200.
[0028] As a stream of polymer fluid flows through drag inducing
apparatus 100, there are a plurality of bypass valves (here 210,
220, 230, and 240) that permit an operator to vary the length of
the total conduit through which said stream of polymer fluid flows
between inlet 160 and outlet 200.
[0029] According to one embodiment, as illustrated by apparatus
100, when bypass valve 210 is open, the stream of polymer fluid,
taking the path of least resistance, flows through header 150
without entering lower tube coil 110. However, when bypass valve
210 is closed, said stream of polymer fluid is diverted at tee (T)
coupling 215 through lower tube coil 110 and fluidly re-coupled to
header 150 at tee (T) coupling 225 from where the polymer fluid may
flow through apparatus 100 towards outlet 200. Similarly, bypass
valve 220 when open permits the stream of polymer fluid to bypass
tube coil 120. When bypass valve 220 is closed, the stream of
polymer fluid is diverted through tube coil 120. Tube coil 120 may,
for example, be approximately 80 feet long. Thus, if both bypass
valves 210 and 220 are closed the stream of polymer fluid must flow
through both tube coil 100 and tube coil 120. Such may, for
example, cause the stream of polymer fluid to flow through 160 feet
of tube coil 110 plus 80 feet of tube coil 120, which is a total of
240 feet of drag inducing coil. Such may gently slow the laminar
flow of the stream of polymer fluid without inducing harmful
turbulence. Similarly, bypass valves 230 and 240, when open, permit
the polymer stream to bypass their respective tube coils 130 and
140. When closed, bypass valves 230 and 240 may be used by an
operator to incrementally increase the drag inducing path length.
For example, such may allow the operator to increase the flow path
length by 40 feet and 20 feet, respectively, to further slow the
flow of any stream of polymer fluid to the injection point to which
apparatus 100 has been fluidly coupled. The amount of drag induced
in the particular flow path is determined by many factors over
which an operator has control.
[0030] It is contemplated that if an operator knows in sufficient
detail the precise characteristics of the formation and the
hydrocarbons at a given well-site, then a custom flow controller
can be designed and assembled to optimally serve each particular
well. Advantageously, the apparatus described herein permits an
operator to incrementally adjust flow control to accommodate less
than perfect information respecting well characteristics, as well
as based on changes to injection point behavior over time and in
different weather conditions. It is to be understood that the
selection of each of: 1) a total of 300 feet in available coil
length; 2) the particular lengths (i.e., 160, 80, 40, and 20 feet)
of each coil; 3) the selection of an upper and a lower bank of
coils; 4) the relative position of the individual coils in their
banks; and 5) the orientation of the coils--are matters of
convenience made to demonstrate the functionality of the apparatus.
Like the size and type of material selected for the tubing or pipe
and the couplers and/or valves, some of these values or parameters
are relevant to accurately predicting unit performance.
[0031] It is further contemplated that banks of coils may be
embedded inside other banks of coils and/or interleaved in order to
achieve even greater flow control density providing undamaged
polymer by ensuring smooth transitions between the arrangement
comprised of multiple banks of coils.
[0032] Prior to the precise design and method of manufacturing the
apparatus, the determination of unit performance was largely
empirical based on rudimentary estimates of a range of expected
performance, assembly, bench and field testing, preparation of
operational guidelines, and in-service adjustments by a skilled
& experienced operator. Advantageously, the apparatus described
herein may permit a less skilled and/or experienced operator to
implement flow control in a more nearly optimal manner over the
life-cycle of the injection field producing better results, in a
shorter time, with less expensive resources.
[0033] According to a plurality of alternate embodiments, rather
than round tubular coils being applied as the conduit through which
the stream of polymer fluid flows, it is to be understood that
conduit may be of any cross-section, for instance square or
rectangular cross-sections. Notably, the shape and internal
diameter or cross-sectional area of the conduit are among the
variables that the fabricator takes into account. While the
mathematical determination of flow rate reduction induced by the
resulting product is perhaps easier to carry out with the more
familiar round tubular flow characteristics, there is no barrier in
nature to the apparatus fabricator applying the present principle
of combining frictional drag induction with the decelerative forces
of motion through tightly looped conduit so as to enhance the
non-turbulent extraction of energy from a polymer stream flowing
through a conduit and also providing a variable length flow path
within a compact space.
[0034] Referring to FIG. 2 there is illustrated an embodiment of an
apparatus according to which any suitable heater 250 is mounted in
proximity to the banks of coils 110, 120, 130, and 140 (as seen in
FIG. 1) so as to prevent aqueous polymer fluid from freezing during
cold weather application. Similarly, a housing 260 comprising any
insulated structure to protect apparatus 100 from the elements is
provided to retain heat and prevent freeze-up. A person of skill in
the art would understand that the power output of heater 250 and
the R-value of the insulation in the housing 260 may be coordinated
with the typical climate at the location where the particular
apparatus will be installed. In warmer climates no heater may be
required if the thermal insulation provided by the housing is
sufficient to protect the coil banks from the convective effects of
wind. Similarly, in colder climates a higher power heater may be
required with heavier insulation. In the North Western United
States, a heater of 1500 watts has been found to operate
satisfactorily when combined with a sheet-aluminum housing having
R-15 value of insulation.
[0035] It is to be understood that an alternate embodiment of the
apparatus may be constructed to include a plurality of banks of
vertically oriented, elongate elliptical loops of pipe, comprising
the conduit element that provides a variable length flow path, and
having threaded rather than welded connections. A person of skill
in the art would understand that the drag induction calculations
must account for the different spatial orientation of the conduit
as applied to this embodiment, but the principle remains.
[0036] These and other changes can be made to the embodiments in
light of the above-detailed description. In general, in the
following claims, the terms used should not be construed to limit
the claims to the specific embodiments disclosed in the
specification and the claims, but should be construed to include
all possible embodiments along with the full scope of equivalents
to which such claims are entitled. Accordingly, the claims are not
to be construed as being limited by the disclosure.
* * * * *
References