U.S. patent application number 13/590658 was filed with the patent office on 2013-02-28 for flow pattern enhancer system for gas wells with liquid load problems.
This patent application is currently assigned to INSTITUTO MEXICANO DEL PETROLEO. The applicant listed for this patent is Fernando ASCENCIO CENDEJAS, Juan Antonio CASTRO RODARTE, Jorge FLORES CASTILLO, Miguel Angel LOPEZ LOPEZ, Isaac MIRANDA TIENDA, Carlos Alberto REYES LOPEZ, Edwin Daniel SAN VICENTE AGUILLON, Gilberto SANDOVAL HERNANDEZ. Invention is credited to Fernando ASCENCIO CENDEJAS, Juan Antonio CASTRO RODARTE, Jorge FLORES CASTILLO, Miguel Angel LOPEZ LOPEZ, Isaac MIRANDA TIENDA, Carlos Alberto REYES LOPEZ, Edwin Daniel SAN VICENTE AGUILLON, Gilberto SANDOVAL HERNANDEZ.
Application Number | 20130048293 13/590658 |
Document ID | / |
Family ID | 47741966 |
Filed Date | 2013-02-28 |
United States Patent
Application |
20130048293 |
Kind Code |
A1 |
MIRANDA TIENDA; Isaac ; et
al. |
February 28, 2013 |
FLOW PATTERN ENHANCER SYSTEM FOR GAS WELLS WITH LIQUID LOAD
PROBLEMS
Abstract
A flow pattern enhancer system mainly for gas-producing oil
wells with liquid load problems, comprising mechanical elements
that atomize the liquids accumulated at the bottom of the well
facilitating their transport to the surface, by decreasing
frictional pressure drops and weight of the hydrostatic column.
Inventors: |
MIRANDA TIENDA; Isaac;
(Mexico City, MX) ; CASTRO RODARTE; Juan Antonio;
(Mexico City, MX) ; SAN VICENTE AGUILLON; Edwin
Daniel; (Mexico City, MX) ; LOPEZ LOPEZ; Miguel
Angel; (Mexico City, MX) ; FLORES CASTILLO;
Jorge; (Mexico City, MX) ; SANDOVAL HERNANDEZ;
Gilberto; (Mexico City, MX) ; ASCENCIO CENDEJAS;
Fernando; (Mexico City, MX) ; REYES LOPEZ; Carlos
Alberto; (Mexico City, MX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MIRANDA TIENDA; Isaac
CASTRO RODARTE; Juan Antonio
SAN VICENTE AGUILLON; Edwin Daniel
LOPEZ LOPEZ; Miguel Angel
FLORES CASTILLO; Jorge
SANDOVAL HERNANDEZ; Gilberto
ASCENCIO CENDEJAS; Fernando
REYES LOPEZ; Carlos Alberto |
Mexico City
Mexico City
Mexico City
Mexico City
Mexico City
Mexico City
Mexico City
Mexico City |
|
MX
MX
MX
MX
MX
MX
MX
MX |
|
|
Assignee: |
INSTITUTO MEXICANO DEL
PETROLEO
Mexico City
MX
|
Family ID: |
47741966 |
Appl. No.: |
13/590658 |
Filed: |
August 21, 2012 |
Current U.S.
Class: |
166/311 ;
166/105 |
Current CPC
Class: |
E21B 43/121
20130101 |
Class at
Publication: |
166/311 ;
166/105 |
International
Class: |
E21B 43/25 20060101
E21B043/25; E21B 43/00 20060101 E21B043/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 24, 2011 |
MX |
MX/A/2011/008907 |
Claims
1. A flow pattern enhancer system for gas wells, comprising the
following elements: a) primary expander, b) homogenization chamber,
c) secondary expander, d) suction veins, and e) anchorage and
tightness system, for displacing the liquids accumulated at the
bottom of the well to the surface, taking advantage of the same
energy of the gas produced, extending the flowing life of the wells
in a continuous form and increasing its recovery factor.
2. The flow pattern enhancer system of claim 1, for gas-producing
oil wells with liquid load problems.
3. The flow pattern enhancer system of claim 1, where the primary
expander has a smaller inner diameter than the homogenization
chamber.
4. The flow pattern enhancer system of claim 1, wherein the primary
expander is connected to the lower part of the homogenization
chamber.
5. The flow pattern enhancer system of claim 1, wherein the
homogenization chamber is connected to the primary expander at the
lower part and to the secondary expander at the upper part.
6. The flow pattern enhancer system of claim 1, wherein the
secondary expander is attached to the homogenization chamber at the
upper part of the homogenization chamber.
7. The flow pattern enhancer system of claim 1, wherein the
secondary expander houses suction veins.
8. The flow pattern enhancer system of claim 1, wherein the
secondary expander at the upper part has a fishing neck.
9. The flow pattern enhancer system of claim 1, wherein said
suction veins are housed in low pressure zones inside the secondary
expander and communicate the low pressure zones inside the
secondary expander with the liquid accumulated outside the
system.
10. The flow pattern enhancer system of claim 1, wherein anchorage
and tightness systems are coupled in the inside to the primary
expander and homogenization chamber, and on the upper extreme to
the secondary expander.
11. The flow pattern enhancer system of claim 10, wherein said
anchorage and tightness system enables installation of the flow
pattern enhancer system at any depth of the production piping of
the well.
12. The flow pattern enhancer system of claim 10, wherein the
anchorage and tightness system forces the flow to take place only
inside the flow pattern enhancer system.
13. The flow pattern enhancer system of claim 10, wherein the
anchorage and tightness system has mechanical anchors which are
attached to the piping and elastomeric seals which allow the system
to anchor and seal the inside in order to perform completely the
flow inside the system.
14. The flow pattern enhancer system of claim 1, wherein the flow
pattern enhancer system is installed in the lower extreme of the
production piping.
15. The flow pattern enhancer system of claim 1, wherein the flow
pattern enhancer system can be placed below the depth to which the
bubbling pressure is present.
16. The flow pattern enhancer system of claim 1, wherein the gas
velocity increases promoting the atomization of liquids, with a
relatively high gas flow velocity of 4-6 m/s, achieving fog flow
and a continuous flow structure having liquid droplets dispersed in
the continuous gas phase.
17. The flow pattern enhancer system of claim 1, wherein the
calculations for each element design consider three different
process: expansion, compression and mixing, and are performed
through specific methods consisting primarily on determining the
flow areas and geometries thereof.
18. The flow pattern enhancer system of claim 1, where the drag
coefficient is determined by the formula: Drag coefficient=Driving
flow/Dragged flow.
19. The flow pattern enhancer system of claim 1, wherein said flow
pattern enhancer system increased gas production over 300% from the
initial production.
20. The flow pattern enhancer system of claim 1, wherein the flow
pattern enhancer system prevents formation of hydrates.
21. The flow pattern enhancer system of claim 1, wherein said flow
pattern enhancer system avoids the re-pressure of surface lines
because of methane hydrate accumulation.
22. A method for enhancing the flow of a gas-producing oil well
with liquid load problems, which comprises passing a gas stream
from the well in sequence through a) a primary expander; b) a
homogenization chamber, c) a secondary expander, and d) suction
veins such that gas velocity increases to 4-6 m/s, achieving fog
flow with liquid drops dispersed in the continuous gas phase.
23. A gas-producing oil well pipe string arrangement having a flow
pattern enhancer system connected in and communicating with the
lower portion of said pipe string arrangement, said flow pattern
enhancer system comprising the following elements: a) primary
expander; b) homogenization chamber, c) secondary expander, d)
suction veins, and e) anchorage and tightness system for displacing
liquids accumulated at the bottom of the well to the surface and
extending the flowing life of the wells and increasing the recovery
factor.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119 of Mexican Patent Application No. MX/a/2011/008907, filed
Aug. 24, 2011, which is hereby incorporated by reference in its
entirety.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to a flow pattern enhancer
system mainly useful in gas-producing oil wells with liquid load
problems, comprising mechanical elements for atomizing the liquids
accumulated at the bottom of the well, and facilitating its
transport to surface, caused by the decrease of the frictional
pressure drop and weight of the hydrostatic column.
BACKGROUND OF THE INVENTION
[0003] The accumulation of liquids in the gas wells occurs
naturally because the decrease of deposit energy during their
productive lives, caused by the decrease of the deposit pressure
and thus the expenditure produced by the well. While the production
expenditure is maintained above the critical expenditure, the
liquids will be carried to the surface and won't be accumulated at
the bottom of the well.
[0004] The liquid load in a gas well is also related to the change
of flow type, the big pressure drops through the production pipes
are caused by fluctuations in the gas and liquid transport, being
normally called these fluctuations potholes. The distribution of
the liquid and gas phases simultaneously flowing through a piping,
may be classified by its form and rate and are called flow
patterns.
[0005] The parameters affecting in the formation of the liquid load
in a gas well are the following:
[0006] Static pressure of the deposit.
[0007] Pressure at the wellhead.
[0008] Pressure at the discharge line.
[0009] Diameter of the production pipe.
[0010] In Mexico, in order to solve the gas deposit exploitation
issues with liquid load problems, at present liquid recovery
systems are applied, allowing the extraction of the liquids of the
bottom of the wells. Its correct selection will depend mainly of
the well characteristics, although all are aimed to solve the same
problem, they don't work under the same conditions; generally, the
artificial systems of production have a technical and temporary
range therefore always be sought the one working longer, optimally
and at lower cost, without being this an impediment to use
different systems during the productive life of the well.
[0011] The state of the art in solving the gas deposits
exploitation issues with liquid load problems, mainly reports the
following technologies:
[0012] Small Tubing
[0013] Small tubing is a piping of smaller diameter than the
production piping, this is introduced in the well in order to
reduce the flow area for maintaining the expenditure above the
critical value. Good yields have been observed in wells with low
production volume, in which the frictional losses are not very
significant.
[0014] The leading disadvantage of this system, besides an unstable
production, is that it stops working optimally in a short time, so
if it is not combined with other system, it is only a temporary
solution.
[0015] Foaming Agents/Reactive Liquids
[0016] Both methods consist on the introduction of surfactants or
foaming agents in the well to reduce the surface tension of the
fluids and form foams. When this happens, the liquid column becomes
foam, becoming lighter and facilitating its transport to the
surface; however, in spite of obtaining good result for water, in
case of the condensates it has been difficult to obtain a substance
to make them foamy, so this is the reason why it is not convenient
to apply this system in wells with water cut below 80%.
[0017] This system is mainly used in wells with a very low
expenditure of production due to the hanging and the high pressure
drops along the piping, however it is not advisable to use in wells
with problems of emulsified liquids because the investment in the
surfactant products may be small compared to the necessary for the
products breaking the emulsions formed. The introduction of foaming
bars is performed through the Production tubing (TP) and the
reagents are injected by a capillary tubing, the can be injected in
the zone of triggers or at the end of the TP.
[0018] Plunger Lift
[0019] Used mainly in wells with intermittent production, the
plunger lift generates a mechanical interface between gas and
liquid. At the beginning, the well is closed and the plunger is on
the surface dropping it inside the TP, in its way down, the plunger
allows the pass of liquid above it preventing its return; once at
the bottom the pressure generated by the gas under the plunger is
increased until it matches the pressure of the motor valve opening
of the well located on the surface. Once the well is opened, the
plunger travels along the production tubing displacing the liquid
pothole; afterwards the well is closed (by indication of the motor
valve) and the plunger falls to the bottom to start again the
cycle. During its travel, this plunger is touching internally the
tubing freeing it of paraffins, salts, carbonates, etc., that may
deposit in the interior of the same.
[0020] It is important for this system that the well produces its
fluids with a relation gas-oil (RGA) and pressure enough to lift
the potholes of liquid; for the case of pipe sizes, this system can
work with big sizes, being this a disadvantage in the other
systems.
[0021] Compressors Installed at the Mouth of the Well
(Compressors)
[0022] The compression increases the gas velocity to be equal or
greater than the critical velocity and at the same time decreases
the pressure flowing in the wellhead causing the pressure in the
side of the deposit near the well to decrease as well and extends
the life of the well.
[0023] There are many types of compressors varying according to the
initial investment, operating costs and functionality of each
particular well.
[0024] Hydraulic Pumping
[0025] In this system, energy is transmitted from a motor fluid to
the fluids contained in the well for its extraction; a pump on the
surface transmits dynamic energy to the motor fluid introduced in
the well, wherein it mixes with the fluids therein and by a pump at
the bottom, this mixture is impelled to the surface where it enters
to a separator sending the well fluids out of the system and the
motor fluid again to the pump on the surface.
[0026] This system does not present a depth limit for its
application and it is applicable in deviated wells.
[0027] For gas wells, the pump located at the bottom must be Jet
type because the reciprocating pump doesn't admit gas and has to
open a line to vent it. The jet type pumps reduce the pressure in
the side of the Formation increasing the velocity of the fluid
introduced in them.
[0028] Gas Lift
[0029] In this system, gas is injected to the well to a certain
depth. The gas is mixed with the liquid column making it lighter,
due to this, its pressure at the bottom is reduce, causing the
pressure from the deposit to be enough to push the column to the
surface.
[0030] Although it is not achieved to reduce the pressure at the
bottom of the well as with other pumping systems, the gas lift is
outstanding because of its versatility and due to this is a good
candidate in certain conditions. While other pumping systems become
inefficient for high values of the gas-liquid relation (RGL), in
this case a big amount of gas from the deposit will directly
decrease the volume of gas to be injected; it has no trouble
handling solids and can be used in deviated wells although as these
become more horizontal, the gas injection doesn't reduce the weight
of the liquid column and may increase the frictional pressure
losses.
[0031] Progressive Cavity Pumps
[0032] This system consists mainly of a stator with internal
helical form, double entrance and a helical rotor rotating in the
stator. The cross section of the rotor is circular and at every
point eccentric to the axis; the centers of the sections are
supported along a helix, which axis is the rotor axis. Both are
linked such that the section of the rotor has a reciprocating
movement through the duct of the stator. This movement causes
cavities that be formed, which are delimited by a line adjustment
between the two elements. When the rotor makes a turn, said
cavities arranged in a helical form move, including the liquid to
be carried, being independent said cavity from the next one to be
form by the adjustment line, therefore avoiding the return of the
liquid.
[0033] Although this system was designed originally to carry solids
and viscous fluids, it has also been used for liquid extraction in
gas wells; its applicability is reduced mainly to the following
general conditions:
[0034] Depths of no more than about 1,250 meters
[0035] Relatively high liquid expenditures
[0036] Low pumping profile
[0037] Low temperatures in the well.
[0038] Automated System of Liquid Recovery for Wells Producing Gas
and Condensate
[0039] It is based on the installation of a small tubing or
flexible piping and of a valve control system automated on the
surface. The target of this system is to "sweep" the accumulated
liquid through a flexible piping (or small tubing) and to produce
gas through the production piping; the control valves, registering
a pressure differential, act opening and closing the system, so the
fluids can be produced continuously and thus avoid the intermittent
production of the wells or its definitive closure.
SUMMARY OF THE INVENTION
[0040] The present invention is an improvement over the above
mentioned technologies, since it relates integrally to the
operation principle of a flow pattern enhancer system for use
mainly in gas-producing oil wells with problems of liquid load and
takes advantage of the deposit energy and its fluids in order to
induce a change in the characteristics of the flow pattern of the
liquid and gas phases from the bottom of the well, enhancing the
transport of liquid through the production piping to reduce the
pressure drops in the latter.
[0041] Therefore, an object of the present invention is to provide
an enhancer system for the flow pattern of gas wells with liquid
load problems, comprising mechanical elements atomizing the liquids
accumulated at the bottom of the well, facilitating its transport
to the surface by decrease of frictional pressure drops and weight
of the hydrostatic column.
[0042] A further object of the present invention is to provide a
flow pattern enhancer system which is used mainly in gas-producing
oil wells with liquid load problems.
[0043] Yet another object of the present invention is to provide a
flow pattern enhancer system located on the lower extremity of the
production piping of the gas producing wells with liquid load
problems, to displace to the surface the liquids accumulated at the
bottom of the well.
[0044] The flow pattern enhancer system of the present invention is
mainly used in gas wells with liquid load problems, and comprises
the following elements:
[0045] a) primary expander,
[0046] b) homogenization chamber,
[0047] c) secondary expander,
[0048] d) suction veins, and
[0049] e) anchorage and tightness system,
for displacing the liquids accumulated at the bottom of the well to
the surface, taking advantage of the same energy of the gas
produced, extending the flowing life of the wells in a continuous
form and increasing its recovery factor.
[0050] The primary expander has a smaller inner diameter than the
homogenization chamber, and is connected to the lower part of the
homogenization chamber. The homogenization chamber is positioned
between the primary expander and the secondary expander, with the
primary expander below and the secondary expander above, i.e., its
lower part is connected to the primary expander and its upper
portion is connected to the secondary expander.
[0051] The secondary expander is located above and attached to the
homogenation chamber. The secondary expander houses the suction
veins, and the upper portion of the secondary expander has a
fishing neck. The suction veins are housed in low pressure zones
inside the secondary expander and communicate the low pressure
zones inside the secondary expander with the liquid accumulated
outside the system. The anchorage and tightness systems are coupled
in the inside to the primary expander and homogenization chamber
and on the upper extreme to the secondary expander.
[0052] The anchorage and tightness system enables installation of
the flow pattern enhancer system at any depth of the production
piping of the well. The anchorage and tightness system forces the
flow to take place only inside the flow pattern enhancer system.
The flow pattern enhancer system has mechanical anchors which are
attached to the piping and elastomeric seals which allow the system
to anchor and seal the inside in order to confine the flow
completely inside the system.
[0053] The flow pattern enhancer system is installed in the lower
extremity of the production piping. Thus, the flow pattern enhancer
system can be placed below the depth to which bubbling pressure is
present. Employment of the flow pattern enhancer system enables
increase of the gas velocity to 4-6 m/s, achieving fog flow and a
continuous flow structure with liquid droplets dispersed in the
continuous gas phase.
[0054] When designing the present flow pattern enhancer system,
each element depends on three different processes, namely
expansion, compression and mixing, and are performed by specific
methods consisting primarily on determining the flow areas and
geometries thereof. The drag coefficient is determined by the
formula:
Drag coefficient=Driving flow/Dragged Flow.
The flow pattern enhancer system of the present invention increases
gas production over 300% from the initial production and prevents
formation of hydrates, thereby avoiding re-pressure of surface
lines because of methane hydrate accumulation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] FIG. 1 shows exterior and interior views of the enhancer
system of the flow pattern of gas wells with problems of liquid
load of the present invention.
[0056] FIG. 2 shows deformation of a liquid drop depending on the
value of Weber's number.
[0057] FIG. 3 shows the transition of flow type experienced by the
gas in the well as the gas velocity decreases.
[0058] FIG. 4 shows a diagram of the secondary expander of the
present invention.
[0059] FIG. 5 shows the behavior of the pressure gradient and
productions of the well Cuitlahuac-802 of Activo Integral Burgos,
with and without the use of the enhancer system of the flow pattern
of gas wells with liquid load problems of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0060] The present invention relates to a flow pattern enhancer
system useful mainly in gas-producing oil wells with liquid load
problems, comprising mechanical elements atomizing the liquids
accumulated at the bottom of the well, thereby facilitating their
transport to the surface, by decrease of the frictional pressure
drops and weight of the hydrostatic column.
[0061] FIG. 1 shows exterior and interior views of the enhancer
system of the flow pattern applied mainly in gas-producing oil
wells with liquid load problems of the present invention, which
comprises five mechanical elements (subsystems):
[0062] 1) Primary expander. It is the first mechanical element, it
allows the expansion of the gas stream from the well that is the
driving fluid to a state of high speed; that is, it has the
function of causing the first pressure drop through a controlled
flow restriction, generating the gas expansion from the well,
driving the fluid to a state of high speed, caused by the pressure
energy of the deposit. The sudden expansion of gas increases the
velocity that, in presence of liquid, promotes the formation of a
homogenous mix.
[0063] 2) Homogenization chamber. It is the second mechanical
element and it is connected to the primary expander, inside the
stabilization and homogenization of the liquid and gas flow from
the first stage of expansion are performed, and the fluids are
transported through the chamber to the third mechanical element
called Secondary expander; that is, it has a larger interior
diameter than the Primary expander and it is connected to the
Primary expander in the lower part and to the Secondary expander in
the upper part, inside the stabilization and homogenization of the
liquid and gas flow from the first stage of expansion are
performed, the fluids are transported through the chamber to the
Secondary expander.
[0064] 3) Secondary expander. It is the third mechanical element
and it is attached to the homogenization chamber, having the
function of provoking a second restriction to flow, it has such a
geometry that it is increases the gas velocity, forming zones of
low pressure inside, where it houses the Suction veins; in the
upper part it has a fishing neck, which is the geometry allowing
the installation and removal of the enhancer system of the flow
pattern inside the production piping.
[0065] 4) Suction veins. They are the fourth mechanical element;
they are located in the low pressure zones of the interior of the
Secondary expander and communicate the low pressure zones of the
interior of the Secondary expander with the liquid accumulated
outside the system; they have the function of allowing the liquid
accumulated outside the system to be suctioned by the gas stream
(driving fluid) decreasing the particle size of the liquid
(atomization process) using the high velocity of the gas stream
achieved in the Secondary expander in the low pressure zones.
[0066] 5) Anchorage and tightness system. It is the fifth
mechanical element; it is attached to the primary expander and
homogenization chamber on its lower part, and to the secondary
expander on its upper part; and it allows to install the enhancer
system of the flow pattern at any depth of the production piping of
the well and at the same time, it forces the flow to take place
only on the inside of all the above-mentioned elements; it has
mechanical anchors which are attached to the piping and elastomeric
seals allowing the system to anchor and cause tightness outside so
that the flow performs completely as mentioned above.
[0067] According to the foregoing, the enhancer system of the flow
pattern of gas wells with liquid load problems of the present
invention, is installed in the lower extreme of the production
piping and has the function of causing an increase in the fluid
velocity by passing by two restrictions inside the system. It
causes expansion of gas flowing along the condensates and/or water.
The process allows obtaining a uniform mixture of
gas/condensates/water (liquid atomization in the gas), which
prevents slippage of gas and pitch problems. Besides it maintains a
minimum counter-pressure over the side of formation and reduces the
frictional pressure drops.
[0068] The enhancer system of flow pattern of the present invention
can be placed below the depth to which it has the bubbling pressure
and it is useful when you are managing high ratios of
dissolved/gas/oil, as in this case the additional amount of
released gas helps to "drag" the liquids accumulated at the bottom
of the well to the surface, without the requirement of an external
energy source.
[0069] The flow pattern enhancer system of the present invention
uses the latent energy in the dissolved gas, by releasing and
expanding to lift the fluids accumulated in the well; when the gas
velocity is lower than the minimum drag velocity, there will be
liquid runoff at the bottom of the well through the walls of the
production piping. When this occurs, the liquids are reincorporated
to the gas stream at high velocity when they are introduced to the
body of the secondary expander via suction veins, that is, low
pressure zones which in turn fractionated, distribute and atomize
the liquids in the gas stream.
[0070] The enhancer system of the flow pattern of the present
invention is based on the principle of conservation of momentum of
the streams of involved fluids (gas, condensed hydrocarbons and/or
water). The flow pattern enhancer system of the present invention
is based on the transmission of impact energy of a fluid at high
velocity (gas), against another fluid in motion or at rest
(condensates and/or water), to provide a fluid mixture at a
moderately high velocity, that decreases until a final pressure
greater than the initial of the lower velocity fluid is
obtained.
[0071] The whole flow pattern enhancer system of the present
invention promotes the gas expansion at the bottom of the well,
increasing the velocity to what is needed in order to incorporate
the existing liquids in atomized form through the production piping
to the surface. Such velocity is termed "critical velocity". On
this regimen the liquid drops move inside the gas stream being
subjected to the gravity and drag forces, fragmenting the liquid
particles by the effects of incorporation through the suction veins
and secondary expander, while the superficial tension of the liquid
acts to avoid its fragmentation (surface pressure). The antagonism
of the two pressures determines the maximum measure that a drop can
achieve, being represented as: [0072] Velocity pressure:
.nu..sub.G.sup.2 .rho..sub.G [0073] Surface pressure: .sigma./d
where: [0074] .nu..sub.G: velocity at which the drop of liquid is
displaced in the gas [0075] .rho.: density of the gas [0076]
.sigma.: surface tension of the drop of liquid [0077] d: diameter
of the drop of liquid
[0078] These two pressures make up the Weber's (We), which is a
dimensionless number useful on the analysis of flows wherein there
is a surface between two different fluids.
We = v G 2 .rho. G d .sigma. g c ( 1 ) ##EQU00001##
[0079] If this number exceeds the critical value, the drop of
liquid will be fragmented, the critical value for the free fall of
a drop is between 20 and 30.
[0080] With a Weber's number within the critical range, the
deformation of drops of the liquid at high velocities of the gas
stream is considered a spherical shape; if the Weber's number is
under 20 or above 30, there will be a pressure difference at the
sides of the liquid drop causing it to deform, which is clearly
seen in FIG. 2.
[0081] The total gravity force is represented by the following
equation:
F g = g g c ( .rho. L - .rho. G ) .times. .pi. d 3 6 ( 2 )
##EQU00002##
and the total drag force is given by:
F d = 1 2 g c .rho. G C a A ( v G - v L ) 2 ( 3 ) ##EQU00003##
where: [0082] g: gravitational constant [0083] d: diameter of the
drop of liquid [0084] .rho..sub.L: density of liquid [0085]
.rho..sub.G: density of gas [0086] C.sub.a: drag coefficient [0087]
A: cross-sectional area of the drop of liquid [0088] .nu..sub.G:
velocity of gas [0089] .nu..sub.L: velocity of drop of liquid
[0090] The critical velocity of gas for transporting the drop of
liquid of the well bottom is defined as the velocity at which the
drop will be suspended in the gas stream. Therefore, the critical
velocity of gas .nu..sub.G is the velocity at which .nu..sub.L=0,
if the velocity of the drop of liquid is zero, the net force on it
is zero. The equation defining this concept of critical velocity is
the following:
F.sub.g=F.sub.d (4)
[0091] Substituting both forces values:
g g c ( .rho. L - .rho. G ) .times. .pi. d 3 6 = 1 2 g c .rho. G C
a Av C 2 ( 5 ) ##EQU00004##
[0092] Rewriting the area A=.pi.d.sup.2/4 and solving for
.nu..sub.C:
v C = 4 g ( .rho. L - .rho. G ) d .beta. p G C H ( 6 )
##EQU00005##
[0093] This equation considers known a liquid drop diameter.
Actually, the liquid drop diameter depends on the gas velocity, but
the Weber's number can be obtained.
[0094] When Weber's number is 30, substituting .nu..sub.G for
.nu..sub.C and clearing d:
d = 30 .sigma. g c .rho. g v C 2 ( 7 ) ##EQU00006##
[0095] Substituting this equation on Equation 6:
v C = 4 3 ( .rho. L - .rho. G ) .rho. G .beta. C a 30 .rho. g c
.rho. G v C 2 or ( 8 ) v C = ( 40 g g c C a ) 1 / 4 ( .rho. L -
.rho. G .rho. G 2 .sigma. ) 1 / 4 ( 9 ) ##EQU00007##
[0096] Considering a drag coefficient C.sub.a of 0.44, which
corresponds to the value used for a completely turbulent flow.
Substituting the drag coefficient for turbulent flow and the g and
gc values we have:
v C = 17.514 ( .rho. L - .rho. G .rho. G 2 .sigma. ) 1 / 4 ( 10 )
##EQU00008##
where: [0097] .rho..sub.L: liquid density (lb.sub.m/ft.sup.3)
[0098] .rho..sub.G: gas density (lb.sub.m/ft.sup.3) [0099] .sigma.:
surface tension (lb.sub.f/ft) [0100] .nu..sub.C: critical velocity
of gas (ft/s)
[0101] If using the surface tension in dyne/cm units is desired, by
using the conversion (lb.sub.f/ft)=0.00006852(dyne/cm) it is
obtained:
v C = 1.593 ( .rho. L - .rho. G .rho. g 2 .sigma. ) 1 / 4 ( 11 )
##EQU00009##
where all the variables keep the units of Equation 10 but
.sigma..
[0102] Once the critical gas velocity is known, the critical
expenditure can be calculated that is a more practical value for
its applicability:
q C = 3.067 pv C A ( T + 460 ) g ( 12 ) ##EQU00010##
where: [0103] A: cross-sectional area of the inside of the
production piping (ft.sup.2) [0104] P: pressure on the wellhead
(lb/pg.sup.2) [0105] T: temperature in the wellhead (.degree. F.)
[0106] q.sub.C: critical expenditure of gas (mmft.sup.3/day)
[0107] The predictions of critical velocity of wells with low
pressures in the wellhead are more uncertain.
[0108] There are two versions of correlations, one for water and
one for condensed hydrocarbons:
v g , water = 5.62 ( 67 - 0.0031 p ) 1 / 4 ( 0.0031 p ) 1 / 2 ( 13
) v g , condensed hcns = 4.02 ( 45 - 0.0031 p ) 1 / 4 ( 0.0031 p )
1 / 2 ( 14 ) ##EQU00011##
where: [0109] p: flowing pressure in the wellhead (lb/pg.sup.2)
[0110] .nu..sub.g: critical gas velocity (ft/s).
[0111] The coefficients 5.321 and 4.043 can be considered
respectively for water and hydrocarbons besides the correlation of
critical velocity, obtaining the critical gas expenditure as
follows:
q C , gas + water = 0.0676 pdt t 2 ( T + 460 ) z ( 45 - 0.0031 p )
1 / 4 ( 0.0031 p ) 1 / 2 ( 15 ) q C , gas + condensed hcs = 0.0890
pdt t 2 ( T + 460 ) z ( 67 - 0.0031 p ) 1 / 4 ( 0.0031 p ) 1 / 2 (
16 ) ##EQU00012##
[0112] While the expenditure of fluids in a well is above the
critical expenditure, there won't be a formation of liquid column
at the bottom of the well.
[0113] FIG. 3 shows the transition of a flow type that a gas in the
well experiences as the gas velocity decreases.
[0114] Based on the above, it can be established that the flow
pattern enhancer system of the present invention increases the gas
velocity promoting the liquid atomization, with a flow velocity
relatively high of 4-6 m/s, achieving fog flow and a continuous
flow structure (in the continuous gas phase there are liquid drops
dispersed). The gas expenditure is enough to lift the liquid (water
and condensate) to the surface. If the liquid drops flow in the
same direction of gas, there is a mist flow structure and if the
liquid drops have a turbulent flow, it can be called foaming or
atomized structure.
[0115] The secondary expander showed on FIG. 4, includes the
entrance section of the liquid stream; in this chamber it is
dragged by the driving fluid (high velocity gas). The mixing
chamber allows the intimate mixing between the driving and dragged
fluids.
[0116] The design calculations consider three different processes:
expansion, compression and mixing, so there are specific methods
for each type of element, consisting primarily on determining the
flow areas and its geometry. Once the equipment is designed, it
must operate at steady state conditions for which it was designed
and the fundamental calculation is the drag coefficient:
Drag coefficient=Driving flow/Dragged flow
[0117] Based on the above, the enhancer system of flow pattern of
gas wells with liquid load problems of the present invention solves
the problems caused by the liquid accumulation at the bottom of
wells, taking advantage of the same energy of the gas produced to
"sweep" the accumulated liquid, so the fluids be produced in a
continuous form and therefore prevent the intermittent production
of wells or its the definitive closure, extending the flowing life
thereof and thereby increasing the recovery factor reflected on the
incorporation of gas reserves allowing the utilization of more
energy resources.
[0118] The flow pattern enhancer system of the invention provides
primarily the following associated benefits:
[0119] a) Increases the recovery factor of well hydrocarbons, due
to the reduction in the pressure requirement needed to administer
the energy of the deposit;
[0120] b) Increases the lifting velocity of the produced fluids to
a relatively high flow velocity of gas of 4-6 m/s; the gas
expansion flows along with the condensed hydrocarbons and water,
generating an uniform atomized mixture with lower density, which
reduces the pressure gradient flowing in the production piping;
[0121] c) Increases the gas production, as the well production is
continuous with a steady behavior even during the liquid discharge,
it has a remarkable improvement in the flow pattern in the
production piping by generating a homogenous dispersion of both
phases;
[0122] d) Decreases the pressure drops along the production piping,
as it is not allowed that the liquid accumulates at the bottom of
the well;
[0123] e) Preserves the deposit energy due to the increase of the
bottom pressure flowing;
[0124] f) Maintains the liquid production with a steady behavior
caused by an improvement in the flow pattern of fluids along the
production piping; and
[0125] g) Extends the flowing life of the wells as it preserves the
energy in the deposit by reducing the pressure drops along the
production piping.
[0126] The following describes a practical example to have a better
understanding of the same, without limiting its scope.
EXAMPLE
[0127] The application of the enhancer system of flow pattern of
gas wells with liquid load problems was made, in the well
Cuitlahuac-802 of Activo Integral Burgos. In this well the liquid
accumulation is a widespread problem at the Cuitlahuac field due to
its conditions of pressure, production and compositions of the
produced fluids.
[0128] The activities performed for the installation of the
enhancer system of patter flow of the present invention consisted
on:
[0129] 1) Well selection: For the selection of the well, those
wells having enough information to perform a simulation of the
behavior of the flow pattern enhancer are identified, and identify
which did not have installed another system obstructing the
production piping.
[0130] 2) Simulation of the production conditions of the well. The
simulation was performed based on a finite element, in order to
determine the production conditions of the well and determine the
optimum installation depth, as well as the diameters of the flow
restrictions, both upper and lower.
[0131] 3) Design and manufacture of the enhancer system of flow
pattern. The suitable enhancer system of flow patter for the
conditions of pressure, temperature, depth and properties of the
fluids produced by the well was designed and manufactured.
Technical Specifications of the Enhancer System of Flow Pattern for
the Cuitlahuac-802 Well of Activo Integral Burgos:
[0132] a) Operating differential pressure of 7,000 psi.
[0133] b) Maximum working pressure of 11,000 psi.
[0134] c) Maximum operating temperature of 177.degree. C.
(350.degree. F.)
[0135] d) Installed and released with steel line.
[0136] e) Interchangeable components and easy maintenance.
[0137] f) Generator interior of a tight seal for preventing
leaks.
[0138] g) Maximum diameter of 2.250 inches.
[0139] h) Length of 2 meters.
[0140] i) System applicable to wells deviated up to 35.degree.
(3.degree. for each 100 meters).
[0141] j) Withstand harsh environments, with CO.sub.2 and H.sub.2S
presence.
[0142] k) Primary expander, homogenization chamber and secondary
expander manufactured with steal 4140 treated with surface coating
with a hardness of 97 RwC.
[0143] 4) Installation of the enhancer system of flow pattern. The
installation of the enhancer system of flow pattern was performed
as follows:
[0144] The enhancer system of flow is installed on the production
piping extreme, it is introduced to the well through a steel line
unit by a disgorging tool JDC called davit; after reaching the
depth of placement, it anchors the production piping by sudden
descendent movements with a mechanical scissors and weight bars,
the tightness of the system is obtained by hitting the upper part
of the system with blind box. The operation sequence to recover the
system is performed by hitting upwards with mechanical scissors and
weigh bars to release.
[0145] 5) The pressure gradient behavior and productions of well
Cuitlahuac 802 of Activo Integral Burgos is shown in FIG. 5, which
is supplemented with the following results:
[0146] a) The enhancer system of flow pattern increased the gas
production over 300% compared to the initial production: from 0.315
to 1.08 million cubic feet per day;
[0147] b) The well production is continuous and had a steady
behavior even during the liquid discharge;
[0148] c) It had a remarkable improvement on the flow pattern in
the production piping by generating a homogeneous dispersion of
both phases, reducing the water shear.
[0149] d) It reduced the pressure drops along the production piping
(TP), as it was not allowed that the liquid accumulate at the
bottom of the well.
[0150] e) The deposit energy was preserved due to the increase of
bottom pressure flowing, as in the case of operation in the
discharge line of high pressure;
[0151] f) The anchorage operation of the enhancer system of flow
pattern was performed successfully. The response of the well,
monitored at the surface with a phase measuring equipment, allowed
to observe that the well was stabilized with a gas production
higher than normal, due to the application of enhancer system of
flow pattern; likewise the liquid production had a more steady
behavior, caused by an improvement in the flow pattern.
[0152] g) The enhancer system of the flow pattern can be used to
extend the flowing life of the wells, as it preserves the deposit
energy by reducing the pressure drops along the production piping,
same as was identified by the register of flowing bottom pressure
taken 2 hours after the installation.
[0153] h) It prevents the formation of hydrates, as it increases
the temperature in head to 45.degree. C. (113.degree. F.), due to
the expansion and heating of gas caused by the enhancer system of
flow pattern located at 2,000 m.
[0154] i) Additionally, the enhancer system of flow pattern
prevents the re-pressure of surface lines because of the
accumulation of methane hydrates, which reduce the flow area
towards the battery, cause of low gas production especially in
winter.
* * * * *