Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
211065g
VISCID OIL WELL COMPLETION
:' .
BACKGROUND OF THE lNv~;Nl~IoN
The Field of the Invention relates to the drilling,
completion and production of wells drilled into formations
containing heavy, viscous hydrocarbons. These hydrocarbons
may be referred to as bitumen or tar. In one embodiment,
the invention relates to the drilling of a well bore
substantially vertically or slanted downwardly, then
curving the well bore out into a substantially horizontal
portion, then thermal treatment and production of the
viscous hydrocarbons from the producing formation. In
other embodiments, the invention relates to the drilling of
a well bore substantially vertically downwardly through one
or more producing formations which contain viscous
hydrocarbons, then thermal treatment and production of the
-viscous hydrocarbons from the producing formation.
The heavy, viscous hydrocarbons are valuable for refining.
The refined products can be used as the basis for road
paving, plastics and can be refined to derive light
hydrocarbons useful for fuels and oils. Such formations as
may be near the earth surface can be strip mined to recover
the hydrocarbons. Many producing zones, however, are
deeper, and may be a few hundred feet or several thousand
feet below the earth surface. For purposes of this
specification, producing zone and producing formation have
the same meaning. For purposes of this specification,
tubing placed in a well casing may also be referred to as
a tubing string, and surface means at or near the earth
*
2110659
surface unless otherwise referenced. For the purposes of
this specification, perforation or perforations includes
the use of slotted liners and pipe that is perforated or
has drilled holes prior to being positioned in a well bore.
Heavy hydrocarbon, also known as heavy crude oil, can have
American Petroleum Institute (API) density from about 8 up
to 20 or more. Lower API density numbers indicate greater
specific gravity. API 10 has a specific gravity of 1.
Such heavy crude oils are very viscous, and are essentially
solid at in situ (in place) temperatures.
Recovery of such heavy crude oil has been accomplished in
the past by heating. Steam is been injected through a well
into a producing formation for a time, then the well is
produced. This process is referred to as the "huff and
puff" method. With several vertical wells drilled into a
zone, several wells may be produced with the "huff and
puff" process. After sufficient oil has been removed from
the formation, communication may be established from one
well to another. Then a continuous flood of steam may be
injected into one well. A mixture of heated oil,
condensate and steam may then be produced from an adjacent
well. This process is known a continuous steam flood.
The Related Prior Art includes U. S. Patent 4,565,245, in
which Mims et al. teach the method and apparatus of a
system of single well completion for carrying a hot
stimulating agent into a tar sand from the remote end of
the well. A progressively movable barrier is used to
extend the flow path pattern in the producing formation.
No provision is made to lift fluids from the remote end of
the casing. The use of a barrier in the casing indicates
the use of a heated flooding process rather than the use of
heat conduction in combination with gravity in this
21106~9
invention to cause hydrocarbons to flow to the well bore.
Mims also teaches that movement of the barrier is needed
during the producing life of the formation.
In U. S. Patent 4,640,359, Livesay teaches the method and
apparatus for use in a single well for conducting a hot
thermal stimulating medium to the remote end of the well.
An expandable diverter forms a barrier which is
progressively lengthened to cause the stimulating medium to
sweep progressively increasing lengths of the producing
formation.
SUMMARY OF THE lNV~NlION
There is disclosed the system of completion and production
of heavy oil from a well comprising a well casing disposed
in a well bore. The well and casing may have a
substantially horizontal portion disposed in an earth
formation containing heavy oil. The well casing has
perforations in the horizontal portion, or in the producing
zone of a vertical well. A well head is provided at the
top end of the well casing. An injection tubing string is
extended from the well head into the producing zone. A
packer seals the casing between the perforations and the
well head. A production tubing string extends from the
well head through and seals with the packer, and a choke
restricts flow in the injection string. The choke is
positioned beyond at least a portion of the perforations in
the casing, whereby steam may be circulated into the
injection string, through the choke, out of the injection
tubing string, through a portion of the perforations, enter
the production tubing string and return to the well head
through the production tubing string. My invention may also
include a jet pump in the production string above the
packer. A jet pump implies a power fluid string extending
from the well head operably connected to the jet pump to
2110659
power the jet pump. In this invention, the horizontal
portion of a well bore and well casing is desirably
disposed in the lower portion of the earth formation
contA;ning heavy oil.
~RIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of the preferred embodiment
in this invention.
Figure 2 is a cross section of the well of the preferred
embodiment of this invention.
Figure 3 is a cross section of the well and a portion of
the producing zone early in the life of the well according
to the preferred embodiment in this invention.
Figure 3 is a cross section of the well and a portion of
the producing zone early in the life of the well according
to the preferred embodiment in this invention.
Figure 4 is a cross section of the well and a portion of
the producing zone later in the life of the well according
to the preferred embodiment in this invention.
Figure 5 is a cross section of the well and a portion of
the producing zone late in the life of the well according
to the preferred embodiment in this invention.
Figure 6 is a cross section of two adjacent wells and a
portion of the producing zone late in the life of the well
according to the preferred embodiment in this invention.
Figure 7 is a perspective view of a well according to this
invention with the earth formation cut away, showing a
portion of the producing formation.
Figure 8 is a perspective view of the well as illustrated
in the Figure 7 at a later stage in the production life.
Figure 9 is a perspective view of an alternate embodiment
in this invention.
Figure 10 is a partial elevation section of a second
alternate embodiment
21106~9
Figure 11 is a third alternate embodiment.
Figure 12 is a cross section of a steam vapor, steam
condensate, heated oil and viscid oil interface.
Figure 13 is a graph of distance along the base of Figure
12 versus temperature.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figure 1 there is shown generally at 10 a perspective
view of a well according to this invention. The well is
drilled from the surface of the earth down in a generally
vertical direction, then deviated by any of a number of
methods well known in the industry. The well is curved so
that the generally horizontal portion 12 of the well is
drilled within the producing zone 14 and generally parallel
to the bottom limit of the producing zone. The horizontal
section 12 of the well can be of considerable length, up to
5000 feet or more. The reservoir also known as the
producing zone 14 most desirable for application of my
invention is a high permeability clean sandstone that
contains a very viscous oil. The producing zone desirably
is consolidated, rather than being, for example, loose
sand. A producing zone of loose unconsolidated sand can be
produced according to this invention by making provision to
control the flow of the sand. These methods and apparatus
are well known in the industry. A steel casing string 16
is run into the well bore and cemented in place as is well
known in the industry. A well head 11 is installed at the
surface of the earth to seal the well casing and to seal
and support any tubing strings suspended within the casing.
The casing is then perforated with perforations 18 along
the length of the portion of the casing 16 within the
producing zone. The far greater number of perforations in
the casing draining a far greater volume of producing zone
in near proximity to the well bore are advantages within
2110659
the prior art that are gained by the horizontal well
completion as described in this paragraph.
A steam injection tubing string 20 inserted into the well
casing 16 is fitted with a choke 22 at or near the end of
the tubing 20 remote from the surface. A production tubing
string 24 is inserted into the casing 16 to conduct the
produced hydrocarbons, condensate and possibly steam from
the bottom of the casing 16. A packer 26 seals between the
casing 16, the injection tubing 20 and the production
tubing 24. The packer 26 has a flow passage sealed to the
production string and communicating the production string
through the packer. The packer 26 is positioned in the
casing 16 near the perforations 18 between the perforations
18 and the surface. The packer 26 thereby seals and seals
between the annulus 40 above the packer 26 and the annulus
42 below the packer where there are perforations 18. The
annulus 40 is the space inside the casing 16, above the
packer 26 and outside any tubing strings in the casing 16.
The portion of the Steam injection tubing 20 in the annulus
40 is surrounded by thermal insulation 21 to reduce the
transfer of heat from the steam in tubing 20 to the
formation adjacent to the well. See Figure 2. Any fluid
left in the annulus 40 above the packer at the start of
steam injection would eventually be expected to boil away
from heat transferred from the injection tubing 20. As an
option, this annulus 40 may be evacuated during the
completion procedure by methods well known in the industry,
therefore these procedures will not be described here. The
air or vapor left in the annulus 40 performs an additional
insulating effect to reduce heat loss from the injection
tubing 20 in addition to the effect of insulation 21.
In some cases, the injection steam pressure will be
sufficient to lift the produced oil and condensate to the
2110659
surface without the need of a pump to lift these fluids.
In cases where the formation is so weak as to be unable to
contain sufficient pressure to lift the fluids to the
surface, some type of artificial lift, such as a pump will
be required.
A jet pump 28 is the preferred device to lift the fluids
from the bottom of the well to the surface. A jet pump is
a device well known in the industry. A power fluid line 30
connects the surface to the jet pump 28. Fluid pumped from
the surface down power fluid line 30 passes through a
venturi in the jet pump 28 as is known in the industry.
The venturi reduces the pressure at the inlet to the jet
pump 28 to mix any fluids present at the pump inlet with
the power fluid and lift the mixture to the surface through
the production tubing string 24. In this manner, the jet
pump 28 can lift the heated hydrocarbons, condensate,
steam, even solids, and any gas without any moving
mechanical parts in the well. Moving mechanical parts as
in a mechanical pump would have frequent malfunctions due
to the orientation of the well bore, the temperature at the
pump and problems from solids carried by the produced
fluids. A person skilled in the art can appreciate that
although the target producing zone 14 is consolidated,
loose, unconsolidated sand can be entrained and pumped to
the surface with the jet pump 28.
A conventional steam generator at the surface, not shown,
is used to heat the water for injection into the well
through injection tubing 20. When water is heated, the
maximum temperature to which the liquid can be heated is
dependent on the pressure of the liquid. The water may be
heated to the vaporization temperature for the injection
pressure. If sufficient heat is added to the water in the
steam generator, the water may be vaporized into steam.
21106~9
A feed water pump for the steam generator, not shown,
supplies the pressure to move the water through the steam
generator, to the injection tubing 20, and through the
choke 22, through the perforations 18 in the casing. It
can be readily seen by those skilled in the art that the
water or steam pressure will be reduced upon passing
through the flow restriction of the choke. Upon this
pressure reduction, the saturation temperature of the water
will be reduced, and therefore, the temperature of the
water will be reduced to this saturation temperature. The
pressure in the formation will be controlled by the flow
rate of steam and water injected and the flow rate of the
production flow as controlled by the jet pump 28, in
combination with the pressure drop of the flow through
choke 22 through the perforations 18, through the producing
zone 14, and to the jet pump 28.
The steam injection tubing 20 in the annulus 40 is
surrounded by thermal insulation 21 as mentioned above.
The substantially horizontal portion of the injection
tubing 32 beyond the packer 26 is not thermally insulated.
Initially, the annulus 42 below the packer would be filled
with steam or water, depending on the temperature and
pressure. Heat will be transferred from the injection
tubing 32 into the producing zone 14. The heat will reduce
the viscosity of the heavy hydrocarbons in place so the
steam, water and condensate flow will cause the
hydrocarbons to flow from the from the producing zone 14 by
gravity to the jet pump where the mixture will be lifted to
the surface. There, the hydrocarbons may be separated from
the water and recovered for use. Startup and production
according to this invention will be described hereinafter.
Referring now to Figure 2, the cross section of the
preferred embodiment of the invention shows the casing 16,
2110659
the steam injection tubing string 20, the production tubing
string 24 and the power fluid line 30 for the jet pump.
Thermal insulation 21 surrounds injection tubing string 20.
The packer 26 with two flow passages may be selected from
several types of hardware known and currently available in
the industry. The production tubing string and power
tubing string may be lowered into the casing individually
in sequence according to known technology.
Figure 3 illustrates the cross section of the horizontal
portion of the well and horizontal portion of the casing 16
and a portion of the producing zone 14. A small volume of
the producing zone 14 shows to have had the heavy oil
liquified, flowed into the well horizontal portion of the
casing 16 and been produced. Steam vapor flow is
represented by arrows 33, as the steam rises through the
permeable oil bearing formation. As the steam comes in
contact with the oil in place in producing zone 14, the
steam transfers heat to the oil and formation and the steam
condenses into water. The steam condensate represented by
arrows 35 flows downwardly by gravity flow. As the viscid
oil in place is heated, the viscosity is reduced so that
gravity causes the reduced viscosity oil, represented by
arrows 37, to flow downwardly, flowing to the horizontal
portion of the casing 16 positioned near the bottom of the
producing formation 14.
Figure 4 shows the same cross section as Figure 3 later in
life. A larger volume of oil has been recovered from the
producing zone 14.
Figure 5 shows the same cross section as Figure 3 and
Figure 4 late in life. The heavy oil has been recovered up
to the upper limit 34 of the producing zone 14. A
2110659
different formation not containing hydrocarbons will lie
above and define the upper limit 34 of the producing zone
14.
Figure 6 illustrates recovery which might be achieved by
two parallel wells according to the invention. Very high
percentages of recovery of viscous materials can be
achieved economically by use of this invention as compared
to conventional methods.
Figure 7 illustrates the well generally at 10. The
horizontal portion 12 of the well bore is in the lower
portion of the producing formation 14. Steam vapor flow is
represented by arrows 33, as the steam rises through the
permeable oil bearing formation. As the steam comes in
contact with the oil in place in producing zone 14, the
steam transfers heat to the oil and formation and the steam
condenses into water. The interfaces where this heat
transfer and change of steam to condensate and change of
the heavy oil to a flowable liquid is represented by the
envelope of surfaces 31. The steam condensate represented
by arrows 35 flows downwardly by gravity flow. As the
viscid oil in place is heated, the viscosity is reduced so
that gravity causes the reduced viscosity oil, represented
by arrows 37, to flow downwardly, flowing to the horizontal
portion of the casing 16 positioned near the bottom of the
producing formation 14. The heated oil and condensate can
enter casing 16 through perforations 18.
Figure 8 illustrates the same well in Figure 7, later in
the producing life. The steam vapor 33 has reached the
upper limit 34 of the producing zone 14. Steam vapor 33 is
still transferring heat to viscid oil lateral to the
horizontal portion 12 if the well. Steam vapor 33
condenses into condensate 35 when heat from the steam is
21106~!~
transferred to the formation 14 lateral to the well.
Reduced viscosity oil 37 flows by gravity down to the
horizontal portion 12 of the well, where it enters the
casing 16 through perforations 18.
Figure 9 illustrates the cross section of an alternate
embodiment of the invention and shows the casing 116, the
steam injection tubing string 120, the production tubing
string 124 and the power fluid line 130 for the jet pump.
Thermal insulation 121 surrounds injection tubing string
120.
Figure 10 illustrates a cross section of a second alternate
embodiment of the invention, generally at 210. A vertical
well bore 212 penetrates a producing zone 214. Steam 233 is
injected through injection string 220. Casing 216 has
perforations 218 to pass the steam under pressure into the
formation. The steam heats the formation 214 to reduce the
viscosity of the viscid oil in the formation 214. The oil
237 flows into the casing 216 through the perforations 218
to be picked up by the production string and brought to the
surface of the well for recovery.
Figure 11 illustrates a cross section of a third embodiment
of the invention. This embodiment is similar to layout and
operation in the alternate embodiment illustrated in Figure
10, except a multiplicity of producing reservoirs of viscid
oil may be stimulated into production. The well completion
is shown generally at 310. A well casing 316 is used in
this completion. Multiple producing zones 314a, 314b, and
314c are shown penetrated by the well completion 310.
These producing zones are usually separated by zones such
as shales which do not produce hydrocarbons.
2110~59
Figure 12 is an enlarged cross section of the interface at
Section 12-12 in Figure 2. Steam vapor flow is represented
by arrows 33, as the steam rises through the permeable oil
bearing formation. As the steam comes in contact with the
oil in place in producing zone 14, the steam transfers heat
to the oil and formation and the steam condenses into
water. The steam condensate represented by arrows 35 flows
downwardly by gravity flow. As the viscid oil in place is
heated, the viscosity is reduced so that gravity causes the
reduced viscosity oil, represented by arrows 37, to flow
downwardly, flowing to the horizontal portion of the casing
16 positioned near the bottom of the producing formation
14. The heated oil and condensate can enter casing 16
through perforations 18. The steam vapor in the formation
could be about .01 pressure gradient in PSI/FT (pounds per
square inch pressure per foot of height), depending on the
pressure of the steam. Viscid oil of API 10 gravity has a
pressure gradient of .433 PSI/FT. For steam vapor at about
700 PSI the temperature of the steam vapor column is 503
degrees Fahrenheit and has a pressure gradient of .01
PSI/FT. For example, for 700 PSI steam, each foot of
height H in Figure 12, the steam column pressure PlA will
be greater that pressure P2A by .01 PSI (pounds per square
inch). For the same height, the oil column pressure PlB
will be greater than pressure P2B by .433 PSI. For each
foot of height in the producing zone, the difference in the
pressure of the steam vapor and 10 degree API oil would be
.433-.01 or .423 PSI. For greater vertical dimensions in
producing formations, the pressures will be in proportion.
Thus it can bee seen that the lighter weight steam will
rise in the permeability of the depleted portion of the
producing zone, and the higher column pressure will cause
the reduced viscosity oil to flow down by gravity force
into the perforations in the casing, along with the
condensate from the steam. Once the fluids flow into the
211065!~
13
casing, they can be recovered by a normal flow, jet pump,
rod pump, or other pumps known to the industry.
Figure 13 is a graph of distance along the base of Figure
12 versus temperature. The X axis of this graph is the
distance perpendicular to the steam-viscid oil interface of
any embodiment of this invention. The Y axis is
temperature in the producing formation. T1 is the
saturated steam temperature of the steam at the steam
pressure maintained in the formation. T2 is the normal
geothermal temperature of the unheated formation.
OPERATION OF THE PREFERRED EMBODIMENT
Upon installation of the completion equipment as
illustrated in Figure 1 and Figure 2, production may be
started. Steam is injected into the injection string 20 at
the surface. An efficient plan is to pump the water into
a steam generator (not shown), then into the injection
string 20, at such a flow rate as to establish sufficient
pressure to heat the water to a temperature to heat the
producing zone 14 to a temperature sufficient to liquify
the heavy oil in the producing zone 14. Heat transfers
from the horizontal portion 32 of the injection string.
Since this portion of the injection string is not
insulated, heat is transferred into the producing zone 14
throughout the entire length of the horizontal section 32.
This horizontal section 32 may be 5000 feet or more in
length. When the steam or water passes through the choke
22, the pressure is reduced beyond the choke. Power fluid
is pumped into the jet pump power fluid string 30. Fluids
in the annulus 42 of the casing below the packer are picked
up by the jet pump 28 and pumped to the surface. The
pressure, and therefore the temperature, in the horizontal
portion 12 of the casing is controlled by the flow rate of
2110659
14
the injection fluid going in, and the flow rate of the
power fluid for the jet pump controlling the flow rate of
the fluids removed from the horizontal section 12 of the
casing. For example, if the pressure was atmospheric, the
steam would condense at 212 degrees Fahrenheit. At a
pressure of 500 psi, the condensing (saturated) temperature
of water is 467 degrees F. Unless the well were very
shallow, and without the jet pump, the bottomhole pressure
would be quite high, and the saturated steam temperature
would be quite high. The steam injection string 20 would
have approximately the same temperature as the injection
temperature. The production string would receive the
fluids at the saturation temperature of the flow after the
pressure drop at the choke and with the pressure controlled
by the flow induced by the jet pump.
As the heavy oil in the producing zone 14 is heated by the
injection fluid, gravity will perform an important role in
causing the oil to flow into the perforations 18 in the
horizontal portion 12. The flow of the injected fluids
from the far end of the well to the jet pump 28 will sweep
the oil which flows into and through the horizontal portion
of the casing 16 to the jet pump 28 to be lifted to the
surface for separation from the power fluid and injection
fluid. As the heated fluid passes through the choke to a
lower pressure, some of the water will flash into steam,
and rise to the uppermost volume available. As the steam
heats the viscous oil at the top of the open reservoir
volume, the heated oil will have reduced viscosity and flow
along with the condensed steam down through the reservoir
to the well through the perforations into the horizontal
portion 12 of the casing where the steam and condensate
flow will push the liquids along to the end of the
production string. In the case of a very shallow well, it
will flow back to the surface. In case of a deeper well,
21106~9
the jet pump will pick up the oil and condensate mixture,
and lift them to the surface.
The great advantage of this invention is that a circulation
passage through the horizontal portion 12 of the well
casing is provided. The flow of the hot steam, water and
condensate will heat the formation adjacent the horizontal
portion of the casing 16. As this oil is heated, it will
flow by gravity through the perforations 18 into the
horizontal portion of the casing 16 where it is picked up
by the steam and condensate flow to the production string
for lift to the surface. ~y controlling the producing
rate, it is possible to withdraw all of the condensate and
flowable oil that enters the horizontal portion of the
casing 16. The steam cavity in the producing zone 14 will
continually expand and cause the oil in contact with the
steam to heat and flow by gravity into the perforations 18
into the horizontal portion of the casing 16 and be
recovered as described above.
With this invention, the maximum economically feasible
depth for steam production stimulation is greater than with
a conventional vertical well. With this invention, the
length of the well in which heat from the steam is lost is
a smaller fraction of the total length of the length than
with a vertical completion.
Referring to Figures 3, 4, 5 and 6, it is assumed that the
oil has greater API gravity than 10, therefore the oil is
lighter than the condensate water. I anticipate that in
the operation of a well according to this assumption and
this invention can result in a pool of condensate water and
a layer of liquid hydrocarbon floating atop the condensate
at the bottom of the producing zone 14. A steam vapor to
oil interface 36 could exist between the pool of oil and
21106a9
16
the steam vapor in the upper volume of the producing zone
14, if the producing zone has sufficient permeability. An
oil to water interface 38 could exist between the pool of
oil and the water in the lower volume of the producing zone
14, if the producing zone has sufficient permeability. If
the producing zone has lower permeability, the vapor-liquid
interface would not be so distinctly defined.
Producing a well according to this assumption and invention
would require regulation of the injection flow rate and
production flow rate so that the layer of oil would enter
the casing through perforations 18. Production of
condensate only would indicate the bottom of the oil layer
has risen above the casing. The production rate would need
to be increased relative to the injection rate so the oil-
condensate interface 38 would fall to the casing level and
cause oil to be picked up by the jet pump 28 and pumped to
the surface. If hotter condensate or steam were produced,
this would indicate the production volume is too high and
the production rate would need to be reduced relative to
the injection rate. The relative rates described in this
paragraph can be accomplished by increasing the flow that
is too low, or decreasing the flow that is too high, or a
combination of these adjustments.
DESCRIPTION OF THE ALTERNATE EMBODIMENT
In Figure 9 there is shown generally at 110 a perspective
view of an alternate embodiment well according to this
invention. The well is drilled from the surface of the
earth down in a generally vertical direction, then deviated
by any of a number of methods well known in the industry.
The well is curved so that the generally horizontal portion
112 of the well is drilled within the producing zone 114
and generally parallel to the bottom limit of the producing
2110659
zone. The horizontal section 112 of the well can be of
considerable length, up to 5000 feet or more. The
reservoir also known as the producing zone 114 most
desirable for application of my invention is a high
permeability clean sandstone that contains a very viscous
oil. The producing zone desirably is consolidated, rather
than being, for example, loose sand. A producing zone of
loose unconsolidated sand can be produced according to this
invention by making provision to control the flow of the
sand. These methods and apparatus are well known in the
industry. A steel casing string 116 is run into the well
bore and cemented in place as is well known in the
industry. A well head 111 is installed at the surface of
the earth to seal the well casing and to seal and support
any tubing strings suspended within the casing. The casing
is then perforated with perforations 118 along the length
of the portion of the casing 116 within the producing zone.
The far greater number of perforations in the casing
draining a far greater volume of producing zone in near
proximity to the well bore are advantages within the prior
art that are gained by the horizontal well completion as
described in this paragraph.
A steam injection tubing string 120 inserted into the well
casing 116 is fitted with steam distribution holes 133
along the length of the horizontal section 132 of the
injection string. A production tubing string 124 is
inserted into the casing 116 to conduct the produced
hydrocarbons, condensate and possibly steam from the bottom
of the casing 116. A packer 126 seals between the casing
116, the injection tubing 120 and the production tubing
124. The packer 126 has a flow passage sealed to the
production string and communicating the production string
through the packer. The packer 126 is positioned in the
casing 116 near the perforations 118 between the
2110659
18
perforations 118 and the surface. The packer 126 thereby
seals and seals between the annulus 140 above the packer
126 and the annulus 142 below the packer where there are
perforations 118. The annulus 140 is the space inside the
casing 116, above the packer 126 and outside any tubing
strings in the casing 116. The portion of the steam
injection tubing 120 in the annulus 140 is surrounded by
thermal insulation 121 to reduce the transfer of heat from
the steam in tubing 120 to the formation adjacent to the
well. The cross section of this embodiment is similar to
Figure 2. Any fluid left in the annulus 140 above the
packer at the start of steam injection would eventually be
expected to boil away from heat transferred from the
injection tubing 120. As an option, this annulus 140 may
be evacuated during the completion procedure by methods
well known in the industry, therefore these procedures will
not be described here. The air or vapor left in the
annulus 140 performs an additional insulating effect to
reduce heat loss from the injection tubing 120 in addition
to the effect of insulation 121.
A jet pump 128 is the preferred device to lift the fluids
from the bottom of the well to the surface. A jet pump is
a device well known in the industry. A power fluid line
130 connects the surface to the jet pump 128. Fluid pumped
from the surface down power fluid line 130 passes through
a venturi in the jet pump 128 as is known in the industry.
The venturi reduces the pressure at the inlet to the jet
pump 128 to mix any fluids present at the pump inlet with
the power fluid and lift the mixture to the surface through
the production tubing string 124. In this manner, the jet
pump 128 can lift the heated hydrocarbons, condensate,
steam, even solids, and any gas without any moving
mechanical parts in the well. Moving mechanical parts as
in a mechanical pump could have frequent malfunctions due
2110659
19
to the orientation of the well bore, the temperature at the
pump and problems from solids carried by the produced
fluids. A person skilled in the art can appreciate that
although the target producing zone 114 is consolidated,
loose, unconsolidated sand can be entrained and pumped to
the surface with the jet pump 128.
OPERATION OF THE ALTERNATE EM~ODIMENT
Referring to Figure 9, operation of the Alternate
Embodiment is similar to the operation of the Preferred
Embodiment.
The difference lies in the absence of a choke 22 and the
use of the steam distribution holes 133 in portion 132 of
the injection string below the packer 140.
In the alternate embodiment, a tail pipe below the packer
has perforations over most of the length in the casing
below the packer. Steam is injected in proximity to the
extent of the formation traversed by the horizontal portion
of the casing. Steam pressure forces contact of the steam
to the oil bearing formation, and gravity drains the heated
and less viscous oil through perforations into the casing
and to the end of the production tubing string.
Steam is injected into the injection string 120 at the
surface. An efficient plan is to pump the water into a
steam generator (not shown), then into the injection string
120, at such a flow rate as to establish sufficient
pressure to heat the water to a temperature to heat the
producing zone 114 to a temperature sufficient to liquify
the heavy oil in the producing zone 114. Steam flows from
the steam distribution holes 133 along the horizontal
portion 132 of the injection string. Since this portion of
the injection emits steam along the length of the
2110659
perforations 118 in the casing 116, and is introduced into
the producing zone 114 throughout the entire length of the
horizontal section 132 through perforations 118. It is
preferred in this embodiment that the perforations
generally cover the interval of casing 116 where
perforations 118 are positioned. This horizontal section
132 may be 5000 feet or more in length. Power fluid is
pumped into the jet pump power fluid string 130. Fluids in
the annulus 142 of the casing below the packer are picked
up by the jet pump 128 and pumped to the surface. The
pressure, and therefore the temperature, in the horizontal
portion of the casing 116 is controlled by the flow rate
of the injection fluid going in, and the flow rate of the
power fluid for the jet pump controlling the flow rate of
the fluids removed from the horizontal section of the
casing 116. For example, if the pressure was atmospheric,
the steam would condense at 212 degrees Fahrenheit. At a
pressure of 500 psi, the condensing (saturated) temperature
of water is 467 degrees F. Unless the well were very
shallow, and without the jet pump, the bottomhole pressure
would be quite high, and the saturated steam temperature
would be quite high. The steam injection string 120 would
have approximately the same temperature as the injection
temperature. The production string would receive the
fluids at the saturation temperature of the flow after the
pressure drop in the injection string and with the pressure
controlled by the flow induced by the jet pump.
As the heavy oil in the producing zone 114 is permeated by
the injection steam, gravity will perform an important role
in causing the oil and steam condensate to flow into the
perforations 118 in the casing 116. The inflow of the oil
and condensate from the formation 114 into substantially
the extent of the perforations in the well the jet pump 128
will sweep the oil which flows into and through the casing
2110659
21
116 below the packer 126 to the jet pump 128 to be lifted
to the surface for separation from the power fluid and
injection fluid. As the steam passes into the casing 116
below the packer 140, the steam will rise to the uppermost
volume available. As the steam heats the viscous oil at
the top of the open reservoir volume, the heated oil will
have reduced viscosity and flow along with the condensed
steam down through the reservoir to the well through the
perforations into the horizontal portion of the casing
where the steam and condensate flow will push the liquids
along to the end of the production string. In the case of
a very shallow well, it will flow back to the surface. In
case of a deeper well, the jet pump will pick up the oil
and condensate mixture, and lift them to the surface.
The system of completion for simultaneous and continuous
steam injection and production of heavy oil from a single
well can comprise a well casing disposed in a well bore,
the well bore and well casing having a substantially
horizontal portion disposed in an earth formation
containing heavy oil, and the well casing having
perforations in the horizontal portion. A well head is
placed at the top end of the well casing. A packer is
installed, sealing the casing between the perforations and
the well head. A production tubing string is installed,
extending from the well head, sealing with and
communicating through the packer. An injection tubing
string is installed, extending from the well head, sealing
with and a portion of the injection string extending
through the packer and extending through at least a portion
of the perforations, with the interior of the casing below
the packer being void of any barriers such that a
continuous annulus is formed between the injection tubing
string and the casing throughout the entire length of the
portion of the injection tubing string below the packer.
2110659
Steam distribution holes are provided in the portion of the
injection string tubing string extending through the packer
and in communication with the perforations in the casing.
Means for injecting steam into the injection string are
provided, and means for controlling the pressure of the
steam and therefore the temperature of steam in the
formation are provided. Preferable, the portion of the
in~ection tubing string extending through the packer and
extending through at least a portion of the perforations
has steam distribution holes in the injection string
positioned substantially adjacent the perforations in the
casing. This provides steam adjacent the perforations in
the casing achieving good distribution of the steam to all
the perforations.
The great advantage of this invention is that a circulation
passage through the horizontal portion of the well casing
116 is provided. The flow of the hot steam, water and
condensate will heat the formation adjacent the casing 116.
As this oil is heated, it will flow by gravity through the
perforations 118 into the casing 116 where it is picked up
by the steam and condensate flow to the production string
for lift to the surface. By controlling the producing
rate, it is possible to withdraw all of the condensate and
flowable oil that enters the casing 116. The steam cavity
in the producing zone 114 will continually expand and cause
the oil in contact with the steam to heat and flow by
gravity into the perforations 118 into the casing 116 and
be recovered as described above.
If it is assumed that the oil has a lesser API gravity than
10, therefore the oil is heavier than the condensate water,
then the oil will sink below the water, and the water will
form a layer on top of the oil. Gravity will then cause
2110659
the oil to flow to the perforations 18. Then the jet pump
can pick up the oil and lift it to the surface.
It will be understood that references to horizontal
portions of a well also include a sloping portion of the
well for purposes of following a sloping lower boundary of
a producing zone. References to horizontal portions of a
well also include any sloping portions through a producing
zone, and portions of wells that slope because of
circumstances at the time the well is drilled.
Referring to Figure 10, in a second alternate embodiment,
the invention is carried out on a single producing zone
214. Casing 216 is placed in the well penetrating and
preferably passing through the producing zone 214.
Perforations 218 are disposed in the lower portion of the
earth formation 214 contA;ning heavy oil. The perforations
214 preferably extend to the lower extent of the producing
formation 214. The perforations 214 preferably extend to
the upper extent of the producing formation 214. It is
more important that the perforations 218 extend to the
lower extent of the formation since gravity causes the oil
to flow downwardly. Any oil below the perforations 218
will not be essentially unrecoverable. If the perforations
214 do not extend to the top of the producing formation
214, some, if not all of this oil is recoverable since the
steam vapor will rise due the pressure and low specific
gravity. Gravity will cause the oil above the perforations
will flow downwardly due to gravity, and be recovered. I
prefer that the perforations extend to the top of the
producing formation since the steam, condensate and oil
flow will be more efficient through the perforations than
through the formation outside casing that is not
perforated. In this arrangement, the steam enters the
upper portion of the perforations, heats the viscid oil as
21I0659
24
described earlier. the heated oil can then flow downwardly
into the perforations and into the lower portion of the
casing which acts as a sump.
In this embodiment it is preferred that the injection
string terminate below the packer, but not necessarily
extend any further in the annulus below the packer. It is
preferred that an injection tubing string extend from the
well head, seal with, and extend through the packer to
communicate with the casing perforations. It is preferred
that a production tubing string extend from the well head,
seal with, and extend through the packer to communicate
with the casing perforations. The interior of the casing
below the packer being void of any barriers such that a
continuous annulus is formed between the production tubing
string and the casing throughout the entire length of the
portion of the production tubing string below the packer.
Variations of the second embodiment could be accomplished
with vertical wells as described above, with slant wells
where the deviation angle of the well is less than 90
degrees from vertical, and with wells with "horizontal"
portions where the "horizontal" portion of a well is
deviated less than 90 degrees from vertical. For the
purposes of this specification and claims, references to
wells includes vertical wells, substantially vertical
wells, wells with substantially vertical portions and
portions deviated from the vertical, slant wells and
combinations of these configurations. For the purposes of
this specification and claims, references to heavy, viscid,
and viscous oil or crude all have the same meaning.
In any of the alternate embodiments described above, the
production tubing string should terminate at or below the
deepest perforations, so that gravity will flood the
2110659
production string intake. In this manner liquids which
flow into the liquids flow into the annulus below the
packer will flow to the production string intake. As
described above, in the alternate embodiments, the
injection string will preferably terminate it the upper,
preferably, the uppermost point of the annulus below the
packer
In the case of a well as shown in Figure 1 where the
"horizontal" the "horizontal" portion of a well is deviated
more than 90 degrees from vertical, it is possible to use
the arrangement without the choke. In the production
tubing string should terminate with the lower portion,
preferably, the lowermost point of the annulus below the
packer, which is immediately below the packer, so that
gravity will flood the production string intake. In this
manner liquids which flow into the annulus below the packer
will flow to the production string intake. As described
above, in the preferred embodiment, the injection string
will preferably terminate at the upper, preferably, the
uppermost point of the annulus below the packer which is
the
far end of the annulus below the packer from the packer.
What I have described is a system of completion for
simultaneous and continuous steam injection and production
of heavy oil from a single well comprising well casing
means disposed in a well bore, the well bore and well
casing means disposed in an earth formation contAining
heavy oil. The well casing means having perforations in
communication with the formation contAining heavy oil, well
head means at the top end of the well casing means,
packer means sealing the casing between the perforations
and the well head means, tubing string means including
production tubing string means extending from the well head
2110659
26
means, sealing with and communicating through the packer
means, and terminating in the lower portion of the casing
below the packer. Injection tubing string means is
provided, extending from the well head means, sealing with
and extending through the packer means and terminating in
the upper portion of the casing below the packer. The
interior of the casing below the packer preferably being
void of any barriers such that a continuous annulus is
formed between the tubing string means and the casing
throughout the entire length of the portion of the tubing
string means below the packer. Means is provided for
injecting steam into the injection tubing string means, and
means for controlling the pressure of the steam and
therefore the temperature of the steam in the formation,
whereby steam is continuously circulated into the injection
string means, out of the injection tubing string means,
through a portion of the perforated casing means, wherein
injection forces drive the steam into the formation where
it condenses, heating the heavy oil, reducing the viscosity
of the heavy oil, allowing the steam condensate and hot oil
to flow downward into the perforated portion of the well
casing means where the condensate and oil flow into the
production tubing string means and flow through the
production tubing string means to the well head means
simultaneously with the steam injection. An improved
system for completing a well and simultaneously and
continuously producing viscous hydrocarbons may be
provided, wherein the means for controlling the steam
pressure in the hydrocarbon bearing zone further comprises
pump means in the production string to lift liquids at a
controlled rate from below the packer to the well head.
The pump means may include a jet pump, a rod pump, gas lift
or other means of artificial lift known in the industry.
2110659
Referring to Figure 11, in a third alternate embodiment
shown generally 310, the invention is carried out on
multiple producing zones 314a, 314b and 314c. Casing 316
is placed in the well penetrating and preferably passing
through the producing zones 314a, 314b and 314c.
Perforations 318a, 318b and 318c, respectively, are
disposed in the lower portion of the earth formations 314a,
314b and 314c containing heavy oil. The perforations 318a,
318b and 318c preferably extend to the lower extent of each
producing formation 314a, 314b and 314c, respectively.
The perforations 318a, 318b and 318c preferably extend to
the upper extent of each producing formation 314a, 314b and
314c, respectively. It is more important that the
perforations 318a, 318b and 318c extend to the lower extent
of each formation since gravity causes the oil to flow
downwardly. Any oil below the perforations 318a, 318b and
318c in the respective formation will not be essentially
unrecoverable. If the perforations 318a, 318b and 318c do
not extend to the top of the producing formations 314a,
314b and 314c, respectively, some, if not all of this oil
is recoverable since the steam vapor will rise due the
pressure and low specific gravity. Gravity will cause the
oil above the perforations will flow downwardly due to
gravity, to the perforations and be recovered. I prefer
that the perforations extend to the top of the producing
formation since the steam, condensate and oil flow will be
more efficient through the perforations than through the
formation outside casing that is not perforated. In this
arrangement, the steam enters the upper portion of the
perforations, heats the viscid oil as described earlier.
the heated oil can then flow downwardly into the
perforations and into the lower portion of the casing which
acts as a sump.
28 2 t 1 0659
In some fields, there are multiple heavy oil producing
formations. In these cases, the well bore and well casing
may penetrate at least two earth formations containing
heavy oil, with the well casing having perforations in
communication with each earth formation containing heavy
oil. Oil in place in each producing zone may be heated and
caused to flow into the casing as described hereinbefore.
One well, then may be used to stimulate and produce heavy
oil from a multiplicity of producing formations.
Although only four embodiments of the invention have been
illustrated in the accompanying drawings and described in
the foregoing Description it will be understood that the
invention is not limited to the embodiments disclosed, but
is capable of rearrangements, modifications, and
substitutions and reversals of parts and elements without
departing from the spirit of the invention.
