U.S. patent number 3,873,238 [Application Number 05/398,571] was granted by the patent office on 1975-03-25 for method and apparatus for flowing crude oil from a well.
Invention is credited to Johnnie A. Elfarr.
United States Patent |
3,873,238 |
Elfarr |
March 25, 1975 |
Method and apparatus for flowing crude oil from a well
Abstract
Method and apparatus for flowing crude oil from wells wherein a
fluid is injected into the oil bearing earth formation for the
purpose of reducing the viscosity of the oil and causing it to
migrate under induced formation pressure to one or more production
wells. The apparatus and method are employed in the production
wells in such manner that flashing of high temperature water to
steam is selectively induced in the apparatus and in the well
casing in which the apparatus is located for lightening the fluid
column in the apparatus and causing a flowing action to occur and
for selectively condensing the steam to its liquid state for liquid
transportation of oil within the apparatus. The apparatus is
received in the well casing in such a manner that the apparatus and
the inner conduit to which it is connected may be removed from the
well casing substantially free of any of the hot liquid that is
present in the apparatus in the operative condition thereof.
Inventors: |
Elfarr; Johnnie A. (Palestine,
TX) |
Family
ID: |
23575886 |
Appl.
No.: |
05/398,571 |
Filed: |
September 19, 1973 |
Current U.S.
Class: |
417/54; 166/372;
166/68; 417/118 |
Current CPC
Class: |
E21B
43/12 (20130101); F04F 1/08 (20130101); E21B
36/00 (20130101) |
Current International
Class: |
E21B
36/00 (20060101); E21B 43/12 (20060101); F04F
1/08 (20060101); F04F 1/00 (20060101); F04f ();
E21b () |
Field of
Search: |
;166/68,105,244R,314
;417/54,55,118 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Abbott; Frank L.
Assistant Examiner: Ebel; Jack E.
Claims
What is claimed is:
1. Apparatus for flowing liquid from a well bore extending from the
surface of the earth to a liquid bearing earth formation, said
apparatus comprising:
casing means extending into said well bore and defining a well head
at the upper extremity thereof, said casing being in fluid
communication with said liquid bearing earth formation;
outer conduit means being supported by said well head and extending
into said casing;
a landing nipple being coupled to the lower extremity of said outer
conduit means and defining support means;
inner conduit means being removably supported by said well head and
extending into said outer conduit means, said inner conduit means
cooperating with said outer conduit means to define flow chamber
means;
landing adapter means being coupled to said inner conduit means and
being releasably and sealingly engaged with said landing
nipple;
outer pump conduit means being supported in sealed relation by said
landing adapter means and depending therefrom, said outer pump
conduit defining a pressure imposing chamber;
first valve means being carried by said outer pump conduit means
and allowing unidirectional flow of said production liquid from
said casing means into said pressure imposing chamber;
inner pump conduit means being supported by said landing adapter
means, said inner pump conduit means extending into said pressure
imposing chamber and being in fluid communication with said outer
conduit means;
second valve means being carried by said inner pump conduit means
and allowing unidirectional flow of said production liquid from
said pressure imposing chamber to said flow chamber means;
means for selectively introducing pressurized fluid into said
pressure imposing chamber; and
means for conducting produced liquid from said flow chamber
means.
2. Apparatus as recited in claim 1, wherein:
said pressure imposing chamber is in fluid communication with said
inner conduit means; and
said flow chamber means is in fluid communication with said outer
conduit means, outwardly of said inner conduit means.
3. Apparatus as recited in claim 1, wherein:
said landing adapter means has first crossover passage means formed
therein communicating said inner conduit means with the annulus
between said inner and outer pump conduit means and second
crossover passage means communicating said inner pump conduit means
with the annulus between said inner and outer conduit means.
4. Apparatus as recited in claim 1, wherein:
said landing nipple is connected to the lower extremity of said
outer conduit means;
said landing adapter is connected to the lower extremity of said
inner conduit means; and
said inner and outer pump conduit means are connected to the lower
extremity of said landing adapter.
5. Apparatus as recited in claim 1, including:
perforated means secured to the lower extremity of said casing
means and having perforations formed therein communicating said
liquid bearing earth formation with said casing means.
6. Apparatus as recited in claim 5, wherein:
at least a portion of said inner and outer pump conduit means
extend into said casing to a level disposing said first valve means
below the level of production liquid within said casing and
perforated means.
7. A method of displacement pumping of a production fluid including
crude oil and water from an oil bearing earth formation wherein
production and injection wells are formed in the earth and are in
communication with said formation and at least one injection well
continuously injects steam into said oil bearing earth formation
and wherein said production wells each have apparatus defining an
injection chamber, a production fluid supply chamber being open to
said formation and receiving production fluid from said formation,
a first pumping chamber having valved communication with said
production fluid supply chamber, a second pumping chamber having
valved communication with said first pumping chamber and a flow
chamber being disposed in communication with said second pumping
chamber, said method comprising the steps of:
causing production fluid including steam, water and crude oil to
enter said first pumping chamber from said production fluid supply
chamber;
condensing at least a portion of said steam in said first pumping
chamber into water;
causing flashing of a portion of the water content of said
production fluid into steam in said first pumping chamber and
causing steam pressure forcing of liquid and steam from said first
pumping chamber to said second pumping chamber;
condensing at least a portion of the steam content of said
production fluid in said second pumping chamber into water;
causing flashing of a portion of the condensed water of said liquid
in said second pumping chamber to steam and causing steam pressure
forcing of said liquid and steam from said second pumping chamber
to said flow chamber;
condensing at least a portion of the steam content of said
production fluid in said flow chamber into water; and
causing flashing of a portion of the condensed water of said
production fluid in said flow chamber to lighten the column of the
liquid in said flow chamber and to cause steam forcing of liquid
from said flow chamber for production.
8. The method of claim 7, wherein:
said condensing of said steam in said first pumping chamber is
accomplished by injecting a fluid under pressure into said
injection chamber at a lower temperature than the temperature of
the steam within said injection chamber.
9. The method of claim 7, wherein: said injected fluid is air.
10. The method of claim 7, wherein:
steam entering said production fluid supply chamber from said
formation is caused to condense in said production fluid supply
chamber by controlled modification of the steam generated pressure
condition within said production fluid supply chamber.
11. The method of claim 8, wherein the steps of claim 7 occur
repetitively to induce cyclic displacement pumping actuation and
including the steps of:
discontinuing injection of fluid into said injection chamber after
cyclic displacement pumping actuation of said pumping has been
conducted in accordance with the steps of claim 7 for a
predetermined period of time;
continuing with cyclic displacement pumping actuation in accordance
with the steps of claim 7 in absence of injection of said fluid
medium; and
maintaining a predetermined back pressure on said flow chamber
after discontinuing injection of fluid into said injection chamber
to allow controlled and substantially continuous flashing of at
least a portion of the water content of said production fluid into
steam within said flow chamber.
12. Apparatus for flowing production fluid including a mixture of
oil and water from an oil bearing earth formation wherein the earth
formation is heated and pressurized by injection of a fluid into
the formation and at least one production well bore extends to the
formation, said apparatus comprising:
casing means extending into said well bore and defining a well head
at the upper extremity thereof, said casing means being in fluid
communication with said oil bearing earth formation;
means communicating said casing means with said formation;
pump means being disposed within said casing and defining an
injection chamber, a flow chamber and first and second pumping
chambers, said pump means defining first restricted passage means
communicating said injection chamber and said first pumping chamber
and defining second restricted passage means communicating said
second pumping chamber and said flow chamber;
first valve means controlling the flow of production fluid from
said casing into said first pumping chamber, said inlet of said
valve means being disposed sufficiently near the oil/water contact
within said casing to prevent the hydrostatic head of the column of
fluid within said well from interfering with flashing of the water
content of said production fluid into steam;
second valve means controlling the flow of production fluid from
said first pumping chamber to said second pumping chamber; and
means for selectively controlling injection of a pressurized medium
into said injection chamber and venting of said injection
chamber.
13. Apparatus as recited in claim 12, wherein:
said means for defining said flow chamber comprises outer conduit
means suspended within said casing by said well head; and
said means defining said injection chamber comprises an inner
conduit means suspended by said well head within said outer conduit
means.
14. Apparatus as recited in claim 12, wherein:
said means communicating said casing means with said formation is
perforated means disposed at the lower extremity of said casing
means, said perforated means having been perforated along the
length thereof to allow production fluid to enter said casing means
from said formation, the lower extremity of said perforated means
extending below the oil/water level within said formation.
15. Apparatus as recited in claim 13, wherein:
said first valve means is disposed in juxtaposed relation with said
oil/water level.
16. Apparatus as recited in claim 14, wherein:
said pump means extends at least partially within said perforated
means.
17. Apparatus as recited in claim 12, including:
means for maintaining a minimum of back pressure on the production
fluid flowing through said flow chamber to allow continuous
flashing of the water content of said production fluid into
steam.
18. Apparatus for flowing production fluid including a mixture of
oil and water from an oil bearing earth formation wherein the earth
formation is heated and pressurized by injection of a fluid into
the formation and at least one production well bore extends to the
formation, said apparatus comprising:
casing means extending into said well bore and defining a well head
at the upper extremity thereof, said casing means being in fluid
communication with said oil bearing earth formation;
first and second casing valves communicating said casing with a
flow line and with a vent conduit, respectively, said casing valves
being closed during operation of said apparatus and being opened to
balance the pressure conditions in said flow chamber and said
casing;
pump means being disposed within said casing and defining an
injection chamber, a flow chamber and first and second pumping
chambers, said pump means defining first restricted passage means
communicating said injection chamber and said first pumping chamber
and defining second restricted passage means communicating said
second pumping chamber and said flow chamber, said flow chamber
being in communication with said flow line;
flow valve means connected in said flow line and controlling flow
of production fluid from said flow chamber;
first check valve means controlling the flow of production fluid
from said casing into said first pumping chamber, said inlet of
said first check valve means being disposed sufficiently near the
oil/water contact within said casing to prevent the hydrostatic
head of the column of fluid within said well from interfering with
flashing of the water content of said production fluid into
steam;
second check valve means interposed between said first and second
pumping chambers and controlling the flow of production fluid from
said first pumping chamber to said second pumping chamber;
a source of pressurized medium;
injection conduit means interconnecting said source and said
injection chamber;
valve means in said injection conduit for selectively controlling
injection of pressurized medium from said source into said
injection chamber;
an exhaust conduit being communicated with said injection chamber;
and
valve means in said exhaust conduit being controllable for venting
of said injection chamber.
Description
FIELD OF THE INVENTION
This invention is directed generally to apparatus for production or
secondary recovery of crude oil from earth formations having
insufficient formation pressure for raising the crude oil to the
surface of the earth and wherein the crude oil within the earth
formation is of sufficient viscosity to prevent it from readily
migrating to production wells. More particularly the invention is
directed to a pneumatic displacement method of primary or secondary
recovery of crude oil wherein air or steam is injected into the
formation to reduce the viscosity of the crude oil and to develop a
formation pressure that causes migration of the oil to production
wells. Where steam is injected into the oil bearing formation, the
steam may be selectively condensed and vaporized simply by varying
the pressure thereof. Specifically, the invention is directed to
the provision of a method and apparatus for pneumatic displacement
pumping, incorporating a down-hole valve mechanism and a surface
located control facility that cooperate to inject a pressurized gas
into the well to cause selective vaporization and condensation of
hot water within the pumping mechanism to produce controlled
displacement pumping of the crude oil entering the production well
from the formation.
BACKGROUND OF THE INVENTION
While the invention will be explained for purposes of simplicity
with regard to its application to production of oil from oil
bearing earth formations having little or no formation pressure, it
is considered obvious that the invention may be utilized
effectively for displacement of other fluids that may or may not be
located within earth formations. The present invention will be
discussed in its application solely for the production of oil from
oil bearing earth formations for purposes of simplicity and to
facilitate ready understanding of the invention. It is in no way
intended to limit the present invention solely to use in connection
with production of oil.
When oil bearing earth formations are discovered that have
insufficient formation pressure for gas energized production of oil
found in the formation, or when a pressurized oil bearing formation
loses a substantial amount of its formation pressure, it will
become necessary to provide for recovery of the oil by methods
other than production by formation pressure flowing. One acceptable
method for producing low pressure or zero pressure oil bearing
earth formation has been the use of mechanically energized pumps
that simply mechanically elevate the oil to the surface of the
earth for production by conventional reciprocating pump mechanisms.
These pumps are generally restricted to production of oil from very
shallow oil bearing earth formations and are not capable of pumping
a viscous crude oil because viscous crude oil, in absence of
formation pressure, will not be capable of migrating through the
earth formation to the well bore.
Another method, successfully utilized in production of otherwise
unproducable oil wells, has been the use of pneumatic displacement
pumps, which may be also referred to as "gas lift valves." These
pumps or valves may be energized by compressed air, compressed
inert gases, steam, or compressed natural gas and are effective to
achieve production of oil bearing formations that are of
substantial depth. U.S. Pat. Nos. 1,326,338 to Gregory, 1,754,945
to Haskell, and 3,106,170 to Gray, each disclose pneumatic
displacement type devices for flowing or pumping oil wells.
Typically, pneumatic displacement pumps inject a gas into a pumping
mechanism disposed below the fluid level within the well which gas
serves a piston like function to raise liquid in the production
tubing in the form of a slug or segment. A small amount of the gas,
of course, mixes with the liquid to some extent, thereby lightening
the load of the column and allowing the column of liquid to be
transported to the earth surface for production.
Where steam is injected into the earth formation, for the purpose
of providing sufficient heat to reduce the viscosity of the crude
oil entrapped in the earth formation and thereby allowing the crude
oil to migrate toward one or more production wells, typically a
number of production wells surround a steam injection well. The
steam injected into the formation will condense to its liquid form,
because of the pressure under which it is maintained, whereupon the
liquid form will also migrate through the oil bearing earth
formation toward the production well. The water at the level of the
oil sand in the production wells will be in the order of
250.degree. to 350.degree.F. Since the water temperature is above
the boiling point of water at atmospheric pressure, reduction of
pressure within the well bore at the formation level will cause
immediate vaporization of the water to steam. This vaporization is
typically referred to in the industry as "flashing" and will be so
referred to in the present application.
Where steam is injected into oil bearing earth formation, for the
purpose of reducing the viscosity of the crude oil contained
therein and causing it to migrate to production wells, and air or
other gases are injected into production wells for the purpose of
lifting the crude oil or a mixture of crude oil and water to the
surface of the earth for production, each time the pumping
mechanism operates the water contained in the production fluid at
the bottom of the well, being in the order of 250.degree. to
350.degree.F will flash to steam, thereby interfering with
effective production of the oil. In fact, the efficiency of
producing crude oil in this manner is typically in the order of 12
percent, thereby rendering pneumatic displacement pumping of hot
production fluid having a water content to be quite expensive and
thereby reducing the commercial feasibility of recovery of oil in
this manner. It is therefore considered desirable to utilize the
pressure generated by the water content of the hot production fluid
to assist in production of the crude oil. It is also desirable to
utilize, as efficiently as possible, the energy that is required to
produce steam and inject it into the oil bearing formation for
production purposes.
One problem presented by the use of pneumatic type fluid
displacement pumps or flowing devices is the physical dimension of
the well casing within which the pump mechanisms must be received.
Because of the substantial physical size of most pneumatic
displacement pumps, it is necessary to provide a well bore and well
casing of substantial dimension to allow sufficient space within
which the pump may be received. Well bores of substantial size are
expensive to drill and therefore detract from the commercial
feasibility of pneumatic displacement pump type oil recovery
systems. It is desirable therefore to provide a pneumatic
displacement pump type pumping mechanism that is of relatively
small cross-sectional dimension and which will be efficiently
received within a well bore without any requirement for enlargement
of the well bore beyond the normal dimension required for receiving
conventional well production tubing.
Another problem with some pneumatic displacement pump mechanisms
occurs when the pumping mechanisms are extracted from the well for
repair or replacement. During steam injection for the purpose of
enhancing formation pressure and simultaneously increasing the
temperature of the formation, thereby reducing the viscosity of the
crude oil contained in the formation and enhancing the ability of
the oil to flow from the formation to the production tubing, the
formation is heated to a temperature near the temperature of
superheated steam and, consequently, and liquid that is trapped
within the well tubing as it is extracted from the well is quite
hot and poses a dangerous condition for workmen accomplishing the
well servicing operation. In most pneumatic well pumping
mechanisms, there is present at the lowermost portion of the well
tubing, one or more check valve mechanisms that seal responsive to
the hydrostatic head of the liquid contained within the tubing,
thereby causing the tubing to be pulled from the well full of hot
production fluid trapped therein. The hazardous condition of such
repair operations is enhanced because the trapped production fluid
frequently spills when the tubing is separated and presents a
safety hazard because of the likelihood of fire and the generally
unsafe conditions that result from oil spills. Moreover, when the
production fluid is extremely hot, because of the steam or fire
flooding operations that provide the formation pressure for
production and provide heat for reducing the viscosity of the oil
to allow it to migrate in the formation, the hot oil/water mixture
presents a safety hazard to workmen involved in disassembly of
sections of tubing that are filled with the hot fluid. Hot
production fluid spilling from fluid filled sections of tubing
presents a safety hazard due to the possibility of causing hot
fluid burn injuries to the workmen separating the tubing. It is
therefore very desirable to remove tubing strings from the well
that are not filled with hot liquid.
Accordingly, it is a primary object of the present invention to
provide a novel method of accomplishing pneumatic displacement of
high temperature fluid from a well which effectively utilizes
pressure generated by high temperature flashing of water into steam
for assisting in elevation of production fluid from a fluid bearing
earth formation to the surface of the earth for production.
It is a further object of the present invention to provide a novel
method of pneumatic displacement pumping of high temperature water
containing fluid from a well wherein the water content of the fluid
is caused to selectively flash into steam and condense into its
water form for the purpose of controlled release of pressure that
assists in production of the fluid from the well.
It is an even further object of the present invention to provide a
pneumatic displacement type pumping mechanism for flowing oil or
any other production fluid from a well that obviates any necessity
for lifting oil filled tubing strings from the well during repair
of replacement operations.
It is an even further operation of the present invention to provide
pneumatic displacement type pumping apparatus having down-hole
valves that may be removed for repair or replacement simply by
removing the intermost light-weight tubing string from the
well.
Another object of the present invention involves the provision of
novel pneumatic displacement type pumping apparatus for flowing
high temperature production fluid from wells which includes valve
apparatus and valve seat structures that may be completely removed
from the well in a single operation, simply by removing the
centermost light-weight tubing string from the well.
Among the several objects of the present invention is contemplated
the provision of novel pneumatic displacement type pumping
apparatus that may be effectively utilized in oil wells of
relatively small casing dimension.
It is also an important object of the present invention to provide
novel pneumatic displacement type pumping apparatus employing a
simple cross-over mechanism that promotes efficient pumping
operation of the apparatus by cooperating with other structure of
the displacement pumping mechanism to cause selective development
of pressure changes within the pumping mechanism and within the
casing to cause selective flashing of the hot water content of the
production fluid into steam and causes selective condensation of
steam into water and utilizes the energy of the steam to assist in
transportation of production fluid to the surface of the earth.
It is an even further object of the present invention to provide
novel pneumatic displacement type pumping apparatus for flowing
high temperature water containing oil from a well, which apparatus
is simple in nature, reliable in use, and low in cost.
Other and further objects, advantages and features of the present
invention will become apparent to one skilled in the art upon
consideration of the written specification, the attached claims and
the annexed drawings. The form of the invention, which will now be
described in detail, illustrates the general principles of the
invention, but it is to be understood that this detailed
description is not to be taken as limiting the scope of the present
invention.
SUMMARY OF THE INVENTION
A preferred embodiment of the present invention may comprise a well
casing extending through a drilled bore in the earth to an oil
bearing earth formation which well casing may be provided with a
well head at its upper extremity and with a perforated element,
typically referred to as a screen, at its lower extremity. Oil, or
water contained oil, typically referred to as production fluid, may
be forced by formation pressure, either induced naturally or
artificially and may enter the well casing through the perforations
of the screen and may rise to a level within the casing. Inner and
outer conduits may be removably suspended from a well head at the
surface of the earth and may extend to the production zone within
the casing. The outer conduit may be provided with a landing nipple
at its lower extremity and a landing adapter, connected to the
inner tubing string, may be received and locked within the landing
nipple in such manner that a sealed relationship is established
between the landing nipple and the landing adapter.
An outer pump conduit may extend downwardly from the landing
adapter and may have a check valve disposed at the lower extremity
thereof to allow unidirectional flow of production fluid from the
well casing into an outer pump chamber. An inner pump tubing may
extend downwardly from the landing adapter and may be disposed
within the outer pump conduit and may have a check valve disposed
at its lower extremity to allow unidirectional flow of production
fluid from the outer pump chamber to an inner pump chamber.
The outer pump chamber may be communicated by restricted crossover
passages to the inner tubing strong supported by the well head and
may cooperate with the intertubing string to define a pressure
imposing chamber wherein pressurized gas is introduced into the
well in order to cause a pneumatic pumping action to occur. The
outer chamber below the crossover mechanism may constitute an outer
pumping chamber wherein hot water disposed therein may be caused to
vaporize into steam and provide a motive force that causes the flow
of oil or oil water mixture disposed within the outer pumping
chamber to flow through a check valve into the inner pumping
chamber. The inner pumping chamber is communicated through
restricted passages formed in the crossover mechanism to a flow
chamber defined by the annulus between the inner and outer tubing
strings within the well bore which annulus is, in turn,
communicated with a flow line to conduct produced fluid from the
well to a handling or storage facility. The restricted passageways
from the inner pumping chamber to the flow chamber allow the
development of pressure changes to cause flashing of water into
steam in the flow chamber which develops a pressure condition that
assists in transporting fluid within the flow chamber upwardly
through the outer tubing string to the flow line.
The inner tubing string is communicated with a pressurized source
of actuating gas such as compressed air, compressed natural gas, or
steam, which may be introduced into the well to provide a motive or
control force for pneumatic displacement pumping of liquid from the
level of the oil bearing earth formation to surface for production
through the flow line extending from the well head.
In employing the method of pneumatic type displacement pumping in
accordance with the present invention, a gas may be introduced into
the inner conduit or injection chamber at much lower temperature
than the temperature of the production fluid within the well. The
cool gas causes condensation of at least a part of the steam
present within the inner conduit at the start of a pumping cycle.
The condensed water will flow through the crossover mechanism into
the outer pumping chamber and steam within the outer pumping
chamber will also condense. Pressure within the inner conduit will
then be reduced by venting the inner conduit, thereby causing
flashing of a portion of the water content within the inner conduit
and through the crossover passages will cause vaporization of a
part of the water content of the production fluid within the outer
pumping chamber, thereby creating sufficient pressure to induce
liquid within the outer pumping chamber to flow through the check
valve mechanism into the inner pumping chamber. The liquid within
the inner pumping chamber will then flow through the restricted
passages of the crossover mechanism into a much larger flow chamber
defined by the annulus between the inner and outer conduits. This
chamber, being of much larger dimension, of course, causes sudden
pressure reduction of the liquid exiting from the restricted
passages of the crossover mechanism and causes a portion of the
water content of the liquid so exiting to vaporize or flash
immediately to steam. The steam, in addition to producing a
pressure that induces upward flow of production fluid within the
flow chamber to the flow line at the well head, also serves to
lighten the column of fluid as to cause an upward flowing action to
occur, thereby transporting oil contained in the mixture to the
well head where it is conducted away through the flow line. With
less than 50 pounds of flow line pressure, the fluid, so produced,
will be transported through the flow line to a storage or handling
facility.
The control valves are then manipulated to vent the inner conduit
and the outer pumping chamber in order to reduce pressure therein.
As the pressure reduces below the formation pressure, the lower
check valve of the outer pumping conduit will open because of the
pressure differential thereacross and will communicate the low
pressure condition of the outer pumping chamber to the well casing
and to the formation. A portion of the water content of the hot
production fluid within the casing will flash into steam and will
force production fluid from the casing into the outer pumping
chamber and through the crossover mechanism into the inner tubing
string. Because there is more steam available than can be exhausted
through the crossover mechanism into the inner conduit, a back
pressure develops within the outer pumping chamber and within the
casing outwardly of the pumping mechanism. When pressure conditions
across the lower check valve become substantially balanced, the
lower check valve will seat thereby entrapping the production fluid
within the outer pumping chamber. Also, because of the increased
pressure developed by the back pressure condition, the steam begins
to condense within the outer pumping chamber and within the casing
outwardly of the pumping mechanism. When enough of the steam has
condensed and sufficiently lowered the pressure within the outer
pumping chamber and the inner conduit, the condensed water will
flash again to steam and force fluid again into the inner pumping
chamber, thereby initiating a subsequent pumping cycle.
The valve mechanism, including the crossover mechanism and the
upper and lower check valve assemblies may be extracted from the
inner conduit simply by unlocking the landing adapter from the
landing nipple and raising the inner conduit relative to the outer
conduit. When this occurs, fluid within the inner conduit will be
drained through the crossover passages into the outer conduit and
the inner conduit may be raised completely free of any hot liquid
that might otherwise be disposed above the crossover mechanism. The
check valves will of course retain a small quantity of fluid below
the crossover mechanism. The outer tubing may also be removed
completely free of fluid since its lower extremity is completely
open after removal of the crossover mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features, advantages
and objects of the present invention, as well as others, which will
become apparent, are attained and can be understood in detail, more
particular description of the invention, briefly summarized above,
may be had by reference to the embodiments hereof which are
illustrated in the appended drawings, which drawings form a part of
this specification.
It is to be noted, however, that the appended drawings illustrate
only typical embodiments of the invention and are therefore not to
be considered limiting of its scope, for the invention may admit to
other equally effective embodiments.
In the Drawings:
FIG. 1 is a sectional view of a well casing extending through a
well bore in the earth's surface to an oil bearing earth formation
and also illustrating in simple mechanical terms the provision of a
pneumatic displacement type pump mechanism constructed in
accordance with the present invention within the casing structure
in position for pumping production fluid from the well.
FIG. 2 is a fragmentary sectional view of the well and pumping
mechanism of FIG. 1 illustrating the landing nipple and landing
adapter structures with the crossover passages formed therein,
showing the mechanism seated at its operative position.
FIG. 3 is a fragmentary sectional view of the mechanism of FIG. 2
illustrating the liquid pumping mechanism of the present invention
as being unseated and moved upwardly relative to the landing nipple
for extraction of the same from the well.
FIG. 4 is a schematic view of an oil production system wherein an
injection well is provided which injection well is surrounded by a
number of production wells, each of which being capable or
producing oil that migrates outwardly away from the injection well
because of the formation pressure that is created at the injection
well by fire flooding operations or by injection of steam into the
formation.
FIG. 5 is a fragmentary sectional view of the upper extremity of a
fluid pumping mechanism constructed in accordance with the present
invention and illustrating a modified well head structure and its
valved connection to a flow line.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings for a more detailed understanding of
the present invention and referring specifically to FIG. 1, there
is depicted in partial section a typical earth formation having a
well bore drilled in intersecting relation with an oil bearing
stratum of the formation. As shown in FIG. 1 of the drawings, A
represents overburden of the formation while B represents a porous
oil bearing portion of the formation, typically referred to as oil
sand. The oil sand may be quite thin, in the order of 4 to 5 feet
thick or it may well be 50 to 100 feet in thickness or greater. In
shallow oil wells the oil sand will typically be in the order of 4
to 10 feet in thickness. Below the oil sand B there typically
exists another earth formation C, referred to as water sand, which
contains either fresh or salt water depending upon the particular
environment involved and an oil water contact level or interface 10
will typically exist.
The well bore 12 in the earth formation will typically be drilled
to sufficient depth for setting of a casing 14 in the earth
formation, which casing may extend slightly below the upper level
of the oil sand. Ordinarily, a cement 16 is employed to firmly
secure the casing 14 to the wall structure defining the bore 12 in
the earth formation. As the casing is cemented, a plug of cement is
formed at the bottom of the casing and, subsequent to setting of
the cement, the plug will be drilled out and a bore 18 will be
drilled or otherwise formed through the oil sand B and slightly
into the water sand C below the level of the oil/water interface
10. A perforated element 20, typically referred to as a screen, may
then be inserted through the casing 14 to a position within the
bore 18 with the lower perforations of the screen substantially at
the oil/water interface. If desired, the lower portion of the
casing 14 may be provided with an internal landing flange 22
cooperating with an external flanged portion 24 formed on the
screen 20 for supporting the screen in proper position relative to
the casing. A packer 26 may be interposed between the screen and
casing to retain the screen in position relative to the casing and
to establish a sealed relationship between the screen and the
casing.
As shown in FIG. 4, an injection well 28 and a plurality of
production wells 30 are drilled in the earth to the oil bearing
formation or oil sand B and each of the wells may have a casing and
screen structure essentially as depicted in FIG. 1. The injection
well 28, however, will be suitably connected to a generating
facility 32 capable of generating the compressed gaseous medium
that is to be employed in order to both heat and pressurize the oil
bearing earth formation and cause migration of the oil away from
the injection well 28 toward the production wells 30.
At this point it should be understood that the crude oil that is
typically produced in flooding operations, where such operations be
fire flooding or steam flooding, is a viscous crude petroleum
product which, cannot be efficiently produced from the formation by
pumping because the viscous crude oil will not flow through the
formation of its own accord in order that it may be pumped by
mechanically driven pumps. It is typical for such oil bearing
formations to be under little or no formation pressure and,
therefore, the oil will not be caused to migrate by pressure toward
the reduced pressure area defined by a production well. It is
necessary, therefore, in order to produce viscous crude oil of such
nature, to heat the crude oil and thereby reduce its viscosity to a
readily flowable nature and to provide artificial formation
pressure in order that the oil contained within the formation may
be caused by such pressure to migrate toward a producton well,
where it may be produced by any number of acceptable methods. One
suitable method of developing heat and pressure necessary for
production of viscous crude oil from shallow earth formations is
typically referred to as "fire flooding." In fire flooding
operations heat in the oil bearing earth formation is created by
actual burning of some of the crude oil that is locked within the
formation and such burning, in addition to developing a formation
pressure because of the expansion of gases during the burning
operation, also produces sufficient heat to reduce the viscosity of
the crude oil to a consistency where flowing will readily occur.
Air or any other gasiform fluid medium containing a controlled
amount of oxygen to support combustion of the crude oil is injected
into the oil bearing earth formation through an injection well. The
air is injected at sufficient pressure to cause combustion of a
small amount of the crude oil that is locked in the earth
formation.
Another acceptable method of generating heat and pressure for
production of viscous crude oil is known as "steam flooding" where
superheated steam is injected into the oil bearing earth formation
through an injection well. The steam when generated may be in the
order of 400.degree.F and may be in the order of 250.degree. to
350.degree.F when entering the oil bearing earth formation and the
steam may be injected into the well at a pressure in the order of
300 psi. The steam will migrate through the oil bearing earth
formation and cause the oil entrapped therein to be reduced in
viscosity such that it migrates along with the steam to the
production wells surrounding the injection well. As the oil
migrates outwardly away from the injection well due to the
formation pressure that is developed by the steam, it is
simultaneously drawn toward the production wells due to the low
pressure condition that is developed as migrating oil and steam
enter the production wells and is pumped to the surface.
Ordinarily, fluid displacement type pumping mechanisms that are
employed to produce wells wherein heat and pressure are induced by
steam or fire flooding operations employ pumping mechanisms that
must be placed at a considerable level above the oil/water
interface that is established at the level of the screen, because
vaporization or flashing of excessive amounts of the water content
of the production fluid into steam will interfere with the pumping
operation. When the water content of the production fluid vaporizes
into steam, which vaporization is typically referred to as
"flashing," the steam vapor may establish a vapor locked condition
between the check valves of the apparatus. When this occurs,
pressure changes within the pumping mechanism merely achieve
compression of the vapor between the check valves but the check
valves will remain closed and prevent any fluid from passing
through the pumping mechanism. It is therefore considered necessary
to place the pumping mechanism sufficiently above the oil/water
contact level within the well that a hydrostatic head of fluid
within the well will prevent flashing of the water content of the
oil into steam.
The present invention, however, is specifically designed to utilize
flashing or vaporization of the water content of the oil into steam
for the purpose of providing a motive force that causes a flowing
condition to exist within the pumping mechanism. In accordance with
the present invention, one suitable fluid displacement type pumping
mechanism that utilizes vaporization of the water content of the
production fluid for assistance in production of fluid from the
well may conveniently take the form illustrated in FIG. 1 where a
well head, illustrated generally at 34, is disposed at the upper
extremity of the casing 14 and provides a physical structure for
supporting a pumping mechanism within the well. An outer conduit 36
may be removably supported by the well head 34 and may extend
downwardly through the casing to a level slightly above the upper
extremity of the screen 20. A landing nipple 38 having an
externally threaded portion 40 may be received by internal threads
42 defined within the lower extremity of the outer conduit 36. An
internal locking groove 44 may be formed in the landing nipple 38
and may receive a locking mechanism 46 of a landing adapter 48 that
may be secured in any suitable manner to the lower extremity of an
inner conduit 50 that is also removably supported adjacent the
upper extremity thereof by the outer conduit 36 and a sealed
relationship may be established between the inner and outer
conduits by means of a packing device 52.
As illustrated in detail in FIGS. 2 and 3, the landing adapter 48
may be provided with an internally threaded connector flange 54
that may receive the externally threaded portion 56 of the inner
conduit 50, thereby causing the inner conduit to support the
landing adapter and the pump mechanism carried thereby.
Again referring to FIG. 1 and also referring to FIGS. 2 and 3, an
outer pump conduit 58 may be provided having an internally threaded
upper extremity 60 that may be threadedly secured to the landing
adapter by external threads 62 formed on a reduced diameter portion
of the landing adapter. An internally threaded flange 64 may depend
from the landing adapter and may receive the externally threaded
upper extremity 66 of an inner pump conduit 68 thereby supporting
the inner pump conduit from the landing adapter.
It will be desirable to control the flow of production fluid from
the formation into the casing and into the pump mechanism and to
provide such control the present invention may incorporate a
valving mechanism essentially as depicted in FIG. 1 of the drawings
where the outer pump conduit 58 may be provided with a valve seat
and cage structure 70 at the lower extremity thereof. A valve ball
72 may be disposed within the valve cage structure and may
ordinarily rest in engagement with a circular valve seat 74 to
provide a seal that separates an outer pumping chamber 76 from the
casing. The ball 72 serves a check valve function and will be moved
upwardly from the seat 74 by pressure differential across the ball
72 in order to allow production fluid to enter into the chamber 76
from the formation. A cage 78 will prevent the ball 72 from being
completely displaced from the valve and cage assembly but will
allow production fluid to flow freely past the valve ball when such
flow is initiated.
A ball and cage assembly 80 is likewise disposed at the lower
extremity of the inner pump conduit 68 having a ball type check
valve 82 that engages a seat 84 to restrict downward flow of
production fluid and to respond to upward flow of production fluid
caused by a predetermined pressure differential to move upwardly
from its seat 84 and allow the flow of production fluid into an
inner pumping chamber 86. A cage element 88 prevents the valve ball
82 from being completely displaced from the check valve and cage
assembly 80.
The inner conduit 50 may represent an injection chamber through
which a pressurized medium is introduced into the well to cause
controlled pumping actuation. It is desirable that communication be
established between the injection chamber 90 and the outer pumping
chamber 76 and such communication may be conveniently established
by intersecting crossover passages 92 and 94 that may be formed in
the landing adapter 48.
The annulus between the outer conduit 36 and the inner conduit 50
may define a flow passage 96 that serves to conduct produced fluid
from the pumping mechanism to the well head structure where it may
be conveniently carried from the well head by means of a flow
conduit 98 to any suitable storage or handling facility. It is
desirable that the flow passage 96 be in fluid communication with
the inner pumping chamber 86 and such communication may be
conveniently established by means of intersecting crossover
passages 100 and 102, also defined within the landing adapter
48.
To provide for controlled actuation of the pumping mechanism it
will be desirable to selectively communicate the pumping mechanism
with a source S of pressurized medium such as air and to
selectively vent the injection chamber 90. Accordingly, the inner
conduit 50 may be provided with a T-connection 104 at the upper
extremity thereof, which T-connection may be connected to an
actuating fluid supply conduit 106 and a vent conduit 108.
Pressurized fluid such as air may be injected from the source S
into the injection chamber 90 defined by the inner conduit 50 under
control of an automatic valve 110 that is selectively energized by
a controller mechanism 112. The controller mechanism also actuates
an automatic vent valve 114 that serves to vent the injection
chamber 90 to the atmosphere or to any other suitable receiver for
the vented fluid from the injection chamber.
OPERATION
Steam assisted operation of the pumping mechanism may be
characterized by venting of the injection chamber 90 through the
vent conduit 108 with the valve 114 in its open condition at the
end of an operative cycle of the pumping mechanism. After the inner
and outer pumping chambers and the flow chamber have become filled
to a suitable level with production fluid entering from the
formation, which formation flow of production fluid will be
discussed hereinbelow a pumping cycle will be initiated by the
controller 112 which causes closure of the vent valve 114 and
simultaneously opens the injection valve 110 thereby causing
pressurized medium to flow from the source S to the conduit 106 and
into the injection chamber 90 defined by the inner conduit 50. When
steam assisted pumping operation is employed, the injected fluid
will be air or any other suitable gas which will be at a much lower
temperature than the temperature of the superheated steam present
in the pumping mechanism and within the chamber 90.
As the low temperature medium is injected into the chamber 90 it
condenses the steam vapors that are present in the injection
chamber and the water, so condensed, descends to the level of the
crossover passages 92 and 94 in the landing adapter 48, whereupon
the water will flow through the crossover passages into the outer
pumping chamber 76. When the water that has resulted from the
condensation within the chamber 90 passes through the crossover
passages into the chamber 76, an immediate pressure change occurs
due to forcing of the water through the restricted passages 92 and
94 and due to the much larger dimension of the chamber 76. The
pressure drop occurring as the superheated water enters the outer
pump chamber causes at least a portion of the water content of the
fluid to flash into steam, creating enough of an explosive effect
that causes the liquid within the outer pumping chamber to be
forced through the check valve mechanism 80 into the inner pumping
chamber 86 and simultaneously causes liquid in the inner pumping
chamber to be forced through the crossover passages 100 and 102
into the flow chamber 96.
Because the flow chamber 96 is of much larger dimension than the
dimension of the inner pumping chamber 86 and because the liquid is
forced through the restricted crossover passages 100 and 102 a
pressure drop will be developed within the chamber 96 causing a
portion of the water content of the production fluid flowing into
the chamber 96 to immediately flash into steam. The steam serves to
lighten the liquid column within the chamber 96 and cause an upward
flowing effect thereby carrying the liquid upwardly within the flow
chamber to the well head structure where it exits through the flow
conduit 98. With less than 50 pounds of flow line pressure the
fluid moves to a storage facility such as a tank battery, where it
is stored under atmospheric conditions until it is transported away
for further handling.
At this time the injection valve 110 will be closed and the vent
valve 114 will be opened thereby venting the injection chamber 90
through the conduit 108 to the atmosphere or to any other suitable
receiver for the vented gaseous medium. When this occurs the outer
pumping chamber 76 will also be communicated to the atmosphere
through the crossover passages 92 and 94 and the inner conduit 50.
As such venting decreases the pressure condition within the outer
pumping chamber below the pressure of the liquid disposed in the
annulus between the screen and the outer pump conduit 58. When this
occurs the pressure differential across the contact area between
the valve ball 72 and the valve seat 74 will cause the ball to move
upwardly thereby communicating the screen chamber with the outer
pumping chamber 76 thereby venting the screen annulus through the
outer pumping chamber, the restricted crossover passages 100 and
102 and the injection chamber 90 to the vent conduit 108. As the
pressure decreases in the screen annulus, the water content of the
fluid within the screen annulus, because of its high temperature,
in the order of 250.degree. to 350.degree.F will immediately flash
to steam, thereby creating steam pressure within the screen annulus
that forces liquid contained therein through the check valve
assembly and into the outer pumping chamber 76. In view of the fact
that steam is continuously generated while the vent valve 114 is
open, the steam in traversing the restricted crossover passages 100
and 102 will develop a back pressure within the outer pumping
chamber 76 and within the annulus between the screen and the outer
pump conduit 58. After the pressure induced by the steam has
increased to a predetermined level, the steam will begin to
condense within the screen annulus and liquid will be forced
through the check valve mechanism 70 into the outer pumping chamber
76 completing the pumping cycle. The next pumping cycle will be
initiated simply by the controller 112 which reverses the surface
valves opening the valve 110 and closing the vent valve 114 in the
manner discussed above.
Although the controller may be utilized for cyclically introducing
a pressurized cool gas into the injection chamber 90 and venting
the injection chamber to cause displacement type pumping actuation
in the manner described above, it has been determined that
displacement pumping of production fluid will occur automatically
without cyclic operation of the valves after the pumping operation
has been initiated. As long as steam is continuously introduced
into the formation through an injection well and enters the well
bore through the oil sand along with migrated crude oil, the pump
mechanism will automatically pump production fluid from the oil
bearing formation and conduct it to the flow conduit 98 as long as
a back pressure of less than b 50 psi is maintained on the flow
conduit. It has been determined that a back pressure less than 50
psi in the flow conduit will allow the pumping operation to be
automatically accomplished without cyclic operation of the valves
110 and 114 as long as the pump mechanism within the well is
disposed at a sufficient level relative to the screen to prevent a
hydrostatic head from developing above the screen to the point that
flashing of steam is prevented in the annulus between the screen
and the outer pump conduit 58. With the control valves closed
condensation will occur naturally within the injection passage 90
and the condensed fluid in the injection passage will flow through
the restricted crossover passages into the outer pump chamber where
flashing of the steam content of the liquid will occur because of
the pressure differential caused by flow across the restricted
passages and the flashing will force liquid within the outer
pumping chamber into the inner pumping chamber and through the
restricted crossover passages 100 and 102 into the flow chamber 96.
Flashing of steam will occur in the flow chamber because of the
pressure differential existing across the restricted passages 100
and 102 thereby causing the liquid column within the flow passage
to be lightened and forced upwardly where it is produced through
the flow conduit.
In order for the pumping actuation to occur automatically without
cycling of the valves, it is necessary that the water content of
the production fluid be quite high. It is therefore desirable to
place the lower extremity of the pump mechanism as close as
conveniently possible to the oil water contact level within the
well and such can be accomplished in accordance with the present
invention by placing the lower extremity of the pumping mechanism
within the screen as shown in FIG. 1. It is also necessary in order
for pumping actuation to be conducted automatically that back
pressure on the flow conduit and flow chamber be as low as
conveniently possible. It has been determined that back pressure
should be below 50 psi in order to achieve automatic operation of
the pumping mechanism without cycling of the valves.
It has also been determined that displacement pumping will occur
when the valves are cycled and yet when no pressurized gaseous
medium is introduced into the injection chamber 96 but only after
injection induced cycling has occurred for a particular period of
time. Flashing of the steam as it is forced in the form of high
temperature water through the restricted crossover passages in the
landing adapter will occur automatically and will induce
pressurized fluid movement within the pumping mechanism to produce
an oil water mixture in the flow conduit even though cycling of the
valves by the controller does not induce injection of a pressurized
gaseous medium into the injection chamber 90.
Referring now to FIG. 5 there is disclosed a modified embodiment of
the well head structure wherein a well head illustrated generally
at 116 includes conduits 118 and 120 that extend from the casing
and are controlled respectively by valves 122 and 124. An outer
conduit 126 may be supported by the well head and may extend into
the well casing in similar manner as illustrated in FIG. 1. An
inner conduit 128 may be supported by the outer conduit 126 and may
extend downwardly into the outer conduit in the same manner as
shown in FIG. 1 with a sealed relationship between the inner and
outer conduits being established by means of a stuffing box 130. An
injection conduit 132 controlled by an injection valve 134 may
control introduction of pressurized gaseous medium from a source S'
similar to the source S illustrated in FIG. 1. An exhaust conduit
136 controlled by an exhaust valve 138 may also be disposed in
communication with the conduit 128 in order to exhaust an injection
chamber in similar manner as discussed above in connection with
FIG. 1.
A flow conduit 140 may extend from the outer conduit 126 and may be
controlled by means of a flow valve 142 to conduit produced fluid
to a suitable storage facility. The flow conduit 140 may
communicate with the conduit 120 and may further be provided with a
pressure gauge 146 in order to monitor the pressure of the flow
conduit.
A controller 148 may be provided for control of the automatic
valves 134 and 138 in the manner discussed above in connection with
FIG. 1 in order to cause pressure induced cycling of the pumping
mechanism or to cause cycling of the valves as appropriate in order
to achieve automatic actuation of the pumping mechanism. The
pumping mechanism of the well structure set forth in FIG. 5 will
function in identical manner to that illustrated in FIG. 1.
In view of the foregoing it is clearly apparent that I have
provided a novel displacement type pumping mechanism that provides
the capability of fluid pressure induced or automatic fluid
displacement pumping of a production fluid from an oil bearing
earth formation. It is apparent that the present invention is one
well adapted to attain all of the objects hereinabove set forth
together with other advantages which will become obvious and
inherent from a description of the apparatus itself. It will be
understood that certain combinations and subcombinations are of
utility and may be employed without reference to other features and
subcombinations. As many possible embodiments may be made of the
invention without departing from the spirit or scope thereof, it is
to be understood that all matters herein set forth or shown in the
accompanying drawings are to be interpreted as illustrative and not
in a limiting sense.
* * * * *