Note: Descriptions are shown in the official language in which they were submitted.
CA 02280323 1999-08-13
1
APPLICATION FOR PATENT
YPF SOCIEDAD ANONIMA
TITLE: ASSEMBLY AND METHOD FOR THE EXTRACTION
OF FLUIDS FROM A DRILLED WELL WITHIN A
GEOLOGICAL FORMATION
SPECIFICATION
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority fi~om Argentinian Patent Application No. P 98
Ol 04089, filed August 19, 1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to an apparatus and method to extract through
pumping, an eft~uent produced by a drilled well within a geological foimati~n.
Preferably, it pertains to the extraction of hydrocarbons. Specifically, the
assembly
and method comprises the use of continuous coiled tubing capable of transpol-
ting
effluents to the surface through its interior.
2. Description of the Related Art
Although the demand for liquid hydrocarbons and gas increases, crude oil
prices are declining. The reduced prices bring about the need to develop new
techniques and methods of artificial lift, and new devices or equipment that
reduce the
I 5 initial investment on a new well, and reduce the lifting cost in new, or
even old wells.
Typically, a well is drilled once an underground oil and gas formation or
formations are detected. The typical diameter of the drilled hole is about 12-
1/4" in
the first 300 feet of borehole, and about 8-1/2" to total depth or T.D.
Once the borehole is drilled to total depth, the borehole is cased fiom the
surface to the bottom with either 5-1/2" or 7" steel pipe or casing. The
casing is
cemented in place by displacing cement through the annular space between the
external wall of the casing and the wall of the borehole. Cementing the casing
1
0530s3.U00O IP 98221 vl
CA 02280323 1999-08-13
2
provides firm anchorage of the casing to the borehole and seals the annular
space
along the entire length of the borehole with the displaced volume of cement.
After the casing has been cemented, the casing is perforated. The perforations
are made in the casing at selected elevations or locations according to the
nature of
the reservoir or reservoirs. The perforations are holes that extend through
both the
casing wall and the cement sheath in the annular space and allow the free flow
of
production fluids to the well bore.
In some regions, the pressure of the reservoir, via natural gas, is sufficient
to
allow the natural lift of the produced fluids to the surface. Such wells are
typically
identified as "flowing wells." However, reservoirs are, in general, of low
pressure,
making necessary the use of artificial lift techniques to convey fluids from
the well to
the surface.
A conventional artificial lift technique comprises a subsurface pump, also
called a "rod pump," placed at the bottom of the well. The rod pump is
mechanically
l5 activated by a string of rods known as "sucker rods" connected on the
surface to a
walking beam pumping unit. The rod pump and string of sucker rods are deployed
or
run inside a string of production tubing within the casing. The pumped fluids
are
conveyed to the surface through the annulw space defined by the bore of the
production tubing and the string of sucker rods. In conventional wells such as
the one
described, the production tubing is either 2-7/8" or 3-1/2" outside diameter
("OD")
and the length of the production tubing string extends from the surface or
wellhead to
near the bottom of the well.
Among other limitations stated below, sucker rods are subjected to wear due
to frictional contact with the wall of the production tubing. The sucker rod
wear
increases in deviated, slant or crooked holes. Sucker rods in general are
subject to
mechanical failures either on the rod itself or in the threaded connections
joining the
individual sections of sucker rods. The various sucker rod failures can result
in
frequent replacement of the sucker rods. Occasionally, the subsurface pump
which
needs to be retrieved to the surface for repair. Additionally, the production
tubing
also requires, from time to time, to be replaced due to mechanical wear or
leaking
connections.
2
Oi~y53.Ofu:ni IP 4R2=1 vl
CA 02280323 1999-08-13
3
In the above cases where there has been a failure in the sucker rod string,
the
subsurface pump, or the production tubing, it is typically necessary to move a
rig,
commonly referred to as a workover rig or pulling unit, onto the well to pull
out of the
hole the worn or damaged items for replacement or repair. Typically, workover
rigs
or pulling units include a dewick provided with working pulleys, a cable drum
and
drawworks to allow running in or pulling out of the hole the pipe or rods. To
keep the
cost of service as low as possible, rig up and rig down procedures, as well as
going in
and out of the hole, needs to be done efficiently and economically. Operations
efficiency will also depend on the costs involved to move such rig or rigs
from well
location to well location, as well as the time involved in making or breaking
tubing or
sucker rod connections.
Various patents have attempted to reduce the costs involved in well
operations. Patent AR 230316 discloses a sucker rod made of fiberglass, whose
weight is considerably less, thus requiting less energy for its operation.
Patent AR
234862 also discloses the replacement of steel sucker rods by fiberglass rods.
U.S. Patent 5,667,369 to Cholet discloses the replacement of sucker rods with
continuous coiled tubing to move the rotor of a progressive cavity pump ("PCP
pump") by connecting the bottom end of the continuous coiled tubing to the
rotor of
the PCP pump. In this case, the rotor of the PCP pump turns by rotating the
coiled
tubing from the surface. Continuous tubing or coiled tubing weighs less and is
easier
to handle than sucker rods, although the use of a production tubing string is
still
necessary in Cholet.
U.S. Patent 4,476,923 to Walling describes a coiled, composite tubing that
allows the effluents to be conducted through its interior. The coiled,
composite tubing
supports an electric activated downhole pump. Electricity is conveyed from the
surface to the downhole electric motor through conductors that extend along
and
through sheaths of the composite tubing. Thus, the composite tubing comprises
a
complex succession of sheaths wrapped in different materials able to provide
the
required strength to the composite tubing.
It is desirable to have an assembly and method to pump an effluent produced
by a drilled well in a geological formation without the use of typical
production
3
n5_~i;3.non0 IP 9S._t vt
CA 02280323 1999-08-13
4
tubing and sucker rods. It is further desirable to provide a lighter
production string
that can be run in the hole and easily retrieved without the need of a
derrick,
substructure and drawworks.
SUMMARY OF THE INVENTION
The present invention provides an assembly and method to pump an effluent
produced by a drilled well in a geological fol~nation without the use of
typical
production tubing and sucker rods.
The assembly and method of the present invention includes a continuous tube
or coiled tubing connected to a subsurface pump. The continuous tube seines
dual
puyoses. The continuous tube serves as a reciprocating pumping sting and also
as a
conduit to raise and convey, simultaneously, effluents from the bottom of the
hole to
the surface. The continuous tube seines as the production string and
eliminates the
conventional production string. The coiled tubing production string is lighter
in
weight than a conventional production suing. The coiled tubing production
string can
be mm in the hole and easily retrieved by coiling it around a reel or drum,
without the
need of a den-ick, substructure and drawworks. The reel or drum can be mounted
on a
trailer and easily u~anspouted from well to well.
The present invention is cost effective in that it provides an assembly and
method to produce hydrocarbons from a well by replacing sucker rods,
production
tubing and their corresponding couplings. This allows for the reduction of
cost, both
in steel, as well as in operating procedures such as making and breaking
connections.
The assembly and method of the present invention also allows the evident
advantages due to the possibility to drill and produce from wells with smaller
internal
diameters than conventional wells. The present invention allows drilling with
small
diameter drill bits and casing the hole with small diameter pipe, thus
involving less
drilling costs, expendables and materials.
The present invention also provides an assembly and method of pumping from
slanted or crooked holes. The present invention is adapted for producing from
a low
volume producer oil well.
4
r~s2r~;3 ~~or.~ cr yszn m
CA 02280323 1999-08-13
The present invention includes an assembly to pump fluids produced by a
drilled well within a geological formation having a borehole wall fixed by
casing.
The assembly includes a subsurface pump, commonly refem-ed to as a rod pump.
The
subsurface pump includes one steady or stationary barrel member and one mobile
5 plunger member. A retl-ievable pump anchor fixes the rod pump to the casing
of the
well at a detemnined depth. A hollow continuous tube, commonly described as
coiled
tubing, extends within the well bore from the surface down to the lower
portion of the
well bore. The bottom end of the continuous tube is connected to the mobile
plunger
member of the rod pump. The connection between the continuous tube and the
mobile plunger member is of a single direct path type allowing fluid flow from
within
the pump body to the hollow continuous tube. Preferably, the continuous tube
is
coiled tubing that can be coiled and uncoiled from a reel located on the
surface. A
hollow polished rod has a bottom end coupled to a fi~ee top end of the
continuous
hollow tubing. The hollow polished rod is connected to means to operate the
continuous hollow rod according to a selected movement, preferably
reciprocating
axial movement. The pumped fluids are recovered on the surface fivom the
hollow
polished rod and continuous tube.
The present invention also comprises a method for pumping fluids produced
by a drilled well within a geological formation having a borehole wall secured
by a
steel casing which is perforated at selected levels. The method comprises the
steps of
connecting a retuevable pump anchor to a stationary barrel member of a
subsurface
pump. A mobile plunger member of the subsurface pump is connected to a free
bottom end of a continuous hollow tube. The connection is of the type that
communicates the inside of the plunger member and pump bai-~~el with the
inside of
the continuous hollow tube. The continuous hollow tube is uncoiled and nun
into the
cased borehole until reaching a predetermined depth. The continuous hollow
tube is
cut on the surface. Anchoring devices of the retrievable pump anchor are set
to secure
the pump anchor to the well casing. The bottom end of a hollow polished rod is
connected to the top end of the continuous hollow tube. At least one packing
element
is installed in the surface casing or wellhead to seal the annulus between the
casing
and the hollow polished rod. The hollow polished rod is operated according to
a
5
0~2053.(ui0f IP 95221 vl
CA 02280323 1999-08-13
6
selected reciprocating axial movement to recover the fluid that ascends
through the
bore of the continuous hollow tube. The recovered production fluid is sent to
a
production manifold through a flexible hose.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to more fully understand the drawings refel-~~ed to in the detailed
description of the present invention, a brief description of each drawing is
presented,
in which:
Figure 1 is a simplified diagram of an assembly according to the present
invention having a subsurface pump or rod pump;
Figure 2 is a detail of the hollow, polished rod and flexible hose arrangement
of the fluid recovery means on the sul-face; and
Figure 3 is a simplified diagram of the installation method of the pumping
assembly.
DETAILED DESCRIPTION OF INVENTION
The present invention will now be described in greater detail with specific
reference to the drawings. Figure 1 shows a well made in a geological
formation that
produces hydrocarbon-containing effluents. The well borehole H is covered by a
casing or pipe 1. Preferably, the casing 1 is fixed or anchored to the
borehole H with
cement (not shown) inj ected in the annular space (not shown) existing between
the
external surface of the casing 1 and the borehole H. As discussed in the
background
of the invention, the cement and casing is perforated in areas at selected
depths and
locations so as to allow the free flow of fluids from the reservoir or
reservoirs into the
well casing 1. Figure 1 illustrates three pay zones Zl, Z2, and Z3 at
different depths.
This is just an example of "multilayer" formations in a well.
Referring to Figure I, the illustrated pumping apparatus P includes a
subsurface pump 4 having a retrievable pump anchor 2 connected through an
adapter
to a lower portion of the subsurface pump 4. The subsurface pump 4 illustrated
in
Figure 1 is of a reciprocating or alternative movement type, and includes a
standing
valve 7, a steady or stationary barrel member 8, a mobile plunger member 9
which
6
ns=os;.onrN~ tl' vs:at vt
CA 02280323 1999-08-13
7
lodges a second or traveling valve 10, and a hollow pull rod 11. A suitable
pump for
the exemplified device is the "hollow rod type" pump available fi~om Harbison-
Fisher.
The retrievable pump anchor 2 includes one or more anchoring devices 3
having sets of slips which enable the setting of the pump anchor 2 of the
pumping
apparatus P to the well casing 1. The anchoring devices 3 of the retrievable
pump
anchor 2 are set inside the casing 1 at a location near the bottom of the
well. An
opening 5 at the bottom end of the retrievable pump anchor 2 allows the flow
of fluids
to the suction chamber of the subsurface pump 4, as indicated by the an-ow in
Figure
1.
It is to be understood that the anchoring devices 3 are of the type that will
allow the free flow of fluids from the annular space 1 a between the outer
wall surface
of the stationary barrel member 8 of the subsurface pump 4 and the inner wall
surface
of the well casing 1 to the opening 5. Stated another way, the anchoring
devices 3
allow the free flow of fluids from above to below the anchoring devices 3, or
vice
versa. A useful anchor for this type of service is the 2-7/8" or 3-1/2"
retrievable
pump anchor provided by Harbison-Fisher or similar, without the packing
element.
Refen-ing to Figure 1, the mobile plunger member 9 includes the traveling
valve 10 at its lower end and the hollow pull rod 11 connected at its upper
end.
Pumped fluid travels upwardly through the inside 6 of the mobile plunger
member 6
of the subsurface pump 4. The upper end of the hollow pull rod 11 of the pump
pl anger member 6 is connected to a continuous hollow tube 12, preferably
coiled
tubing. The connection 13 is preferably the type of "roll on" connector with
the
addition of an outer liner to avoid further deformation. Furtheumore, the
connector
allows the free flow of fluids from the inside 6 of the pump bore to the bore
of the
continuous hollow tube or coiled tubing 12.
The continuous hollow tube or coiled tubing 12 extends towaavd the upper part
of the well or the wellhead W at the surface, typically the ground surface.
The upper
end of the coiled tubing 12 is coupled to a hollow rod 14, typically a hollow
polished
rod, by an appropriate connector 15. The hollow polished rod 14 has a bore
which
allows the flow of fluids. The hollow polished rod 14 is suspended through a
crosshead 16 so as to be operated by a "pumping unit" (not shown) that impacts
an
7
~ 5=0>3.«(.if~1 IY JS?~t v1
CA 02280323 1999-08-13
8
alternative or reciprocating axial movement to the hollow polished rod 14, the
coiled
tubing 12, the hollow pull rod I 1 and the mobile plunger member 9.
As shown in Figures 1 and 2, the upper end of the hollow polished rod 14 is
coupled with an appropriate coupler 20, preferably a "quick hydraulic
connector," to a
flexible hose 21. The flexible hose 21 conveys the produced fluids to a
production
manifold 24 and follows the movement of the hollow polished rod 14 in its
reciprocating up and down motion.
At the wellhead W, the casing 1 is extended and connected to a reduction
member 17. The reduction member 17 is provided with packing elements 18 around
the hollow polished rod 14.
Refea-ing to Figure 1, the hydrocarbon fluids, gases, etc. that may
spontmeously flow through the annulus between the continuous hollow tube or
coiled
tubing 12 and the well casing 1 are released through a lateral port 19
provided with
valves. Typically, gas fi-om hydrocaa~bons is released due to a reduction in
bottom
l5 hole pressure. In other instances, the well may accumulate sufficient
internal energy
such that gas or oil will flow freely. In these cases, the fluids or gas ai-e
released
through the port 19.
Figure 2 shows the prefen-ed assembly of the hollow polished rod 14 and the
flexible hose 21 in greater detail. Preferably, the hollow polished rod 14 is
connected
to the flexible hose 21 through the quick hydraulic connector 20, an inverted
"U"
shaped tubing 22, and a second coupler 23, preferably a quick hydraulic
connector.
The flexible hose 21 is then connected and delivers fluids to the production
manifold
24. The production manifold 24 is connected to a flow line to transport the
produced
fl uids.
The continuous hollow tube or coiled tubing 12 according to the preferred
embodiment of the present invention is preferably made of metal plate,
preferably
steel. U.S. Patent 4,863,991 to Dubois describes a method and apparatus to
make a
long continuous tubes. It is to be understood that this type of coiled tubing
12 is
provided coiled over a drum 37 on a reel 36 as shown in Figw-e 3.
Preferably, the continuous hollow tube used presents an outer diameter
between 1" and 2" inches with different grades and wall thicknesses as
required by
8
O5.Ii53.Ori0n IP 98231 vl
CA 02280323 1999-08-13
9
well pumping conditions. A prefen-ed suitable size is a coiled tubing having a
1-1/2"
OD and a wall thickness of 0.134".
The installation method for the pumping assembly according to the present
invention will now be described with reference to Figure 3. Figure 3 shows a
drilled
well borehole H secured with the casing 1. Preferably, a reel 36 having a drum
37 of
coiled tubing or continuous hollow tube 12 is transpouted on a vehicle to the
well
location, close to the cased borehole H.
At the ground surface, a pump anchor 2 is coupled to the lower end of a
subsurface pump 4. The free bottom end of the continuous hollow tubing 12 is
L O connected to the hollow pull rod 11 of the subsurface pump 4. The
continuous hollow
tube 12 is then uncoiled, in a continuous motion from the drum 37 and is run
into the
cased borehole H through adequate guide means (not shown).
Eventually, and particularly in the case of slant or crooked holes,
centralizers
(not shown) Ca,l1 be attached to the continuous hollow tubing 12 at
predetermined
lengths and spacing.
Once a predetermined depth is reached with the continuous hollow tube 12
and its bottom pumping apparatus P, the uncoiling action is interrupted and
the
continuous hollow tube 12 is cut. The top end of the hollow tube 12 is held in
place at
the surface by means of retrievable slips (not shown). The retrievable pump
anchor 2
is set in position in the casing 1 following the manufacturer's setting
procedures.
Referring to Figure l, a hollow polished rod 14 is then connected to the free
end of the continuous hollow tube 12 and at least one packing element 18 is
installed
between the hollow polished rod 14 and the wellhead W or the casing annulus.
The hollow polished rod 14 is suspended through a crosshead 16 so as to be
operated by a "pumping unit" (not shown) that imparts an alternative or
reciprocating
axial movement to the hollow polished rod 14, the coiled tubing 12, the hollow
pull
rod l 1 and the mobile plunger member 9.
As shown in Figure 2, the hollow polished rod 14 is preferably connected to
the flexible hose 21 through the quick hydraulic connector 20, the inverted
"U"
shaped tubing 22, and the quick hydraulic connector 23. The flexible hose 21
is then
9
fn=0;3fuy(,y IP 9231 v1
CA 02280323 1999-08-13
connected and delivers fluids to the production manifold 24 which is connected
to a
flow line to transpoa the produced fluids.
The described assembly allows the production fluids to pass up through the
opening 5 in the pump anchor 2, through the pump plunger 9, the hollow pull
rod 1 l,
5 the coiled tubing 12, the hollow polished rod 14, the flexible hose assembly
21, into
the production manifold 24 and the flowline.
The pumping assembly and pumping method of the present invention provides
an efficient lifting method in oil wells ranging between 2,000 and 4,500 feet
deep to
pump approximately 180 barrels of fluid per day. Additionally, it has been
found that
10 the pumping assembly and pumping method of the present invention provides
an
efficient artificial lift method in oil wells of up to approximately 6,000
feet deep with
an average production of approximately 350 ba~-~-els per day.
It is to be understood fi-om the above description of the present invention
that
the present invention replaces the conventional production tubing and the
string of
l5 sucker rods by a continuous hollow tube that performs both functions
simultaneously.
The continuous hollow tube results in weight savings, time and cost savings,
and the
elimination of numerous joint connections in conventional production tubing
and
sucker rods. The continuous hollow tube provides the operating axis of the
pump as
opposed to the string of sucker rods and also provides the conduit for
bringing the
produced fluids to the surface as opposed to the conventional production
tubing.
The novel and original design of the present invention also allows for the
drilling of new wells having a considerably smaller diameter borehole H than
conventional wells which are usually in the range of approximately 8-1/2". A
well
borehole of approximately 6-1/8" diameter or even less is deemed appropriate
for the
present invention.
Likewise, the diameter of the casing 1 can also be reduced when drilling a new
well in accordance with the present invention. The casing diameter used in
conventional wells is typically between 5-1/2" and 7" OD, while in the present
invention can be approximately 3-1/2" or less depending on well conditions.
The present invention has great significance and application. Bearing in mind
that more than 50% of the new wells drilled throughout the world do not exceed
n;~n53.nnpp IY 98.1 v1
CA 02280323 1999-08-13
11
depths of more than 5,000 feet, the cost reduction obtained though the use of
the
present invention becomes evident to those skilled in the ant.
The foregoing disclosure and description of the invention we illustrative and
explanatory thereof, and various changes in the details of the illustrated
apparatus and
construction and method of operation may be made without departing from the
spirit
of the invention.
11
n5=os;.oo~x~ Ir vsa_t ~t
