Wells – Processes – Placing fluid into the formation
Reexamination Certificate
2000-06-30
2003-05-27
Neuder, William (Department: 3672)
Wells
Processes
Placing fluid into the formation
C417S410100
Reexamination Certificate
active
06568475
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an isolation container for use with a downhole electric pump and the method of its application. The downhole electric pump is of the type used in the oil and gas industry. Such pumps usually are used for pumping oil and gas production to the surface when naturally occurring formation pressure is insufficient to raise the oil and gas to the surface. However, downhole electric pumps are also used in a downhole environment to increase the pressure of pressurized and un-pressurized fluids supplied from the surface. In these instances, the pressurized fluid is injected into the adjacent oil and gas bearing formation to treat or “fracture” the formation. In other applications, a downhole electric pump pressurizes fluid for injection into a formation to urge oil in the area of the wellbore in the direction of another nearby well where the oil is more easily produced. In these operations, any number of wells may be used to “chase” the underground oil to the collecting well.
FIG. 1
is a sectional view of a prior art configuration utilizing a downhole electric pump assembly to inject high pressure fluid into a formation. The prior art configuration of
FIG. 1
has a surface platform
10
(shown schematically) extending above ocean surface
12
. Production riser
14
extends downwardly to hydraulically actuated connector
16
which is sealingly connected to wellhead housing
18
in a manner well known to those of ordinary skill in the art. Casing
20
extends from wellhead housing
18
to subsurface formation
22
and is cemented in place in ocean floor
24
. Production tubing
26
extends from surface platform
10
through wellhead housing
18
to downhole packer
28
positioned in casing
20
. Extension nipple
30
and coupling
32
connect production tubing
26
to downhole electric pump assembly
34
. Lower extension nipple
36
extends from downhole electric pump assembly
34
through lower downhole packer
38
to that area of the wellbore adjacent subsurface formation
22
. Downhole electric pump assembly
34
includes electric motor
40
, motor seal section
41
and downhole electric pump
42
. Electrical cable
44
extends from the surface to electric motor
40
in a manner well known to those of ordinary skill in the art.
A typical sequence of operation has fluid
46
supplied from surface platform
10
through production tubing
26
to downhole electric pump assembly
34
where it is taken into the pump assembly through intake ports
35
. Thereafter, downhole electric pump assembly
34
increases the pressure of fluid
46
and then discharges it through lower extension nipple
36
into subsurface formation
22
. In this manner, pressurized fluid
46
may be used to cause fracturing of the subsurface formation
22
to increase production capacity or it can be used to urge oil to another area of a field for collection at another well.
There are problems associated with prior art electric pumps used in a wellbore. As is visible in the apparatus of
FIG. 1
, the fluid for injection into the formation
22
must first be deposited in an annular area between the pump intake ports
35
and the well casing wall
20
, subjecting the well casing
20
to any fluid used in the injection operation. Fluids used in these operations are often corrosive. For example, a fracturing operation can utilize additives like surfactants and acidizing fluids. In cases where water is injected into a formation, the water itself, especially sea water, can be corrosive. In those cases where the pressure of a fluid is increased at the well surface and then boosted by the downhole pump, the casing wall is subjected to the pressure of the fluid. Continued exposure of casing wall to the effects of corrosive and high pressure fluids can lead to a collapse of the casing well and ultimate exposure of the wellbore to the surrounding elements.
2. Background of the Related Art
U.S. Pat. No. 5,203,682 to B. A. Inklebarger shows a submersible pump assembly mounted in a container for use at the surface for pressurizing fluid.
The modular pump shown in U.S. Pat. No. 5,626,467 to G. A. Cantey discloses a fluid driven by an air motor.
U.S. Pat. No. 5,799,834 to D. D. Small et al. shows an adjustable length column pipe for connecting a submersible electric pump in a fuel storage tank to dispenser units.
SUMMARY OF THE INVENTION
The isolation container of the present invention is designed for use with a downhole electric pump or other electrical pump commonly used in oil and gas drilling and production operations. The isolation container includes an annular vessel with an axial inlet and outlet bore. A downhole electric pump is centrally located within the isolation container. The downhole electric pump includes an electric motor positioned above and coupled to a motor seal section, which is then coupled to a centrifugal pump, thereby providing a means of powering the pump. A blind coupling is positioned above the electric motor with a tubular member connected thereto and extending through the inlet of the isolation container. The tubular member connects to a tubing string supplying fluid from the surface. The blind coupling has a plurality of radially disposed ports to allow fluid from the surface to flow into the annulus between the downhole electric pump and the isolation container. This fluid then flows to inlet ports on the downhole electric pump. The pressure of the fluid is increased or boosted by the operation of the downhole electric pump and the fluid is discharged through a tubular member, which is sealed in the outlet bore of the isolation container. The tubular member extends through a packer positioned below the isolation container and the pressurized fluid is injected into the desired subsurface formation or zone for fracturing or for displacing oil towards an adjacent formation. An electrical cable from the surface supplies power to the electric motor and a check valve may be provided on the upper end of the isolation container for releasing entrained air in the isolation container. The container effectively isolates the casing well of the well from the harmful effects of the fluid pumped by the pump.
A second embodiment using the isolation container of the present invention is disclosed. This embodiment uses the isolation container with an downhole electric pump commonly used in oil and gas drilling and production operations to inject a treatment fluid into a subsurface formation. The isolation container has the same construction as in the first embodiment. The tubing string above the isolation container has a remotely operable valve, such as by wireline, disposed in its bore. The tubing string extends above the isolation container typically is 200 to 500 feet in length and is filled with the fluid to be used in the operation. The top of tubing string is capped and electrical cable or “E” line as it referred to in the industry is attached to the cap. The “E” line is of the type commonly deployed from a wireline truck and typically is ¾″ in diameter. The wireline truck is used to lower the tubing string and isolation container into position. As in the first embodiment, a blind coupling is positioned above the electric motor with a tubular member connected thereto and extending through the inlet of the isolation container. The blind coupling has a plurality of radially disposed ports to allow the fluid from the tubing string to flow into the annulus between the downhole electric pump and the isolation container when the tubing string valve is opened. The fluid then flows to inlet ports on the downhole electric pump. The pressure of the fluid is then increased or boosted by the operation of the downhole electric pump. The fluid is then discharged through a tubular member, which is sealed in the outlet bore of the isolation container. The tubular member extends through a packer positioned below the isolation container and the boosted pressure fluid is injected into the desired subsurface formation or zone for acidizing.
Grubb William A.
Haugen David M.
Hoffman Corey E.
Moser, Patterson & Sheridan L.L.P.
Neuder William
Stephenson Daniel P
Weatherford / Lamb, Inc.
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