Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
PROVISIONAL PATENT APPLICATION
TITLE
Gravitational Displacement Apparatus (GDA)
ABSTRACT
This invention relates to the Oil & Gas industry and can be used to remediate
gas
migration behind the casing, sustained casing pressure and surface casing vent
flow on
any type of oil and gas well. GDA is a device that uses gravitational force to
apply the
"lube and bleed" method to gradually fill micro channels in cement sheath
between inner
and outer casings with heavy fluid, and displace hydrocarbon gas and other
lightweight
fluid as it migrates downward.
BACKGROUND
Field of the Invention:
This invention relates to the Oil & Gas industry and can be used to remediate
gas
migration behind the casing, sustained casing pressure and surface casing vent
flow on oil
and gas (petroleum) wells using the "lube and bleed" remediation method. The
apparatus
creates a simple, low cost and low maintenance solution compared to what is
currently
being used in the industry.
Description of the Related Art:
The existing application of the "lube and bleed" method in the industry
typically requires
frequent use (daily, weekly etc) of pumping equipment at the well site, in
order to inject
small amounts of fluid into the annulus of a well. Not only is this method
time
consuming, labor intensive and costly, it also can be difficult to perform on
wells in
remote locations and wells with limited access.
There are other systems on the market that attempt to remediate these issues.
For
example, Casing Annulus Remediation System (CARS), US patent US 6186239 Bl
(U.S.
Pat. No. 5,927,405). CARS is a system for remediation of casing pressure by
pumping
heavy brine between casing strings. The system uses a hose, which is inserted
between
the casings through a casing spool outlet to required depth, then heavy brine
is pumped to
displace lighter fluid with heavy one. This system is not very practical and
not widely
used in the industry due to its limitations, which include difficulty
inserting the hose into
the very narrow space between casings. Additionally, for wells with the casing
cemented
to surface, it would be impossible to insert the hose using the CARS method.
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FIELD OF THE INVENTION
This invention relates in general to well remediation systems
in the oil and gas industry, and in particular to the
apparatus and methods used for filling an annulus in a well
with high density brine, or other similar media, to control or
eliminate sustained casing pressure.
BACKGROUND
Sustained casing pressure (SC?) and surface casing vent flow
(SCVF) is exhibited by many wells and is a large-scale problem
in the oil and gas industry worldwide. It presents safety
hazards, regulatory concerns and environmental impacts. A
failure to manage casing annulus pressures may result in well
blowouts or other events that may cause significant damage to
property, the environment, and personnel.
In the petroleum industry, oil and gas wells have multiple
casings of different sizes that are suspended from a wellhead.
SOP is often caused by persistent gas and liquid migration
through the leaking cement sheath in a well's casing annuli,
but can also be caused due to, but not limited to, leaks in
casing wellhead seals or poor primary cement job.
In some jurisdictions, wells are operated with a surface
casing vent in the open position. A well that has a leak or
exhibits SOP, may also exhibit surface casing vent flow (SCVF)
if the fluid or gas entering the annulus is allowed to escape
through the surface casing vent and released into the
atmosphere, causing environmental damage.
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To control the annular pressure, the "bleed-and-lube" method
is often used in the industry. This typically involves rigging
up to a well and pumping high-density fluid, typically brine,
into the annulus through one vent at the upper end of the
well, then bleeding off lighter fluid and gas using a second
well valve, which gets displaced when heavy brine migrates
downward. This technique is time consuming, expensive, and may
not get the pressure under control if incorrectly administered
by a field engineer or a service company.
DESCRIPTION OF RELATED ART
Another method of SCP remediation utilizes a CARS unit (Casing
Annulus Remediation System, VS61E36239E1), which pumps high-
density fluid into the annulus using a pressurized tube
through an access port in the wellhead. However, in addition
to multiple steps and equipment required, this system is
relatively impractical because the delivery tube typically
encounters various obstacles, making it difficult to insert
deep into the annulus. Further, if the casing itself is
cemented to the surface, the tube cannot be inserted to the
annulus at all, limiting its use.
Other SCP remediation methods focus on the composition of
high-density fluids by adding various additives to prevent the
fluid from dissipating or mixing with the lighter density
fluid.
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BRIEF SUMMARY OF THE INVENTION
This apparatus and method addresses the ongoing industry need
for an effective, cost efficient and low maintenance
remediation process to manage SCP and SCVF within an annulus.
This apparazus, placed on the ground slightly above the well
with equipped support stands, attaches to two well valves
using standard industry piping and connectors. Once the
pressure vessel is filled with high-density brine or other
similar media, the equipped needle valve is opened, allowing
pressure to equalize between the well annulus and the vessel.
The brine will then start to drip feed into the casing annulus
by gravitation, without the need for a pump. The drip rate can
be adjusted by the needle valve. As the brine slowly migrates
downward, it displaces lighter fluids and gases, which rise up
the annulus column and eventually through the second valve
back into the vessel, to be bled off upon refill with more
high density brine.
In the preferred method, the high-density brine is drip fed
into the casing annulus using the equipped needle valve with
sight. By decreasing the flow, the brine is allowed to slowly
absorb and migrate downwards without dispersing out of the
second valve. This method allows for the use of any type of
high-density brine, without the need for any specific type of
formulation.
The pressure vessel can be of any shape (ex. sphere, cylinder,
cube) and any size. The size of the vessel would determine the
amount of brine it can store, thereby requiring fewer refills
and/or faster drip rate. The apparatus may further optionally
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have a digital fluid level sensor with wireless connection to
notify an operator when a refill is required.
These and other features of the present invention are more
fully set forth in the detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawing illustrates an example of the
apparatus, in the shape of a cylinder, coupled to a wellhead
assembly.
DETAILED DESCRIPTION
The apparatus and method of the present invention will now be
described more fully hereinafter with reference to the
accompanying drawings in which some, but not all, embodiments
of the invention are shown. Indeed, various embodiments of the
invention may be embodied in many different forms and should
not be construed as limited to the embodiments set forth
herein; rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully
convey the scope of the invention to those skilled in the art.
Like numbers refer to like elements throughout. For the
convenience in referring to the accompanying figures,
directional terms are used for reference and illustration
only. For example, the directional terms such as "upper",
"lower", "above", "below", and the like are being used to
illustrate a relational location.
Referring to the accompanying drawing, the pressure vessel in
the shape of a cylinder 2 is placed on the ground next to a
well 4 with the equipped support stands 1, such that it sits
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slightly higher than the wellhead valves 5 and 6. Using
standard industry piping and fittings 3, the cylinder connects
to a well through two outlet wellhead valves, into one of
which the higher density fluid is injected 5 and from the
other 6 where the lower density fluid and gasses are returned
back into the cylinder through displacement, to be bled and
withdrawn upon refill. The cylinder has a minimum of two
connections, one lower 7, from which the higher density fluid
flows through the piping 3 and into the wellhead valve 5, and
one higher 8, into which lower density fluid and gasses are
returned back into the cylinder from the second wellhead valve
6.
The larger the cylinder, the greater the volume of brine it
can store, which allows for less frequent refills and bleed
offs.
Once filled with high-density brine or other similar media
through fill valve 9, the equipped needle valve with sight 10
is opened and adjusted to allow the brine to drip feed into
the casing annulus by gravitation through the well valve 5.
The rate of drip feed is can be adjusted depending on the type
of well and its immediate requirements.
As the brine slowly migrates downward and deep into the casing
annulus, it fills up micro channels and cracks along the way,
displacing lighter fluids and gases. By raising the density
and hydrostatic pressure in the fluid column, the casing
annulus pressure is brought under control or into regulatory
compliance. The displaced lower density gasses and fluids rise
to the top of the wellhead, then exit from the second well
valve 6 and back into the cylinder through the higher
connection 8. Once in the cylinder, the lighter density fluid
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will be bled off upon refilling wiLh more high-density brine.
Using a lower bleed valve 11 at the lower connection on the
cylinder, the lower density fluid is drained. Once the bleed
process is complete, the cylinder is refilled with high-
density brine using the fill valve 9. A fluid level indicator
12 is used to visually determine when the cylinder needs to be
refilled. Optionally, the fluid indicator can be digital with
information transmission capability. The apparatus also
includes industry standard pressure gauge 13 and an optional
flow indicator 14, which can measure and record volume of
fluid injected.
It should be noted that a well may have more than two wellhead
valves, depending on the number of casings a well contains.
Therefore the apparatus should be connected to the valves
where SPC is exhibited.
Generally it should be appreciated by one of skill in the art
that many industry standard high-density fluids could be used
with this apparatus, therefore not limited to any specific
formulation. These fluids are generally comprised of liquid
brine, including halide brines, formate brines, and acetate
brines and may include additional additives and modifiers to
meet specific needs and requirements.
This invention has significant advantages to current systems
and methods. Once initially set up on site next to a well, the
remediation process can be continual and consistent without
the need for periodic manual 'bleed-and-lube' process from a
field operator, thereby reducing cost, time and without
production interruption. Depending on size, the apparatus is
relatively mobile and can be placed on any well site,
including wells in remote locations and can be left on site as
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long as needed. Additionally, the apparatus can be placed on
non-producing abandoned wells, which typically get overlooked
because of high costs involved in the traditional process,
thereby reducing environmental impact and meeting regulatory
requirements at minimal cost, with the added benefit of
powerless operation due to gravity.
It is to be understood that the subject of the present
disclosure is intended to demonstrate a preferred embodiment
of the invention and is not limited to the exact details of
construction, operation, exact materials, or embodiments shown
and described, as modifications and equivalents will be
apparent to those skilled in the art. As such, the techniques
disclosed in the description represent techniques discovered
by the inventors to function well in the practice of the
invention, and thus can be considered to constitute preferred
modes for its practice. However, those of skill in the art
should, in light of the present disclosure, appreciate that
many changes can be made in the specific embodiments which are
disclosed and still obtain a like or similar result without
departing from the scope of the invention. For example, in an
alternative embodiment, a pump can be used to assist the
injection of high-density fluid into the well valve, without
needing the apparatus to be lifted higher such that the fluid
will flow due to gravity alone. Accordingly, the subject
disclosure is therefore to be limited only by the scope set
out in the following claims.
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