Note: Descriptions are shown in the official language in which they were submitted.
CA 02654848 2009-06-25
MODULAR WELLPAD CONSTRUCTION SYSTEM
FIELD OF THE INVENTION
This invention relates to a system for extracting oil from an underground
source of bitumen using steam-assisted gravity drainage (SAGD). In particular,
the
present invention provides a modular wellpad system for servicing and
supporting
injection and extraction wells. The system is intended to be installed as a
plurality
of interconnectable modules on site to minimize field labour requirements.
BACKGROUND OF THE INVENTION
Oil sands, also referred to as tar sands or bituminous sands, are a
combination of solids (generally mineral components such as clay, silt and
sand),
water, and bitumen. Although the term "sand" is commonly used to refer to the
mineral components of the mixture, it is well known that this term is meant to
include various other components such as clay and silts. Technically speaking,
the
bitumen is neither oil nor tar, but a semisolid form of oil which will not
flow toward
producing wells under normal conditions.
Oils sands are found in a number of large deposits around the world, such as
the Athabasca Tar Sands in Alberta, Canada. If the deposits are close enough
to the
surface, the oil sands are preferably mined using open pit mining techniques
to
extract the bitumen which is processed further at specialized refineries. If
the
deposits are too deep underground for open pit mining, the oil must be
recovered by
in situ techniques such as steam-assisted gravity drainage (SAGD). The SAGD
process involves using horizontal wells to inject steam and/or other solvents
into the
deposit to heat the oil sand thereby lowering the viscosity of the bitumen.
Hot
bitumen and condensed steam migrate towards horizontal production wells which
bring the bitumen to the surface. Most of the sand is left in place.
Production in the
form of mixed condensed water and bitumen can be recovered to the surface by
natural or artificial lift. In natural lift, stream pressure is the motive
force. Various
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forms of artificial lift may be employed. In gas lift, a gas (usually natural
gas) is
injected into the production stream to lift the column of fluid. In mechanical
lift,
pumps are installed in the production string to transport production to the
surface.
The SAGD process described above employs a great deal of equipment
including piping, valves and instrumentation to control and monitor the steam
injection and bitumen extraction. A collection of steam injection and
extraction
wells, arranged in well pairs, with associated SAGD process equipment
positioned at
the surface above a site of an underground oil sand deposit is generally
termed a
wellpad.
The SAGD process also requires a great deal of water to generate steam for
injection into the ground at the injection wells. This water is generally
processed at a
central plant to produce steam for delivery to the wellpad. The bitumen
produced at
the extraction wells requires transport from the wellpad to the central plant
for
collection, further processing to remove water, and eventual delivery to an
upgrader
plant to convert the bitumen into petroleum products. The handling of steam
and
production at the wellpad requires insulated piping, pumps, control valves and
monitoring equipment at the wellpad.
According to current practice, the wellpad equipment necessary for
transporting steam and heated bitumen between the central plant and the well
pairs is
assembled at the wellpad site. This involves moving the unassembled equipment
to
the wellpad, organizing and arranging the equipment and making connections
between the various components. This approach adds significant costs to the
construction of a new wellpad as labour for performing the field work is
expensive.
Work in the field must often be performed under less than ideal site
conditions
outside.
I
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SUMMARY OF THE INVENTION
In an aspect of the present invention, to address the foregoing issues with
current SAGD wellpad construction, there is provided a modular wellpad
assembly
Accordingly, the present invention provides a modular wellpad assembly for
a wellpad site comprising:
at least one injection wellhead for application of an injection fluid under
pressure into an area adjacent the site;
at least one extraction wellhead for receiving an extracted product from the
area; and
manifold means releasably connectable to the at least one injection wellhead
for communication with a source of fluid under pressure and releasably
connectable
to the at least one extraction wellhead for communication with a processing
facility;
the manifold means comprising at least one wellhead control module joined
in a side-by-side configuration to at least one piping module, the at least
one
wellhead control module being connectable between the at least one injection
and
extraction wellheads and the at least one piping module, and at the at least
one
piping module being connectable to the source of fluid under pressure and to
the
processing facility.
In a further aspect of the present invention, there is provided a modular
wellpad assembly comprising:
a wellpad site;
a source of fluid under pressure;
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at least one injection wellhead for application of an injection fluid under
pressure into an area adjacent the site;
at least one extraction wellhead for receiving an extracted product from the
area;
manifold means releasably connectable to the at least one injection wellhead
for communication with a source of fluid under pressure and releasably
connectable
to the at least one extraction wellhead for communication with a processing
facility;
the manifold means comprising at least one wellhead control module joined
in a side-by-side configuration to at least one piping module, the at least
one
wellhead control module being connectable between the at least one injection
and
extraction wellheads and the at least one piping module, and at the at least
one
piping module being connectable to the source of fluid under pressure and to
the
processing facility.
In a still further aspect of the present invention, there is provided a
modular
wellpad component for communicating a wellpad site to a processing facility,
the
wellpad site having at least one injection wellhead for application of an
injection
fluid under pressure into an area adjacent the site and at least one
extraction
wellhead for receiving an extracted product from the area, and the processing
facility
having a source of injection fluid, the modular wellpad component comprising:
at least one wellhead control module joined in a side-by-side configuration to
a piping module, the at least one wellhead control module being connectable
between the at least one injection wellhead and the piping module for
communication with the source of fluid and between the at least one extraction
wellhead and the piping module for communication with the processing facility,
with at least one piping module being connectable to the source of fluid under
pressure and to the processing facility;
1
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whereby the wellhead control modules serve to connect the wellheads with
the piping module and the piping module serves to connect the establish
communication between the wellheads, the source of injection fluid and the
processing facility.
The present invention also provides a wellpad assembly for a wellpad site
comprising:
at least one injection wellhead for application of an injection fluid under
pressure into an area adjacent the site;
at least one extraction wellhead for receiving an extracted product from the
area, the at least one extraction wellhead and the at least one injection
wellhead
forming at least one wellhead pair;
a wellhead control module releasably connectable to each wellhead pair; and
at least one piping module releasably connectable to the wellhead control
module via a control module connection region to allow the piping module to
communicate the wellhead control module with a source of fluid under pressure
and
a processing facility for the extracted product.
In a further aspect, the present invention provides a modular wellpad system
for communicating a wellpad site to a processing facility, the wellpad site
having at
least one injection wellhead for application of an injection fluid under
pressure into
an area adjacent the site and at least one extraction wellhead for receiving
an
extracted product from the area, with injection and extraction wellheads being
paired
to define a wellhead pair, and the processing facility having a source of
injection
fluid, the modular wellpad system comprising:
a wellhead control module releasably connectable to each wellhead pair;
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at least one piping module releasably connectable to the wellhead control
module at
a control module connection region to allow the piping module to communicate
the
wellhead control module with the source of fluid under pressure and the
processing
facility.
In most arrangements at a typical wellpad site, there will be a plurality of
piping modules connected to each other via piping module connection regions to
define a pipe line for the transport of fluid under pressure and a pipe line
for
extracted product. There will also be a plurality of wellhead control modules
with
each wellhead control module servicing a wellhead pair and being connected to
a
particular piping module via the control module connection region for that
piping
module. In a preferred arrangement, each piping module includes two control
module connection regions for connection to two well head control modules. In
another preferred configuration, the wellhead control modules extend outwardly
from the piping module to which they are connected at approximately right
angles.
The wellpad assembly and system provide a safer and more effective way to
install equipment on a wellpad site. Modules are constructed offsite and
transported
to the site as needed where connections between modules and wellheads can be
made. This serves to minimize field construction and labour costs.
Use of modules also permits ready relocation of equipment at the end of a
wellpads' production lifespan. Just as the modules are efficiently assembled
at a
wellpad, they can also be efficiently dismantled when the well site is
depleted and
abandoned. The modules are recycled by moving to a new site or being
incorporated
into a different, existing wellpad.
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BRIEF DESCRIPTION OF THE DRAWINGS
Aspects of the present invention are illustrated, merely by way of example, in
the accompanying drawings in which:
Figure 1 is an overall schematic plan view of an exemplary SAGD operation
with a central processing plant and associated wellpads;
Figure 2 is a schematic plan view of a wellpad employing the modules
according to an embodiment of the invention;
Figure 3 is a detail cross-section view taken through the wellpad;
Figure 4 is a perspective view of the wellpad of Figure 2 showing the layout
of the modules;
Figure 5 is a cross-sectional schematic view taken through the wellpad along
line 5-5 of Figure 2; and
Figure 6 is a plan view of an exemplary wellhead control module and
represents a detail view of the indicated region of Figure 4;
Figure 7 is a perspective view of an exemplary wellhead control module and
represents a detail view of the indicated region of Figure 4;
Figure 8 is a plan view of an exemplary arrangement of wellhead control
modules and piping modules and represents a detail view of the indicated
region of
Figure 4; and
Figure 9 is a detail perspective view of wellhead control modules and the
piping modules of Figure 8.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 1, there is shown a schematic plan view of a typical
SAGD operation site layout. A central processing plant 2 provides steam
generation
and water processing and bitumen processing facilities at a location above a
known
buried oil sand deposit 4 shown in dashed lines. Plant 2 also serves as a
distribution
hub for electrical power which is brought to the plant via powerline 5. A main
access road 7 provides worker access. Positioned about the central processing
plant
2 are a plurality of wellpads 6. Wellpads 6 are located as necessary to access
zones
of the buried oil sand deposit 4. Each pad 6 is connected to the central
processing
plant 2 by a steam line 8, a bitumen product line 9, and a power line 10. A
pad
access road (not shown) extends from the plant to each wellpad to facilitate
movement of equipment to and from the wellpads.
At each wellpad 6, wellheads 12 are installed to inject steam into the deposit
and extract bitumen from the site according to the SAGD process. Each pad has
at
least one injection wellhead for application of steam into the site and at
least one
extraction wellhead for receiving bitumen from the area. Injection wellheads
and
extraction wellheads are grouped in pairs 12. The number and positioning of
the
wellhead pairs 12 will depend on geology of the deposit in the vicinity of the
wellpad. The bitumen product extracted from the deposit via the extraction
wellhead is a mixture of water, bitumen and gas which is delivered by pumping
back
to central plant 2 via bitumen product line 9. At central plant 2, the bitumen
product is processed to remove water and gas and stored, and/or pumped to an
upgrader facility (not shown) via plant pipeline 14 for conversion into
petroleum
products.
Figure 2 is a detail schematic view of an exemplary wellpad 6 employing the
module system described above. Figure 4 is perspective view of the pad
comprising
a drilling area 20, an equipment area 22, and retention ditches 24 within the
drilling
area 20. Figure 3 shows a typical cross-section through the wellpad 6 in which
the
original grade 26 of the site is generally levelled by using fill 28 overlaid
with a clay
-
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layer 30 and a gravel layer 32. Fill 28 is preferably distributed atop a
geotextile layer
29. Retention ditches 24 are formed about the periphery of the wellpad in the
clay
layer adjacent berms 34 defining the edge of the pad. The pad surface 36 is
preferably developed with a constant high point elevation down the centre of
the pad
under the equipment sloping to the ditches at each side. Ditches 34 are
provided to
collect surface runoff from the equipment area 22. In an alternative
arrangement,
instead of ditches 34, the pad may be formed with a pond adjacent a side to
retain
runoff.
Returning to Figures 2 and 4, wellpad 6 is the site for a plurality of paired
wellheads 40a and 40b. Each pair of wellheads comprises an injection wellhead
40a
for injecting steam under pressure into the subterranean oil sand deposit over
which
the wellpad is built, and an extraction wellhead 40b for receiving production
in the
form of bitumen, water and gas which has migrated toward the extraction well.
The
spacing and positioning of the wellheads is determined by the geology of the
oil sand
deposit.
As shown schematically in Figure 2, each pair of wellheads 40a and 40b is
connected to steam line 8, and bitumen product line 9 via manifold means in
the
form of a plurality of modular manifold units. In the illustrated arrangement,
the
manifold portions include a plurality of wellhead control modules 42 and a
plurality
of piping modules 44. Wellhead control modules 42 extend from pairs of
wellheads
40a,40b for connection to a piping module 44 at a control module connection
region
43 in a side-by-side configuration. In one preferred arrangement, each module
is
design to a unilevel plan for the sake of simplicity. It will be appreciated
the
modules may also be designed according to a layout that includes multiple
levels.
Piping modules 44 in turn are connected to each other at piping module
connection regions 45 to form a "pipeline corridor" that communicates with
steam
line 8 and bitumen product line 9 from the central plant such that the
wellhead
control modules 42 and the piping modules 44 co-operate to communicate the
wellheads to the central plant.
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Each type of module 42 or 44 is preferably a standard unit for ease of
construction and interconnection between module units. Figure 5 is a cross-
section
through an exemplary pair of modules 42 and 44 taken along line 5-5 of Figure
2. In
general, wellhead control module 42 comprises an open structural steel
framework
adapted to support pipelines and valve equipment for control of the flow of
fluids
through the pipelines. Figure 5 illustrates a single level of pipes, however,
it will be
appreciated that the framework can be designed to include multiple levels for
carrying pipes at different levels. Similarly, piping module 44 comprises an
open
structural steel framework 83 adapted to support pipelines and ancillary
control
equipment for control flow through the pipelines.
In particular, a wellhead control module 42 includes valving 60 and piping
62 to carry injection fluid (steam) to the injection wellhead 40a from steam
pipeline
8 on piping module 44. Similarly, module 42 includes valving 64 and piping 66
to
deliver bitumen product from extraction wellhead 40b to pipeline 9 on the
piping
module. Conventional flexible joints 68 are used to connect the pipelines of
the
wellhead control module 42 to the wellheads 40a and 40b. In other words, as
its
name implies, the wellhead control module 42 preferably includes the
specialized
equipment in the form of piping and monitoring equipment necessary to control
and
oversee the flow of material between a pair of wellheads and the piping module
44.
The equipment is supported on a framework 69 which is supported above the
surface
36 by piles 72.
Still referring to Figure 5, piping module 44 preferably comprises an external
framework 83 that supports pipelines. Each piping module 44 is connectable to
other piping modules to define a piping corridor that includes steam pipeline
8 and
extracted product pipeline 9. Additional pipelines 80 and 82 may be provided
in
some of the piping modules 44 to transport other materials such as natural gas
from
the central facility to the wellpad 6. As well, additional pipelines 80 and 82
may be
used for production testing which involves directing the production flow from
a
particular well pair to a test separator instead of having the production flow
directly
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to product pipeline 9.
As best shown in Figure 2, each piping module 44 has ends which define
piping module connection regions 45 for connecting one piping module to
another
adjacent module to form one or more continuous pipelines. In other words, one
or
both side of each piping module 44 may include a wellhead control module
connection region 43 to allow for joining of a wellhead control module 42 to
the
piping module 44, and at the same time, one or both ends of the piping module
may
include a piping module connection region 45 to permit joining of piping
modules
one to another.
It should be emphasized that Figures 2 and 5 show the modules and their
interconnection in schematic form. By way of example, Figures 6 and 7 show
plan
and perspective views, respectively, of a wellhead control module 42 and
associated
piping and equipment. Figures 6 and 7 are detail views of the regions
indicated on
Figure 4. For ease of access for workers, stairs 75 and a walkway 76 are
provided
with piping 62, 66 and valve stations being located on either side of the
walkway to
facilitate access to equipment for inspection and maintenance. As previously
described, piping 62 carries injection fluid (steam) to the injection wellhead
40a
from steam pipeline 8, and piping 66 delivers bitumen product from extraction
wellhead 40b to pipeline 9.
In particular, Figure 6 shows a wellhead control module connection region 43
which defines a zone at the wellhead control module 42 in which piping from
the
module 42 is configured in a substantially standard arrangement to align and
mate
with similarly configured piping connections at the adjacent piping module 44.
In
the example of Figure 6, four primary connections have to be made at joints
200,
201, 202 and 203 to link control module 42 to piping module 44. These primary
connections may be field welds or some other conventional pipe joining
technique
performed by a field worker to quickly and efficiently establish connections
between
the two modules.
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Figures 8 and 9 show detailed plan and perspective views, respectively, of
wellhead control modules 42 and piping modules 44. Figure 8 is a detail view
of the
region indicated on Figure 4. In Figures 6 to 9, elements previously
identified and
described are labelled with identical reference numbers.
In particular, Figure 8 shows details of a piping module connection region 45
in which a pair of piping modules 44 are joined end to end. Region 45 defines
a
zone at a first piping module 44 in which piping from the module is configured
in a
substantially standard arrangement to align and mate with similarly configured
piping connections at the adjacent piping module 44. In the example of Figure
8,
four primary connections have to be made at joints 300, 301,302 and 303 to
link the
adjacent piping modules together. These connections may be made by a worker as
field welds or some other conventional piping joining technique.
In the illustrated embodiment, each module is typically uncovered. Heated
protective enclosures are used to house and protect instrumentation. If
required, the
pipelines may be heated, traced and insulated.
Preferably, each module is constructed offsite and shipped to the site for
assembly. The dimensions of each module are therefore limited due to handling
and
shipping constraints. For example, in the illustration embodiment, the
limiting
dimensions for each module are about 30 meters in length and about five meters
wide. In a preferred arrangement, these dimensions permit a piping module 44
to be
connected with two wellhead control modules 42 and, thus, two wellhead pairs
or
four wellheads in total.
As best shown in Figure 4, at least two adjacent piping modules 44 are fitted
with piping configured to provide a thermal expansion loop 46. By way of
example,
the dimensions of loop 46 would be approximately 10 metres by 10 metres for
24'
NPS pipeline. In general, such expansion loops are installed in the field. Due
to the
physical size of the loops, it is not currently considered economical to
design an
expansion loop into each module.
.Lr
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It is emphasized that a piping module 44 is not necessarily connected to a
wellhead control module 42. As best shown in Figure 2, a plurality of piping
modules 44 may be connected end to end at adjacent piping module connection
regions 45 to form pipeline sections 51 which do not connect directly to a
wellhead
control module 42. When two pipeline sections 51 join to define a turn as at
53 in
Figure 2, the pipeline module connection region 45 of a first pipeline module
44' is
preferably joined to the connection region 43 of a second pipeline module 44"
to
ensure a straight forward connection that is readily created by a worker in
the field.
In regard to design and construction of the modules, the more repetitive and
similar the modules are to each other, the less engineering design is required
and
improved fabricating efficiencies are achieved. Preferably, where possible,
identical
modules would allow prefabrication to be completed for numerous wellpads for
use
and reuse, as required. In particular, ensuring that module connection zones
43 and
45 are standardized to as great an extent as possible may still allow non-
identical
modules to be interconnected in the field with minimal work. Due to different
well
layouts and the requirement for expansion loops, it is recognized that it is
not
generally possible to make all modules identical. To some extent, each module
will
be partially tailored for its particular location. In a preferred arrangement,
the
wellhead 40a,40b layout at the wellpad is set up as a consistent pattern of
injection
wellhead and extraction wellhead to make repetitive interconnections of
identical
modules possible. Similarly, as long as equipment in the module connection
zones
43 and 45 is laid out in a standard configuration despite the layout of the
equipment
on the associated module, adjacent wellhead control modules 42 and piping
modules
44 may be joined together with minimal work in the field.
Although the present invention has been described in some detail by way of
example for purposes of clarity and understanding, it will be apparent that
certain
changes and modifications may be practised within the scope of the appended
claims.
