Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR SAMPLING HIGH VISCOSITY
FORMATION FLUIDS
BACKGROUND
2. Field of this disclosure
[0002] This invention relates broadly to oilfield exploration. More
particularly, this
invention relates to apparatus and methods for expediting the downhole
sampling of
formation hydrocarbons via formation modification.
3. State of the Art
[0003] One technique utilized in exploring a subsurface formation is to obtain
samples of formation fluid downhole. Tools such as the MDT and the CHDT (both
trademarks of Schlumberger) tools are extremely useful in obtaining and
analyzing such
samples.
[0004] * The MDT tool or other sampling tools typically include a fluid entry
port or
tubular probe cooperatively arranged within one or more wall-engaging packers
for
isolating the port or probe from the borehole fluids, one or more sample
chambers which
are coupled to the fluid entry by a flow line having one or more control
valves arranged
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therein, means for controlling a pressure drop between the formation pressure
and sample
chamber pressure, and sensors for obtaining information relating to the
fluids. Examples
of sampling tools may be found in U.S. Patent #3,104,712 to Whitten, U.S.
Patent
#3,859,851 to Urbanosky, and U.S. Patent #4,860,581 to Zimmerman et at.
The sensors may include
pressure transducers for monitoring fluid pressure and temperature. In
addition, optical
sensors may be supplied by an OFA, CFA or LFA (all trademarks of Schlumberger)
module in order to determine the phase, the chemical composition, etc, of the
fluid being
admitted into the tool.
[0005] The use of the CHDT tool is similar in various aspects to the use of
the MDT
tool, but mostly in cased boreholes. The CHDT tool includes a mechanism for
perforating the casing with a drilling mechanism (see, e.g., "Formation
Testing and
Sampling through Casing", Oilfield Review, Spring 2002)
and for plugging the casing after testing. The CHDT
tool may alternatively be used in open hole, for example with modifications as
shown in
U.S. Patent Application Pub. No. 2005/0279499 or U.S. Patent Application Pub.
No.
2006/0000606, both assigned to the same assignee of the present invention.
[0006] The MDT and CHDT tools in their normal applications are used to obtain
formation oil samples with a low viscosity; typically up to 30 cP. In certain
circumstances, oils with a higher viscosity have been sampled, but the
sampling process
often requires several adaptations and can take many hours. It is believed
that the
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maximum viscosity of an oil that has been sampled using an MDT or CHDT tool is
approximately 3200 cP.
[0007] It will be appreciated by those skilled in the art that exploitation of
more
viscous hydrocarbons is becoming increasingly important due to the depletion
of
conventional low viscosity hydrocarbon reserves. Sampling viscous oils for
reservoir
characterization is very challenging as oils with a higher viscosity have a
low mobility.
Thus, depending on the local circumstances, viscous oils are very difficult to
pump out of
the formation. In fact, the low mobility of these oils often results in very
long sampling
times or makes it impossible to retrieve a representative sample, for example,
because of
the formation of emulsions. In some cases, the low mobility of these oils even
makes it
impossible to retrieve a sample. In addition, if sampling times are too long
there is an
increased probability that the tool will get stuck in the borehole.
[0008] Tools and techniques have been proposed for sampling heavy oils and
bitumen, for example as shown in International Application Publication No.
W02007/04899 1, assigned to the same assignee as the present invention.
[0009] While straddle packers mounted on the sampling tool above and below a
sampling port, or large diameter packer can improve the flow of oil into the
sampling
tool, there is still a need for sampling tools and sampling methods that can
be used,
amongst other things, for sampling viscous hydrocarbons.
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SUMMARY
[0010] It is therefore an object of this disclosure to provide tools and
methods
which expedite the sampling of formation hydrocarbons, and particularly,
although not
exclusively, the sampling of high viscosity hydrocarbons.
[0011] According to one aspect, there is provided a method of obtaining a
fluid
sample from an underground formation traversed by a borehole, the method
comprising: lowering a tool into the borehole, the tool including at least one
perforation mechanism disposed through a sidewall of the tool, and at least
one port
fluidly connected to a sample container; creating a first hole through a
borehole wall
into the formation with the at least one perforation mechanism; increasing a
mobility
of formation fluid, wherein the formation fluid is disposed between the
borehole wall
and the first hole, wherein increasing the mobility includes engaging at least
one of a
packer and a pad against the borehole wall and activating a heating element
disposed in the at least one of the packer and the pad; and obtaining the
fluid sample
from the formation, wherein at least one of increasing and obtaining is
performed
utilizing the first hole.
[0011a] In one embodiment, the method further comprises mixing at least two
fluids downhole.
[0011b] In one embodiment, the method further comprises creating a second
hole through the borehole wall into the formation and increasing the mobility
of
formation fluid includes increasing the mobility of the formation fluid
between the first
and the second hole.
[0012] According to another aspect, there is provided an apparatus for
obtaining a sample of formation fluid from a hydrocarbon reservoir traversed
by a
borehole, the apparatus comprising: at least a first perforation mechanism
disposed
on a sidewall of a downhole tool, for creating a first hole through a borehole
wall into
the formation; at least one packer or pad for engaging the borehole wall;
means
positioned within the at least one packer or pad for heating a portion of the
formation
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for enhancing the mobility of formation fluid located adjacent the first hole,
when the
means for heating is activated; and at least one sampling port disposed on a
sidewall
of the downhole tool, the sampling port being fluidly connected to a sampling
container disposed in the downhole tool.
According to another aspect, there is provided a method of obtaining a
fluid sample from an underground formation traversed by a borehole,
comprising:
lowering a tool into the borehole, the tool including at least one perforation
mechanism disposed through a sidewall of the tool, and at least one port
fluidly
connected to a sample container; creating a first hole through a borehole wall
into the
formation with the at least one perforation mechanism; increasing a mobility
of
formation fluid disposed between the borehole wall and the first hole by
generating
electromagnetic radiation, wherein the electromagnetic radiation spectrum
comprises
a frequency coincident with an absorption frequency of the formation fluid, an
injected
fluid, or connate water; and obtaining a sample of fluid from the formation,
wherein at
least one of increasing and obtaining is performed utilizing the first hole.
According to another aspect, there is provided a method of obtaining a
fluid sample from an underground formation traversed by a borehole, the method
comprising: lowering a tool into the borehole, the tool including at least one
perforation mechanism disposed through a sidewall of the tool, a sampling port
fluidly
connected to a sample container, and an injection port; creating a first hole
through a
borehole wall into the formation with the at least one perforation mechanism;
creating
a second hole in the formation using one of the at least one perforation
mechanism
and a second perforation mechanism; injecting fluid through the injection port
into the
first hole from a tank located on the surface; and obtaining the fluid sample
from the
formation from the second hole through the sampling port; wherein the
injection fluid
is at least one of air and oxygen for creating an in-situ combustion so as to
increase a
mobility of the formation fluid.
According to another aspect, there is provided a system for obtaining a
sample of formation fluid from a hydrocarbon reservoir traversed by a
borehole,
4a
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system comprising: at least one perforation mechanism disposed on a sidewall
of a
downhole tool, for creating a first hole through a borehole wall into the
formation; an
injection port disposed on a sidewall of the downhole tool; the injection port
being
adapted to inject fluid into the formation for enhancing the mobility of
formation fluid
located adjacent the first hole; and a sampling port disposed on a sidewall of
the
downhole tool, the sampling port being fluidly connected to a container
disposed in
the downhole tool; wherein one of the at least one perforation mechanism and a
second perforation mechanism creates a second hole in the borehole; wherein
the
injection port injects fluid into the first hole and the sampling port samples
the
formation fluid from the second hole; wherein the injection port is fluidly
connected to
a tank located on the surface; and wherein the injection fluid is at least one
of air and
oxygen for creating an in-situ combustion.
4b
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[0013] Additional objects and advantages of this disclosure will become
apparent to
those skilled in the art upon reference to the detailed description taken in
conjunction
with the provided figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic representation of a system deployed via a wire
line in a
wellbore and coupled to surface equipment;
[0015] FIG. 2 is a schematic illustration of a sampling tool having formation
drilling
means, shown deployed downhole and ready to be used;
[0016] FIG. 2A is a schematic illustration of the sampling tool of Fig. 2
deployed
downhole and being used according to some of the methods of this disclosure;
[0017] FIG. 3 is a schematic illustration of an alternate sampling tool having
formation drilling means;
[0018] FIG. 4 is a schematic illustration of a packer portion of a tool, for
example the
tool of Fig. 3, having a heating element mounted on a drill shaft;
[0019] FIG. 5 is a schematic illustration of an alternate packer portion of a
tool, for
example the tool of Fig. 3, having a, flow- line in a drill shaft;
[0020] FIG. 6A is a schematic broken perspective of a packer portion of a
tool, for
example the tool of Fig. 3, having a guarded sampling packer around a drill
shaft;
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[0021] FIG. 6B is a schematic frontal view of the guarded packer of Fig. 6A;
[0022] FIG. 7 is a schematic illustration of yet another sampling tool having
formation drilling means;
[0023] FIG. 7A is a schematic illustration of additional components of the
tool of Fig.
7 and being used according to some of the methods of this disclosure;
[0024] FIG. 8A is a schematic illustration of a sampling tool capable of
enhancing the
mobility of a reservoir fluid by delivering heat from a heat source;
[0025] FIG. 8B is a schematic illustration of another sampling tool capable of
enhancing the mobility of a reservoir fluid by delivering heat from a heat
source;
[0026] FIG. 9 is a schematic illustration of a packer portion of a tool
capable of
enhancing the mobility of a reservoir fluid by delivering heat with one or
more
electrodes;
[0027] FIG. 10 is a schematic illustration of a packer portion of a tool
capable of
enhancing the mobility of a reservoir fluid by delivering heat with one or
more induction
coils; and
[0028] FIG. 11 is a schematic illustration of a packer portion of a tool
capable of
enhancing the mobility of a reservoir fluid by delivering heat with an
ultrasonic emitter.
DETAILED DESCRIPTION
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[0029] Turning now to Fig. 1, the basics of a reservoir exploration (borehole
logging)
system are shown. A borehole tool or sonde 10 is shown suspended in a borehole
14 of a
formation 11 by a cable 12, although it could be located at the end of coil
tubing, coupled
to a drill-pipe, or deployed using any other means used in the industry for
deploying
borehole tools. Cable 12 not only physically supports the borehole tool 10,
but typically,
signals are sent via the cable 12 from the borehole tool 10 to surface located
equipment
16. In addition, cable 12 is often used to provide electrical power from the
surface to the
borehole tool 10. The surface located equipment 16 may include a signal
processor, a
computer, dedicated circuitry, or the like which is well known in the art.
Typically, the
equipment/signal processor 16 takes the information sent uphole by the
borehole logging
system 10, processes the information, and generates a suitable record such as
a display
log 18 or the like. Suitably, the information may also be displayed on a
screen and
recorded on a data storage medium or the like.
[0030] Turning now to Fig. 2, a first embodiment of a tool 10 according to
this
disclosure is shown schematically inside the borehole 14 of the formation 11.
The tool
includes two packers 20, 22 which are extendable out of the tool toward the
borehole
wall 14a. Each packer 20, 22, surrounds a respective drilling means 24, 26.
Suitable
packers include packers as shown in U.S. Patent Application Pub. No.
2006/0000606.
Alternatively or additionally, inflatable straddle packers (not shown) may be
used. A
suitable drilling means may be that found in the Cased Hole Dynamics Tester
(CHDT)
tool referred to above. The drilling means each include a drill bit 24a, 26a
and a
respective drill shaft 24b, 26b. In accord with one embodiment of the
disclosure, the drill
shafts 24b, 26b are surrounded by annular fluid flow spaces 24c, 26c. The
fluid flow
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spaces 24c, 26c are coupled by flowlines 24d, 26d to respective pumps 28, 30.
The
pumps 28, 30 are coupled by respective flowlines 28a, 28b 28c, 30a, 30b, 30c
to
respective valves 32a, 32b, 32c, 34a, 34b 34c. The valves 32a, 32b are coupled
by
respective flowlines 36a, 36b to respective fluid containers 38a, 38b. The
valves 34a,
34b are coupled by respective flow lines 40a, 40b to respective fluid
containers 42a, 42b.
The valves 32c and 34c are coupled by respective flow lines 45 and 47 to the
ambient
environment (for example the borehole). An optional fluid analyzer (FA) 48a is
coupled
to the pump 30 and is capable amongst other things of monitoring a property of
the fluid
drawn at the packer 22 and exiting the pump 30. Another optional fluid
analyzer (FA)
48b is coupled to the pump 28 and is capable amongst other things of
monitoring a
property of the fluid drawn at the packer 20 and entering the pump 28. A fluid
analyzer
is capable of measuring in situ a fluid property and may comprise one or more
of a
pressure sensor, a temperature sensor, a resistivity and/or a conductivity
sensor. Optical
sensors may be supplied by an OFA, CFA or LFA as discussed above, or by a
sensor
capable of measuring the fluorescence of the fluid in the flow line.
Alternatively or
additionally, the density and/or the viscosity of the fluid in the flow line
may be measured
by one or more sensors known in the art, including sensor(s) based on acoustic
and NMR
measurement principles. One example of sensor based on acoustic is a
viscometer
including a vibrating object, and in particular the sensor described in U.S.
Patent
Application Pub. No. 2006/0137873. Note that the location of fluid analyzers
with
respect to pumps and packers may be adapted for various use of tool 10 by
using a
modular design as well known in the art, and may be placed on both side of a
pump.
Electronics 44 are preferably provided to control the valves, the pumps and
the drilling
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means, to communicate with the surface equipment (16 in Fig. 1), and/or to
analyze the
contents of the fluid containers, etc, in conjunction with the optional fluid
analyzers 48a-
b and/or other sensors (not shown).
[00311 Referring now to Fig. 2A, according to one method, the packers 20, 22
of the
tool 10 are extended out of the tool to engage the borehole wall 14a, and
preferably seal
one or more locations along the borehole wall. The drilling means 24, 26 are
activated
such that the drill bits 24a, 26a drill holes I I a, 1 l b through the
isolated locations of the
borehole wall 14a into the formation 11. When the tool 10 is so deployed, the
annular
fluid flow spaces 24c, 26c are in fluid communication with the holes i 1 a, 11
b in the
formation 11, and essentially sealed to the fluids in'the wellbore. According
to this first
method, the valves 32a, 32b are opened and the pump 28 is activated such that
the
contents of the fluid containers 38a and 38b are pumped into the fluid flow
space 24c,
through the packer 20 and into the hole 1 la. The contents of the containers
38a and 38b
may be chosen so that they react with each other exothermically as disclosed
in
commonly-owned U.S. Patent Publication No. 2068 0066 904.
The hot fluid enters the porous formation 11 and mobilizes
formation fluids in its vicinity. Pump 30 is then activated to extract
mobilized formation
fluid from the hole l lb. The fluids extracted by pump 30 may be sent through
the optical
analyzer 48a in order to determine whether they should be stored or dumped. If
they are
to be stored, one or more of valves 34a, 34b are opened and the fluid is sent
to one or
both of the containers 42a, 42b for storage. If initially or later, the fluids
being extracted
are to be dumped, valve 34c is opened. When it is desired to move the tool 10,
the drills
24, 26 are retracted into the tool, and packers 20, 22 are disengaged from the
borehole
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wall. The tool 10 may then be moved to another location in the borehole, or
brought
uphole so that the samples can be accessed and analyzed uphole.
[0032] According to an alternate embodiment, the tool 10 may be used for in-
situ
(controlled) combustion. In this alternate embodiment, at least two drilled
holes, as
shown for example by holes l la and 11 b in Fig. 2A, may be used. In a first
example, in-
situ combustion is initiated in a first hole (for example 11 a). Air, oxygen
or air together
with oxygen may be pumped, for example using pump 28, into the first hole to
sustain the
combustion process. The injection rate of air or oxygen may be varied by the
tool, for
example to control the combustion rate. In addition, steam or water may also
be pumped
in the first hole for controlling the combustion front temperature. The
combustion may
consume some of the in-situ oil and produce heat, combustion gases and water
vapor.
Alternatively, or additionally, a hydrocarbon may be mixed to and injected
with the air or
oxygen. The injected mixture may also sustain a combustion process. The ratio
of
oxygen to hydrocarbon may be controlled so that the chemical composition of
the
mixture is within the combustion boundaries.
[0033] The combustion products may reduce the viscosity of the oil and serve
to
drive the oil ahead of the combustion front. In particular, part of the
formation oil may
be driven towards a second drilled hole where it can be pumped into the tool.
For
facilitating the sampling process, the second hole (for example 11 b) may be
kept at a
lower pressure, for example using pump 30. The composition of the produced oil
may be
monitored, for example at fluid analyzer 48a, to determine when to selectively
sample the
produced stream, for example in fluid containers 42a or 42b. The combustion
products in
the hole in which the combustion was initiated may also be monitored, for
example they
CA 02599827 2007-08-30
may be sampled in the tool and analyzed at fluid analyzer 48b. The heat
generated by the
combustion may be recorded by temperature sensors to control the efficiency of
the
downhole combustion process and/or to collect fundamental reaction process
data. The
temperature sensors may be located in a flow line (part of fluid analyzer
48a), or remotely
deployed (not shown) in the formation as known in the art. The data collected
by the
sensors on the tool may be used to model or simulate large-scale in-situ
combustion
processes, as used for example in reservoir exploitation.
[0034] In a second example of in-situ initiated combustion, air/oxygen may be
injected into one first drilled hole and combustion may be initiated in one
second drilled
hole. It may be necessary to inject air/oxygen into the second hole in which
the
combustion is initiated in order to sustain the reaction for some time until
the combustion
is sustained by oxygen injected in the first drilled hole. In this method the
formation
crude oil moves from upstream of the combustion front and through the
combustion front
and burned zone towards the hole in which the combustion is initiated and, in
so doing, is
decomposed and refined into a range of heavier and light components, the
heavier
components, most likely, being left behind as a residue. In using this method,
it is
preferable to insure that there is sufficient initial permeability of the
formation to
air/oxygen so the air/oxygen may reach the reaction front and cause the
combustion front
to propagate towards the first hole in which the oxygen is being injected. The
nature of
this combustion process is, however, to enhance the permeability to injected
gas with
time. A s mentioned previously, information may be gathered to both control
the reaction
kinetics and to gather fundamental physical and property data for later use in
modeling
the physics/chemistry of the exploitation processes.
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[0035] Air, oxygen or their combination may be either pumped from surface
through
a separate conduit (not shown) to the tool or it may be generated down hole
within the
tool via a chemical, oxygen generating, process and/or reaction.
Alternatively, air or
oxygen may be stored in one of the fluid containers (for example 38a or 38b)
and
delivered to the formation. Moreover, steam or water may also be either pumped
from
surface through a separate conduit (not shown) to the tool or it may be
conveyed down
hole within the tool.
[0036] Using the same tool 10, other methods may be implemented. For example,
the container 42a may be filled with a hot fluid which optionally is generated
downhole
by heating elements (not shown) or by any technique described in U.S. Patent
Publication
No. 2008 0066 904. The hot fluid is injected into the hole 1 lb and mobilized
formation fluid can then be extracted from the hole l lb by reversing the pump
30. The
fluids extracted from the hole 1 lb may then be analyzed in the fluid analyzer
(FA) 48a
over a period of time in order to determine whether they should be stored or
dumped. For
example, fluid initially extracted from the hole 11 b may contain a
significant amount of
the hot fluid which was injected, and that fluid may either be dumped into the
borehole
via flow line 30c, valve 34c and flow line 47, or reinjected into the
formation. After a
period of time, the fluid being extracted may be substantially pure formation
fluid
(defined herein as 90% or more pure). If it is desirable to sample the
substantially pure
formation fluid, that fluid may be fed to a previously empty container, e.g.,
container 42b.
[0037] Those skilled in the art will appreciate that since injection and fluid
extraction
from only a single hole is required, that according to another embodiment of
the tool,
only a single drill bit, packer, pump, etc., is required rather than the two
shown in Figs. 2
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and 2A. In fact, even where two holes are desired, only a single drill bit,
packer, pump
etc. is required, as a first hole can be drilled, fluid injected into that
hole, the tool then
moved, and then a second hole can be drilled for sampling. It will also be
appreciated
that where a single drill bit is provided, it may still be desirable to
include two packers or
a packer and a probe, two pumps, etc. By having an additional packer or probe,
and as
described hereinafter, it is easier to sample formation fluids which are
mobilized away
from the drilled hole.
[0038] Thus, according to another method, one container of the tool 10 may
contain a
mobility enhancer, such as by way of example and not limitation a miscible
solvent such
as a halogenated or otherwise polar normally liquid hydrocarbon, and most
preferably a
chlorinated solvent in which asphaltenes dissolve, or hot water, or steam, or
carbon
dioxide. Other containers may be used to collect mobilized formation fluid
samples at
different formation locations. For example, tool 10 can be set in the borehole
and used to
drill through the borehole wall into the formation to generate hole 11 a.
Mobility
enhancer stored in container 38a can be injected into hole l la through use of
pump 28.
After a period of time, if desired, pump 28 can be reversed, and mobilized
formation fluid
can be collected via hole l la and stored in container 3 8b or dumped as
desired, for
example, based on information collected by the fluid analyzer (FA) 48b. At the
same
time, or at some other time earlier or later, a second pump 30 can be
activated if desired
in order to pull mobilized formation fluids from the formation at a second
location
removed from hole 11 a via the packer 22. Again, these fluids can be stored or
dumped as
desired. After the desired sampling is completed, tool 10 can be moved to
another
location, and one or both of pumps 28 and 30 can be activated to pull yet
additional
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formation fluids from the formation which may be have been mobilized via the
injection
of the mobility enhancer into hole 11 a.
[0039] As illustrated in Fig. 2A, in one embodiment the drilled holes are
substantially
perpendicular to the borehole wall 14a. However, as described in more detail
below with
reference to Figs. 7 and 7A, holes may be drilled obliquely relative to the
borehole wall.
According to any of the methods, the fluid for enhancing mobility can be a hot
fluid
which is made hot at the surface before lowering the tool downhole or is made
hot
downhole as needed. Alternatively, hot fluid from the surface may be fed to
the
downhole tool via tubing (not shown). A solvent or a hot solvent can also be
used to
enhance mobility. The obtained sample may be brought to the surface for
analysis and/or
it may be analyzed downhole using an optical analyzer or other tools.
[0040] While Figs. 2 and 2A have been described with fluid injection located
uphole
of fluid collection, it should be appreciated by those skilled in the art that
those locations
could be reversed. Also, while particular methods have been described for
utilizing the
tool shown in Figs. 2 and 2A, other methods could be utilized. For example,
mobility
enhancing fluids may be injected through both holes 11 a and 11 b until
sufficient mobility
is achieved to allow sampling. According to another method, only the injection
site is
drilled and the sample is taken from a porous borehole wall location.
[0041] Turning now to Fig. 3, a second embodiment of a tool 110 according to
this
disclosure is shown. The tool includes a drill bit 124 having a shaft 125. The
drill shaft
125 is preferably provided with a shaft guide 130. The drill bit 124 is driven
by a motor
132. The motor 132 and the drill shaft 125 can be extended from or retracted
into the
14
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tool with the displacement mechanism 140. Such displacement mechanism
comprises for
example a rotative motor coupled to a lead screw. The drill bit and shaft are
surrounded
by a packer 119. The packer 119 may be placed into sealing engagement with the
wellbore wall (not shown) by activating the setting pistons 150a-150b.
Alternatively, the
tool 110 may be equipped with an extendable packer mounted on a backing plate,
as
shown for example in Figs. 2 and 2A. As will be appreciated by those skilled
in the art,
formation fluids can flow through the annulus 126 between the drill shaft 125
and the
packer 119 into the tool 110. In this example, a pump 134 is used to generate
a pressure
differential between the tool and the formation. Thus, the flow of formation
fluids is
enhanced by increasing a pressure differential.
[0042] As shown in Fig. 3, the motor 132 is powered by a power supply 136
which
may also power heating elements (not shown) and the pump 134 for collecting
formation
fluid. Such a power supply may comprise, for example, a powerful chemical
source such
as a battery or a fuel cell, an alternator driven by a turbine which itself is
driven by the
flow of circulating well fluid as in the case of a drilling-type tool, etc.
Those skilled in
the art will appreciate that a power supply may not be needed if the power
requirements
can be met by the uphole equipment and conducted to the tool via, for example,
the cable
that suspends it. (See, cable 12 in Fig. 1)
[0043] While not shown in Fig. 3, tool 110 can include a plurality of drill
bits with
one or more of the bits having a heating element thereon. In addition, tool
110 can be
provided with all or some of the aspects of the embodiment of Figs. 2 and 2A,
including,
but not limited to fluid mobility enhancers, multiple pumps, containers,
valves, a fluid
analyzer (FA), etc. Moreover, tool 110 can be provided with all or some of the
aspects of
CA 02599827 2007-08-30
the hereinafter described embodiment of Figs. 4 or 5. Also, tool 110 can be
used in
conjunction with any of the methods described above with reference to Figs. 2
and 2A.
Similarly, some components of tool 110 may be used for energizing and
deploying drill
bits 24a and 26a of the tool 10 of Figs. 2 and 2A.
[0044] Fig. 4 shows in more details a probe portion of a tool 110', for
example
similar to the tool 110 of Fig. 3. A heating element 127 is provided about the
shaft 125'.
The heating element may comprise a resistive wire wound up around the shaft
125'. The
drill bit and shaft are surrounded by a packer 119' and a packer backing plate
121. The
drill bit 124' extends out of the tool 110' while drilling a hole 129 through
the mud cake
wall 14a of the borehole into the formation 11. The drill bit may be piloted
by the tool
110' using the shaft guide 130'.
[0045] According to an alternate embodiment, the heating element 127 may
comprise
an antenna or coil which emits electromagnetic radiation. It should be noted
that the
frequency of the electromagnetic radiation can vary from kHz to GHz. The
electromagnetic radiation power may be partially absorbed by the formation
hydrocarbon
fluid, connate water, or a fluid injected in the formation 11 by the tool
110'. The
frequency of the electromagnetic radiation may be selected by considering the
following
elements. The power absorption mechanism is typically dipole relaxation. Thus,
the
power absorption characteristics usually vary from fluids to fluid. The power
absorption
characteristics of a fluid are related to the complex electric permittivity of
this fluid,
which can be measured in a laboratory. The absorption maxima occur about the
frequencies corresponding to the maxima of the complex part of the
permittivity. Also, it
should be noted that the penetration of the electromagnetic wave decreases
with
16
CA 02599827 2007-08-30
increasing frequency, and that the absorption coefficient is about the
reciprocal of the
penetration depth and decreases as the frequency decreases. In some cases, the
power
absorption may be significant at frequencies coincident with an absorption
frequency of a
molecular mode of motion other than dipole relaxation.
[0046] In one example the coil is wound up around the shaft and generate
current
loops in the formation 11 that encircle the hole 129. According to another
alternate
embodiment, the heating element 127 may be replaced by an acoustic transducer
(e.g.
ultrasound) which stimulates the oil or adjacent fluid either directly or
indirectly. For
example, the ultrasonic transducer 127 may vibrate the drill bit 124' axially
and generate
acoustical waves in the formation 11. As shown in Fig. 3, the heating element
or the
acoustic transmitter 127 may be located on the shaft 125 of a drilling device.
In these
configurations, a sufficiently robust shaft, as already used in the industry,
is desirable,
even if it may not be possible to drill perpendicular to the borehole
immediately after
exiting the tool.
[0047] According to one exemplary method, the tool 110' may be used to drill a
hole
129 in the formation 11. The mobility of the oil in the vicinity of the hole
129 may be
enhanced by delivering heat, and or vibrations to the formation 11, utilizing
the element
127. For example, the heating element 127 can be activated through electrical
control of
the tool 110' and used as a mobility enhancer in order to expedite flow of
formation
fluids. As will be appreciated by those skilled in the art, formation fluids
can flow
through the annulus 126' between the drill shaft 125 and the hole 129 into the
tool 110'.
The packer 119' is preferably pressed against the formation for sealing the
annulus 126'
from fluid in the wellbore.
17
CA 02599827 2007-08-30
[0048] Fig. 5 illustrates a probe portion of a third embodiment of a tool 210
according to this disclosure. Here the tool includes a drill bit 224 having a
shaft 225 with
a fluid passage 227 that extends through the shaft 225 and out of the bit 224.
As shown
in Fig. 4, the distal end of the fluid passage 227 is angled so that it does
not extend out of
the very tip of the bit 224 so as to not weaken the bit. The drill bit and
shaft are
surrounded by a packer 219 and a packer backing plate 221. The drill bit is
used to drill a
hole 229 through the mud cake wall 14a of the borehole and into the formation
11. A
mobility enhancing fluid is injected into the formation 11 via the fluid
passage 227.
Formation fluid is withdrawn via the annular passage 226 between the shaft 225
and the
hole 229. Optionally, a compression packer 240 is provided on the shaft 225
near the bit
224 to isolate the bit from the annular passage 226.
[0049] According to one method, the probe portion of Fig. 5 may be used for
analyzing the in-situ combustion of oil contained in the formation 11. The
drill bit 224
and drill shaft 225 are used to drill a single hole 229 in the formation 11.
The flow line
227 is used for injecting oxygen or air, thus sustaining a combustion reaction
of the
formation oil. Fluids are recovered from the annulus 226. The recovered fluid
may
consist of reaction products, decomposed/cracked oil, etc. The composition of
the
recovered fluid may, however, be of great interest and can be useful to those
versed in the
art of simulating in-situ combustion. Indeed, it is believed that there is no
available
method for collecting information regarding in-situ combustion under down hole
conditions prior to field exploitation.
[0050] While not shown in Fig. 5, tool 210 can include a plurality of drill
bits with
one or more of the bits having a shaft with a fluid passage extending
therethrough. In
18
CA 02599827 2007-08-30
addition, tool 210 can be provided with all or some of the aspects of the
embodiment of
Figs. 2 and 2A, including, but not limited to fluid mobility enhancers,
multiple pumps,
containers, valves, a fluid analyzer (FA), etc. Similarly, tool 210 can be
provided with all
or some of the aspects of the hereinafter described embodiment of Fig. 3. In
addition,
tool 210 can be used in conjunction with any of the methods described above
with
reference to Figs. 2 and 2A. Moreover, the drilling means and the flow line
may be
separate elements in the tool, for example as shown in U.S. Patent Application
Pub. No.
2005/0279.
[0051] Figs. 6A and 6B illustrate a guarded packer 319'c which has a centrally
positioned drilling element 319'd which is surrounded by an annular sampling
conduit
319'e. The drill and the sampling conduit are surrounded by a compliant
isolation
element 319'f which serves to prevent hydraulic communication between the
annular
sampling conduit 319'e and the annular guard conduit 319'g, and an outer
isolation
element 319'h, both of which are shown mounted on a backing plate 319'k. A
hydraulic
circuit which can be adapted to control the guarded probe 319'c is shown in
published
U.S. Patent Application Pub. No. 2006/0042793.
[0052] The guarded packer 319'c is particularly useful in practicing some of
the
methods of the invention. For example, the guarded packer can be used for
sampling
viscous oils when the formation has been invaded by less viscous mud filtrate
(for
example water). The guarded packer 319'c has the advantage of very quickly
sampling
connate formation fluid in the sampling conduit 319'e. On the one hand, the
hole drilled
by the drill bit 319'd may bypass at least a portion of the zone of the
formation invaded
by mud filtrate. Thereby, the time required for the connate formation fluid to
break
19
CA 02599827 2007-08-30
through and reach the sampling conduit 319'e may be reduced. On the other
hand, the
guard conduit 319'g may be used to advantage for drawing mud filtrate away
from the
sampling conduit 319'e, reducing thereby the contamination by mud filtrate of
the fluid
entering the sampling conduit 319'e. Thus, the guarded packer 319'c is capable
of
obtaining pristine samples in a reduced time with respect to prior art probes,
even in
unfavorable conditions of a viscous formation fluid and a less viscous mud
filtrate.
[0053] In other methods, the guarded packer 319'c may be used for injecting
mobility
enhancer, either through the sampling conduit 319'e or through the guard
conduit 319'g.
Consecutively or simultaneously, fluid may be drawn into the tool either
through the
sampling conduit 319'e or through the guard conduit 319'g.
[0054] While shown essentially circular on Figs. 6A and 6B, the guarded packer
319'c may have any shape, for example an elongated shape in the direction of
the tool
longitudinal axis. Also, although the port of the guarded conduit 319'g is
shown fully
encircling the port of sample conduit 319'e in Figs. 6A and 6B, the guarded
conduit port
may comprise a plurality of ports partially surrounding the sample conduit
port.
[0055] Turning now to Figs. 7 and 7A, a fourth embodiment of a tool 310
includes
two drills 324a, 324b with respective drill shafts 325a, 325b coupled to
respective motors
332a, 332b which are powered by a power supply 336. The drills are arranged to
drill
two holes 329a, 329b into the formation 11 at angles oblique to the borehole
wall 14a. In
some cases, the drill shaft may be tilted or oriented by using a shaft guide.
In other cases,
a force may be preferentially applied on one side of the drill bit, as known
for well
directional drilling systems. The force may be applied in an essentially
constant direction
CA 02599827 2007-08-30
and the direction should not rotate as the drill bit rotates. The holes are
drilled in such a
way that they intersect inside the formation as shown in Fig. 7A. The tool 310
also
includes flowlines 320 and 322 which are coupled to respective containers 332,
334 via
valves (not shown). The tool 310 is preferably provided with packers 319a,
319b through
which drills 324a and 324b extend and which establish a seal so that flowlines
320 and
322 are in fluid communication with holes 329a, 329b.
[0056] According to one method of using the tool 310, a mobility enhancer is
delivered from the container 332 into the hole 329a via the flowline 320 and
the probe
324. The mobilized formation fluid then flows through hole 329b into probe 326
and
through flowline 322 to the container 334.
[0057] According to an alternate embodiment (seen in Fig. 7A), an additional
probe
327 with a packer 319c is arranged between the probes 324, 326. The probe 327
is
coupled to the container 332 via flowline 327a. In this embodiment, fluid may
be
collected at the borehole wall by the probe 327. The makeup of the fluid
collected by
probe 327 can be analyzed with a fluid analyzer (not shown) or other sensors.
The fluid
collected by probe 327 is optionally re-circulated into the container 332 via
valves (not
shown), particularly where the fluid is primarily mobility enhancing fluid. If
the fluid is
primarily formation fluid, the fluid may be forwarded via valves (not shown)
to container
334 via flow line 322a. According to another alternate embodiment, no third
probe is
utilized. However, fluid flowing into probe 326 is analyzed with a fluid
analyzer (not
shown) or other sensors. If the fluid is primarily mobility enhancing fluid,
the fluid is
optionally recirculated into the container 332 via valves (not shown) and flow
line 322a.
21
CA 02599827 2007-08-30
If the fluid is primarily formation fluid, the fluid may be forwarded via
valves (not
shown) to container 334.
[0058] According to another aspect, the tool 310 of Fig. 7A can also be
arranged such
that mobility enhancing fluid is injected into the formation using all three
probes 324,
326, and 327. The flow of fluids into and out of tool 310 can be enhanced by
the use of
pumps or pressure differentials.
[0059] According to a further aspect, the drills 324a, 324b of tool 310 can be
provided with aspects of one or more of the drills 24, 124, 124' and 224 of
Figs. 2, 3, 4
and 5. Also, tool 310 can be provided with all or some of the other aspects of
the
embodiment of Figs. 2 and 2A, including, but not limited to multiple pumps,
multiple
fluid storage containers, multiple valves, etc. In addition, tool 310 can be
used in
conjunction with any of the methods described above with reference to Figs. 2
and 2A.
[0060] Referring now to Figs. 8A and 8B, sampling tools capable of delivering
heat
for enhancing formation fluid mobility are described in further details. The
tool 800
(shown in Fig. 8A) and 800' (shown in Fig. 8B) are conveyed downhole with
wireline
cables 850 and 850' respectively. The tool 800 and the tool 800' comprise a
sampling
system. As shown, the sampling system may comprise at least extendable packers
830,
830', for establishing a fluid communication between the formation 11 and the
tools 800
and 800' respectively. Downhole pumps 832 and 832' are hydraulically coupled
to the
packers 830 and 830' respectively via flowlines 831 and 831' respectively. The
pumps
may be used to advantage for lowering the pressure in the flowlines 830 or
831' below
the formation pressure, while maintaining the pressure at the pump outlet
above the
22
CA 02599827 2007-08-30
wellbore pressure. Valves 833a, 833'a are communicatively coupled to
controllers 841,
841' respectively, and may be used for selectively dumping pumped fluid in the
wellbore
14. Similarly, valves 833b, 833'b are communicatively coupled to the
controller 841 and
841' respectively, and may be used for selectively routing pumped fluid into
fluid
containers 834 and 834' respectively. The tools 800, 800' also comprise drill
bits 810,
810' respectively, mechanically coupled to drill shafts 812, 812'
respectively. The drill
shaft 812, 812' are operated via a motor (not shown) as to drill a hole 811,
811'
respectively, in the formation 11. The motor may be powered by a downhole
battery 840,
840' or via the wireline cable 850, 850' or a combination. In these
embodiments, the
holes 811, and 811' may be used for delivering heat deeper into the formation
11, and
thus, enhancing the oil mobility in a region adjacent to sampling packers 830,
830',
expediting thereby the sampling process.
[0061] Turning now specifically to Fig. 8A, the tool 800 is configured for
delivering
heat to the formation 11 by thermal conduction. The tool 800 comprises a heat
source
820. The heat source 820 may be the wellbore fluid, a resistive heater powered
by any of
the current provided by the wireline cable 850 or the battery 840, a chemical
reactor
where an exothermic chemical reaction is conducted, or some power electronics
in the
tool 800, for example the power electronics powering the pump 832. Optionally,
the heat
flow from the heat source 820 may be controlled by using a heat pump 822,
thermally
coupled to the heat source 820 and to the drill shaft 812 via optional heat
exchangers 821.
The heat pump 822 may be communicatively coupled to the controller 841 that
controls
the heating process based on temperature measurement(s) provided by the
sensor(s) 842.
Alternatively, the measurements of sensor(s) 842 may be telemetered to the
surface via
23
CA 02599827 2007-08-30
wireline cable 850, where they can be utilized by a surface controller or a
surface
operator for monitoring and controlling the heating and/or sampling process.
In this
embodiment, the drill shaft 812 preferably comprises a portion made of a good
thermal
conductor (not separately shown), for example copper or aluminum. This thermal
conductor may further comprise a working fluid, for example water, and may
operate as a
heat pipe. Heat generated at the heat source 820 may then be delivered to the
formation
11 by following the schematic path shown by arrows 823a to 823f. The heat
delivered to
the formation increases the temperature of the oil in the formation. The
temperature
increase of the oil translates into a viscosity decrease and thus a mobility
enhancement.
The mobilized oil may be sample by probe 830 and stored in fluid container 834
and
brought to surface, for example for further analysis.
[0062] Turning now specifically to Fig. 8B, the tool 800' is configured for
delivering
heat to the formation 11 by thermal convection. The tool 800' may comprise a
downhole
heat source 820', thermally coupled to a downhole fluid 860a circulated in a
flow line
868 in the shaft 812', for example as shown in greater detail in Fig. 5. The
downhole
fluid may be water or steam, depending on its temperature and pressure. The
downhole
heat source 820' may be similar to the downhole heat source 820 shown in Fig.
8A. The
tool 800' may also comprise optional heat exchangers 821' and optional heat
pump 822'
similar to the heat exchangers 821 and the heat pump 822 shown in Fig. 8A. The
downhole fluid 860a may be stored in a downhole tank 861 a in the tool 800'.
The
downhole fluid 860a may be pressurized via a downhole pump 862a and injected
into the
formation at the hole 811'. The heat generated by the downhole source 820' is
then
transferred to the fluid 868, as schematically indicated by arrows 823'a and
823'b. The
24
CA 02599827 2007-08-30
heat is then transported by the fluid into the formation as indicated by
arrows 823'c to
823'f. Alternatively, or additionally, injection fluid may be provided from
the surface as
indicated by surface fluid 860b stored in surface tank 862b. The surface fluid
may
alternatively or additionally be pressurized by a surface pump 862b. The
surface fluid
may alternatively or additionally be heat at the surface via heater 865. The
surface fluid
is conveyed downhole via a pipe or tubing 864, in fluid communication with the
flow line
868. It should be understood that any combination of downhole fluid, surface
fluid,
downhole pump, surface pump, downhole heater and surface heater may be used to
advantage in this embodiment, and that the choice may depends on operational
conditions
such as depth of the formation, expected viscosity of the fluid to be sampled,
etc.
[0063] While Figs. 8A and 8B show heat delivered at a hole 811 or 811' in the
formation 11, and a sampling probe sealed against a porous portion of the wall
of the
wellbore 14, it should be appreciated that the heat may be delivered at the
wall of the
wellbore using a packer 830, 830' or a straddle packer (not shown), and the
formation
fluid may be sampled at a hole in the wellbore 18, using for example the
embodiment
shown in Figs. 6A and 6B. Further, it should be understood that the relative
position of
the heat delivery point and the sampling point may be reversed, i.e. the
sampling point
may be lower than the heat delivery point, for example to take advantage of
gravity
drainage. In particular, the heat delivery point and the sampling point may be
located at
the same level, for example the drill bit may be surrounded by a packer port.
In addition,
the holes drilled by the tools of Figs. 8A and 8B may be oblique, as shown
previously
with respect to Figs. 7 and 7A.
CA 02599827 2007-08-30
[0064] Referring now to Figs. 9, 10, and 11, it should be noted that in these
alternate
embodiment, the mobility enhancer is a current or a wave propagating in the
formation.
These embodiments do not require having transmitters physically introduced in
a hole
into the formation for delivering the mobility enhancer to the formation. For
example in
Fig. 9, a portion of a tool 900 is shown having, articulated pads 912a and
912b. These
pads may be placed against the formation by the tool, using known deployment
means,
such as arms 911 a and 91 lb respectively. When not used, the pads are
preferably
recessed below the outer surface of the tool, for example in apertures 91 Oa
and 91 Oa in
the tool body. As shown, the pads may include a plurality of electrodes such
as
electrodes 913a, 914a on pad 912a and electrodes 913b and 914b on pad 912b. In
one
embodiment, the electrodes on each pad may be kept at the same potential, and
a
potential difference in applied between the group of electrodes on each pad.
This
potential difference may be constant or may vary with time, and is provided by
a
electrical power source at surface or in the tool 900. Thus, current flows
between two or
more pads, at least in part in the formation. In another embodiment, a
potential
difference is applied between electrodes on a same pad. Thus, current flows
between
electrodes as desired. In both embodiments, the current may flow preferably in
the
invaded zone of the formation, especially if the mud filtrate has a better
conductivity that
the oil in the formation. In some cases, the current flow generates heat in
the formation.
The mobility enhancer is heat that is introduced into the formation by thermal
conduction
or thermal convection if fluids in the formation are displaced, for example
when injection
from the tool is also used.
26
CA 02599827 2007-08-30
[0065] The tool 900 is also provided with an extendable packer 920 for
establishing a
fluid communication between the tool and the formation. The packer may be
detachably
coupled to a backing plate 924 for facilitating the replacement thereof. The
packer 920,
made of a resilient material may comprise an internal support 925 for
preventing
deformation of the packer under pressure differential between the wellbore and
the tool.
The packer is also provided with a recess 921 and a port 922 for the flow of
wellbore
fluids in the tool when the packer is applied against the wellbore wall. The
packer is
provided with a drilling means 923, for drilling a hole in the wellbore wall.
The hole
maybe used for facilitating the injection of fluids from the tool 900 or for
drawing
formation fluid in the tool 900 and capturing a sample. In particular, fluid
may be
injected in the formation for modifying locally the resistivity of the
formation and
improving the efficiency of the heating via pads 912a and/or 912.
[0066] Although shown with electrodes, the pads 912a and 912b may
alternatively
comprise any of electromagnetic antenna(e), acoustic transmitter(s),
resistor(s) or other
element(s) for generating heat. Further, the heating pads can be configured
with one or
more inlets through which a hole is drilled into the formation. The inlet may
be in fluid
communication with the tool so that the formation fluid can be sampled. Also,
the
heating elements, or electrodes, on the pad are preferably arranged so that
the depth to
which the heat is able to penetrate into the formation is sufficient for
mobilizing a volume
of oil corresponding to the sampling requirements and are not limited to two
per pads.
Similarly, any number of pads may be used and the tool 900 is not limited to
two pads.
[0067] Turning now to Fig. 10, a packer portion of a tool capable of enhancing
the
mobility of a reservoir fluid by delivering heat with one or more induction
coils is shown
27
CA 02599827 2007-08-30
in greater details. The packer of Fig. 10 comprises a backing plate 1000
pivotally
mounted on extendable pistons 1001 and 1002 on a downhole tool (not shown).
The
backing plate 1000 supports a packer 1020 for isolating a port 1012 of the
downhole tool
from the wellbore when the packer is pushed against a wellbore wall (not
shown). The
packer may be provided with a drill shaft 1010 and a drill bit 1011 at a
distal end thereof
for drilling a hole in a formation wall. The tool is may be in fluid
communication with
the drilled hole, through the cylinder 1003 and the port 1012.
[0068] In Figure 10, a coil 1021 is shown embedded in the packer 1020 body.
The
coil may have any number of turns. The coil 1021 is driven preferably by an
alternate
current source (not shown), for example in the tool body. The driving
frequency may be
of the order of kHz, or of the order of radio frequencies. As shown on Fig.
10, the coil
may be configured to surround the drill shaft 1010 and may be used for
generating an
alternate magnetic field essentially aligned with a drilled hole (not shown)
in the
formation. Current induced by the coil may flow in the formation. In this
configuration,
the current lines typically are circles surrounding the drilled hole.
[0069] Referring now to Fig. 11, a packer portion of a tool capable of
enhancing the
mobility of a reservoir fluid by delivering heat with an ultrasonic emitter is
shown in
cross section. As described in Fig. 11, a packer 1113 is pressed against the
formation 11
for establishing a fluid communication between an inlet 1114 of a downhole
tool and the
formation. The packer 113 is supported by a backing plate 1100 extended
towards the
wellbore wall via pistons rams 1102 and 1101. The probe portion is preferably
capable
of drilling a hole 1110 in the formation 11 with a drill bit 1111 mounted at
the distal end
of a drill shaft 1112 operated by the tool.
28
CA 02599827 2007-08-30
[0070] The backing plate 1100 of Fig. 11 is further provided with ultrasonic
emitters
for generating heat in the formation. As shown in Fig. 11, two emitters
comprise
piezoelectric disks 1121a and 1121b. The disks may be polarized in their
thickness and
may be driven by the tool at or near the thickness resonance. The emitters may
further
comprise adaptation layers 1122a and 1122b respectively, for enhancing the
acoustical
coupling of the piezoelectric disks (high acoustic impedance) to the formation
(low
acoustic impedance). The adaptation layers may further be pressed against the
formation
by using spring members 1121a and 1121b, for example Belleville washer stacks.
It
should be understood that while two emitters are shown on Fig. 11, any number
of
emitter may be used instead.
[0071] There have been described and illustrated herein many embodiments of
methods and apparatus for modifying a formation in order to obtain a formation
fluid
sample. While particular embodiments have been described, it is not intended
that the
invention be limited thereto, as it is intended that the invention be as broad
in scope as the
art will allow and that the specification be read likewise.
[0072] Thus, while some embodiments have been disclosed with reference to two
drills, it will be appreciated that a tool with one drill could be used if
only one hole is to
be drilled, or if the tool is moved between first and second drilling
locations. Similarly,
while an embodiment has been shown with two drills which drill in a manner
oblique to
the formation, it will be appreciated that a single drill could be utilized
which can be
controllably angled relative to the borehole wall. In this manner, a first
oblique hole can
be made, and then the drill moved to a second location either by moving the
drill within
the tool or by moving the tool, and the drill reset at another angle so that a
second hole
29
CA 02599827 2007-08-30
can be made which may or may not intersect the first hole. In fact, the second
hole can
be perpendicular to the borehole wall or oblique relative thereto.
Alternatively, a
perforation mechanism other than a drill may be used to create one or more
holes into the
formation. For example, the perforation mechanism may include, but is not
limited to,
perforation guns.
[0073] Also, while the disclosure described delivering a mobility enhancer
into the
formation with the drill(s) in place in the formation, it will be appreciated
that the drill(s)
could be withdrawn from the formation prior to the introduction of a mobility
enhancer.
Thus, the delivery of the mobility enhancer and the sampling of formation
fluids can
occur with the drill(s) withdrawn into the tool or with the drill(s) located
in the formation.
Alternatively, a shaft that may not include a drill bit at its end may be
introduced in the
formation after the hole has been drilled and perform operations similar to a
shaft with a
drill bit. Further, it will be appreciated that while the disclosure described
sealing a
location along the borehole wall with a packer, and then drilling into the
formation at the
isolated location(s), it is within the scope of the disclosure to use the
drill(s) to drill into
the formation without first isolating the drilling location with a packer. In
this way, the
drill(s) of the tool need not be located at the packer or probe locations.
With the drill(s)
displaced from the packers or probes, the methods of utilizing the tool can be
modified
such that after drilling a hole or holes, the drill(s) could be withdrawn into
the tool and
then the tool can be moved so that the packer or probe will locate at or
around the hole(s)
in order to establish a fluid path between the drilled hole(s) and the tool.
Once the fluid
path is established, any of the described methods of the invention can be
utilized.
CA 02599827 2007-08-30
[0074] Those skilled in the art will appreciate that the tool can also be
provided with
backup anchoring pistons or other anchoring means. Further, while various
embodiment
of a tool according to this disclosure are shown with specific features, a
downhole tool
having features found in different figures, or combining features found in
this disclosure
with features known in the art, is to be considered within the scope of this
disclosure. In
particular, downhole tools combining means of delivering a mobility enhancer
may be
used to advantage in some cases, for example, a tool combining two or more
means for
delivering heat. Similarly, a system comprising a plurality of tools including
the
feature(s) shown in one or more tools described in this disclosure is within
the scope of
this disclosure.
[0075] Also, while the embodiments of the disclosure were illustrated in
details for a
tool conveyed by a wireline cable, those skilled in the art and given the
benefit of the
disclosure will appreciate that the scope of the disclosure includes tools
deployed through
other conveyance means. In particular, the tools and methods discussed herein
may be
used in a drilling situation, i.e. when the tool conveyed/deployed as part of
a bottom hole
assembly or on drill pipe. In this example, the tool string is preferably
equipped by a
power source and a downhole-surface telemetry system known in the art and
suitable to a
conveyance mode by string. Note also that a tool conveyed of drill pipe may or
may not
be equipped with a drill bit and may be used alternatively for appraising a
well or a
reservoir.
[0076] Finally, while the embodiments of the disclosure were primarily
directed to
drilling into a formation from an uncased borehole, it will be appreciated
that the
described apparatus and methods can be utilized even if the borehole is cased.
It will
31
CA 02599827 2007-08-30
therefore be appreciated by those skilled in the art that yet other
modifications could be
made to the provided invention without deviating from its spirit and scope as
claimed.
32
