Note: Descriptions are shown in the official language in which they were submitted.
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METHODS AND APPARATUS TO SAMPLE HEAVY OIL FROM A SUBTERANEAN
FORMATION
FIELD OF THE DISCLOSURE
100011 The present disclosure relates generally to sampling formation
fluids and, more
particularly, to methods and apparatus to sample heavy oil from a subterranean
formation.
BACKGROUND
[0002] Shallow subterranean hydrocarbon-bearing formations, which are
typically at a depth
of less than one thousand meters from the surface often contain heavy oil. The
temperatures and
hydrostatic pressures associated with these shallow formations are often less
than 100 C and 30
MPa, respectively. The United States Geological Survey (USGS) categorizes
heavy oil based on
the density and viscosity of the fluid. In particular, according to the USGS,
medium heavy oil
exhibits a density of 903 to 946 kg/m3 that corresponds with an API gravity of
25 to 18, and a
viscosity from 10 to 100 mPa.s. Such medium heavy oil is typically mobile at
reservoir
conditions. Also, according to the USGS, extra heavy oil exhibits a density of
944 to 1021 kg/m3
that corresponds with an API gravity of 20 to 7, and a viscosity from 100 to
10,000 mPa.s. Such
extra heavy oil is typically not mobile at reservoir conditions. The viscosity
of heavy oil, such as
those mentioned above, in combination with the permeability of the formation
containing the
heavy oil, determines the mobility of the heavy oil. In turn, the mobility of
the heavy oil can
impact significantly the techniques needed to sample and produce the heavy oil
from the
formation.
[0003] When sampling a heavy oil from a formation, it is desirable and
often required that
the sample is chemically representative (i.e., representative of the
constituents and mole
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fractions) of the fluid in the formation from which the sample is extracted.
Thus, the sample is
preferably substantially free of contaminants such as drilling fluid or
filtrate, and otherwise
substantially chemically unaltered by the sampling process. A sample that
represents
accurately the characteristics of the fluid in the formation enables a
suitable production
strategy to be determined. However, sampling processes can, and often do,
cause non-
reversible, significant changes to the hydrocarbon fluid sampled from a
formation, thereby
significantly increasing the difficulty of selecting an appropriate production
strategy.
[0004] In practice, techniques for sampling formation fluid must
typically contend
with constraints related to fluid mobility, formation type, undesirable phase
transitions, the
formation of emulsions or other mixtures with other phases (e.g., connate
water), etc. In the
case of sampling heavy oil, the above-mentioned constraints are sometimes
compounded
because heavy oil is often found in unconsolidated (e.g., sand) formations and
the heavy oil is
often not sufficiently mobile to permit sampling using a sampler having a
probe assembly that
contacts a borehole wall. More specifically, sampler pumps typically provide a
minimum
pump fluid-flow rate of about 0.1 cm3/s which, given the relatively low
mobility of the heavy
oil through the formation, can generate relatively large pressure drops that
can result in the
development of emulsions and/or collapse of the formation or a phase
transition of the fluid.
SUMMARY
[0005] According to one embodiment of the disclosure, there is
provided a method of
sampling fluid from a subterranean formation, comprising: positioning a first
tool having a
heater in a borehole so that the heater is adjacent a portion of the
subterranean formation;
heating with the heater the portion of the subterranean formation so as to
decrease a viscosity
of the formation sufficiently for sampling; controlling the heating to ensure
that the resulting
temperature gradient does not exceed a value that would result in the
formation being
compromised; moving the first tool in the borehole; orienting a second tool
having a sampling
probe in the borehole so that the sampling probe is to contact a portion of
the subterranean
formation heated by the heater; and obtaining via the sampling probe a fluid
sample from the
portion of the subterranean formation heated by the heater.
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[0006] According to another embodiment of the disclosure, there is
provided an
apparatus comprising: a first tool comprising a heating module and a heating
control unit,
wherein the heating module is configured to convey heat energy to a portion of
a subterranean
formation, wherein the heating control unit is configured to control the heat
energy provided
by the heating module to the portion of the subterranean formation and further
wherein the
first tool obtains data relating to a location of or a position of the
portion; and a second tool
comprising a sampling inlet and an orientation module, wherein the orientation
module is
configured to orient the sampling inlet relative to the portion of the
subterranean formation
using the data.
[0006a] According to another embodiment of the disclosure, there is
provided an
apparatus comprising: a downhole apparatus, comprising: a first tool
comprising a heating
module and a heating control unit, wherein the heating module is configured to
convey heat
energy to a portion of a subterranean formation, and wherein the heating
control unit is
configured to control the heat energy provided by the heating module to the
portion of the
subterranean formation; a second tool comprising a sampling inlet, an
orientation module, and
at least one of a packer and a probe, wherein the orientation module is
configured to orient the
sampling inlet relative to the portion of the subterranean formation, and
wherein the at least
one of a packer and a probe is configured to isolate at least a section of a
portion of the
borehole; and wherein the first tool further comprises a heat reflector
adjacent to the heating
module and configured to reflect at least some of the heat energy provided by
the heating
module toward a wall of the borehole.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 depicts an example downhole formation heating tool that
has been
deployed into a wellbore or borehole to heat a portion of a subterranean
formation from which
a sample of a heavy oil is to be obtained.
[0008] FIG. 2 is a more detailed view of the example heating tool of
FIG. 1.
[0009] FIG. 3a depicts an example formation sampling tool that may be
used to obtain
a sample of heavy oil from a previously heated volume of a formation.
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[00101 FIG. 3b depicts another example formation sampling tool that may
be used to
obtain a sample of heavy oil from a previously heated volume of a formation.
100111 FIG. 4 depicts in greater detail the example sampling module shown
in
FIG. 3a.
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[0012] FIG. 5 is a flow diagram that depicts an example method that may be
used to heat a
subterranean formation.
[0013] FIG. 6 is a flow diagram that depicts an example method to sample
formation fluid
from a previously heated area of a subterranean formation.
[0014] FIG. 7a depicts an example tool string including a heating tool and
a remote sampling
tool in a heating position.
[0015] FIG. 7b depicts the example tool string of FIG. 7a in a sampling
position.
[0016] FIGS. 8a-8b depict another example tool string including a heating
tool and a remote
sampling tool that may be used to mobilize and obtain a sample of heavy oil.
[0017] FIG. 9 is a flow diagram that depicts an example method to mobilize
and sample
formation fluid.
DETAILED DESCRIPTION
[0018] Certain examples are shown in the above-identified figures and
described in detail
below. In describing these examples, like or identical reference numbers are
used to identify
common or similar elements. The figures are not necessarily to scale and
certain features and
certain views of the figures may be shown exaggerated in scale or in schematic
for clarity and/or
conciseness.
[0019] In general, the example methods and apparatus described herein may
be used to
facilitate the sampling of heavy oil from a subterranean formation. The term
"heavy oil" as used
throughout is not intended to limit the scope of the application, but for
brevity reasons will be
used to identify all variations of oils including heavy oil, medium heavy oil,
extra heavy oil and
bitumen. As described in greater detail below, the example methods and
apparatus use a
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downhole tool having a heater to increase the temperature of a portion of a
formation that
decreases the viscosity of the fluid in the formation so it can be sampled
with a formation tester.
In particular, in the described examples, a portion of a downhole tool having
a heater or heating
unit is engaged against or near a borehole wall in an area associated with a
formation from which
sample fluid is to be obtained. The heater is held in contact with the
borehole wall for a time
sufficient to raise the temperature of a volume of the formation to decrease
the viscosity of the
fluid and, thus, increase the mobility of the fluid in the heated volume of
the formation.
100201 Once the formation has been sufficiently heated, the location within
the borehole
associated with the heated volume of the formation is determined or verified.
For example, the
depth and orientation of the heater and, thus, the heated portion of the
formation is determined or
verified and stored for later reference. The downhole tool providing the
heater is then moved in
the borehole and a sampling tool, previously placed in the borehole, is
located within the
borehole so that the sampling probe(s) of the sampling tool are positioned to
extract sample fluid
from the previously heated volume of the formation. Pre-heating the sampling
tool minimizes
any cooling effect the tool may have on the fluid sampled and, thus, would
facilitate the flow of
sampled fluid within the sampling tool. Also, the sampling tool is preferably
positioned using
the earlier stored heater orientation information so that the sampling
probe(s) can be positioned
precisely at the depth and orientation that enables the probe(s) to contact
the borehole wall in the
area of formation that was previously heated. The sampling tool then extracts
fluid from the
heated portion or volume of the formation and, when the sampling is complete,
the sampling tool
can be retrieved to the surface to enable analysis of the sampled heavy oil.
Alternatively, the
fluid can be analyzed in the downhole tool, and thus not required to be
brought to the surface.
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[0021] The example methods and apparatus described herein provide a
sampling process that
does not permanently change the characteristics (i.e., the characteristics of
the hydrocarbon) of
the sample fluid. As a result, the example methods and apparatus can be used
to obtain heavy oil
samples that represent accurately the heavy oils in subterranean formations so
that appropriate or
optimal production strategies can be selected and employed to extract the
heavy oils to the
surface. One known sampling tool described in U.S. Patent No. 6,941,804 uses a
heating device
located on or integral with the sampling tool (e.g., near the sampling probe)
to heat the formation
to facilitate sampling of heavy oil. However, in contrast to this known
sampling device and
other known methods and apparatus that provide only a heated sampling probe,
the example
methods and apparatus described herein decouple the formation heating and
sampling systems
(e.g., as two separate tools), thereby enabling more optimal control of the
heating and sampling
operations for formations containing heavy oil. Further, decoupling the
formation heating and
sampling systems may provide a better protection of the sampling elements that
are sensitive to
high temperatures, such as elastomeric sealing parts of the probe. Still
further, having a separate
heating and sampling tools permits modularity of the downhole tool string,
enabling thereby
various string configurations to be implemented as desired with a limited
number of tool assets.
100221 FIG. 1 depicts an example downhole formation heating tool 100 that
has been
deployed (e.g., lowered) into a wellbore or borehole 102 to heat a portion or
volume of a
subterranean formation F from which a sample of a heavy oil is to be obtained.
The formation
heating tool 100 is depicted as a wireline type tool and, thus, is lowered
into the borehole 102 via
a cable 104, which bears the weight of the formation heating tool 100 and
which includes
electrical wires or additional cables to convey power, control signals,
information carrying
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signals, etc. between the formation heating tool 100 and an electronics and
processing unit 106
on the surface adjacent the borehole 102.
100231 The formation heating tool 100 includes a plurality of sections,
modules, or portions
commonly referred to as subs to perform various functions. More specifically,
the formation
heating tool 100 includes a heater section or heating module 108 that, as
described in greater
detail below, applies a controlled amount of heat energy (e.g., a controlled
temperature for a
predetermined time) to the formation F to heat a volume of the formation F
from which a sample
of heavy oil is to be extracted.
[0024] The formation heating tool 100 may also includes packers 110 and
112. One or both
of the packers 110 and 112 may be used to remove borehole fluid (e.g.,
drilling fluid) from a
portion of the borehole 102 to minimize or eliminate the conduction of heat
away from an area of
the formation F being heated by the heating module 108. For example, both of
the packers 110
and 112 may be expanded to hydraulically isolate a section of the borehole
occupied by the
heating module 108. Thus, with the heating module 108 aligned with a section
of the borehole
102 corresponding to the formation F, hydraulically isolating the heating
module 108 also
hydraulically isolates the portion of the formation F to be heated, thereby
enabling the heating
module 108 to deliver substantially all of its heat energy to the formation F.
In other words,
using one or both of the packers 110 and 112 to hydraulically isolate the area
of the formation F
to be heated minimizes or prevents the heat energy generated by the heating
module 108 from
being carried away to other portions of the borehole 102 via borehole fluid.
[0025] To extract borehole fluid from the area to be isolated by one or
both of the packers
110 and 112, the heating tool 100 includes one or more pumping modules 114.
The pumping
module 114 may include one or more hydraulic motors, electric motors, valves,
flowlines, etc. to
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enable borehole fluid to be removed from a selected area of the borehole 102
surrounding a
portion of the heating tool 100.
100261 To determine the location or position of the heating tool 100 in the
borehole 102, the
heating tool 100 includes a position detector 116. The position detector 116
may detect the
depth and orientation (e.g., rotational or angular position) of the heating
tool 100 within the
borehole 102. The position detector 116 may be implemented using, for example,
one or more
magnetometers or the General Purpose Inclinometry Tool (GPIT TM) provided by
Schlumberger
Technology Corporation. Alternatively, the position detector 116 may be
configured to provide
only information relating to the orientation of the heating tool 100 and the
depth of the heating
tool 100 within the borehole 102 may instead be determined using any known
method of
determining depth such as, for example a gamma-ray device, cable flagging, or
any other method
of determining or measuring the length of the cable 104 extending from the
surface into the
borehole 102.
100271 To convey power, communication signals, control signals, etc.
between the surface
(e.g., to/from the electronics and processing unit 106) and among the various
sections or modules
composing the heating tool 100, the heating tool 100 includes an electronics
module 118. The
electronics module 118 may, for example, be used to convey position
information provided by
the position detector 116 to the electronics and processing unit 106 to enable
an operator and/or
system on the surface to determine the location or position of the heating
module 108 in the
borehole 102. In particular, the position information may be used to align the
heating module
108 with the formation F and, as described in more detail below, may
subsequently be used to
position a sampling tool and its sampling probe(s) in substantially the same
location of the
formation F previously heated by the heating module 108. The electronics 118
may also control
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the operation of the pumping module 114 in conjunction with operation of the
packers 110
and/or 112 to, for example, hydraulically isolate a portion of the borehole
102 to facilitate
heating of a portion of the formation F.
[0028] As depicted in FIG. 1, the heating tool 100 may also includes a heat
reflector 120 and
a bow spring 122. The heat reflector 120 is attached to a side of the heating
tool 100 so that heat
applied by the heating module 108 to a wall 123 of the borehole 102 is
reflected and/or focused
on the side of the heating tool 100 that is in contact with the portion of the
formation F to be
heated. The heat reflector 120 is preferably, but not necessarily, configured
to have a curved
shape that is complementary to the shape of the heating tool 100.
Additionally, the heat reflector
120 may be sized to encircle about ninety degrees or more of the outer
circumference of the
heating tool 100 and to extend over at least the length of the heating module
108 portion of the
heating tool 100. However, a variety of other geometries and/or sizes could be
used to
effectively reflect heat generated by the heating module 108 back onto the
area of the borehole
wall 123 being heated by the heating module 108. The bow spring 122 is
positioned on the
heating tool 100 adjacent the reflector 120 to orient the heating tool 100
against or in contact
with the wall 123 of the borehole 102 and, thus, to cause the heating module
108 to engage or
contact an area of the formation F to be heated. While the example heating
tool 100 is depicted
as having one bow spring 122, additional bow springs could be employed and/or
different
mechanisms or techniques could be employed to ensure that the heating module
108 engages or
contacts the wall 123 of the borehole 102 in the area of the formation F.
Further, while the
example heating tool 100 is depicted as being deployed in the borehole 102 as
a wireline device,
the heating tool 100 could alternatively or additionally be deployed in a
drill string, using coiled
tubing, or by any other known method of deploying a tool into a borehole.
Still further, the
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example heating tool 100 may be implemented by modifying one or more existing
tools. For
example, either or both of the Hydrate MelterTM and the PatchFlexTM products
provided by
Schlumberger Technology Corporation could be modified to provide the features
and functions
of the example heating tool 100 of FIG. 1.
[0029] FIG. 2 is a more detailed view of the example heating tool 100 of
FIG. 1. As shown
in FIG. 2, the heating module 108 includes a heating element 200, a heater
control unit 202, and
a temperature sensor 204, all of which are operatively coupled to heat an area
or volume of a
formation (e.g., the formation F) to a desired temperature to decrease the
viscosity and increase
the mobility of a fluid to be sampled from the formation F. The heating
element 200 may be
implemented using, for example, one or more resistive wires that may, for
example, be coiled
about an inside or outside surface of the example tool 100 in the area of the
heating module 108.
The wires used to implement the heating element 200 may be similar to those
used in the
Hydrate MelterTM and/or the PatchFlexTM products provided by Schlumberger
Technology
Corporation. Alternatively and/or additionally, the heat provided by the
heating module may be
produced through electrical resistivity in the formation F, RF Induction,
Ultrasonic or through a
chemical reaction. It is also contemplated that the hot fluid, such as steam
for example, may be
transferred from the surface to the module 108 in order to heat the formation
F.
[0030] The temperature sensor 204 may be implemented using any suitable
temperature
sensing device and is mounted on the heating tool 100 to sense the temperature
of the formation
being heated and/or the temperature of the heating element 200. The
temperature sensor 204
sends signals (e.g., a changing resistance value) to the heater control unit
202 which, in turn,
controls the heat energy being generated by the heating element 200. For
example, based on the
signals received from the temperature sensor 204 (e.g., based on the
temperature of the portion of
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the borehole wall 123 corresponding to the area of the formation being
heated), the heater control
unit 202 varies the heat energy generated by the heating element 200. In some
examples, the
heater control unit 202 may provide a continuously variable current or voltage
to the heating
element 200, may pulse modulate a substantially fixed peak current or voltage
to the heating
element 200, or may vary the electrical energy provided to the heating element
200 in any other
manner to increase or decrease the heat energy generated by the heating
element 200. By
controlling the heat energy generated by the heating element 200 based on the
temperature
sensed by the temperature sensor 204, the heater control unit 202 can control
the temperature
gradient to which the formation being heated is subjected, thereby minimizing
or preventing the
possibility that the formation F will be compromised by thermal cracking
and/or the degradation
of the fluid to be sampled. The thermal conductivity of the formation F may be
relatively low,
which results in slow temperature propagation through the formation F. Thus,
by controlling the
temperature of the portion of the borehole wall 123 associated with the area
of the formation F
being heated, the maximum temperature gradient to which the formation F is
subjected can be
controlled or limited to prevent any damage (e.g., thermal cracking) to the
formation F.
100311 The heater control unit 202 and/or signals received from the
electronics module 118
via signals lines 206 may cause the heater control unit 202 to heat the
formation F for a
predetermined amount of time. In general, a longer heating time increases the
temperature of a
larger volume of the formation F to a temperature that facilitates extraction
of heavy oil from the
formation F. In some cases, heating a formation for several hours increases
the temperature of a
volume of the formation by 50 C and enables about one liter of heavy oil to
be extracted.
However, the amount of time required to heat a formation depends on many
factors such as, for
example, the properties (e.g., heat capacity, viscosity, dependence of
viscosity on temperature,
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density, etc.) of the heavy oil to be extracted, the characteristics (e.g.,
heat capacity, thermal
conductivity, density, thermal diffusivity, permeability, etc.) of the
formation from which the
heavy oil is to be extracted, the power or maximum heat energy that can be
delivered by the
heating module 108, the maximum safe thermal gradient to which the formation
can be
subjected, the size or volume of the sample desired (i.e., a larger sample may
require heating a
larger volume of the formation), etc. The temperature increase must be
controlled so the fluid is
maintained as a single phase and not permitted to extend through the bubble
pressure and into the
two-phase region.
100321 FIG. 3a depicts an example formation sampling tool 300 that may be
used following
the heating of an area or volume of the formation F to obtain a sample of
heavy oil from the
heated volume of the formation F. To sample fluid from the formation F, the
sampling tool 300
includes a sampling module 302. The sampling module 302 includes an extendable
sampling
assembly 304 (shown in an extended position) having a packer or probe 305
disposed at an end
thereof to extract fluid from the formation F and an extendable anchoring
member 306 (shown in
an extended position) to anchor the sampling tool 300 and the probe 305 in
position to contact
the formation F. The probe 305 is preferably the QuicksilverTM probe provided
by Schlumberger
Technology Corporation. However, any other single or dual inlet (i.e., guard
type) sampling
probe or probes or inflatable packer sampling module could be used instead.
The sampling tool
300 may also include packers 308 and 310, one or both of which may be used to
hydraulically
isolate a portion of the borehole 102, a position detection module 312, a
borehole wall
temperature detection module 314, a tool positioning module 316, and
electronics 318. As
depicted in FIG. 3a, the sampling tool 300 is suspended or deployed in the
borehole 102 via a
cable 320 that is coupled to an electronics and processing unit 322 on the
surface. The cable 320
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may include multiple cables and/or wires to provide strength to hold the
weight of the tool 300
and to convey power, communication signals, command signals, etc. between the
electronics and
processing unit 322 and the sampling tool 300. When the formation has
substantial connate
water, the Quicksilver probe is preferred because the more mobile aqueous
phase can be pumped
through the guard (outer) probe while the less mobile oil through the inner
(sample) probe.
[0033] The
sampling module 302 may also include a temperature sensor 324 to detect the
temperature of the wall 123 of the borehole 102. By detecting the temperature
of the wall 123 of
the borehole 102, the sampling tool 300 and/or the electronics and processing
unit 322 can locate
the portion of the formation F previously heated by the heating tool 100. In
turn, once the
portion of the formation F that was previously heated by the tool 100 is
detected, the inlet of the
sampling probe 305 can be located (e.g., by moving the sampling tool 300
slightly downward a
distance equal to about the space between the temperature sensor 324 and the
inlet of the
sampling probe 305) against the heated portion of the formation F to extract a
sample of fluid
therefrom. Additionally or alternatively, the borehole wall temperature
detection module 314
may include a plurality of extendable fingers, arms, or probes 326 and 328
having respective
temperature sensors 330 and 332 at the ends of the arms 326 and 328 to contact
the wall 123 of
the borehole 102. In this manner, the extendable fingers, arms, or probes 326
and 328 can be
used to determine or locate the portion of the wall 123 of the borehole 102
previously heated by
the heating tool 102. Once the previously heated portion of the wall 123 of
the borehole 102 is
located, the tool 300 can be positioned (e.g., moved downwardly a distance
equal to about the
space between the inlet of the sampling probe 305 and the temperature sensors
330 and 332 and
optionally rotated to position the probe opening directly opposite the heated
portion of the wall)
so that the inlet of the probe 305 is in contact with the portion of the
borehole wall 123
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previously heated by the heating tool 100. While only two extendable fingers,
arms, or probes
326 and 328 are shown, six such fingers, arms, or probes are desirable.
However, any other
number of such fingers, arms or probes may be used instead. Examples of known
tools that
include multiple fingers, arms, or probes include the PMIT-BTm and PMIT-CTm
multi-finger
caliper tools provided by Schlumberger Technology Corporation. While these
known tools are
configured to measure radial distances within a borehole, such a configuration
could be modified
to include temperature sensors at the end(s) of one or more of the fingers so
that the temperature
sensors are held in contact with the wall 123 of the borehole 102. The
temperature sensors used
(e.g., to implement the sensors 330 and 332) can be elements that provide a
resistance that varies
as a function of temperature, infrared devices, or any other suitable
temperature sensing
element(s).
[0034] To
position the sampling tool 300 in the borehole 102, the tool positioning
module
316 includes a plurality of tool positioners 334 and 336, each of which may be
independently
actuated or moved to cause the sampling tool 300 to rotate in the borehole
102. While two tool
positioners 334 and 336 are shown in FIG. 3a, more or fewer such positioners
could be used
instead. Additionally or alternatively, the sampling tool 300 could be
positioned within the
borehole 102 using other or different mechanisms or techniques suitable for
the geometry,
deviation, and diameter of the borehole 102. For example, in boreholes having
an at least
somewhat oval geometry, powered calipers such as the tool positioners 334 and
336 can be used
to position or orient the sampling tool 300. For boreholes having a
substantially circular
geometry, tool turners and/or bow springs can be employed (not shown). Bow
springs are
particularly useful to turn or rotate the tool 300 more than forty-five
degrees. Where the
diameter of the tool 300 is only slightly smaller than that of the borehole
102, the sampling tool
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300 may be oriented by moving it upward and downward and thus causing small
rotations of the
tool 300. In the case of horizontal boreholes, the sampling tool 300 is
coupled to a drill string
and the Schlumberger Technology Corporation Tough Logging Conditions (TLCTm)
system may
be used and the drill pipe rotated to orient the sampling tool 300.
100351 To determine the location or position of the sampling tool 300 in
the borehole 102,
the position detection module 312 provides tool depth and orientation
information. For example,
the position detection module 312 may use magnetometers (e.g., a GPITTm
provided by
Schlumberger Technology Corporation) to detect the orientation of the sampling
tool 300 and
may additionally use a gamma ray device to determine the depth of the sampling
tool 300. The
position detection module 312 may continuously or periodically communicate
tool position or
location information via communication circuitry in the electronics module 318
and the cable
320 to the electronics and processing unit 322 on the surface. In this manner,
an operator or
other person on the surface can monitor the position or location of the
sampling tool 300 to
determine when the inlet of the sampling probe 305 is aligned with the portion
of the formation F
that was previously heated by the heating tool 100. Alternatively or
additionally, the tool
position or location information may be used by the electronics and processing
unit 322 to
automatically adjust the depth and/or orientation of the sampling tool 300 to
align the inlet of the
sampling probe 305 with the previously heated portion of the formation F.
Alternatively or
additionally, the electronics processing unit 322 may be a module of the
downhole tool, and it
may include algorithms and methods to adjust the depth and/or orientation of
the sampling tool
300 to align the inlet of the sampling probe 305 with the previously heated
portion of the
formation, without need to communicate to the surface, or communicate to a
person or operator
at the surface.
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[0036] FIG. 3b depicts another example formation sampling tool 300' that
may be used
following the heating of an area or volume of the formation F to obtain a
sample of heavy oil
from the heated volume of the formation F. To sample fluid from the formation
F, the sampling
tool 300' includes a sampling or probe module 302'. The sampling module 302'
includes an
extendable sampling assembly 304' and a probe 305'. The probe 305' is a multi
inlet or guard
probe, such as the QuicksilverTM probe provided by Schlumberger Technology
Corporation.
However, the multiple inlets may be disposed over a number of packers or
probes. The sampling
tool 300' may also include a position detection module, a borehole wall
temperature detection
module, a tool positioning module, electronics (not shown), and a temperature
sensor 324',
which may operate similar to the corresponding modules in sampling tool 300.
In addition, the
tool 300' may further include any features and assemblies found in the tool
300.
[0037] Shown more clearly in FIG. 3b, the tool 300' (and 300) may include
one or more
pumpout modules 309, one or more sample bottle carrier modules 303, and one or
more
downhole fluid analysis (DFA) modules 307. In particular, the sample module
302' includes a
first flowline 311 and a second flowline 313 fluidly coupled to an exterior of
the tool. As
illustrated in FIG. 3b, the flowlines 311, 313 are each coupled to the probe
305', with the first
flowline 311 being positioned and adapted to receive virgin formation fluid
and the second
flowline 313 being positioned and adapted to receive contaminated formation
fluid or water.
Alternatively, the first flowline 311 may receive contaminated fluid and the
second flowline 313
may received virgin formation fluid or the first and the second flowlines 311,
313 may receive
the same or combinations of fluids. Disposed to either side of the sample
module 302' may be a
sample bottle carrier modules 303, with the module 303a being disposed to a
top of the sample
module 302' and the module 303b being disposed to a bottom of the sample
module 302'. A
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pair of (DFA) modules 307a and 307b may then be disposed to either side of the
sample bottle
carrier modules 303a and 303b, respectively, followed by a pair of pumpout
modules 309a and
309b disposed to either side of the DFA modules 307a and 307b, respectively.
As such, the
flowlines 311, 313 may be located in each of the modules to enable a fluid
connection to the
various modules and the assemblies located therein.
[0038] In this configuration, the tool 300' can be configured to handle a
multiple flowline
configuration and, as will be discussed in more detail below, the warming of
the flowline 311
and/or the flowline 313. For example, formation fluid may be traversed through
the first
flowline 311 into the sample bottle carrier module 303a, where the formation
fluid may be stored
in one or more sample bottles 315 utilizing a valve system (not shown). The
formation fluid may
then enter the DFA module 307a where a determination about the formation fluid
can be made.
For example, the DFA modules 307 may include one or more fluid sensors,
including but not
limited to a pressure sensor, an optical sensor, a viscosity sensor, a density
sensor, a resistively
sensor and a H20, for determining various fluid parameters. To provide
movement of the
formation fluids into and through the various modules the pump-out unit 309a,
having a pump
317 fluidly coupled to the flowline 311, may be disposed next to the DFA
module 307a.
[0039] This configuration provides several advantages. For example, as the
sample bottle
carrier module 303a is disposed adjacent or nearest the probe module 302', the
formation fluid
traversing through the tool 300' and specifically thought the flowline 311
only travels a short
distance before entering the sample bottle(s) 315. Thus, if the formation
fluid and/or the
flowline 311 requires heating in order to lower the viscosity of the formation
fluid sufficiently to
ensure flow through the flowline 311, the heating period and/or heating
distance is greatly
reduced.
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[0040] The heating of the flowline 311 may be accomplished in several
manners, some of
which will be discussed in more detail below. In this configuration, however,
heated fluid, such
as H20 for example, may be carried, heated and/or stored in the bottle(s) 315
in the carrier
module 303a, thus enabling the flowline 311 to be flushed with the heated
fluid, thereby pre-
heating or heating the flowline to permit the sampling of high viscosity
fluid. The second
flowline 313 may be set-up or configured relative to the modules in a
substantially similar
manner as described above with respect to flowline 311.
100411 It is worthy to note that the some of the modules and/or features
described in FIG. 3b
may be duplicative of modules and/or features described in FIG. 4, each having
different
identifiers. This was done to ensure clarity of the application. However, one
of ordinary skill in
the art would understand how the modules and/or features described in FIGS. 3a-
4 would
interact and operate.
[0042] FIG. 4 depicts in greater detail the example sampling module 302
shown in FIG. 3.
As shown in FIG. 4, the sampling module 302 includes a hydraulic system 400
that may be
fluidly coupled to the sampling probe assembly 304 to selectively extend the
sampling probe 305
into engagement with the formation F to enable a sample of fluid to flow into
the sampling probe
305. Additionally, the hydraulic system 400 may also selectively retract the
sampling probe
assembly 304 toward or into a chassis or body 402 of the sampling module 302
when the
sampling operation is completed. As noted above, the sampling probe 305 is
preferably a guard
type probe (e.g., the QuicksilverTM probe provided by Schlumberger Technology
Corporation)
having a guard flowline 404 and a sample flowline 406.
[0043] A pump or pumpout 408 draws fluid (e.g., from the formation F)
through the guard
and sample flowlines 404 and 406 in a manner that results in a more rapid
sampling of a
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substantially contamination free formation fluid. In particular, the pumpout
408 discards
formation fluid from the guard flowline 404 to a flowline 410 that exits the
body 402 of the
sampling module 302 (e.g., fluid in the flowline 410 may be passed to the
annulus surrounding
the sampling tool 300 in the borehole 102). At the same time the pumpout 408
is drawing fluid
through the guard flowline 404 and discarding that fluid via the line 410, the
pumpout 408 draws
fluid through a spectrometer 412 that is positioned on the sample flowline
406. The sampling
tool 300 may of course include more than one pumpout 408 to facilitate various
sampling
configurations, such as one having a plurality of inlets for example. The
spectrometer 412
monitors the contamination level(s) of (e.g., the amount of drilling fluid or
filtrate within) the
formation fluid flowing in the sample flowline 406 and communicates
information relating to the
contamination level(s) to a controller 414. The spectrometer 412 may be
implemented using the
Live Fluid AnalyzerTM (LFA) provided by Schlumberger Technology Corporation or
any other
spectrometer or device capable or detecting the contamination of a formation
fluid sample. The
pumpout 408 conveys fluid drawn through the spectrometer 412 via the sample
flowline 406 to a
valve 416, which has a first selectable outlet 418 that is fluidly coupled to
a fluid store 420 and a
second selectable outlet 422 that passes fluid out of the sampling module 302
(e.g., to the
annulus) between the borehole wall 123 and the sampling tool 300.
100441 The guard flowline 404, sample flowline 406, the pumpout 408, the
spectrometer 412
and/or the fluid store 420 may have respective heating elements 424, 426, 428,
430, and 432 to
maintain the temperature of heavy oil drawn in by the probe assembly 304
sufficiently high to
ensure that the heavy oil remains sufficiently mobile within the sampling
module 302 and its
internal components. However, while one or more such separate heating elements
(e.g., the
heating elements 424, 426, 428, 430, and 432 are shown in FIG. 4, fewer such
elements or a
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single larger heating element (e.g., encompassing a portion or all of the body
402 of the sampling
module 302) could be used instead. The heating elements 424, 426, 428, 430,
and 432 may also
include respective temperature sensors 434, 436, 438, 440, and 442 to monitor
and control the
temperature of the flowlines 404 and 406, the pumpout 408, the spectrometer
412, and the fluid
store 420 to ensure that the formation fluid within these components remains
sufficiently mobile
(i.e., the viscosity remains sufficiently low).
[0045] The controller 414 is operatively coupled to the hydraulic system
400, the pumpout
408, the spectrometer 412, the valve 416, and/or the fluid store 420 via wires
or lines 444. The
wires or lines 444 may include a databus (e.g., carrying digital information
and/or analog
information), power signals, etc. and may be implemented using a single
conductor or multiple
conductors. Additionally, the controller 414 receives temperature signals from
the temperature
sensor 324.
[0046] In operation, the controller 414 may use the temperature information
received from
the temperature sensor 324 to detect the location of the formation F that was
previously heated
by the heating tool 100 to enable the sampling module 302 to be located at a
depth and
orientation such that the sampling probe 305 is aligned with the previously
heated location of the
formation F. Once located, the controller 414 may control the hydraulic system
400 to extend
the sampling probe assembly 304 to engage or contact the borehole wall 123 to
fluidly couple the
probe 305 to the formation F. The controller 414 may then control the pumpout
408 to draw
fluid through the guard flowline 404 and the sample flowline 406 while
monitoring the
contamination level of the fluid in the sample flowline 406 via the
spectrometer 412. Initially,
fluid drawn into the guard and sample flowlines 404 and 406 is discarded
(e.g., conveyed to the
annulus). Thus, the controller 414 initially controls the valve 416 to route
fluid in the sample
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flowline 406 to the annulus so that the fluid in the sample flowline 406 is
not stored in the fluid
store 420. As the pumpout 408 continues to draw fluid from the formation F
through the
sampling probe 305, the level of contamination (e.g., the amount of filtrate)
in the fluid passing
through the sample flowline 406 decreases. When the controller 414 determines
via the
spectrometer 412 that the formation fluid in the sample flowline 406 is
substantially free of
contamination (e.g., substantially free of filtrate) and/or has reached an
acceptably low level of
contamination, the controller 414 causes the valve 416 to route fluid from the
sample flowline
406 to the fluid store 420. When a sufficient quantity of sample fluid has
been transferred to the
fluid store 420, the controller 414 may terminate the sampling process by
deactivating the
pumpout 408 and retracting the sampling probe assembly 304.
[0047] During the sampling process, the pumpout 408 may be operated to
control the flow
rates and/or pumping rates in the guard and sample flowlines 404 and 406 to
achieve a relatively
rapid reduction in the contamination level of the fluid in the sample flowline
406. Further, the
controller 414 may also control the absolute and relative pumping rates of the
fluid in the guard
and sample flowlines 406 and 408 to prevent pressure drops that could reduce
the pressure of the
formation fluid below its bubble pressure, result in the formation of
emulsions, and/or collapse
the formation F. For example, the controller 414 may operate the pumpout 408
so that its
internal pumps are cycled on/off, operated for single strokes, or in any other
manner to prevent
an excessive pressure drop.
[0048] While the example of FIGS. 3 and 4 depicts the sampling probe 305 as
a dual inlet or
guard probe, a single inlet probe (e.g., the extra large diameter (XLD) probe
provided by
Schlumberger Technology Corporation) could be used instead. However, the use
of a dual inlet
or guard probe (e.g., the QuicksilverTM probe provided by Schlumberger
Technology
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Corporation) typically enables a relatively rapid reduction in sample fluid
contamination and,
thus, typically reduces sampling times, which is particularly useful in the
examples described
herein because the viscosity of the heavy oil in the formation F will tend to
increase over time
following the removal of the heating tool 100. As a result, decreasing the
time required to draw
sample fluid from the formation F enables the sample fluid to be extracted
while it remains at a
relatively higher temperature, lower viscosity, and higher mobility within the
formation F.
Additionally, drawing the sample fluid while it exhibits a relatively lower
viscosity and higher
mobility may facilitate the ability of the controller 414 to maintain the
pressure drops associated
with the sampled fluid in an acceptable range.
[0049] FIGS. 5 and 6 are flowcharts of example methods that can be used to
sample heavy
oil from a subterranean formation (e.g., the formation F). The example methods
of FIGS. 5 and
6 may be implemented using software and/or hardware. In some example
implementations, the
flowcharts can be representative of example machine readable instructions and
the example
methods of the flowcharts may be implemented entirely or in part by executing
the machine
readable instructions. Such machine readable instructions may be executed by
one or more of
the electronics and processing units 106 (FIG. 1) and 322 (FIG. 3), the heater
control unit 202,
and/or the controller 414. In particular, a processor or other suitable device
to execute machine
readable instructions may retrieve such instructions from a memory device
(e.g., a random access
memory (RAM), read only memory (ROM), etc.) and execute those instructions. In
some
examples, the one or more of the operations depicted in the flowcharts of
FIGS. 5 and 6 may be
implemented manually. Further, the order of execution of the blocks depicted
in the flowcharts
of FIGS. 5 and 6 may be changed, and/or some of the blocks described may be
rearranged,
eliminated, or combined.
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100501 FIG. 5 is a flow diagram depicting an example method 500 that may be
used to heat a
subterranean formation (e.g., the formation F). Initially, the method 500
determines an area of a
formation (e.g., the formation F) to be sampled (block 502). For example, a
formation logging
tool (e.g., having a gamma-ray based device) may be run into the borehole
(e.g., the borehole
102) to determine the depth of the formation to be sampled. A formation
heating tool (e.g., the
heating tool 100) is then positioned within the borehole (e.g., the borehole
102) relative to the
area of the formation (e.g., the formation F) to be sampled (block 504). For
example, to position
the heating tool 100 within the borehole 102, the heating tool 100 may be
lowered to a depth
(e.g., based on a depth determined at block 502) such that the heating module
108 is adjacent to
or aligned with the formation F. The depth of the heating module 108 may be
determined using
any known technique such as, for example, cable flagging of the cable 104.
Additionally, the
position detector 116 may be used to determine the orientation of the tool 100
relative to the
formation F to determine the portion or area of the formation F that is in
contact with the heating
module 108.
100511 The area of the formation to be sampled is then heated (block 506).
For example, the
heater control unit 202 (FIG. 2) may apply electrical power to the heating
element 200 (FIG. 2)
based on the temperature of the borehole wall 123 in the area of the formation
F as provided by
the temperature sensor 204 (FIG. 2). The temperature of the borehole wall may
be controlled to
a desired elevated temperature (e.g., 50 C above reservoir conditions) and
maintained at the
elevated temperature. The selected or controlled elevated temperature
maintained by the heating
module 108 is selected to minimize or substantially prevent the possibility of
causing thermal
cracking of the fluids in formation F or otherwise compromising the integrity
of the formation F
and the integrity of the formation fluids in formation F. However, the
selection of an appropriate
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elevated temperature may be based on numerous factors such as, for example,
the geophysical
properties of the formation, the properties of the heavy oil in the formation
F, etc.
[0052] The method 500 continues to heat the formation F until the formation
F is ready to
sample (block 508). The formation F may be heated for a predetermined amount
of time that
heats a volume of the formation F sufficiently to provide a desired volume of
sample fluid. For
example, several hours may be required to sufficiently heat a volume of a
formation to facilitate
the extraction of about a one liter sample of heavy oil. After the method 500
determines that the
formation F is ready to be sampled (block 508), the method 500 verifies the
position (e.g., the
depth and orientation) of the sampling tool 100 within the borehole 102 (block
510). Such
verified position information may be stored for subsequent reference during
sampling of the
formation F. After verifying the position of the sampling tool 100 within the
borehole 102, the
sampling tool 100 is removed from the borehole 102 (block 512).
[0053] FIG. 6 depicts an example method 600 to sample formation fluid from
a previously
heated area of a subterranean formation. Initially, the sampling tool (e.g.,
the sampling tool 300)
is pre-heated on the surface of the earth (block 602). Alternatively, the
sample tool may be
heated in the borehole. For example, the sampling tool 300 may be heated to at
least the
temperature of the heating module 108 using a tool oven, heating blankets,
and/or by winding
insulated resistive elements around the tool 300. Heating the sampling tool
300 to a temperature
of about that to which the area of the formation F to be sampled has been
heated that, but which
does not exceed the maximum operating temperature of the tool 300, reduces the
potential
cooling effect that the tool 300 could have when brought into proximity or
contact with the
previously heated portion of the formation F. Additionally, pre-heating the
sampling tool 300
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facilitates the flow of sampled formation fluid within the sampling tool 300
by maintaining the
temperature of the sampled fluid at a relatively high temperature and, thus,
low viscosity.
[0054] The pre-heated sampling tool 300 is then positioned in the borehole
102 to obtain a
sample of formation fluid from the area of the formation F that was previously
heated by the
heating tool 100 (block 604). The sampling tool 300 is positioned in the
borehole 102 by placing
the sampling tool 300 at a depth and orientation such that the sampling probe
305 is aligned with
and enabled to fluidly couple to the area of the formation F that was
previously heated by the
heating module 108 of the heating tool 100. As described above in connection
with FIG. 3, the
position detector 312, the temperature sensor 324, the temperature detection
module 314, and/or
the tool positioning module 316 may be used to position the sampling tool 300
so that the
sampling probe 305 is properly aligned with the previously heated portion of
the formation F.
[0055] When the sampling tool 300 is properly positioned within the
borehole 102 the
example method 600 samples the formation fluid from the formation F (block
606). The
sampling tool 300 may sample the fluid from the formation F as described above
in connection
with FIG. 4. After the example method 600 completes the sampling (block 606),
the sampling
tool 300 is removed to the surface (block 608).
[0056] FIGS. 7a and 7b depict an example downhole tool string 700 that has
been deployed
(e.g., lowered) into a wellbore 102 to heat a portion of a subterranean
formation F from which a
sample of a heavy oil is to be obtained. More specifically, FIG. 7a depicts
the tool string 700 in
a heating position and FIG. 7b depicts the tool string 700 in a consecutive
sampling position.
The two positions differ at least by the location of the tool string 700 with
respect to the
formation F. In particular, the controlled movement of the tool string 700
between the two
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positions permits that the heating and sampling operations are performed at
substantially a single
location or depth.
[0057] In FIGS. 7a and 7b, the tool string 700 is depicted as a wireline
type tool. Thus, the
tool string 700 is lowered from an electronics and processing unit 706 located
on the surface
adjacent the wellbore 102, and into the wellbore 102 via a cable 704. In
particular, the
electronics and processing unit 706 is configured to measure and display a
length of cable, a
cable tension, etc... that can be used to track the location or position of
the tool string 700 along
the wellbore 102.
[0058] The tool string 700 includes a plurality of modules or tools to
perform various
functions. More specifically, the tool string 700 may include a swivel 708
configured to reduce
or prevent torque transmission between the cable 704 and the string 700. The
swivel 708 may
prevent rotation of the tool string 700 in the wellbore 102 as the cable 704
is reeled for raising
and/or for lowering the tool string 700. The tool string 700 may also include
one or more sensor
cartridge(s) 710. The sensor cartridge 710 preferably comprises one or more
formation
evaluation sensor(s) that can be used to correlate the position of the tool
string 700 with
measured geological features of the formation penetrated by the wellbore 102.
Alternatively or
additionally, the sensor cartridge 710 may comprise position or movement
detectors such as
accelerometers, magnetometers, etc... that can be used to track the location
or position of the
tool string 700 in the wellbore 102. The tool string 700 further includes a
heating tool or heating
module 720 that, as described in greater detail therein, applies a controlled
amount of heat
energy to the formation F to heat a portion of the formation F from which a
sample of heavy oil
is to be extracted. Finally, the tool string 700 includes a formation sampling
tool that may be
used following the heating of the formation F to obtain a sample of heavy oil
from the heated
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portion of the formation F. As shown in FIGS. 7a and 7b, the formation
sampling tool comprises
a probe module 730, an optional flowline heating module 740, a fluid property
sensing module
750, a sample carrier module 760 and a pump out module 770.
[0059] To determine an area of formation to be sampled, the sensor
cartridge 710 may be
provided with one or more sensor evaluation sensor(s) configured to detect
geological features of
the formation penetrated by the wellbore 102. For example, the sensor
cartridge may include
formation evaluation sensors such as natural gamma ray sensors, nuclear
magnetic resonance
(NMR) sensors, dielectric sensors, and the like. Additionally, the detected
geological features
may be correlated to locations or positions of the tool string 700 in the
wellbore 102, and in
particular to the relative position of the heating tool 720 and/or a sampling
probe 732 with
respect to the formation to be sampled F.
[0060] To determine the location or position of the tool string 700 in the
wellbore 102, the
sensor cartridge 710 may be also provided with movement and/or position
sensors.
Implementation examples of position detectors include, but are not limited to,
one or more
magnetometers configured to measure an orientation of the tool string 700.
Implementation
examples of movement detectors include, but are not limited to, one or more
accelerometers
configured to determine the tool string acceleration along the axis of the
wellbore 102, and thus,
an absolute or relative position of the tool string 700 along the wellbore
102.
[0061] To heat a portion of interest of the formation to be sampled (e.g.
the formation F), the
heating tool 720 is provided with a heater, e.g. an electrical heater, a
chemical heater, a
microwave heater or other heater known in the art. The heater may be at least
partially disposed
in a heating pad 722 (e.g. a rectangular pad) protruding from the housing of
the heating tool.
The heating pad 722 is preferably pressed against the wall 123 of the wellbore
102 with a bow
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spring 724 for promoting thermal coupling between the heating pad 722 and the
formation F.
The heating tool is preferably provided with suitable monitoring and control
electronics as
described for example with respect to FIG. 2. In one particular example, the
heating tool also
includes a portion of the electronics that transforms the electrical power
provided by the wireline
cable 704 to the tools or modules in the tool string 700. This configuration
may be advantageous
as high electrical power may not need to be conveyed across the different
modules of the string
700. Also, power electronics may already generate heat can be used to heat the
formation F.
[0062] To establish an exclusive fluid communication between the tool
string 700 and a
portion of interest of the formation, the probe module 730 is provided with an
extendable probe
assembly 732 having a sampling inlet. The probe assembly is remotely located
from the heating
pad 722, for example to avoid damage of an elastomeric seal of the probe
during heating of the
formation. Also, the probe assembly 732 and the heating pad 722 are in angular
or azimuthal
positional agreement with each other.
[0063] The probe assembly 732 is shown in a retracted position in FIG. 7a
and in an
extended position in FIG. 7b. The probe assembly is pressed against the
wellbore wall with
setting pistons 734, also show retracted in FIG. 7a and extended in FIG. 7b.
When the probe
sealingly engages the wellbore wall 123, fluid extracted from the formation
may flow through
the inlet of the probe to various components of the sampling tool through a
flowline 780. The
flow of formation fluid in the tool string 700 may be selectively routed to
the components of the
sampling tool by using valves, such as valves 734, 736, 764, 766, and 768.
[0064] To draw formation fluid from the formation, the pump out module 770
is provided
with a pump 772, e.g. a reciprocation pump, fluidly coupled to flowlines 780
and 782. If
desired, the fluid may be unloaded into the wellbore at exit port 784.
Additionally or
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alternatively, small volumes of formation fluid may be drawn into the tool by
using a drawdown
piston 738. A surface operator may switch the operations of the tool string
700 back and forth
between drawing fluid with the pump 772 and drawing fluid with the drawdown
piston 738 by
sending commands to the tool string to operate the valves 732 and 734.
[0065] To analyze the properties of the fluid being drawn in the flowline
780, the sensing
module 750 is provided with one or more fluid sensor(s) 752 operatively
coupled to the flowline
780. The fluid sensor 752 may be implement as one or more of a pressure
sensor, a
thermometer, a viscometer, a densimeter, a spectrometer (optical, NMR) and the
like. The
information sensed by the sensor 752 may be used to selectively route the
formation fluid in the
flow line 780 between the flowline 782 and a sample storage tank 762 by
manipulating valves
764, 766 and 768. In the shown example, the fluid sensor 752 is positioned
between the probe
assembly 732 and the pump 772 for measuring a property of the fluid prior the
routing to the
sample storage tank 762 for efficiently characterizing the fluid entering the
tool string. However,
the fluid sensor may alternatively be positioned between the pump 772 and the
exit port 784 (not
shown). This alternate configuration may be useful when connate water and
formation oil
segregate in the pump 772. Thus, water portions of the formation fluid and oil
portions of the
formation fluid may be separately characterized by the sensor 752.
[0066] To capture fluid extracted from the formation, the sample carrier
module 760 is
provided with one or more sample tank(s) 762. In the shown example, the sample
tank is located
close to the sampling port of the tool string 700 for minimizing the amount of
fluid that needs to
be drawn from the formation and to fill the flowline 780 before it reaches the
storage tank 762.
However, the sampling tank may alternatively be located elsewhere in the tool
string 700, for
example in a configuration referred to as a low shock sampling configuration.
Alternatively,
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small volumes of formation fluid may be captured in the drawdown piston 738,
and sealed
during transportation using the valve 734.
[0067] To heat the formation fluid drawn in the tool string 700, the tool
string 700 may be
provided with one or more flowline heating module(s) 740, disposed as desired
in the tool string
700. The flow line heating module comprises a heater 742, thermally coupled to
the flowline
780. In some examples, the heater may be used to selectively vary the
temperature of the fluid
entering the sensing module 750, and determine the variations of a fluid
property resulting from
temperature variations.
[0068] While the heating tool 720 is depicted above the probe module 730 in
the
embodiment of FIGS. 7a and 7b, the arragement of modules 720, 730, 740, 750,
760 and 770
may be flipped if desired (not shown). In this alternate flipped
configuration, the tool string 700
would have to be lowered instead of raised between the heating operation and
the sampling
operation. Other configurations of the tool string 700 may also be implemented
and do not
depart from this disclosure. Indeed, the tool 700 is preferably provided as
modular and therefore
can be configured based on objectives particular to each wells to be
evaluated.
[0069] In operation the tool string 700 may be used to mobilize and sample
fluid contained
in a formation of interest. Once an area F of formation to be sampled has been
determined, for
example using the measurements collected by the sensor cartridge 710, the
heating tool 720 is
aligned with the formation. To assist the alignment of the heating tool 720
with the formation F,
the depth of the heating tool 720 within the wellbore 102 may be determined
using any known
method of determining depth such as provided by the electronics and processing
unit 706.
Techniques such as cable flagging may be used to improve the positioning of
the heating tool
720. Additionally, the geological features detected by the sensor 710 may be
concurrently used
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with the depth provided by the electronics and processing unit 706 to further
improve the
positioning of the heating tool 720. Then heating of the formation to be
sampled may begin as
depicted in FIG. 7a.
[0070] Once the formation is deemed to be sampled, the sampling probe 732
is aligned with
the portion of the formation that has been heated with the heating tool 720.
Since in the
embodiment of FIGS. 7a and 7b the probe assembly 732 and the heating pad 722
are in angular
or azimuthal positional agreement with each other, the tool string 700 may
just be moved
upwardly a distance equal to about the space between the inlet of the sampling
probe 732 and the
heating pad 722, so that the inlet of the probe 432 faces with the portion of
the formation F
previously heated by the heating tool 720. To do so, controlling the depth of
the tool string 700
provided by the electronics and processing unit 706 may suffice. Indeed, since
the heating
module 720 and the probe module 730 are adjacent in the tool string 700, the
space between the
inlet of the sampling probe 432 and the heating pad 722 is on the order of 10
to 30 feet. The
known depth monitoring provided by surface unit 706 are usually accurate over
such range.
However, techniques such as cable flagging may be used to improve the
positional agreement of
the probe 732 with the heated portion of the formation. Additionally, the
geological features
detected by the sensor 710 may be concurrently used with the depth provided by
the electronics
and processing unit 706 to further improve the positional agreement of the
probe 732 with the
heated portion of the formation.
[0071] To insure that the rotation of the tool string 700 is limited as it
is raised in the
wellbore 102, the heating pad 722 and the bow spring 724 may be used to steer
the tool string
700 along a particular azimuth, maintaining thereby the angular position
agreement of the
sampling probe 732 with the heated portion of the formation. In addition,
reducing the amount
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of torque transmitted from the cable 704 to the tool string 700 with the
swivel 708 also facilitates
maintaining the angular position agreement of the sampling probe 732 with the
heated portion of
the formation. Finally, an operator at the surface may check that the angular
position agreement
has been maintained during moving the tool string 700 by monitoring for
example the orientation
of the tool string determined by the magnetometers provided by the sensor
cartridge 710.
[0072] Once the sampling probe 732 is aligned with the portion of the
formation that has
been heated with the heating tool 720, the sampling probe may be extended as
shown in FIG. 7b
and sampling of the formation F may begin, for example as described in greater
details therein.
[0073] FIGS. 8a-8b depict another example downhole tool string 1010
including a heating
tool 1038 and a remote sampling tool 1020 that may be used to mobilize and
obtain a sample of
heavy oil. In particular, the tool string 1010 includes an anchoring section
1014 and a movable
section 1016. In the shown implementation, the heating tool 1038 and the
sampling tool 1020
are both disposed in the movable section 1016 of the tool string 1010. The
distance between the
anchoring section 1014 and the movable section 1016 can be precisely varied by
extending
and/or retracting a thrust or rod operatively coupled therebetween. Thus,
multiple or a sequence
of operations using the heating tool 1038 and the sampling tool 1020 may be
performed at
substantially a single location or depth.
[0074] In operation the tool string 1010 may be suspended to a wireline
cable 1104 or other
conveyance means, and lowered into the wellbore 102. Once an area F of
formation to be
sampled has been determined, for example using the measurements collected by
the sensor
cartridge (not shown), the heating tool 1038 is aligned with the formation,
and anchors 1012 are
selectively extended away or outwardly from the downhole tool 1010 to contact
or engage the
wall 123 of the wellbore 102, thereby anchoring or fixing the position of the
section 1014
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relative to the wall 123 of the wellbore 102. Alternatively, the anchors 1012
may be extended to
contact the wall 123 of the wellbore 102 prior to aligning the heating tool
1038 with the
formation to be sampled. In this case, the section 1016 may be moved with
respect to the section
1014 relatively precise distances along a longitudinal axis of the downhole
tool string 1010 to
align the heating tool 1038 with the area to be sampled. In this manner, the
heating tool 10381
can be more precisely positioned at depths or locations within a wellbore than
would otherwise
be possible using conventional techniques such as, for example, flagging a
wireline cable, using
gamma ray or other sensor correlation techniques, etc... Further, the coupling
mechanism
between the anchoring section 1014 and the moving section 1016 may be used to
selectively
orient the heating tool along a desired orientation in the wellbore 102. Then,
heating of the
formation to be sampled may begin as depicted in FIG. 8a. In particular, a
heating pad 1030 may
be extended from the heating tool 1038 into thermal contact with the wellbore
wall 123. The
heating tool may further be stabilized with an extendable arm 1032.
100751 Once the formation is deemed to be sampled, the heating pad 1030 and
the arm 1032
may be retracted for permitting movement of the heating tool 1038. Then the
inlet of a probe
1022 provided by the sampling tool 1020 is aligned with the portion of the
formation that has
been heated with the heating tool 1038. As mentioned before, the movable
section 1016 of the
example downhole tool string 1010 includes both the heating tool 1038 and the
sampling tool
1020, spaced apart a known distance along the longitudinal axis of the
downhole tool 1010 from
the heating tool 1038. Thus, by extending the movable section 1016 by the
known distance
separating the heating tool from the sampling tool, the probe 1022 may be
positioned at the level
of the heated portion of the formation. Further, the anchors 1012 may be
configured to prevent
rotary movement of the tool string 1010 when extending the section 1016. Thus,
the orientation
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of the probe 1022 will align with the portion of the formation F previously
heated by the heating
tool 1038. Once the sampling probe 1022 is aligned with the portion of the
formation that has
been heated with the heating tool 1038, the sampling probe and setting pistons
1024 may be
extended as shown in FIG. 8b and sampling of the formation F may begin.
[0076] FIG. 9 shows a flow diagram that depicts an example method 900 to
mobilize and
sample formation fluid. In particular, in the method 900 facilitates the
positioning of a sampling
tool at a location previously occupied by a heating tool. The method 900 may
be implemented
using for example with the tool string 700 of FIGS. 7a-b or the tool string
1010 of FIGS. 8a-b.
[0077] At step 902, a tool string is suspended in a borehole. The tool
string includes a
heating module to convey heat energy to a portion of the subterranean
formation and a heating
control unit to control the heat energy provided by the heating module. The
tool string also
includes a sampling probe remote from the heating module. In addition, the
tool string includes
an orientation module to control the orientation of the sampling probe
relative to the
subterranean formation as the tool string is moved along the borehole. At
optional step 904, an
area of formation to be sampled is determined. For example, a portion of the
well is logged
using a formation evaluation sensor conveyed by the tool string lowered at
step 902. The log is
analyzed to select the sampling area. Then at step 906, a heating tool is
positioned adjacent the
selected sampling area using one or more techniques discussed therein. The
heating operation
starts at step 908 and continues until the formation is deemed to be sampled
(step 910). At step
912, the heating tool is moved in the borehole to leave space to a sampling
tool at a location
adjacent to the heated portion of the formation. Indeed in method 900, the
heating and sampling
operations are decoupled, thereby enabling more optimal control of the heating
and sampling
operations for formations containing heavy oil. Further, decoupling the
formation heating and
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sampling systems may provide a better protection of the sampling elements that
are sensitive to
high temperatures, such as elastomeric sealing parts of the probe. Still
further, having a separate
heating and sampling tools permits modularity of the downhole tool string,
enabling thereby
various string configurations to be implemented as desired with a limited
number of tool assets.
At step 912 however, the sampling tool is positioned in the borehole so that a
sampling inlet
defined by the sampling probe is to be fluidly connected to the portion of the
subterranean
formation previously heated by the heating tool. To do so, the methods for
aligning the sampling
probe with the heated portion of the formation discussed with respect to FIGS.
7a, 7b, 8a, and 8b
may be used, as well as other methods discussed therein. At step 914, the
formation may be
sampled. At step 916, the heating and/or sampling operations may be repeated
as desired, either
at the formation area previously selected or at a new selected area.
[0078] While the foregoing examples describe example heating and sampling
tools as being
implemented as wireline devices, any other manner of deploying tools in
boreholes could be
used instead. For example, drill pipe and/or coiled tubing may be used to
deploy one or both of
the example heating and sampling tools described herein to achieve similar or
identical results.
Further, while the examples described herein are depicted in use with an
uncased borehole, the
example methods and apparatus described herein could also be employed in cased
boreholes.
[0079] Although certain methods, apparatus, and articles of manufacture
have been described
herein, the scope of coverage of this patent is not limited thereto. To the
contrary, this patent
covers all methods, apparatus, and articles of manufacture fairly falling
within the scope of the
appended claims either literally or under the doctrine of equivalents.
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