Note: Descriptions are shown in the official language in which they were submitted.
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MINIMIZATION OF CONTAMINANTS IN A SAMPLE CHAMBER
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] None.
FIELD OF THE INVENTION
[0002] Aspects relate to downhole drilling. More specifically, aspects relate
to
minimization of contaminants in sample chambers in downhole tools.
BACKGROUND INFORMATION
[0003] Wellbores are drilled to locate and produce hydrocarbons. A downhole
drilling tool with a bit at an end thereof is advanced into the ground to form
a
wellbore. As the drilling tool is advanced, a drilling mud is pumped through
the
drilling tool and out the drill bit to cool the drilling tool and carry away
cuttings. The
fluid exits the drill bit and flows back up to the surface for recirculation
through the
tool. The drilling mud is also used to form a mudcake to line the wellbore.
[0004] During the drilling operation, various evaluations of the formations
penetrated
by the wellbore can be performed. In some cases, the drilling tool may be
provided
with devices to test and/or sample the surrounding formation. In some cases,
the
drilling tool may be removed And a wireline tool may be deployed into the
wellbore to
test and/or sample the formation. In other cases, the drilling tool may be
used to
perform the testing or sampling. These samples or tests may be used, for
example, to
locate valuable hydrocarbons. Examples of drilling tools with testing/sampling
capabilities are provided in U.S. Pat. Nos. 6,871,713, 7,234,521 and
7,114,562, the
entireties of which are incorporated herein by reference.
[0005] Formation evaluation often requires that fluid from the formation be
drawn
into the downhole tool for testing and/or sampling. Various devices, such as
probes,
are extended from the downhote tool to establish fluid communication with the
formation surrounding the webore and to draw fluid into the downhole tool. A
typical probe is a circular element extended from the downhole tool and
positioned
against the sidewall of the we bore. A rubber packer at the end of the probe
is used to
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create a seal with the wellbor; sidewall. Another device used to form a seal
with the
wellbore sidewall is referred t.o as a dual packer. With a dual packer, two
elastomeric
rings expand radially about the tool to isolate a portion of the wellbore
therebetween.
The rings form a seal with the wellbore wall and permit fluid to be drawn into
the
isolated portion of the wellbore and into an inlet in the downhole tool.
[0006] The mudcake lining the wellbore is often useful in assisting the probe
and/or
dual packers in making the seal with the wellbore wall. Once the seal is made,
fluid
from the formation is drawn into the downhole tool through an inlet by
lowering the
pressure in the downhole tool. Examples of probes and/or packers used in
downhole
tools are described in U.S. Pat. Nos. 6,301,959; 4,860,581; 4,936,139;
6,585,045;
6,609,568; 6,719,049 and 6,964,301, the entireties of which are incorporated
herein
by reference.
[0007] The collection and sampling of underground fluids contained in
subsurface
formations is well known. In the petroleum exploration and recovery
industries, for
example, samples of formation fluids are collected and analyzed for various
purposes,
such as to determine the existence, composition and/or producibility of
subsurface
hydrocarbon fluid reservoirs. This aspect of the exploration and recovery
process can
be crucial in developing drilling strategies, and can impact significant
financial
expenditures and/or savings.
[0008] To conduct valid fluid analysis, the fluid obtained from the subsurface
formation should possess sufficient purity, or be virgin fluid, to adequately
represent
the fluid contained in the formation. As used within the scope of the present
disclosure, the terms "virgin fluid," "acceptable virgin fluid" and variations
thereof
mean subsurface fluid that is pure, pristine, connate, uncontaminated or
otherwise
considered in the fluid sampli rig and analysis field to be sufficiently or
acceptably
representative of a given formation for valid hydrocarbon sampling and/or
evaluation.
[0009] Various challenges may arise in the process of obtaining virgin fluid
from
subsurface formations. Again with reference to the petroleum-related
industries, for
example, the earth around the borehole from which fluid samples are sought
typically
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contains contaminates, such as. filtrate from the mud utilized in drilling the
borehole.
This material often contaminates the virgin fluid as it passes through the
borehole,
resulting in fluid that is generally unacceptable for hydrocarbon fluid
sampling and/or
evaluation. Such fluid is referred to herein as "contaminated fluid." Because
fluid is
sampled through the borehole, mudcake, cement and/or other layers, it is
difficult to
avoid contamination of the fluid sample as it flows from the formation and
into a
downhole tool during sampli g. A challenge thus lies in minimizing the
contamination of the virgin fluid during fluid extraction from the formation.
[0010] FIG. 1 depicts a subst lace formation 102 penetrated by a wellbore 104.
A
layer of mud cake 106 lines a iidewall 108 of the wellbore 104. Due to
invasion of
mud filtrate into the formatio during drilling, the wellbore is surrounded by
a
cylindrical layer known as th: invaded zone 110 containing contaminated fluid
112
that may or may not be mixed with virgin fluid. Beyond the sidewall of the
wellbore
and surrounding contaminak d fluid, virgin fluid 114 is located in the
formation 102.
As shown in FIG. 1, contaminates tend to be located near the wellbore wall in
the
invaded zone 110.
[0011] FIG. 2 shows the typical flow patterns of the formation fluid as it
passes from
subsurface formation 102 into a downhole tool 202. The downhole tool 202 is
positioned adjacent the formation and a probe 204 is extended from the
downhole tool
through the mudcake 106 to the sidewall 108 of the wellbore 104. The probe 204
is
placed in fluid communication with the formation 102 so that formation fluid
may be
passed into the downhole tool 202. Initially, as shown in FIG. 1, the invaded
zone 110
surrounds the sidewall 108 and contains contamination. As fluid initially
passes into
the probe 204, the contamine ed fluid 112 from the invaded zone 110 is drawn
into
the probe with the fluid thereby generating fluid unsuitable for sampling.
However, as
shown in FIG. 2, after a certai amount of fluid passes through the probe 204,
the
virgin fluid 114 breaks throug4, and begins entering the probe.
[0012] Formation evaluation i c typically performed on fluids drawn into the
downhole tool. Techniques currently exist for performing various measurements,
pretests and/or sample collection of fluids that enter the downhole tool.
Various
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methods and devices have been proposed for obtaining subsurface fluids for
sampling
and evaluation. For example, U.S. Pat. Nos. 6,230,557, 6,223,822, 4,416,152,
and
3,611,799, and PCT Patent Application Publication No. WO 96/30628, the
entireties
of which are incorporated herein by reference, describe certain probes and
related
techniques to improve sampling. However, it has been discovered that when the
formation fluid passes into the downhole tool, various contaminants, such as
wellbore
fluids and/or drilling mud, m.4 enter the tool with the formation fluids.
These
contaminates may affect the quality of measurements and/or samples of the
formation
fluids. Moreover, contamination may cause costly delays in the wellbore
operations
by requiring additional time for more testing and/or sampling. Additionally,
such
problems may yield false results that are erroneous and/or unusable. Other
techniques
have been developed to separate virgin fluids during sampling. For example,
U.S. Pat.
No. 6,301,959, the entirety of which is incorporated herein by reference,
discloses a
sampling probe with two hydraulic lines to recover formation fluids from two
zones
in the borehole. In this patent, borehole fluids are drawn into a guard zone
separate
from fluids drawn into a probe zone. Despite such advances in sampling, there
remains a need to develop tecl-miques for fluid sampling to optimize the
quality of the
sample and efficiency of the sampling process.
[00131 To increase sample ,4uality, it is desirable that the formation fluid
entering
into the downhole tool be sufficiently "clean" or "virgin" for valid testing.
In other
words, the formation fluid should have little or no contamination. Attempts
have been
made to eliminate contaminates from entering the downhole tool with the
formation
fluid. For example, as depicted in U.S. Pat. No. 4,951,749, filters have been
positioned in probes to block contaminates from entering the downhole tool
with the
formation fluid. Additionally, as shown in U.S. Pat. No. 6,301,959, a probe is
provided with a guard ring to ,lvert contaminated fluids away from clean fluid
as it
enters the probe. The entiretie, of both of these are incorporated herein by
reference.
[0014] Techniques have also been developed to evaluate fluid passing through
the
tool to determine contamination levels. In some cases, techniques and
mathematical
models have been developec for predicting contamination for a merged flowline.
See,
for example, PCT Patent Application No. WO 2005065277 and PCT Patent
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Application No. 00/50876, the entireties of which are hereby incorporated by
reference. Techniques for predicting contamination levels and determining
cleanup
times are described in P. S. Hammond, "One or Two Phased Flow During fluid
Sampling by a Wireline Tool," Transport in Porous Media, Vol. 6, p. 299-330
(1991),
the entirety of which is hereby incorporated by reference. Hammond describes a
semi-
empirical technique for estimating contamination levels and cleanup time of
fluid
passing into a downhole tool ihrough a single flowline.
[0015] Despite the existence of techniques for performing formation
evaluation,
conventional systems fail to adequately mitigate the problem of contamination.
SUMMARY
[0016] The following presents a simplified summary of the innovation in order
to
provide a basic understanding of some aspects of the innovation. This summary
is not
an extensive overview of the innovation. It is not intended to identify
key/critical
elements of the innovation or to delineate the scope of the innovation. Its
sole purpose
is to present some concepts of the innovation in a simplified form as a
prelude to the
more detailed description that is presented later.
100171 The innovation disclosed and claimed herein, in one aspect thereof,
comprises
an apparatus that facilitates removal of contaminants from a fluid sample. One
embodiment of such an apparatus can include an intake section capable of
sealingly
engaging a borehole wall to o'Ytain formation fluid through the wall, and a
first flow
line in fluid communication with the intake section. At least a portion of the
formation fluid obtained by the intake section can be made to pass through the
first
flow line. Additionally, the Tparatus can include a sample chamber with a
floating
piston. The floating piston can draw at least a first quantity of the portion
into the
sample chamber from the firs i flow line, and then the first quantity of the
portion can
be forced out of the sample chamber. This process can be repeated until
sufficient
contaminants have been removed, such as those contained in a dead volume
between
the flow line and the sample chamber. Finally, the floating piston can draw at
least a
second quantity of the portion into the sample chamber for storage therein as
the fluid
sample.
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[0018] In another aspect of tile ...subject innovation, the innovation can
comprise a
method for obtaining samples with lower levels of contaminants. Such a method
can
remove contaminants from a fluid sample, and can include the steps of
obtaining fluid
from a formation and passing a first quantity of the fluid through a sample
flow line.
A connection between the sample flow line and a sample chamber can be opened,
and
a first portion of the first quantity of the fluid can be drawn into the
sample chamber
via a floating piston. The fir portion can be forced out of the sample
chamber, and
this process can be repeated tintil sufficient contaminants have been removed.
Finally, a second portion of the first quantity of the fluid can be drawn into
the sample
chamber as the fluid sample.
[0019] To the accomplishmelt of the foregoing and related ends, certain
illustrative
aspects of the innovation are described herein in connection with the
following
description and the annexed drawings. These aspects are indicative, however,
of but a
few of the various ways in wl-ich the principles of the innovation can be
employed
and the subject innovation is intended to include all such aspects and their
equivalents. Other advantages and novel features of the innovation will become
apparent from the following detailed description of the innovation when
considered in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic view of a subsurface formation penetrated by a
wellbore
lined with mudcake, depictinc. the virgin fluid in the subsurface formation.
[0021] FIG. 2 is a schematic view of a down hole tool positioned in the
wellbore with
a probe extending to the formation, depicting the flow of contaminated and
virgin
fluid into a downhole sampliN tool.
[0022] FIG. 3 is a schematic liew of downhole wireline tool having a fluid
sampling
device.
[0023] FIG. 4 is a schematic view of a downhole drilling tool with an
alternate
embodiment of the fluid sam:. ling device of FIG. 3.
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[0024] FIG. 5 is a detailed view of the fluid sampling device of FIG. 3
depicting an
intake section and a fluid flow section.
[0025] FIG. 6 illustrates a system that can reduce levels of contaminants in a
sample
chamber in accordance with an embodiment of the subject innovation.
[0026] FIG. 7A illustrates an embodiment of another system capable of reducing
levels of contaminants obtained in a sample chamber.
[0027] FIG. 7B illustrates an embodiment of a further system capable of
reducing
levels of contaminants obtain44 in a sample chamber.
[0028] FIG. 8 illustrates a method of obtaining a sample of fluid with reduced
levels
of contaminants.
[0029] FIG. 9 is a schematic view of a wellsite having a rig with a downhole
tool
suspended therefrom and into a subterranean formation.
DETAILED DESCRIPTION
[0030] The innovation is now described with reference to the drawings, wherein
like
reference numerals are used to refer to like elements throughout. In the
following
description, for purposes of e-t.planation, numerous specific details are set
forth in
order to provide a thorough understanding of the subject innovation. It may be
evident, however, that the innovation can be practiced without these specific
details.
In other instances, well-known structures and devices are shown in block
diagram
form in order to facilitate describing the innovation.
[0031] It is to be understood ihat the following disclosure provides many
different
embodiments, or examples, kr implementing different features of various
embodiments. Specific examples of components and arrangements are described
below to simplify the present disclosure. These are, of course, merely
examples and
are not intended to be limiting. In addition, the present disclosure may
repeat
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reference numerals and/or letters in the various examples. This repetition is
for the
purpose of simplicity and cle4.ity and does not in itself dictate a
relationship between
the various embodiments and, or configurations discussed. Moreover, the
formation of
a first feature over or on a second feature in the description that follows
may include
embodiments in which the fir t and second features are formed in direct
contact, and
may also include embodiments in which additional features may be formed
interposing the first and secorid features, such that the first and second
features may
not be in direct contact.
[0032] Referring to FIG. 3, an example environment with which aspects of the
present disclosure may be used is shown. In the illustrated example, a
downhole tool
302 can be provided, such as a Modular Formation Dynamics Tester (MDT) by
Schlumberger Corporation, ad further depicted, for example, in U.S. Pat. Nos.
4,936,139 and 4,860,581, the t.ntireties of which are incorporated by
reference herein.
The downhole tool 302 can Ix deployable into bore hole 104 and suspended
therein
with a wire line (e.g., conventional, etc.) 304, or conductor or tubing (e.g.,
conventional or coiled tubing, etc.), below a rig 306 as will be appreciated
by one of
skill in the art. The illustrated Doi 302 can be provided with various modules
and/or
components 308, including, but not limited to, a fluid sampling device 310
used to
obtain fluid samples from the subsurface formation 102. The fluid sampling
device
310 can be provided with a probe 312 extendable through the mudcake 106 and to
sidewall 108 of the borehole 04 for collecting samples. The samples can be
drawn
into the downhole tool 302 thiough the probe 312.
[0033] While FIG. 3 depicts a modular wireline sampling tool that can be used
for
collecting samples according t one or more aspects of the present innovation,
it will
be appreciated by one of skill in the art that the subject innovation may be
used in any
downhole tool. For example, FIG. 4 shows an alternate downhole tool 402 having
a
fluid sampling system 404 the-ein. In this example, the downhole tool 402 can
be a
drilling tool including a drill string 406 and a drill bit 408. The downhole
drilling tool
402 may be of a variety of dr.1 ling tools, such as a Measurement-While-
Drilling
(MWD), Logging-While Drilling (LWD) or other drilling system. The tools 302
and
304 of FIGS. 3 and 4, respectitvely, may have alternate configurations, such
as
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modular, unitary, wireline, co ited tubing, autonomous, drilling and other
variations of
downhole tools.
[0034] Referring now to FIG. 5, the fluid sampling system 310 of FIG. 3 is
shown in
greater detail. The sampling system 310 can include an intake section 502 and
a flow
section 504 capable of selectwely drawing fluid into a portion of the downhole
tool.
[0035] The intake section 502 can include a probe 312 mounted on an extendable
base 30 having a seal 508, such as a packer, capable of sealingly engaging the
borehole wall 108 around the probe 312. The intake section 502 can be
selectively
extendable from the downholc tool 302 via extension pistons 510. The probe 312
can
be provided with an interior channel 512 and an exterior channel 514 separated
by
wall 516. In some embodime'Es, the wall 516 can be concentric with the probe
312.
However, the geometry of tit probe and the corresponding wall may be of any
geometry. Additionally, one or more walls 516 may be used in various
configurations
within the probe. Alternatively, an intake section can employ dual packers, as
discussed elsewhere herein or in documents incorporated herein by reference.
[0036] The flow section 504 includes flow lines 518 and 520 driven by one or
more
pumps 522. A first flow line 518 is in fluid communication with the interior
channel
512, and a second flow line 520 is in fluid communication with the exterior
channel
514. The illustrated flow section may include one or more flow control
devices, such
as the pump 522 and valves 524, 526, 528 and 530 depicted in FIG. 5, capable
of
selectively drawing fluid into various portions of the flow section 504. Fluid
can be
drawn from the formation through the interior and exterior channels and into
their
corresponding flow lines.
[0037] In aspects, contamin-Aed fluid may be passed from the formation through
exterior channel 514, into flow line 520 and discharged into the wellbore 104.
In the
same or other aspects, fluid c;..n pass from the formation into the interior
channel 512,
through flow line 518 and eitkr diverted into one or more sample chambers 532,
or
discharged into the wellbore. Once it is determined that the fluid passing
into flow
line 518 is virgin fluid, a valve 524 and/or 530 may be activated using known
control
techniques by manual and/or automatic operation to divert fluid into the
sample
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chamber. In accordance with aspects of the subject innovation, systems and/or
methods discussed further ht :ein can be employed to reciprocate the piston in
the
sample bottle to minimize contaminants obtained in the sample, particularly
from
fluid volume between a sample flow line and a floating piston in the sample
chamber
532 (e.g., contaminants along flow line 518, such as between valve 524 and
sample
chamber 532, etc.). Upon a determination that contaminants have been
sufficiently
minimized, a sample of fluid can then be obtained in sample chamber 532 and
retained.
[00381 The fluid sampling system 310 (or 404, etc.) can also be provided with
one or
more fluid monitoring systems 534 capable of analyzing the fluid as it enters
the
probe 312. The fluid monitonng system 534 may be provided with various
monitoring
devices, such as optical fluid analyzers, as will be discussed more fully
herein.
[0039] The details of the various arrangements and components of the fluid
sampling
system 310 (or 404, etc.) described above as well as alternate arrangements
and
components for the system 310 (or 404, etc.) are apparent to a person of skill
in the art
in light of the subject disclosure and those of patents and publications
incorporated by
reference herein. Moreover, tr e particular arrangement and components of the
downhole fluid sampling system 310 (or 404, etc.) may vary depending upon
factors
in each particular design, use or situation. Thus, neither the system 310 (or
404, etc.)
nor the present disclosure are limited to the above described arrangements and
components and may include any suitable components and arrangement. For
example,
various flow lines, pump plact-ment and valving may be adjusted to provide for
a
variety of configurations. Similarly, the arrangement and components of the
downhole
tool 302 may vary depending .pon factors in each particular design, or use,
situation.
The above description of exemplary components and environments of the tool 302
with which the fluid sampling ,levice 310 (or 404, etc.) of the present
disclosure may
be used is provided as an exalt. ple only and is not limiting upon the present
disclosure.
[0040] With continuing reference to FIG. 5, the flow pattern of fluid passing
into the
downhole tool 302 is illustrated. Initially, as shown in FIG. 1, an invaded
zone 110
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surrounds the borehole wall 108. Virgin fluid 114 is located in the formation
102
behind the invaded zone 110. At some time during the process, as fluid is
extracted
from the formation 102 into the probe 312, virgin fluid breaks through and
enters the
probe 312 as shown in FIG. 5. As the fluid flows into the probe, the
contaminated
fluid 114 in the invaded zone 110 near the interior channel 512 is eventually
removed
and gives way to the virgin fluid 114. Thus, primarily virgin fluid 114 is
drawn into
the interior channel 512, while the contaminated fluid 112 flows into the
exterior
channel 514 of the probe 312. To facilitate such result, fluid can be pumped
into and
out of the sample chamber one or more times to remove contaminants initially
present, or those remaining in the dead volume between the sample flow line
518 and
the sample chamber 532. Ado itionally, it is to be understood that while FIG.
5
illustrates a single sample chEinber 532, substantially any number of sample
chambers
can be used in various emboetments. Moreover, in various embodiments, systems
and
methods of the subject innovation can be used in connection with other fluid
sampling
systems, such as those described in U.S. Pat. No. 8,210,260, the entirety of
which is
incorporated herein by reference.
[0041] Turning now to FIG. 6, illustrated is a fluid sampling system 600 with
multiple sample chambers tin, t- can be used with systems and methods of the
subject
innovation. Although two sets of three sample chambers 532 are illustrated in
system
600, it is to be appreciated that substantially any number of sample chambers
532 can
be used in connection with flit subject innovation. Each sample chamber can be
associated with a normally clo.ied valve 602 and a normally open valve 604,
and
throttle/seal valves 606 can be associated with the flowline from the
probe/packer
inlet at 608 to the wellbore o'Alet at 610. These valves 602, 604, and 606 can
be
controlled by electronics (or :omputer, etc.) 612. A relief valve 614 can be
included
to control or limit the pressu.e in system 600.
[0042] In operation, valves 602, 604, and 606 can be controlled to direct
fluid into
sample chambers 532. As explained herein, fluid directed into sample chambers
can
contain contaminants, such as from the dead volume between a sample flow line
and
the floating piston of the sample chamber(s) 532. The volume of fluid in one
or more
of the sample chambers 532 (e.g., each sample chamber 532) can then be pumped
out
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of the back side of the sampic chamber by using the floating piston 616 in a
manner
similar to a displacement un;l. This action of the floating piston 616 can be
controlled
automatically or manually (e.g., e.g., by a user at the surface, a remote
location, etc.).
This fluid can be discharged into the wellbore 104, e.g., via an optional
relief valve
614 or otherwise. In some situations, this process may need to be repeated
more than
once in order to obtain a sample of virgin fluid. Drawing fluid into the
sample
chamber(s) 532 and back out via reciprocation of floating piston(s) 616 can be
repeated until a sufficient level of confidence is gained that the
contaminated fluid
(e.g., of the dead volume in the flow line 518, etc.) has been removed. This
confidence can be gained based at least in part on any of a number of factors,
which
can include the relative volume of potentially contaminated fluid to that of
the sample
chamber (e.g., determining a number of iterations based on the ratio of the
volumes,
so as to ensure virgin fluid will ultimately be drawn into the sample chamber,
etc.),
based on a measured level of .ontamination of the fluid prior to entering the
sample
chamber 532 as determined tiling techniques known in the art or discussed
herein
(e.g., via an optical fluid anal:,zer (OFA), etc.), based on a measured level
of
contamination of fluid pumped out of the sample chamber 532, etc. After the
fluid is
sufficiently free from contaminants, virgin fluid can be drawn into the sample
chamber 532 for storage ther: in.
[0043] Turning to FIGS. 71, and 7B, illustrated are two alternate embodiments
of a
system according to the subject innovation. In FIG. 7A, as illustrated, sample
chamber 532 can employ a mechanical device 702 (e.g., a spring, etc.) to force
fluid
back into a flow line (e.g., fle N line 518) to remove potential contaminants
and ensure
virgin fluid is obtained in sample chamber 532. Similarly, in FIG. 7B, a
pressure-
based, pneumatic or similar device 704 (e.g., a closed nitrogen charge, etc.)
can be
similarly used to push fluid beck into a flow line. As illustrated, a system
such as in
FIG. 7B can include manual Naives 706. Embodiments similar to those of FIGS.
7A
and 7B, that can employ a deu Ice to force fluid back into the flow line, can
be used in
systems where it is not possib e to push fluid out the back side of a sample
chamber
532. The actions of mechanical and/or pressure-based devices discussed in
connection with FIGS. 7A a- d 7B can be controlled automatically or manually
(e.g.,
by a user at the surface, a rerlote location, etc.).
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[0044] FIG. 8 illustrates a rre,thodology 800 of improving the quality of
fluid
obtained in a sample chamber in accordance with aspects of the subject
innovation.
While, for purposes of simplicity of explanation, the one or more
methodologies
shown herein, e.g., in the form of a flow chart, are shown and described as a
series of
acts, it is to be understood and appreciated that the subject innovation is
not limited by
the order of acts, as some acni may, in accordance with the innovation, occur
in a
different order and/or concur:ently with other acts from that shown and
described
herein. For example, those skilled in the art will understand and appreciate
that a
methodology could alternativ,:ly be represented as a series of interrelated
states or
events, such as in a state diagram. Moreover, not all illustrated acts may be
required to
implement a methodology in iccordance with the innovation.
[0045] Method 800 can begin at step 802, wherein fluid can be allowed to pass
through a sample flow line, such as flow line 518. Next, at 804, a
determination can
be made that the fluid passing through the sample flow line is virgin fluid,
i.e., that it
is sufficiently free of contaminants. This determination can be made based on
analysis such as discussed he!ein (e.g., via an OFA, etc.). If necessary, such
as if the
fluid is determined to have ur Acceptably high levels of contaminants, steps
802 and
804 can be repeated with further monitoring of the fluid until the fluid is
determined
to be virgin fluid. Next, at 80vi, a connection between the sample flow line
and a
sample chamber can be opene :. At 808, fluid can be drawn into the sample
chamber.
However, this fluid may have unacceptable levels of contaminants, for example,
due
to the dead volume of fluid between the flow line and the sample chamber.
Because
of this, at 810, the fluid can b.: forced out of the sample chamber to "flush"
the sample
chamber and remove contaminants that may be contained in it. The fluid can be
forced out of the sample chamber by pushing out of the back of the sample
chamber
by using the floating piston, 11 y using a mechanical device (such as a
spring, etc.) to
force it out of the sample chamber, by using pressure (e.g., a pneumatic
device such
as a closed nitrogen charge, ot=.) to force the fluid out of the sample
chamber, etc.
[0046] Next, at 812, a determination can be made whether to re-"flush" the
sample
chamber by repeating steps 808 and 810, by determining whether sufficient
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contaminants have been removed, i.e., whether the fluid that will next enter
the
sample chamber is virgin fluid. This determination can be based on
measurements of
fluid before or after being drawing into and forced out of the sample chamber,
based
on system parameters (e.g., one or more relevant volumes, etc.), other
factors, or a
combination of factors. If it is determined that it is necessary to re-"flush"
the sample
chamber, method 800 can return to step 808, and can repeat steps 808, 810, and
812
until it is determined that suf icient contaminants have been removed. If not,
the
method can finish at step 814, by drawing fluid into the sample chamber to be
retained therein as a representative sample of the formation (e.g., for
testing, etc.).
[0047] FIG. 9 illustrates a wellsite system 900 that the subject innovation
can be used
in connection with. The wellsite system includes a surface system 902, a
downhole
system 904 and a surface control unit 906. In the illustrated embodiment, a
borehole
908 can be formed by rotary drilling in a conventional manner. In light of the
teachings herein, those of ordinary skill in the art will appreciate, however,
that the
subject innovation can be applied in downhole applications other than
conventional
rotary drilling, and is not limi,ed to land-based rigs. Examples of other
downhole
application may involve the use of wireline tools (see, e.g., FIG. 2 or 3),
casing
drilling, coiled tubing, and other downhole tools.
[0048] The downhole system 904 includes a drill string 910 suspended within
the
borehole 908 with a drill bit 912 at its lower end. The surface system 902
includes the
land-based platform and derrick assembly 914 positioned over the borehole 908
penetrating a subsurface forniation 102. The assembly 914 includes a rotary
table 916,
kelly 918, hook 920 and rotary swivel 922. The drill string 910 is rotated by
the rotary
table 916, energized by appantus not shown, which engages the kelly 918 at the
upper end of the drill string. The drill string 910 is suspended from a hook
920,
attached to a traveling block (,lso not shown), through the kelly 918 and the
rotary
swivel 922, which permits rot3tion of the drill string relative to the hook.
[0049] The surface system ft, ther includes drilling fluid or mud 926 stored
in a pit
928 formed at the well site. it pump 930 delivers the drilling fluid 926 to
the interior
of the drill string 910 via a port in the swivel 922, inducing the drilling
fluid to flow
downwardly through the drill string 910 as indicated by the directional arrow
932.
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The drilling fluid exits the drdl string 910 via ports in the drill bit 912,
and then
circulates upwardly through the region between the outside of the drill string
and the
wall of the borehole, called the annulus, as indicated by the directional
arrows 934. In
this manner, the drilling fluid lubricates the drill bit 912 and carries
formation cuttings
up to the surface as it is returned to the pit 928 for recirculation.
[0050] The drill string 910 further includes a bottom hole assembly (BHA),
generally
referred to as BHA 936, near the drill bit 912 (in other words, within several
drill
collar lengths from the drill bit). The bottom hole assembly includes
capabilities for
measuring, processing, and storing information, as well as communicating with
the
surface. The BHA 936 can include one or more of drill collars 938, 940, or 942
for
performing various other measurement functions.
[0051] The BHA 936 inclu& s the formation evaluation assembly 944 for
determining and communicating one or more properties of the formation 102
surrounding borehole 908, s..µch as formation resistivity (or conductivity),
natural
radiation, density (gamma ray or neutron), and pore pressure. The BHA also
includes
a telemetry assembly 946 for communicating with the surface unit 906. The
telemetry
assembly 946 includes drill c. liar 942 that houses a measurement-while-
drilling
(MWD) tool. The telemetry assembly further includes an apparatus 948 for
generating
electrical power to the downhc le system. While a mud pulse system is depicted
with a
generator powered by the flow of the drilling fluid 924 that flows through the
drill
string 910 and the MWD drill collar 942, other telemetry, power and/or battery
systems may be employed.
[0052] Formation evaluation assembly 944 includes drill collar 940 with
stabilizers
or ribs 950 and a probe 952 positioned in the stabilizer. The formation
evaluation
assembly is used to draw fluid into the tool for testing. The probe 952 may be
similar
to the probe as described else' /here herein or in documents incorporated by
reference.
Flow circuitry and other featut t..s may also be provided in the formation
evaluation
assembly 944. The probe may )e positioned in a stabilizer blade as described,
for
example, in U.S. Patent Application Publication No. 2005/0109538, the entirety
of
which is incorporated by reference herein.
CA 02826537 2013-09-09
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[0053] Sensors are located about the wellsite to collect data, for example in
real time,
concerning the operation of the wellsite, as well as conditions at the
wellsite. For
example, monitors, such as cameras 954, may be provided to provide pictures of
the
operation. Surface sensors or gauges 956 are disposed about the surface
systems to
provide information about the surface unit, such as standpipe pressure, hook
load,
depth, surface torque, rotary rpm, among others. Downhole sensors or gauges
958
may be disposed about the dflling tool and/or wellbore to provide information
about
downhole conditions, such as wellbore pressure, weight on bit, torque on bit,
direction, inclination, collar rpm, tool temperature, annular temperature and
toolface,
among others. Additional formation evaluation sensors 960 may be positioned in
the
formation evaluation sensors to measure downhole properties. Examples of such
sensors are described elsewht re herein or in documents incorporated by
reference.
The information collected by the sensors and/or cameras is conveyed to the
surface
system, the downhole system and/or the surface control unit.
[0054] The telemetry assembly 946 uses mud pulse telemetry to communicate with
the surface system. The MWD tool 942 of the telemetry assembly 946 may
include,
for example, a transmitter thzi generates a signal, such as an acoustic or
electromagnetic signal, whic' is representative of the measured drilling
parameters.
The generated signal is received at the surface by transducers (not shown),
that
convert the received acousti ',al signals to electronic signals for further
processing,
storage, encryption and use k--;cording to conventional methods and systems.
Communication between the downhole and surface systems is depicted as being
mud
pulse telemetry, such as the one described in U.S. Pat. No. 5,517,464, the
entirety of
which is incorporated herein by reference. It will be appreciated by one of
skill in the
art that a variety of telemetry systems may be employed, such as wired drill
pipe,
electromagnetic or other known telemetry systems. It will be appreciated that
when
using other downhole tools, sitch as wireline tools, other telemetry systems,
such as
the wireline cable or electrorr ;Ignetic telemetry, may be used.
[0055] The telemetry system provides a communication link 962 between the
downhole system 904 and the surface control unit 906. An additional
communication
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link 964 may be provided between the surface system 902 and the surface
control unit
906. The downhole system 904 may also communicate with the surface system 902.
The surface unit may communicate with the downhole system directly, or via the
surface unit. The downhole system may also communicate with the surface unit
directly, or via the surface system. Communications may also pass from the
surface
system to a remote location 964.
[0056] One or more surface, remote or wellsite systems may be present.
Communications may be manipulated through each of these locations as
necessary.
The surface system may be located at or near a wellsite to provide an operator
with
information about wellsite conditions. The operator may be provided with a
monitor
that provides information concerning the wellsite operations. For example, the
monitor may display graphical images or other data concerning wellbore output.
[0057] The operator may be provided with a surface control system 966. The
surface
control system includes surface processor 968 to process the data, and a
surface
memory 970 to store the data. The operator may also be provided with a surface
controller 972 to make changes to a wellsite setup to alter the wellsite
operations.
Based on the data received ani/or an analysis of the data, the operator may
manually
make such adjustments. These adjustments may also be made at a remote
location. In
some cases, the adjustments may be made automatically.
[0058] Drill collar 938 may be provided with a downhole control assembly 974.
The
downhole control assembly includes a downhole processor for processing
downhole
data, and a downhole memo!) for storing the data. A downhole controller may
also be
provided to selectively activ )te various downhole tools. The downhole control
assembly may be used to co ect, store and analyze data received from various
wellsite sensors. The downhc le processor may send messages to the downhole
controller to activate tools in ,=esponse to data received. In this manner,
the downhole
operations may be automated to make adjustments in response to downhole data
analysis. Such downhole controllers may also permit input and/or manual
control of
such adjustments by the surface and/or remote control unit. The downhole
control
system may work with or sepa -ate from one or more of the other control
systems.
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[0059] The wellsite setup itw,ludes tool configurations and operational
settings. The
tool configurations may include for example, the size of the tool housing, the
type of
bit, the size of the probe, the type of telemetry assembly, etc. Adjustments
to the tool
configurations may be made by replacing tool components, or adjusting the
assembly
of the tool.
[00601 For example, it may be possible to select tool configurations, such as
a
specific probe with a predefined diameter to meet the testing requirements.
However,
it may be necessary to replace the probe with a different diameter probe to
perform as
desired. If the probe is provided with adjustable features, it may be possible
to adjust
the diameter without replacing the probe.
[0061] Operational settings -nay also be adjusted to meet the needs of the
wellsite
operations. Operational settit 3s may include tool settings, such as flow
rates,
rotational speeds, pressure settings, etc. Adjustments to the operational
settings may
typically be made by adjusting tool controls. For example, flow rates into the
probe
may be adjusted by altering the flow rate settings on pumps that drive flow
through
sampling and contamination flowlines. Additionally, it may be possible to
manipulate
flow through the flowlines by selectively activating certain valves and/or
diverters
(e.g., those illustrated in FIGS. 5, 6, 7A, and 7B).
[0062] What has been desci i bed above includes examples of the innovation. It
is, of
course, not possible to describe every conceivable combination of components
or
methodologies for purposes of describing the subject innovation, but one of
ordinary
skill in the art may recognize that many further combinations and permutations
of the
innovation are possible. Accor lingly, the innovation is intended to embrace
all such
alterations, modifications and ariations that fall within the spirit and scope
of the
appended claims. Furthermore, to the extent that the term "includes" is used
in either
the detailed description or the ; laims, such term is intended to be inclusive
in a
manner similar to the term "comprising" as "comprising" is interpreted when
employed as a transitional wcid in a claim.
18
