Note: Descriptions are shown in the official language in which they were submitted.
FORMATION SAMPLING APPARATUS
Background of -the Invention
The present invention relates to a device for sampling
earth formations and, more particularly to a device for taking
fluid samples within a Barlow, by laterally piercing the earth
formations of interest surrounding the Barlow and sampling the
fluids which are within such formations.
The conventional manner of collecting fluid samples
within the formations surrounding a Barlow involves lowering
a specialized tool into Barlow on a wire line or similar con-
vines device. This tool includes sample collection means such
as are described in US. Patent 3,530,933, in which a specialized
projection on the tool is extended into contact with an adjacent
earth formation in order to establish communication with any
connate fluids situated therein. The collection means also in-
eludes one or more sample chambers for receiving separate samples
of the formation fluid when collected. These sample chambers
are typically at atmospheric pressure which is substantially less
than the pressure of the connate fluids. The connate fluids are
therefore caused to flow into the sample chambers as long as an
open passage-way exists between the chambers and the formations,
in which such fluids can flow. The pressure of the sampled fluid
in each chamber is generally measured, and the projection is then
withdrawn from the formation and the fluid sample is either ox-
polled or carried -to -the surface with the tool.
Although such tools are generally effective, there con-
tinges to be a problem in certain earth formations which consist
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of loosely or unconsolidated formation materials which can be
eroded by the relatively high velocity flow of fluids which
occurs during the sample-taking process. The erosion of these
loosely consolidated materials not only causes the eroded mater-
tats to be included within the sample taken, thereby potentially
clogging the fluid passageways within the sample taking device;
it also interferes with
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the sealing engagement that the projection on the tool makes with the Barlow wall.
Since various gases are also present withirl the Barlow, any leaks within the engagement
between the tool and the formation can potentially introduce such gas in the samples
being taken. The inclusion of this gas can contaminate the sample as well as introduce
errors into the pressure measurements being made.
In order to minimize the occurrence of erosion modifications have previously been
made to the tool in order to control the rate of flow of the fluid as the sample is being
- taken. The conventional manner of controlling this rate is to employ a water cushion
system within the tool. This water cushion includes a slide able piston that is operatively
arranged within the sample receiving chamber so as to divide this sample chamber into
two compartments. Prior to using the tool, this piston is displaced to the end of the
sample chamber which is proximate the sampling entrance to the sample chamber. The
compartment created on the other side of the piston is then filled with water The
opposing end of the chamber contains a passageway with a predetermined diameter
orifice that leads into an adjacent chamber that has been kept at atmospheric pressure.
As the sample is being taken, the slide able piston moves within the sample chamber and
causes the expulsion of the water through the orifice and into the adjacent atmospheric
chamber. Since the rate of the flow of water through the orifice is predetermined by the
size of the orifice chosen the rate at which the sample is admitted can be controlled.
Although the use of a water cushion has diminished the problem of erosion during the
taking of the sample, there are still some difficulties For example, at such high
pressures as are present within a Barlow, there is a finite compression of the water
within the water cushion during the initial moments of the sample-takir~ process This
compression is enough to cause an initial erosion of the loosely consolidated material
adjacent the sample taking passageway- In addition, the space occupied by the water
cushion system necessitates a longer tool This added length can introduce problems in
the lowering or remover of the tool into or from the Barlow.
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One aspect of the present mention is directed to an apparatus for
obtaining samples of connate fluids from earth formations that are located
peripheral to a Barlow, said apparatus comprising: sample collection means
for establishing communication between the apparatus and a peripheral earth
formation, said sample collection means including at least one control valve
controlling the admission of fluids from the earth formation into the sampling
apparatus; means for applying the pressure of the connate fluids within the
formation prior to the collection of a sample to bias said control valve
toward its closed position thereby tending to restrict the admission of fluids
into said sampling apparatus; means for applying the pressure of the connate
fluids Winnie the formation as a sample is being taken to bias said control
valve toward its open position, and means for applying a differential force to
said control valve, whereby said control valve will open and remain open as
long as the force of the pressure of the connate fluids within the formation
during the collection of a sample exceeds a fraction of the force due to the
recollection pressure, thereby affording the controlled admission of
formation fluids into the sampling apparatus.
Another aspect of the present invention is directed to a method for
obtaining samples of connate fluids from earth formations that are located
peripheral to a Barlow, said method comprising: establishing communication
between an apparatus adapted to obtain such fluid samples and a peripheral
earth formation; applying the pressure of the connate fluids within such
formation prior to the collection of a sample in a manner restricting the
admission of fluids into the apparatus; applying the pressure of the connate
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fluids within such formation as a sample is being taken in a manner opposing
said restriction of the admission of fluids into the apparatus, and applying a
differential force in a manner affecting the admission of fluids into the
apparatus, whereby fluids will be admitted into the apparatus as long as the
force of the pressure of the connate fluids within the formation during the
collection of a sample exceeds a fraction of the force due to the
recollection pressure, thereby affording the controlled admission ox
formation fluids into the sampling apparatus
Ike formation sampling apparatus of the present invention therefore
affords a control on the flow of the formation fluids into the sample-taking
apparatus based on the change of the pressure of the connate fluids within the
formation during the sample taking process. Iris invention further minimizes
the problem of erosion of any adjacent formations as well as the multiplicity
of difficulties associated wherewith. Furthermore the present invention
minimizes the problem of erosion without substantially lengthening the tool.
Brief eke e drawings
Ike present invention will be further described hereinafter with referent ox
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to the accompanying drawing wherein:
Figure 1 illustrates a fluid sampling apparatus of the present invention as tight
appear within the Barlow;
F inure 2 is a partial schematic representation of the fluid sampling apparatus
according to the present invention;
Detailed Description
A fluid sampling apparatus 10 according to the present invention is illustrated in
Figure 1 as it appears within a Barlow 12. The fluid sampling apparatus 10 is suspended
from 8 multi~onductor cable 11 which not only supports the apparatus 10 but which also
10 contains the various electrical conductors necessary to operate the fluid sampling
apparatus 10. Typically this cable 11 is rifted to as a wire line. The apparatus 10 is
lowered into a Barlow 12 on the wire line 11 until it is positioned adjacent a particular
- . formation interval 13 in which it is desired to collect A sample of the connate fluids thaw.
are located within that formation 13. The opposing end of the cable 11 is in turn spooled
15 in the usual manner and suspended from a winch 14 at the essayers surface. Some of the
- conductors within cable 11 are connected to switch 15 for the selective connectioll of the
apparatus 10 to a power source 16. Ours conductors within cable U are connected to
conventional indicating and recording apparatus 17 which are used to monitor theoperation of the apparatus 10. To afford a number of tests to be made during a single
20 trip into the Barlow 12~ the fluid sampling apparatus 10 typically comprises a
corresponding number of randomly arranged sample collection means 20. Each of these
sample collection means 20 is generally capable of independent operation for recovering
such multiple samples as are desired. Some of the standard components and operation of
such sample collection means 20 have already been described in the Background section
25 of this application. For example, as has been noted the sample collection means 20
include an e~tendable projection 18 capable of achieving a sealed interface with the
formation 13, i.e., in order to avoid sampling Barlow (as closed to formation) fluids
end gases in addition to or instead of the connate fluids within the formation 13. As has
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also already been described, it is important that the sample be taken in a manner
minimizing the erosion of the formation 13 adjacent the sample collection means 20 in
order to maintain this sealed interface between the projection 18 and the formation 13.
The components of the present invention making this controlled collection of a sample
possible are schematically illustrated in Figure 2.
The sample collection means 20 Mcludes a passageway 21 therein leading from the
projection 18 toward two valves. One of these valves is a reference pressure valve 22 and
the other is a elbow line valve 23. The sample collection means 20 also includes a control
valve 26 connected to valves 22 and 23 via passageways 24 and 28 respectively, and at
least one sample chamber 35 coMected to control valve 26 via passageway 33. The
entirely valve 26 has three chambers 25, 29 and 32. The passageway 24 from the
erroneous pressure valve 22 opens into chamber 25. The passageway 28 from the flow
Lowry valve 23 opens into chamber 29 and the passageway 33 leading to the samplechamber 35 opens into chamber ;32. Boundaries exist between the various chambers 25,
.,~ and 32 prelrenting the flow of fluid there between. Thus for example, chamber 25 can
eye used to trap the reference pressure of the formation as will be described. The
undoer between chambers 29 and 32 however contains an orifice 31 which when openremits the passage of fluid between these chambers. This orifice 31 can be closed by
.,~ toe movement of a shuttle 30 which is mounted within the control valve 26. The shuttle
~,~ and the various chambers 25, 29, and 32 are operatively disposed withinthecontr
valve 26 such that any fluid pressure within chamber 25 will tend to force the shuttle 30
on a direction closing orifice 31. Contrastingly any fluid pressure within chamber 29 will
Tandy to force the shuttle 30 in a direction opening orifice AL The control valve 26 also
intones a spring 34 which is positioned to bias the shuttle 30 in a direction tending to
open orifice AL
When ye tool 10 has been lowered into the Barlow 12, and the projection 18 has
established contact with the formations 13, the reference pressure valve 22 is opened.
This permits a small quantity of the formation fluid to pass through line 21, valve 22, lint
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24, and into chamber 25 of control valve 26. The dimensions of line 21, valve 22, line 24,
and chamber 25 are chosen to minimize the volume of formation fluid which actually
flows while this initial pressure measurement is being made, while still providing
sufficient compressible fluid volume to afford the movement of the shuttle 30. Apressure sensor 27 is also in communication with line 21. This pressure sensor 27 is able
to sense the static pressure of the fluids within the formation 13 that exists prior to
taking a sample of these fluids. The pressure as sensed by sensor 27 is communicated to
the recording apparatus I on the surface by thy wire line 11. This initial static or pro-
collection pressure also serves as a reference pressure for the present invention.
As the tool 10 is being lowered into the Barlow 12 flow line valve 23 is normally
closed and remains closed during the initial sensing of the static pressure of the connate
fluids within the formation by sensor I Line 28 and chamber 29 of valve 26 are
therefore at atmospheric pressure, which is substantially less than the typical static
pressure of the fluids within the formation. Thus the pressure within chamber 25 is
typically substantially greater than the pressure within chamber 29. Although the shuttle
30 of control valve 26 is biased toward its open position by a spring 34, this spring 34 is
chosen such that the force it exertsisinsignificantwhencomParedtoth~ difference
between the static formation pressure and atmospheric pressure. For this reason control
valve 26 typically closes when the reference pressure valve 22 is opened, wit the shuttle
30 ox control valve 26 being driven into sealing engagement with the orifice 31 that exists
between chambers I and 32.
_ _ In order to take a sample, switch 15 is closed and the appropriate solenoids (not
shown) within the tool 10 are actuated by power source 16 to close the reference pressure
ye 22 and open flow line valve 23- The closing of valve 22 traps the static reference
pressure in chamber 25 of valve 26. The opening of the flow line valve 23 causes the
dynamic pressure of the fluid within the formation. to be present within chamber 29 of
control valve 26. This pressure when combined Vito the force exerted by the spring 34 is
typically greater than the initial static reference fluid pressure of the formation as
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trapped within chamber 25. The shuttle 3û of valve Z6 therefore moves to its open
position, compressing the fluid trapped within the reference pressure circuit, and
formation fluid is allowed to pass through the orifice 31 and from chamber 29 to chamber
32 and into line 33 leadislg from chamber 32 to the sample chamber 35. Since the volume
OX the sample chamber 35 is large compared to the volume of formation fluids contained
within the various flow lines and valves thus far described, there is typically a slight
decrease in the pressure that is present within chamber 29 of valve 26. This decrease in
pressure occurs as a result of the flow of formation fluids through the formation, and
within the viruses lines and valves and into the sample chamber 35. When the pressure in
the chamber 29 decreases to the extent that the combined force of the pressure within
chamber plus the force due to the spring 34 is less than the force due to the trapped
static formation pressure in chamber 25, the control valve 26 will close. The control
valve 26 will remain closed until the formation fluid pressure in chamber 29 increases to
the minimum pressure necessary for the combined force of the pressure and the spring 34
to again open the valve 26.
In practice the control valve 26 will either remain open at such a position that the
opposing forces are in balance or rapidly shuttle between its open and closed positions till
the sample chamber 35 is eventually filled. The filling of the sample chamber 35 can be
sense by means such as pressure sensor 27. This pressure information can again be
communicated to the recording equipment 17 on the surface by the cable 11. When the
sample chamber 35 is filled, the reference pressure valve 22 is opened and the flow line
valve 23 is again closed in order that the sample can be released or transported to the
surface.
It is therefore possible with the present invention to control the flow of formation
fluids into the sample chamber 35 based upon the selection of spring force exerted by
spring 34. This construction minimizes the initial pressure surges which were otherwise
present with the water cushion of the existing tools- The present invention also affords a
control of the pressure drop which occurs as formation fluids flow into the sample
chamber 35.
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Having thus described one embodiment of the present invention, it will be
understood that changes may be made in the size, shape, or configuration of some of the
parts or fluid circuits described herein without departing from the present invention as
recited in the appended claims. One such modification for example is the replacement of
spring 34 and shuttle 30 with a shuttle having a slightly increased surface area exposed in
chamber 29 than is exposed in chamber 25.
