Note: Descriptions are shown in the official language in which they were submitted.
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EARLY EVALUATION SYSTEM FOR CASED WELLBORE
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to the early evaluation of a
formation and, in particular, to the early evaluation of formation fluids in a
well
after the borehole has been drilled and casing cemented therein.
BACKGROUND OF THE INVENTION
During the drilling and completion of oil and gas wells, it is often necessary
to test and evaluate the production capabilities of the well. This is
typically done
by isolating a subsurface formation or zone of interest which is to be tested
and
subsequently flowing a sample of well fluid either into a sample chamber or up
through a tubing string to the surface. Various data such as pressure and
temperature of the produced well fluids may be monitored downhole to evaluate
the long term production characteristics of the formation.
One commonly used well testing procedure is to first cement a casing in
the borehole or zone of interest. Subsequently, the well is flow tested
through the
perforations. Such flow tests are commonly performed with a drill stem test
string
which is a string of tubing located within the casing. The drill stem test
string
carries packers, tester valves, circulation valves and the like to control the
flow of
fluids through the drill stem test string.
Although drill stem testing of cased wells provides very good test data, it
takes time to perforate the casing and then position and operate the drill
stem test
string. Better reservoir data can often be obtained shortly after the casing
has
been set rather than later. Therefore, there is a need for an apparatus and
method for evaluating the well as early as possible.
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SUMMARY OF THE INVENTION
The present invention disclosed herein is an early evaluation system for
use in a cased wellbore which includes a gun, a packer, a sample chamber and
logging-while-drilling telemetry equipment which allows quick correlation of
the
tool depth to insure that the proper formation or zone of interest is tested.
More
specifically, the apparatus comprises a tool string, a perforating gun on a
lower
end of the tool string, a packer having a set position for sealingly closing a
well
annulus between the tool string and the wellbore, a control valve adapted for
controlling fluid flow between the gun and an upper portion of the tool
string, a
sampler disposed in the tool string and in communication with the control
valve,
and a logging-while-drilling or other logging device disposed in the tool
string for
generating data indicative of the nature of the subsurface formations
intersected
by the wellbore so that the tool string may be positioned adjacent to a
specific
formation or zone of interest. The packer, control valve and sampler are all
disposed in the tool string. When the tool string is positioned using the
logging-
while-drilling device, and after the packer is set, the gun is fired to
perforate the
casing at the formation or zone of interest such that formation fluid will
flow from
the formation into the sampler after opening of the control valve.
The control valve is normally closed and is adapted for being opened after
setting of the packer and firing of the gun. The sampler may include mini-
samplers, such as the Halliburton pressure-actuated mini-samplers. The gun
preferably comprises a surge chamber into which the formation fluid will flow
prior
to opening of the control valve.
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The packer valve is normally closed and is adapted for being opened after
setting of the packer and firing of the gun. The sampler may include mini-
samplers, such as the Halliburton pressure-actuated mini-samplers. The gun
preferably comprises a surge chamber into which the formation fluid will flow
prior
to opening of the control valve.
The packer may be a compression packer or hydraulic packer, and may be
a straddle packer having a pair of spaced sealing elements thereon wherein the
gun is disposed between the packer elements.
The apparatus may further comprise a receptacle in the tool string, and an
inner well tool positionable in the tool string and adapted for connecting to
the
receptacle such that fluid may be flowed into the inner well tool. In one
embodiment, the inner well tool is a length of tubing such that fluid may be
flowed
upwardly from the sampler through the tubing to the surface. In another
embodiment, the inner well tool is a line-conveyed sampler which may be
retrieved to the surface with a sample therein without removing the tool
string
from the wellbore. The line-conveyed sampler may comprise a pressure sensor
and other fluid identification sensors.
In still another embodiment, the apparatus may comprise a second control
valve above the sampler whereby fluid may be pumped down the tool string into
the formation or zone of interest.
The early evaluation system of the present invention also includes a
method of early evaluation of a well having a cased wellbore intersecting a
subsurface formation or zone of interest. This method comprises the step of
providing a testing string in the wellbore in which the testing string
comprises a
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perforating device, a logging tool, a packer and a fluid testing device. The
method further comprises the steps of logging the well with the logging tool
and
thereby determining the location of the subsurface formation or zone of
interest,
setting the packer into sealing engagement with the wellbore adjacent to the
subsurface formation, firing the perforating device to perforate the casing
and
subsurface formation, flowing fluid from the subsurface formation and trapping
a
sample of the fluid in the fluid testing device.
The step of flowing fluid may comprise flowing fluid into a surge chamber
defined in the perforating device. The step of trapping a sample of the fluid
may
comprise trapping the sample in a pressure-actuated sampler. The step of
firing
the perforating device may comprise applying annulus pressure to the
perforating
device or by other telemetry.
The method of the present invention may further comprise providing the
testing string with a receptacle, running an inner well tool into the tool
string and
engaging the receptacle, and flowing a quantity of fluid into the inner well
tool. In
one embodiment, the inner well tool is a line-conveyed sampler and the step of
flowing a quantity of fluid into the inner well tool comprises trapping a
fluid sample
in the line-conveyed sampler. In this embodiment, the method may further
comprise the step of retrieving the line-conveyed sampler with the fluid
sample
therein to the surface. In another embodiment, the inner well tool is a length
of
coiled tubing and the step of flowing a quantity of fluid into the inner well
tool
comprises flowing fluid through the tubing to the surface to the surface or
limited
entry. The method may further comprise pumping fluid back into the subsurface
formation by pumping fluid down the testing string.
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BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, including its
features and advantages, reference is now made to the detailed description of
the
invention, taken in conjunction with the accompanying drawings of which:
Figure 1 is a schematic illustration of an early evaluation system of the
present invention after it has been run into the well to a position adjacent
to a
subsurface formation;
Figure 2 is a schematic illustration of the system of figure 1 after the
packer
has been set and the perforating gun fired;
Figure 3 is a schematic illustration of an early evaluation system of the
present invention including a receptacle;
Figure 4 is a schematic illustration of the system of figure 3 with a slick-
line-conveyed or wireline-conveyed sampler connected to the receptacle;
Figure 5 is a schematic illustration of the system of figure 3 with coiled
tubing connected to the receptacle; and
Figure 6 is a schematic illustration of an early evaluation system of the
present invention incorporating a straddle packer.
DETAILED DESCRIPTION OF THE INVENTION
While the making and using of various embodiments of the present
invention is discussed in detail below, it should be appreciated that the
present
invention provides many applicable inventive concepts which can be embodied in
a wide variety of specific contexts. The specific embodiments discussed herein
are merely illustrative of specific ways to make and use the invention, and do
not
delimit the scope of the invention.
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Referring now to the drawings, and more particularly to figure 1, an early
evaluation system for a cased wellbore of the present invention is shown and
generally designated by the numeral 10. Apparatus 10 is shown as it is run
into
casing 12 which is positioned in a wellbore 14 which intersects a subsurface
formation or zone of interest 16. As used herein, "formation" will refer to
any
typical well formation or other zone of interest in a well.
Apparatus 10 is connected to the lower end of a testing or tool string 18
and thus may be considered a portion of the tool string. At the lower end of
apparatus 10 is a perforating gun 20 having a plurality of perforating charges
22
therein. Preferably, but not by way of limitation, perforating gun 20 is a
tubing-
conveyed perforating (TCP) gun suitable for select firing in multiple zones on
a
single trip, such as the Vann Systems Vanngun. Disposed above perforating gun
20 is a packer 24, such as a Halliburton RTTS or CHAMP~ packer.
Above packer 24 is a valve 26 which provides communication between
packer 24 and the upper portion of tool string 18. Preferably, but not by way
of
limitation, valve 26 is a Halliburton perforate test sample (PTS) control
valve
which is opened after a predetermined time. Control valve 26 is originally
closed
as shown in figure 1.
A fluid testing device such as a sampler 28 is disposed above control valve
26 and defines a sample chamber 30 therein. As will be further described
herein,
a fluid sample from formation 16 may be received in sample chamber 30 when
control valve 26 is opened.
If desired, a plurality of independently activated samplers 32, electronic or
mechanical pressure and temperature recording instruments 34 or recorders 34,
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and other similar devices of identifying specific characteristics of the fluid
sample
from formation 16 may be disposed in sampling chamber 30. Samplers 32 may
be similar to the Halliburton mini-samplers, and pressure and temperature
recording instruments 34 may be similar to the Halliburton HMR. Examples of
mini-samplers are shown in U.S. Patent Nos. 5, 240,072; 5,058,674; 4,903,765
and 4,787,447, which are incorporated herein by reference. Recorders 34 may
include an electronic memory recording fluid resistivity tool, such as
manufactured
by Sondex or Madden. Samplers 32 and instruments 34 are in fluid
communication with control valve 26 through sample chamber 30.
Also disposed in tool string 18 is a logging tool 36 having instrumentation
used to correlate the depth of the tool string to insure that the proper
formation 16
is tested. This instrumentation may be of the type generally referred to as a
logging-while-drilling device. Typically, a logging-while-drilling device
contains
instrumentation for logging subterranean formations during drilling. As such,
when a formation has been intersected by the wellbore being drilled, the
formation is logged while the drill string is being raised, whereby the
logging-
while-drilling device is moved through the formation. Logging tool 36 provides
constant remote communication with a surface command station by means of a
remote communication system such as further described herein.
In operation, apparatus 10 is run into casing 12 in wellbore 14. Telemetry
from logging device 36 provides the operator with the necessary information as
to
when apparatus 10 is adjacent to formation 16. Thus, apparatus 10 is quickly
and
easily positioned at the desired location in wellbore 14.
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Referring now to figure 2, packer 24 is set into sealing engagement with
the inside of casing 12 at a position at or near the upper portion of
formation 16.
Perforating gun 20 is fired, such as by applying annulus pressure on other
telemetry. That is, perforating charges 22 are triggered so that perforations
38
are created through casing 12 and into formation 16 in a manner known in the
art.
Upon the firing of perforating charges 22, an opening 40 is created in
perforating
gun 20 at the location of each of perforating charges 22 such that flow from
formation 16 may enter the spent gun 20.
Perforating gun 20 is initially empty, but the firing of perforating charges
22
creates openings 40 that allows the gun to act as a surge chamber which
quickly
fills because of formation pressure from formation 16. Initially, "dirty"
fluid will flow
through openings 40 and into the spent gun 20. Eventually, after a period of
time,
clean fluid will flow from formation 16.
After the time delay necessary for clean fluid to flow from formation 16,
control valve 26 is opened to create a flow path 42 therethrough which is in
communication with sample chamber 30 in sampler 28. At any desired time, any
of mini-samplers 32 may be activated and a sample of fluid taken by flowing
into
sampler 32. Operation of any of mini-samplers 32 is optional.
If desired, the measurement of zone pressures, temperatures or other
parameters by recorders 34 may be carried out with or without capturing a
sample
in a mini-sampler 32. That is, recorders 34 may be activated to take the
appropriate pressure/temperature measurements as desired and send them to
the surface. The operation of mini-samplers 32 and recorders 34 is known in
the
art.
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After completion of the test, apparatus 10 is retrieved to the surface. At
this point, the fluid in sample chamber 30 and in mini-samplers 32 may be
drained
on location, or the contents thereof may be transferred to a sample bottom for
local evaluation or shipment to a pressure-volume-test (PVT) laboratory, or
the
entire sampler 28 may be shipped to a PVT laboratory for fluid transfer and
testing. The data obtained by recorder 34 is also analyzed to determine
various
properties of the formation fluids.
A control valve 44 is disposed above sampler 28 and is initially in the
closed position shown in figure 1. If desired, after a fluid sample has been
captured in sampler 30 as previously described, control valve 44 may be
actuated
to its open position so that a flow path 46 is provided in communication with
central opening 48 in tool string 18. In this configuration, fluid may be
pumped
down tool string 18 through flow path 46 in opened controlled valve 44 and
thus
through sampler 28, flow path 42, packer 24 and openings 40 in perforating gun
20. Thus, formation fluid may be forced back into formation 16 in an operation
known as "bull-heading." The formation pressure could then be monitored at the
surface to insure that the hydrostatic pressure in the well will keep the
formation
fluid from blowing out. Also, if the well is found to be sour, the produced
fluid may
be pumped back into the formation. In this way, the disposal costs and hazard
of
bringing a large sour gas sample to the surface are greatly reduced or
eliminated.
Referring now to figure 3, a cased hole early evaluation system of the
present invention is shown and generally designed by the numeral 50. Apparatus
50 includes all of the same components as apparatus 10, namely a perforating
gun 20, a packer 24, a control valve 26, a sampler 30 and a logging device 36.
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Apparatus 50, however, includes a coiled tubing receptacle 52 disposed between
sampler 28 and logging device 36. As will be further described herein,
receptacle
52 is adapted for receiving an inner well tool.
In operation, apparatus 50 is run into casing 12 and wellbore 14 in a
manner similar to that of apparatus 10. Logging device 36 allows the operator
to
quickly and easily position apparatus 50 in the desired location adjacent to
formation 16. Packer 24 is actuated into sealing engagement with casing 12,
and
perforating gun 20 is operated to form perforations 38. Spent gun 20 then acts
as
a surge chamber for initial "dirty" fluid flowing from formation 16 into the
gun
through openings 40. Samples may then be taken in sampling chamber 30 and in
mini-samplers 32, and pressure and temperature measurements and other fluid
measurements may be taken and recorded by recorders 34 as previously
described.
Referring now to figures 4 and 5, two variations of apparatus 50 are shown.
In the first variation, as shown in figure 4, an inner well tool is a line-
conveyed tool
such as a sampler 54 that may be lowered into receptacle 52 on a slick line or
wireline 56. Sampler 54 may include a pressure sensor or other fluid
identification sensors or gage 57 thereon and has a stinger 58 thereon adapted
for engagement with receptacle 52 and for being received therein. When in this
position, sampler 54 is thus placed in fluid communication with formation 16
so
that the sampler can be used to collect a fluid sample which can then be
brought
to the surface by retrieving sampler 54 with the slick line or wireline 56. In
this
way, the operator is able to get a small sample to evaluate, as well as check
pressures either in real time or upon receiving the gauges back at the
surface.
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Referring now to figure 5, the second variation of apparatus 50 is shown.
In this case, the inner well tool is characterized by an inner coiled tubing
string 60
with a stinger 62 at the lower end thereof. In this embodiment, when coiled
tubing
string 60 is run into tool string 18, and stinger 62 engaged with and received
by
receptacle 52, fluid from formation 16 may be flowed upwardly through the
coiled
tubing string to a surface location on limited entry. Also, treatment fluids
can be
pumped down through the coiled tubing string into formation 16.
Referring now to figure 6, a cased hole early evaluation system of the
present invention is shown and generally designated by the number 64.
Apparatus 64 is essentially the same as apparatus 10 except that it includes a
straddle packer with upper and lower packer elements 68 and 70 which can be
used to provide a seal above and below formation 16. Otherwise, operation of
apparatus 64 is identical to that of apparatus 10.
It will be seen, therefore, that the cased hole early evaluation system of the
present invention is well adapted to carry out the ends and advantages
mentioned
as well as those inherent therein. While presently preferred embodiments of
the
apparatus have been shown for the purposes of this disclosure, numerous
changes in the arrangement and construction of parts may be made by those
skilled in the art. All such changes are encompassed within the scope and
spirit
of the appended claims.
What is claimed is:
