Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR ISOLATING AND TESTING ZONES
DURING REVERSE CIRCULATION DRILLING
FIELD OF USE
The present invention relates to an apparatus and method for isolating and
testing individual zones in a vertical, directional or horizontal wellbore
during
drilling. More particularly, the present invention relates to a zone isolating
and testing apparatus and method of use thereof to allow testing of isolated
zones for flow of hydrocarbons, formation fluids and/or drill cuttings during
vertical, horizontal or directional reverse circulation drilling of wellbores
using
concentric drill pipe, concentric coiled tubing, or the like.
BACKGROUND OF THE INVENTION
The oil and gas industry uses various methods to test the productivity of
wells
prior to completing a well (see, for example, U.S. Patent No. 4,898,236).
After drilling operations have been completed and a well has been drilled to
total depth, or prior to reaching total depth in the case of multi-zoned
discoveries, it is common to test the zone to estimate future production of
oil
and gas. Current technologies used for testing reservoirs such as drill stem
testing (DST) are often too expensive to test multi-zone reservoirs,
particularly at shallow depths; Furthermore, isolating and testing zones using
conventional packer technology can be slow, expensive and sometimes
difficult to set and then release.
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Traditionally the DST process involves flowing a well through a length of
drill
pipe reinserted through the static drilling fluid. The bottom of the pipe will
attach to a tool or device with openings through which fluid can enter. This
perforated section is placed across an anticipated producing section of the
formation and sealed off with packers, frequently a pair of packers placed
above and below the part of the formation being tested. This packing off
technique permits an operator to test only an isolated section or cumulative
section.
The present invention allows a fast, safe and economic way to isolate and test
zones during reverse circulation drilling by using the already inserted
concentric drill string used during drilling. This alleviates the need to
first
remove the drill string used for drilling and then reinsert a length of drill
pipe or
coiled tubing for testing.
SUMMARY OF THE INVENTION
A zone isolating and testing apparatus comprising an isolation tool and a
downhole flow control means and a method of using such apparatus is
disclosed. The zone isolating and testing apparatus is particularly useful for
testing zones during reverse circulation drilling using concentric drill
string,
e.g., concentric drill pipe, concentric coiled tubing and the like, said
concentric
drill string comprising an inner tube and an outer tube forming an annular
conduit therebetween. The zone isolating and testing apparatus is operably
connected to a concentric drill string so as to be in fluid communication with
both the inner tube and the annular conduit of the concentric drill string.
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The isolation tool of the zone isolating and testing apparatus comprises a
center tube and an outer casing, forming an annular passage therebetween.
The isolation tool further comprises an expandable packer means surrounding
the outer circumference of the outer casing. The isolation tool is adapted to
connect to the bottom of a piece of concentric drill string and is generally
positioned near the drilling means.
When the isolation tool is connected to the concentric drill string, the
center
tube of the isolation tool is in fluids communication with the inner tube of
the
lo concentric drill pipe and the annular passage of the isolation tool is in
fluid
communication with the annular conduit of the concentric drill string.
The packer means of the isolation tool can assume two functional positions.
When the packer means is in the expanded position, the isolation tool is in
the
"closed position" and when the packer means is in the contracted position the
isolation tool is in the "open position". In a preferred embodiment, the
expansion of the packer means is controlled by an electric current for quicker
opening and closing of the isolation tool.
It is understood in the art that the area of the zone tested will be dictated
by
the distance the isolation tool is placed away from the drilling means. In
some
instances where the bands of the pay zones are known to be quite broad the
isolation tool and the drilling means can be separated from one another by
several joints of concentric drill string.
The downhole flow control means of the zone isolating and testing apparatus
also comprises a center tube and an outer casing forming an annular passage
therebetween. The downhole flow control means is attached either directly to
the isolation tool or to an intervening piece of concentric drill string in
such a
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fashion so as to be in fluid communication with both passageways of the
concentric drill string. The downhole flow control means further comprises two
valves, one for closing off its annular passage, thus closing off the annular
conduit of the concentric drill string and the other for closing off the inner
passage of its center tube, thereby closing off the inner conduit of the inner
tube of the concentric drill string.
During the drilling process, the isolation tool is in the open position, i.e.
the
packer means is contracted. When the tool is in the open position it does not
1o significantly restrict the flow of hydrocarbons through the annulus formed
between the wellbore and the concentric drill string, as the outside diameter
of
the isolation tool when in the open position is preferably equal to or less
than
the outside diameter of the concentric drill string. However, it is understood
that the outside diameter of the open isolation tool can also be less than or
greater than the outside diameter of the concentric drill string and still not
significantly restrict the flow of hydrocarbons.
The downhole flow control means is also in the complete open position during
drilling, i.e., both valves are open. This allows drilling fluid to be pumped
down
either the annular conduit or inner conduit of the inner tube of the
concentric
drill string and exhaust drilling fluid and drill cuttings to be removed
through the
other of said annular conduit or inner conduit.
However, when testing is required during the reverse circulation drilling
process, the isolation tool is in the closed position, i.e. the packer means
expands to abut the adjacent wellbore walls. Further, one of the two valves of
the downhole flow control means is also in the closed position. Which valve
will be closed is dependent upon whether drilling fluid is being pumped
through the annular conduit or the inner conduit. For example, if drilling
fluid
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were being pumped down the annular conduit then during testing the annular
passage valve would be closed during testing.
Thus, during testing, the zone of the wellbore below the isolation tool is
shut
off or isolated from the portion of the wellbore above the tool as the
expanded
packer means will not allow hydrocarbons to flow passed it. The materials
present in the isolated zone can then flow through either the annular conduit
or inner conduit of the concentric drill string to the surface of the well for
testing.
The disclosed invention has one or more of the following advantages over
conventional isolation packer technology and drill stem testing:
= when drilling vertical, directional, and/or horizontal wellbores, individual
zones can be isolated and tested much quicker and cheaper without
having to interrupt drilling for extended periods of time;
= open hole testing provides very valuable production data;
= zones which may otherwise be damaged by testing fluids when using
drill stem testing can now be tested without damage as testing fluids
are not necessary;
= easier to measure the flow of formation fluids into a zone;
= decisions on well stimulation can be made while the well is being
drilled; and
= more accurate information on reservoir pressure, temperature, flow rate
etc. can be obtained from individual zones.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic of one embodiment of the isolation tool of the
invention.
Figure 2 is a cross-sectional view of the isolation tool shown in Figure 1.
Figures 3a and 3b are schematics of the isolation tool in the open and closed
position, respectively.
Figure 4 is a cross-section view of the downhole blow out preventor.
Figure 5 is a schematic of the surface drilling and testing equipment used in
the invention.
Figure 6 is a schematic of one embodiment of the inner drill string of
concentric drill string of the invention.
Figure 7 is a cross-sectional view of one embodiment of the zone isolating and
testing apparatus typically used with concentric drill pipe.
Figure 8 is a cross-sectional view of one embodiment of the zone isolating and
testing apparatus typically used with concentric coiled tubing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A zone isolating and testing apparatus comprising an isolation tool and a
downhole flow control means and method of using such apparatus will now be
described with reference to the following preferred embodiment.
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Figure 1 schematically illustrates the isolation tool 30 of the zone isolating
and
testing apparatus and means for attaching the isolation tool 30 between two
pieces of concentric drill string 45 and 47. Concentric drill string 45 and 47
both comprise an inner tube 57 and an outer tube 59. Concentric drill string
is
designed such that at one end of concentric drill string is a threaded pin end
and at the other end is a threaded box end. Thus, pieces of concentric drill
string can be connected end to end by screwing the threaded pin end of the
new piece of concentric drill string to be added into the box end of the drill
lo string below.
As can be seen in Figure 1, concentric drill string 45 has threaded pin end 31
at its bottom end and concentric drill string 47 has threaded box end 35 at
its
top end. Isolation tool 30 is adapted to be inserted between concentric drill
string 45 and 47 by means of threaded box end 37 and threaded pin end 33.
Thus, threaded pin end 31 of concentric drill string 45 screws into threaded
box end 37 and threaded pin end 33 screws into threaded box end 35 of
concentric drill string 47.
Isolation tool 30 further comprises packer means 39. Packer means 39 can
be expanded or contracted by any means known in the art, for example, by
means of an electric current flow path as shown in Figure 6. In another
embodiment, the packer means comprises an inflatable ring which can be
inflated and deflated by pumping various types of fluid into and out of the
ring.
With reference to Figure 2, isolation cementing tool 30 further comprises a
center tube 34, an outer casing 32, an annular passage 36 between the center
tube and outer casing, an inner passage 38, and a packer means 39
surrounding said outer casing 32. When isolation cementing tool 30 is
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inserted between concentric drill string 45 and 47, the center tube 34 of the
isolation cementing tool 30 is in fluid communication with the inner tube 57
of
the concentric drill string 45 and 47 and the annular passage 36 of the
isolation cementing tool 30 is in fluid communication with the annular conduit
16 of the concentric drill string 45 and 47.
Figures 3a and 3b schematically illustrate the isolation tool 30 attached to
the
concentric drill string in the open and closed position, respectively. During
drilling the isolation tool 30 is in the open position and during testing it
is in the
lo closed position.
When packer means 39 is contracted or deflated as shown in Figure 3a, the
isolation tool 30 is in the open position and hydrocarbons can flow freely
through the wellbore annulus 43 formed between the outer wall of the
concentric drill string and the wellbore wall 41. When packer means 39 is
expanded or inflated as shown in Figure 3b, the packer means 39 is forced
against wellbore wall 41 thereby closing annulus 43 to hydrocarbon movement
above or below the packer means 39. Thus, the testing region below the
packer is isolated from the surface of the wellbore.
In order to test for hydrocarbon flow, formation fluids, drill cuttings and
the like
present in the testing zone, the isolation tool is used in conjunction with a
downhole flow control means or downhole blow out preventor (downhole BOP)
as shown in Figure 4. In Figure 4, downhole BOP 10 is shown in cross-
section attached to the lower end of concentric drill string 47 by threaded
pin
end 72 of concentric drill string 47 screwing into threaded box end 70 of
downhole BOP 10.
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In this embodiment, downhole BOP 10 comprises two valve means 3 and 5
for shutting off the flow of drilling fluid, exhausted drilling fluid, drill
cuttings
and/or hydrocarbons through one or the other of the annular conduit 16
formed between inner tube 57 and outer tube 59 of concentric drill string 47
and inner conduit 9 of inner tube 57. It is understood that other downhole
flow control means can also be used, for example, the downhole flow control
means as described in U.S. Patent Applications Publication Nos.
20030155156 and 20030173088.
Thus, in one embodiment of the invention, the isolation tool 30 and the
downhole BOP 10 of the zone isolating and testing apparatus can be
separated by a single joint of varying lengths of concentric drill string 47.
However, it is understood that in some instances the isolation tool and
downhole BOP can be directly threaded or connected by other connection
means to each other. Further, it can be appreciated that the orientation of
the
two components is not critical; in some instances it may be desirable to have
the downhole BOP attached to the bottom of the concentric drill string first
and the isolation tool connected either directly or by means of one or more
joints of concentric drill string below the downhole BOP.
It is understood that the drilling means (not shown) can be either directly
attached to the bottom of the downhole flow control means, the isolation tool,
other downhole tools or an intervening joint of concentric drill string. In
general, however, the drilling means is attached to the last in the series of
downhole tools.
During reverse circulation drilling with concentric drill string, both valves
3 and
5 of the downhole BOP 10 are in the open position (not shown). In one
embodiment, drilling fluid is pumped from surface equipment through the
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annular conduit 16 of the concentric drill string and exhausted drilling
fluid, drill
cuttings and/or hydrocarbons 19 flow through the inner conduit 9 to the
surface of the wellbore. It is understood that drilling fluid could also be
pumped from surface through the inner conduit 9 and exhausted drilling fluid,
drill cuttings and/or hydrocarbons removed through the annular conduit 16.
When drilling is stopped for testing, the isolation tool 30, which is located
at or
near the downhole BOP, is put in the closed position as shown in Figure 3b to
isolate the testing region below the packer means. In the instance where
1o drilling fluid is being pumped down the annular conduit 16 and exhausted
drilling fluid, drill cuttings and/or hydrocarbons flow through the inner
conduit 9
to the surface of the wellbore, valve means 3 of the downhole BOP 10 is also
put in the closed position as shown in Figure 4, as no fluids are being flowed
from surface equipment during testing.
Valve means 5, however, remains in the open position as shown in Figure 4
thereby allowing hydrocarbons, formation fluids and/or drill cuttings
(collectively referred to as reference 19) present in the isolated zone to
flow to
surface. Well flow test equipment known in the art will be able to determine
the hydrocarbon content of the isolated testing area. Optionally, a surface
blow out preventor (surface BOP, not shown) is provided to shut off the flow
of
hydrocarbon from the annulus formed between the concentric drill string and
the wellbore walls that may be present in the zone above the packer means.
Figure 5 schematically shows the surface equipment used during drilling and
testing. Drilling rig 70 is equipped with well testing equipment 74. The
hydrocarbons in the test region flow through the inner conduit of the inner
tube
of the concentric drill string and then through the choke manifold system as
shown in 72. Well flow test equipment can also be located at the end of
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blewie line 78. Surface BOP 76 ensures that there is no escape of
hydrocarbons to the surface through the annulus formed between the
concentric drill string and the wellbore walls.
The isolation tool is preferably powered by an electric current for quicker
opening and closing operations. Figure 6 is a schematic of a portion of
concentric drill string having threaded pin end 31 at one end. The outer tube
has been removed to reveal inner tube 57, which is preferably made of a
rubber type material, rubber/steel, fiberglass or composite material, capable
of
1o withstanding the forces and pressures of the drilling operations. Inner
tube 57
further comprises electrical wires 51 that allow the flow of the electric
current.
Wire coils 53 and 55 are compressed in each end of the concentric drill string
when two pieces of concentric drill string are torqued (screwed) together.
This
provides the electric current to operate the isolation tool, e.g., to expand
or
contract the packer means as needed.
Other means of operating the isolation tool could include fiber optic cables,
radio frequency and electric magnetic forces. When using concentric coiled
tubing the isolation tool can be operated using small diameter capillary tubes
which transmit hydraulic or pneumatic pressure to an actuator at or near the
tool.
Figure 7 shows a cross-section of one embodiment of the assembled zone
isolating and testing apparatus of the present invention, which is typically
used
with concentric drill pipe. In this embodiment, the isolation tool 30 and the
downhole BOP 10 are spatially separated by means of a single joint of varying
lengths of concentric drill pipe 47. Typically, the drilling means (not shown)
is
attached either directly to the downhole BOP 10 or to other downhole tools
that can be attached to the downhole BOP. It may be desirable, however,
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particularly in instances where the bands of the pay zones are known to be
quite broad (i.e., 40 ft or greater), to have the isolation tool and the
drilling
means separated even further by additional joints of concentric drill string.
Figure 8 shows another embodiment of the assembled zone isolating and
testing apparatus, which is typically used when the concentric drill string
comprises a continuous length of concentric coiled tubing 65 having a
continuous length of inner coiled tubing 66 and a continuous length of outer
coiled tubing 68, thereby forming annular conduit 16 and inner conduit 9. In
lo this embodiment, the isolation tool 30 is connected to the bottom of the
concentric coiled tubing 65 by connection means 62 known in the art. The
downhole BOP 10 is then connected to the isolation tool 30 by similar
connection means 62 known in the art.
The foregoing disclosure and description of the invention are illustrative and
explanatory thereof. Various changes in the size, shape and materials as well
as the details of the illustrated construction may be made without departing
from the spirit of the invention.
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