Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND SYSTEM FOR DRILLING UNDERBALANCED RADIAL
WELLS UTILIZING A DUAL STRING TECHNIQUE IN A LIVE WELL
BACKGROUND OF THE INVENTION
1. Field of the Invention
The apparatus of the present invention relates to underbalanced
multilateral drilling of oil wells. More particularly, the present invention
relates
to a system for drilling a series of radial wells off of a single wellbore in
an
underbalanced system, utilizing a two-string technique, without having to kill
the well so that all of the radials are drilled while the well is alive.
2. General Background of the Invention
In the drilling of oil wells, one of the most critical elements in drilling
has always been to maintain the well in a balanced state, so that should the
drill
bit strike a pocket of hydrocarbons, that the formation pressure does not
overcome the hydrostatic pressure in the well, and thus a blow out does not
occur. In conventional drilling, what has always been done, is during the
drilling process,
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to flow heavy fluids; i.e., muds, into the drill bore or into the oif well
bore, during
drilling, so that the hydrostatic pressure of the muds within the bore hole is
heavier than the pressure from the formation. Therefore, any potential blowout
which may occur otherwise is prevented due to the heavy muds which create
the higher hydrostatic pressure downward into the formation.
It has been recently found, that when such a hydrostatic head is placed
on the formation, often times the heavy muds or fluids flow into the
formation,
and by doing so, create severe damage of the formation, which is a detriment
to the formation and to the productivity of the well itself. Therefore, there
has
been developed the technique that is called underbalanced drilling, which
technique allows for greater production, and does not create formational
damage which would impede the production process. Furthermore, it has been
shown that productivity is enhanced in multilateral wells combined with the
non-formation damaging affects of the underbalanced drilling. These results
are accomplished by introducing a lighter fluid such as nitrogen or air into
the
drill hole, or a combination of same or other type fluids or gases,
sufficiently as
to create an underbalance so that fluid in the borehole does not move into the
formation during drilling. In order to accomplish this, often times the
drilling is
undertaken through the use of coil tubing, which is a continuous line of
tubing
which unreels off of a spool on the rig floor, and the tubing serves as a
continuous drill string for the drill bit at the end of the tubing. Another
technique
of underbalanced drilling is referred to as micro-annulus driIling where a low
pressure reservoir is drilled with an aerated fluid in a closed system. In
effect,
a string of casing is lowered into the wellbore and utilizing a two string
drilling
technique, there is circulated a lighter fluid down the outer annulus, which
lowers the hydrostatic pressure of the fluid inside the column, thus relieving
the
formation. This allows the fluid to be lighter than the formation pressure
which,
if it weren't, would cause everything to flow into the wellbore which is
detrimental. By utilizing this system, drillers are able to circulate a
lighter fluid
which can return up either inner or outer annulus, which enables them to
circulate with a different fluid down the drill string. In doing so, basically
air
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and nitrogen are being introduced down the system which allows them to
circulate two different combination fluids with two different strings.
However, when not utffizing a two-string system, the well is being driIled
as an underbalanced well. In order to do so, one must kill the well so that
the
drill string may be tripped out of the hole, until sufficient fluid in the
bore to
bring the flow to neutral so the wells aren't flowing. When this is done, the
fluid
which maintains the hydrostatic pressure on the well, may create formation
damage because what is actually occurring is sufficient heavy fluid is in the
well bore which forces the fluids into the formation thus the well is kiAed.
Therefore, what is currently being accomplished in the art is the attempts
to undertake underbalcmced drilling and to trip out of the hole without
creating
formation damage thereby controlling the pressure, yet hold the pressure so
that one can trip out of the well with the well not being killed and
maintaining
a live well.
It is well known in the cQt that anytime a heavy fluid must be introduced
into the borehole, in order to stop flowing of fluids of the borehole, there
is
damage being done to the reservoir downhole, which is not desirable. In the
prior art which is being submitted with appliccmt's prior art statement,
applicant
brings attention to the many articles which have been written on
underbalanced drilling, and the techniques which companies are introducing
in order to attempt to maintain the wells alive while tripping in and out of
the
hole. For example, a company called Sperry Sun, in attempting
underbalanced drilling, wiIl aerate the fluid into the casing string which
lowers
the hydrostatic pressure of the well then you proceed to the micro-annulus
system which is becoming the method of choice in combination with coiled
tubing. However, the basic wells which are being done are regular, singular
horizontal wells and even with the micro-annulus system, restricted to a
single
well either horizontal or vertical.
Therefore, at this time in the art of micro-annulus drilling, what is needed
is a system for micro-annulus drilling, utflizing the two string technique,
which
would allow you to go into drilling multiple radial wells off of the single
vertical
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or horizontal well, without having to kill the well when the radial wells are
drilled
during the process.
BRIEF SUMMARY OF THE INVENTION
The system and method of the present invention solves the problems in
the art in a simple and strcaght forward manner. What is provided is a system
for drilling radial wells from a single verticol or horizontal well, using an
underbalcnced drilling technique, which provides a first outer casing lining
the
wellbore, a second inner casing, called a carrier string, as a second inner
string, and either coiled tubing or regular drill pipe as the inner drill
string. At
this point in the process, there would be provided an orientation means for
orienting the mud motor assembly off of the coil tubing. There is further
provided an orientation sub that attaches to the motor assembly in the coil
tubing so that the upstock or whipstock may be oriented in the proper
orientation when the radials are drilled through the wo11s of the casing.
Following this orientation, there would be provided a whipstock or upstock
attached to the carrier string, which is lowered into the cased or uncased
wellbore. The carrier string is lowered into the outer casing, hung off in
either
the well head or rotary table. Next the inner drilling assembly is lowered
into
the carrier string and when the drill bit makes contact with the deflecting
surface of the whipstock or upstock, there is a bore drilled through the wall
of
the casing or into the open hole through conventional means depending on the
type of material which the casing is constructed of or the type of wellbore to
be
drilled. In the preferred embodiment, the inner drill string is preferably a
continuous string of coiled tubing having a drill bit and a mud motor assembly
at the end of the tubing for rotating the drill bit.
It should be known at this time, that although this discussion is centering
around a cased borehole, this process as will be discussed can be utilized in
the drilling of radial wells in open hole applications, and does not
necessarily
have to be utilized in conjunction with cased boreholes.
In the process of the underbalanced drilling, a first fluid is circulated
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down the annulus of the coiled tubing which fluid can be air or nitrogen or
water which would drive the mud motor assembly and rotate the drill bit. This
would in the preferred embodiment be a non-dcunaging type fluid which would
not cause dcunage to the surrounding formation. Simultaneously, there would
be circulated down the annulus between the outer drill string and the inner
drill
string a second and different fluid such as aerated nitrogen or water in a
combination so as not to cause damage to the formation. The two fluids would
then be co-mingled at the point of the drill bit and returned as a co-mingled
fluid in the cmnular space between the carrier string and the casing of the
borehole and returned to the separator above the hydrill.
When the drill bit is to be retrieved from drilling a radial well, a kill slug
would then be pumped down the annulus between the carrier string and the
drill string, the kill slug comprising fluids in a weight ratio to displace
the pipe
so that the hydrostatic pressure in the carrier string would not allow fluid
to flow
up the carrier string while the drill string is being retrieved through it so
that the
clear lighter fluid that was being circulated in combination is still making
contact with the formation and the kill slug does not dcunage the formation
and
the well is essentially being driIled as a live well within the main well
bore. The
carrier string with the upstock on its end would then be repositioned at a
different point in the borehole, while the well is still alive, and the coiled
tubing
could be relowered into the borehole to drill the next radial. This drilling
of
additional radials and various orientations could be accomplished while the
well is maintained as a live well, so long as the fluid pressure is
underbalanced
within the well bore through a combination of fluids in the drill string and
carrier
string.
Therefore, it is a principal object of the present invention to provide a
drilling technique for multiple radials, utilizing an underbalanced system
which
allows radials to be drilled off of a single borehole while the well is
maintained
as a live producing well during the process;
It is a further principal object of the present invention to provide a system
of underbalanced drilling in drilling radial wells, so that each of the radial
wells
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is drilled while the well is alive, and no damaging fluids or muds make
contact
with the formation which may do dcunage to the formation;
It is a further object of the present invention to drill multiple radial wells
without having to kill the well in order to drill the additional radial wells;
It is a further object of the present invention to provide a two-string
technique in underbalcmced drilling so that at least two different fluids are
pumped down the annulus's of the coiled tubing or drill pipe, and a second
fluid
is pumped down the annulus between a carner string and the inner drill string,
so that the co-mingled fluids cire returned up to the surface fluid handling
facilities through an outer annulus between the casing and the carrier string;
It is the further object of the present invention to provide a two-string
drilling technique utilizing coil tubing as a driIl string, and a carrier
string as the
outer string, so that two different fluids can be utilized in an underbalanced
drilling system of radial boreholes while the well is being maintained as a
live
producing well.
It is a further object of the present invention to provide an underbalanced
drilling technique for multiple radial wells, by utilizing two different
fluids
pumped down the borehole with at least one of the fluids making contact with
the formation so that the formation is not harmed by the fluid flowing past
the
formation.
BRIEF DESCRIPTION OF THE DRAWINGS
For a further understanding of the nature, objects, and advantages of the
present invention, reference should be had to the following detailed
description,
read in conjunction with the following drawings, wherein like reference
numerals denote like elements and wherein:
Figure 1 illustrates an overall view of the two string underbalanced
drilling technique utilizing coiled tubing as the drill string in the drilling
of
multiple radials;
FIGURE 2 illustrates a partial cross-sectional view of the whipstock or
upstock portion of the two string drilling technique and the fluids flowing
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therethrough during the underbalanced drilling process;
FIGURES 3A - 3C illustrate views of the underbalanced drilling technique
utilizing the fluid for maintcaning the underbalanced status of the well
during a
retrieval of the coiled tubing drill string;
FIGURES 4A & 4B illustrate a flow diagram for under drilling utilizing a
two-string drilling technique in an upstock assembly with the fluid being
returned through the annulus between the drill string and the carrier string;
FIGURE 5 illustrates a partial view of the underbalanced drilling
technique showing the drilling of multiple radial wells from a single vertical
or
horizontal well while the well is maintained in the live status within the
bore
hole;
FIGURE 6 illustrates an overall schematic view of an underbalcmced
drilling system utilized in the system of the method of the present invention;
FIGURE 7A illustrates an overall schematic view of an underbalanced
radial drilling (with surface schematic) while producing from a wellbore being
drilled, and a wellbore that has been drilled and is currently producing, with
FIGURE 7B illustrating a partial view of the system;
FIGURE 8A illustrates an overall schematic view of underbalcmced
horizontal radial driIling (with surface schematic) while producing from a
radial
wellbore being drilled, and additional radial wellbores that have been
drilled,
with FIGURE 8B illustrating a partial view of the system; and
FIGURE 9 illustrates a flow diagram for underbalanced drilling using the
two string drilling technique with the upstock assembly where there is a
completed radial well that is producing and a radial well that is producing
while drilling.
DETAIL,ED DESCRIPTION OF THE INVENTION
FIGURES 1-9 illustrate the preferred embodiments of the system and
method of the present invention for drilling underbalanced radial wells
utilizing
a dual string technique in a live well. As illustrated in FIGURE 1, what is
provided is a drilling system 10 utilizing coil tubing as the drill string. As
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illustrated, the coil tubing 12 which is known in the art, and comprises a
continuous length of tubing, which is lowered usually into a cased well having
an outer casing 14 placed to a certain depth within the borehole 16. It should
be kept in mind that during the course of this application, reference will be
made to a cased borehole 16, although the system and method of the present
invention may be utilized in a non-cased or "open" borehole, as the case may
be. Returning to FIGURE 1, the length of coil tubing 12 is inserted into the
injector head 19 of the coil tubing assembly 20, with the coil tubing 12 being
rolled off of a continuous reel mounted adjacent the rig floor 26. The coil
tubing
12 is lowered through the stripper 22 and through the coil tubing blowout
preventor stack 24 where it extends down through the rig floor 26 where a
carrier string 30 is held in place by the slips 32. Beneath the rig floor 26
there
are a number of systems including the rotating drill head 34, the hydril136,
and
the lower BOP stack 38, through which the coil tubing 12 extends as it is
moved
down the carrier string 30.
Since the system in which the coil tubing 12 is being utilized in this
particular application is a system for drilling radial wells, on the lower end
of
the coil tubing 12, there are certain systems which enable it to be oriented
in a
certcan direction downhole so that the proper radial bore may be drilled from
the horizontal or vertical lined cased borehole 16. These systems include a
monel drill collar 40, positioned above a muleshoe sub 42, at the end of which
includes a mud motor 44, which rotates the drill bit 46 for driIling the
radial well.
As further illustrated in FIGURE 1, on the lower end of the carrier string 30
there
is provided a deflector means which comprises an upstock 50, which is known
in the art and includes an angulated ramp 52, and an opening 54 in the wall 56
of the upstock 50, so that as the drill bit 46 makes contact with the rcunp
52, the
drill bit 46 is deflected from the ramp 52 and drills through the wall 56 of
the
casing 14 for drilling the radial borehole 60 from the cased borehole 16. In a
preferred embodiment, there may be a portion of fiberglass casing 64 which
has been placed at a predetermined depth within the borehole, so that when
the drill bit 46 drills through the wal156 of the casing 14 at that
predetermined
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depth, the bit easily cuts through the fiberglass and on to drill the radial
well.
Following the steps that may be taken to secure the radial bore as it
enters into the cased well 14, such as cementing or the like, it is that point
that
the underbalanced drilling technique is undertaken. This is to prevent any
blowout or the like from moving up the borehole 16 onto the rig 26 which would
damage the system on the rig or worse yet, injure or kill workers on the rig.
As
was noted earlier in this application, the underbalanced technique is utilized
so that the fluids that are normally pumped down the borehole 16, heavy fluids
and muds which are normally dumped down the borehole 16, in order to
maintain the necessary hydrostatic pressure, are not utilized. What is
utilized
in underbalanced drilling, is a combination of fluids which are of sufficient
weight to maintain a lower than formation hydrostatic pressure in the borehole
yet not to move into the formation 70 which can cause damage.
In order to carry out the method of the system, reference is made to
FIGURES 1 and 2. Again, one should keep in mind that the outer casing 14
lines the formation 70, and within the outer casing 14 there is a smaller
carrier
string 30 casing, which may be a 5" casing, which is lowered into the outer
casing 16 thus defining a first annulus 72, between the inner wall of the
outer
casing 16 and the outer wall of the carrier string 30. The carrier string 30
would
extend upward above the rig floor 26 and would receive fluid from a first pump
means 76 (see FIG. 6), located on the rig floor 26 so that fluid is pumped
within
the first annulus 72. Positioned within the carrier string 30 is the coil
tubing 12,
which is normally 2" in dicaneter, and fits easily within the interior annulus
of the
carrier string, since the driIl bit 46 on the coil tubing 12 is only 43/a" in
dicuneter.
Thus, there is defined a second annulus 78 between the wall of the coil tubing
12 and the wall of the carrier string 30. Likewise, the coil tubing 12 has a
continuous bore therethrough, so that fluid may be pumped via a second pump
79 (see FIG. 6) through the coil tubing bore 13 in order to drive the 33/s"
mud
motor and drive the 43/4" bit 46.
Therefore, it is seen that there are three different areas through which
fluid may flow in the underbalanced technique of drilling. These areas include
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the inner bore 13 of the coil tubing 12, the first annulus 72 between the
outer
wall of the carrier string 30 and the inner wall of the outer casing 16, and
the
second cmnulus 78 between the coil tubing 12 and the carrier string 30.
Therefore, in the underbalanced technique as was stated ecalier, fluid is
pumped down the bore 13 of the coil tubing 12, which, in turn, rotates the mud
motor 44 and the drill bit 46. After the radial well has been begun, and the
prospect of hydrocarbons under pressure entering the annulus of the casings,
fluids must be pumped downhole in order to maintain the proper hydrostatic
pressure. However, agcan this hydrostatic pressure must not be so great as to
force the fluids into the formation. Therefore, in the preferred embodiment,
in
the underbalanced multi-lateral drilling technique, nitrogen gas, air, and
water
is the fluid pumped down the borehole 13 of the coil tubing 12, through a
first
pump 79, located on the rig floor 36. Again, this is the fluid which drives
the
motor 44 and the driIl bit 46. A second fluid mixture of nitrogen gas, air and
water is pumped down the second annulus 78 between the 2" coiled tubing
string 12 and the carrier string 30. This fluid flows through second annulus
78
and again, the fluid mixture in annulus 78 in combination with the fluid
mixture
through the bore 13 of the coil tubing 12 comprise the principal fluids for
mcrintcdning the hydrostatic pressure in the underbalanced drilling
technique. So that the first fluid mixture which is being pumped through the
bore 13 of the coil tubing 12, and the second fluid mixture which is being
pumped through the second cmnular space 78 between the carrier string 30
and the coil tubing 12, reference is made to FIGURE 2 in order understand the
manner in which the fluid is returned up to the rig floor 26 so that it does
not
make contact with the formation.
As seen in FIGURE 2, the fluid mixture through the bore 13 of the coil
tubing 12 flows through the bore 13 and drives the mud motor 44 and flows
through the drill bit 46. Simultaneously the fluid mix is flowing through the
second annular space 78 between the ccurier string 30 and the coil tubing 12,
and likewise flows out of the upstock 50. However, reference is made to the
first
cmnulcu space between the outer casing 14 and the carrier string 30, which is
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that space 72 which returns any fluid that is flowing downhole back up to the
rig
floor 26. As seen in FIGURE 2, arrows 81 represent the fluid flow down the
bore
13 of the coil tubing 12, arrows 83 represent the second fluid flowing through
the
second annular space 78 into the borehole 12, and arrow 82 represents the
return of the fluid in the first annular space 72. Therefore, all of the fluid
flowing
into the drill bit 46 and into the bore 12 so as to maintain the hydrostatic
pressure is immediately returned up through the outer annular space 72 to be
returned to the separator 87 through pipe 85 as seen in FIGURES 1& 6.
During the drilling technique should hydrocarbons be found at one point
during this process, then the hydrocarbons will likewise flow up the annular
space 72 together with the return air and nitrogen and drilling fluid that was
flowing down through the tube flowbores or flow passageways 13 and 78. At
that point, the fluids canying the hydrocarbons if there are hydrocarbons,
flow
out to the separator 87, where in the separator 87, the oil is separated from
the
water, and any fumes then go to the flare stack 89 (FIG. 6). This schematic
flow
is seen in FIGURE 6 of the application.
One of the more critical aspects of this particular manner of drilling wells
in the underbalanced technique, is the fact that the underbalanced drilling
technique would be utilized in the present invention in the way of drilling
multiple radial wells from one vertical or horizontal well without having to
kill
the well in order to drill additional radials. This was discussed earlier.
However, as illustrated in FIGURES 3A - 3C, reference is made to the
sequential
drawings, which illustrate the use of the present invention in drilling radial
wells. For example, as was discussed earlier, as seen in FIGURE 3A, when the
coil tubing 12 encounters the upstock 50, and bores through an opening 54 in
the wall of outer casing 14, the first radial is then drilled to a certcmn
point 55.
At some point in the driIling, the coil tubing string 12 must be retrieved
from the
borehole 16 in order to drill additional radials. In the present state of the
art,
what is normally accomplished is that the well is killed in that sufficient
weighted fluid is pumped into the wellbore to stop the formation from
producing
so that there can be no movement upward through the borehole by
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hydroccabons under pressure while the drill string is being retrieved from the
hole and subsequently completed.
This is an undesirable situation. Therefore, what is provided as seen in
FIGURES 3B and 3C, where the coil tubing 12, when it begins to be retrieved
from the hole, there is provided a kill slug 100, lowered into the second
cmnulcQ
space 78 between the wall of the coil tubing 12 and the wall of the carrier
string
30. This kill slug 100 is a combination of fluids, which are sufficient to
maintain
any hydrocarbons from flowing through the carrier string 30 upward, yet do not
go into the formation. Rather, if there are hydrocarbons which flow upward
they encounter the kill slug 100 and flow in the direction of arrows 73
through
the first annular space 72 between the carrier string 30 and the outer casing
14,
cmd flow upward to the rig floor 26 and into the separators 87 as was
discussed
earlier. However, the carrier string 30 is always "alive" as the coil tubing
12 with
the drill bit 46 is retrieved upward. As seen in FIGURE 3C, the kill slug 100
is
placed to a certain depth 102 within the carrier string 30, so that as the
drill bit
46 is retrieved from the bore of the carrier string 30, the kill slug 100
maintains
a certain equilibrium within the carrier string 30, and the well is maintained
alive.
Therefore, FIGURE 5 illustrates the utilization of the technique as seen
in FIGURES 3A - 3C, in drilling multiple radials off of the vertical or
horizontal
well. As illustrated for example, in FIGURE 5, a first radial would be drilled
at
point A along the bore hole 16, utilizing the technique of the kill slug 100
as
described in FIGURE 3C. Maintaining the radial well in the underbalanced
mode, through the use of kill slug 100, the drill bit 46 and coil tubing 12 is
retrieved upward, cmd the upstock 50 is moved upwccrd to a position B as
illustrated in FIGURE 5. At this point, a second radial well is drilled
utilizing the
same technique as described in FIGURE 3, until the radial well is drilled and
the
kill slug forms an underbalcmced well at that point. The coil tubing 12 with
the
bit 46 is retrieved once more, to level C at which point a third radial well
is
drilled. It should be kept in mind that throughout the drilling of the three
wells
at the three different levels A, B, C, the hydrostatic pressure within the
carrier
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string 30 will be maintcuned as a balanced pressure, and any hydrocarbons
which may flow, may flow upward within annulus 72 between the carrier string
30 and the outer casing 14. Therefore, utilizing this technique, each of the
three
wells are drilled and completed as live wells, and the multiple radials can be
drilled while the carrier string 30 is alive as the drill bit 46 and carrier
string 30
are retrieved upward to another level.
Figures 4A and 4B illustrate a two string drilling technique, whereas as
seen in 4A the coil tubing 12 with the drill bit 46 on its end is drilling a
radial
well, with the driIl bit being driven by mud motor 44. The coil tubing is
housed
within carrier string 30, with carrier string 30 housed within outer casing
14. As
seen in Figures 4A and in isolated view in 4B, the fluid is pumped down the
bore
of coil tubing 12 (arrows 81), and is returned up the annulus between carrier
string 30 and the outer casing 14 (arrows 90), while additional fluid 81 is
pumped down the annulus between the coil tubing 12 and the carrier string 30
(arrows 91), as seen in Figure 4B, to enhance the movement of the fluid
therethrough.
FIGURE 6 is simply an illustration in schematic form of the various
nitrogen units 104, 106, and rig pumps 76, 79 including the air compressor 108
which are utilized in order to pump the combination of air, nitrogen and
drilling
fluid down the hole during the underbalanced technique and to likewise receive
the return flow of air, nitrogen, water and oil into the separator 87 where it
is
separated into oi1110 and water 112 and any gases are then burned off at flare
stack 89. Therefore, in the preferred embodiment, this invention, by utilizing
the
underbalanced technique, numerous radial wells 60 can be drilled off of a
borehole 16, while the well is still alive, and yet none of the fluid which is
utilized
in the underbalanced technique for maintaining the proper equilibrium within
the borehole 16, moves into the formation and causes any damage to the
formation in the process.
FIGURES 7A and 7B illustrate in overall and isolated views respectively,
the well producing from a first radial borehole 60 while the radial borehole
is
being drilled, and is likewise simultaneously producing from a second radial
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borehole 60 after the radial borehole has been completed. As is illustrated,
first
radial borehole 60 being drilled, the coil tubing string 12 is currently in
the
borehole 60, and is drilling via driIl bit 46. The hydrocarbons which are
obtained during drilling return through the radial borehole via annulus 72
between the wall of the borehole, and the wall of the coiled tubing 12.
Likewise,
the second radial borehole 60 which is a fully producing borehole, in this
borehole, the coil tubing 12 has been withdrawn from the radial borehole 60,
and hydrocarbons are flowing through the inner bore of radial borehole 60
which would then join with the hydrocarbon stream moving up the borehole via
first radial well 60, the two streams then combfning to flow up the outer
cmnulus
72 within the borehole to be collected in the seporator. Of course, the return
of
the hydrocarbons up annulus 72 would include the air/nitrogen gas mixture,
together with the drilling fluids, all of which were used downhole during the
underbalanced drilling process discussed earlier. These fluids, which are
comingled with the hydrocc[rbons flowing to the surface, would be separated
out later in separator 87.
Likewise, FIGURES 8A and 8B illustrate the underbalanced horizontal
radial drilling technique wherein a series of radial boreholes 60 have been
drilled from a horizontal borehole 16. As seen in FIGURE 7A, the furthest most
borehole 60 is illustrated as being producing while being drilled with the
coil
tubing 12 and the drill bit 46. However, the remaining two radial boreholes 60
are completed boreholes, and are simply receiving hydroccQbons from the
surrounding formation 70 into the inner bore of the radial boreholes 60. As
was
discussed in relation to FIGURES 7A and 7B, the hydrocarbons produced from
the two completed boreholes 60 and the borehole 60 which was currently being
drilled, would be retrieved into the annular space 72 between the wall of the
borehole and the carrier string 30 within the borehole and would likewise be
retrieved upward to be separated at the surface via separator 87. And, like
the
technique as illustrated in FIGURES 7A and 7B, the hydrocarbons moving up
annulus 72 would include the air/nitrogen gas mixture and the drilling fluid
which would be utilized during the drilling of radial wel160 via coil tubing
12,
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and agcdn would be comingled with the hydrocarbons to be separated at the
surface at separator 87. As was discussed earlier and as is illustrated, all
other
components of the system would be present as was discussed in relation to
FIGURE 6 earlier.
Turning now to FIGURE 9, the system illustrated in FIGURE 9 again is
quite similar to the systems iIlustrated in FIGURES 7A, 7B and 8A, 8B and
again
illustrate a radial borehole 60 which is producing while being drilled with
coil
tubing 12 and drill bit 46. The second radial well 60 is likewise producing.
However, this well has been completed and the hydrocarbons are moving to the
surface via the inner bore within the radial bore 60 to be joined with the
hydrocarbons from the first radial well 60. Unlike the drilling techniq-ues as
illustrated in FIGURES 7 and 8, PIGURE 9 would iIlustrate that the
hydrocarbons
would be collected through the annular space 78 which is that space between
the wall of the coil tubing 12 and the wall of the carrier string 30. That is,
rather
than be moved up the outermost annular space 72 as illustrated in FIGURES
7 and 8, in this particular embodiment, the hydrocarbons mixed with the
air/nitrogen gas and the drilling fluids would be collected in the annular
space
78, which is interior to the outermost annular space 72 but would likewise
flow
and be collected in the separator for separation. Although this is a
particular
embodiment, it is not necessarily the preferred embodiment, in view of the
fact
that the annular space 78 is somewhat reduced than the annular space 72 and
therefore, the flow of the hydrocarbons to be collected on the surface would
be
slower and therefore would not be as efficient as seen in the embodiment
shown in FIGURES 7 and 8. However, as illustrated in all other respects, the
system would operate substantially the same as the system shown in FIGURES
7 and 8 with the same components as discussed earlier.
PARTS LIST
The following is a list of suitable pcQts and materials for the various
elements of the preferred embodiment of the present invention.
CA 02305253 2000-04-07
WO 99/19595 PCT/US97/18486
Description Part No.
drilling system 10
coil tubing 12
bore 13
outer casing 14
bore hole 16
injector head 19
tubing assembly 20
stripper 22
stack 24
rig floor 26
carrier string 30
slips 32
drill head 34
hydrill 36
BOP stack 38
casing head 39
monel drill collar 40
mule shoe sub 42
mud motor 44
drill bit 46
upstock 50
angulated raanp 52
opening 54
point 55
wall 56
radial bore hole 60
fiberglass casing 64
formation 70
first cmnulus 72
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CA 02305253 2000-04-07
WO 99/19595 PCT/US97/18486
arrow 73
first pump means 76
second annulus 78
second pump 79
arrows 81
arrows 83
pipe 85
pits 86
separator 87
flare stack 89
spool 92
point 98
kill slug 100
depth 102
nitrogen units 104, 106
air compressor 108
oil 110
water/drilling fluid 112
The foregoing embodiments are presented by way of example only; the
scope of the present invention is to be limited only by the following claims.
What is claimed as invention is:
17
