Improved Method for Drilling Multi-Lateral Wells and
Related Device
TECHNICAL FIELD
The present invention relates generally to an improved method for drilling multi-lateral wells and related device. More particularly, the present invention relates to an improved method for drilling one or more multi-lateral wells from an existing well whereby the junction about the lateral well is sealed.
RELATED APPLICATION
This is a related Application to another application entitled "Improved Method for
Drilling Multi -Lateral Wells With Reduced Under-reaming and Related Device" filed on August
28, 2000. BACKGROUND ART
Drilling or utilizing multi-lateral or horizontal wells has become increasingly popular for enhancing production and recovery of oil and gas from well-bores. Multi-lateral drilling methods
have been lαiown for a relatively short period of time and only recently have methods and
apparatuses been developed to make the drilling of such wells cost-effective and technically
sound to the oil industry.
However, drilling of multi-lateral wells is in increased demand because it has been shown
that the economic viability from a multi-lateral well is dramatically increased when compared to that of conventional wells. As a result of an increased return on investment on oil and gas recovery, the drilling of multi-lateral wells has become an important aspect of well enhancement.
As such, the drilling of multi-lateral wells has become very important for efficient oil and gas
recovery. Multi-lateral wells have been found very effective in areas where the pay-zone or
oil/gas deposit may be thin or hard to reach with standard down-hole drilling operations.
However, one of the primary reasons an operator would drill a multi-lateral well is to take advantage of the existence of a previously drilled wellbore. In drilling a multi-lateral well, a
driller can reduce the cost of the well dramatically by beginning the new drilling operations at
a point already down from the surface. Therefore, many of the modern methods that have been
developed attempt to make use of an existing well-bore and thereby eliminate the cost of drilling
from the surface..
The technique of drilling a multi-lateral well has typically consisted of laterally drilling
from a previous drilled borehole, sometimes referred to herein as the primary borehole. The
previous drilled borehole from which a lateral well is drilled is typically cased and cemented, but
methods exist in the art for un-cased and un-cemented well -bores. However, these prior art
methods of drilling lateral boreholes suffer from a common problem of maintaining a sealed
junction between the primary well-bore and the lateral well-bore. The present invention is an
improved method for establishing and maintaining such sealed junction.
A common example of the prior art drilling methods is embodied in U.S. Pat. No.
5,458,209 to Hayes et al. (the '209 patent). The '209 patent discloses a method and system for
drilling a lateral well with respect to a primary well which is cased. The method discloses
positioning a guide means; defined as comprised of three main parts; a lower end, a central part
with an angled ramp and an upper end., and drilling out the casing along the guide at a
preselected location. This method has effectively drilled multi-lateral wells, but does not insure
a sealed junction.
Accordingly, the art field is in search of a method to drill a lateral well and to establish
a sealed junction about one portion of the lateral well, such as between the lateral well and the
primary well-bore.
A prior art method that has had some success in sealing the well -bore around the junction is disclosed in U.S. Pat. No. 5,564,503 to Longbottom et al (the '503 patent). This patent discloses a method of drilling a multi-lateral well encompassing the steps of setting a diverter within a well-bore, boring through the sidewall of the well-bore at a desired location, lining the lateral well, and cementing the periphery of the junction around the lateral well to obtain a
pressure-bearing seal around the well-bore. Conventional cementing techniques are disclosed
to inject cement or an elastomeric cement in the interstices about the junction. One difficulty
encountered when utilizing this method is ensuring a homogeneous filling with cement at the peripheiy of the junction because of the presence of tubulars and the limited space between the tubulars and the formation about the junction. Another common difficulty is ensuring a uniform
fill of the cement about the junction without leaving spaces or voids because of the irregular shape of the interstices area about the junction. Accordingly, this method does not necessarily
provide a homogeneous cement bond around a lateral well. Therefore the art field desires a
method of effectively sealing the lateral well-bore from the primary well-bore.
Another difficulty encountered with the prior art method disclosed in the '503 patent is the practical impossibility of the method to effectually warranty the seal of the junction with the passage of time. The method discloses using conventional techniques to cement about the junction, such as flowing cement into the well-bore and allowing the cement to fill the interstices
area between the liner and the lateral well-bore as the cement fills from below the junction.
However, the amount of cement is limited to the cement that will fill within the interstices area
around the junction between the casing and the formation. Accordingly, mud pockets that are not filled with the cement would result in structural weakness of the junction. As well, the dirt and debris from the formation can easily contaminate the cement as it fills the interstices
Therefore, the art field desires a method that effectively fills the area where a junction is to be
established by providing a sufficient amount of a cement or resin material to ensure an adequate volume of the cement or resin down-hole about a junction.
A prior art cement that has proven effective in resisting cracks and fissures is disclosed
inU.S. Patent Nos. 5,795,924 to Chatterji et al. (the '924 patent), 5,820,670 to Chatterji et al. (the
'670 patent) and 6,006,835 to Onan et al (the '835 patent). These prior art methods generally
disclose an epoxy resin material or cement slushy that may be used in a well-bore Numerous
advantages have been found from the use of such epoxy resin materials. Some of the advantages
are the reduced cracking from stress through the life of the well. Accordingly, the art field
desires a method of drilling a lateral well that is able to realize benefits of a cement or resin
material that resists cracks and fissures.
Typically, prior art multi-lateral wells with sealed junctions have required a large amount
of under-reaming of the primary well-bore to drill the lateral well-bore from the primary bore.
Under-reaming is the process whereby the primary well-bore is made wider, in this case, about
the area where the lateral bore is desired. The increased width allows for room for the
establishment of the junction and the lateral well. The under-reaming is usually accomplished
after a section milling operation has removed the casing about the area where the lateral bore is
desired. Prior art operations have required the diameter of the under-reaming to be about
equivalent to 3.5 times the size of the primary well-bore. However, high ratio under-reaming can
be a risky operation, especially in highly deviated wells. Accordingly, the art field has searched
for a method of drilling a multi-lateral well whereby the risks associated with under-reaming may
be reduced.
As well, the prior art methods of drilling a multi-lateral well with a sealed junction have often required that the lateral well be of a smaller diameter than the primary well-bore. This
reduction in size can severely limit further operations in the lateral well. Accordingly, the art
field has searched for a method of drilling a lateral well whereby the diameter of the lateral well
is not reduced from the diameter of the primary well-bore.
Therefore, what is needed in the art is a method of sealing a junction of the primary well
and a lateral well to provide isolation of the lateral well-bore while maintaining an effective seal
with the passage of time. Additionally, what is needed is a method of drilling the aforementioned
lateral well-bore whereby the amount of under-reaming required to drill the lateral well is reduced.
SUMMARY OF THE INVENTION
The present invention generally relates to the an improved method of drilling multi-lateral
wells, comprising filling a portion of a primary well-bore with a stress resistant cement or epoxy
resin and drilling a lateral well from the primary well-bore whereby the substance used in the
primary well-bore seals and isolates the formation about the lateral well-bore while allowing a
lateral well to be drilled that is substantially the size of the primary well-bore. More particularly,
the substance used to fill the area about the junction resists cracks and fissures and retains a seal
through the passage of time.
BRIEF DESCRIPTION OF DRAWINGS
For a further understanding of the nature and objects of the present invention, reference
should be made to the following detailed description, taken in conjunction with the
accompanying drawings, in which like elements are given the same or analogous reference
numbers and wherein:
Fig. 1 is an illustration of an existing well-bore, cased and cemented.
Fig. 2 is an illustration of a well-bore where the casing has been milled out at the pre¬
selected location.
Fig. 3a is an illustration of an under-reamed area of an embodiment of the present invention.
Fig. 3b is an illustration of the prior art under-reaming operation.
Fig. 3c is an illustration of a top side view of the under-reaming required under
embodiments of the present invention.
Fig. 3d is an illustration of a top side view of the under-reaming required under
embodiments of the present invention and prior art methods of drilling.
Fig.4a is an illustration of a pre-bent guide run into the well-bore at about the preselected
under-reamed location.
Fig. 4b is an illustration of a pre-bent guide with an inflatable packer element run into
the well-bore at about the preselected under-reamed location.
Fig.4c is an illustration of a guide run into the well-bore at about the preselected under-
reamed location.
Fig. 4d is an illustration of a guide with an inflatable packer element run into the well-
bore at about the preselected under-reamed location.
Fig. 5a is an illustration of an embodiment of the present invention where an epoxy
material has been injected into the well-bore to fill about the preselected under-reamed location
with a pre-bent guide..
Fig. 5b is an illustration of an embodiment of the present invention where an epoxy
material has been injected into the well-bore to fill about the preselected under-reamed location with a straight guide.
Fig.6a is an illustration of an embodiment of the present invention where a path is drilled
through the hardened epoxy along the pre-bent guide path.
Fig.6b is an illustration of an embodiment of the present invention where a path is drilled
through the hardened epoxy along the guide path.
Fig. 7 is an illustration of a completed drill path through a preselected location.
Fig. 8 is an illustration of an orienting sleeve and whipstock in the drill path.
Fig.9 is an illustration of an embodiment of the present invention whereby a lateral well-
bore is drilled.
Fig. 10 is an illustration of a completed lateral bore.
Fig. 11 is an illustration of the completed lateral bore with a liner installed.
Fig. 12 is an illustration of the completed, lined lateral bpre with a bridge installed.
Fig.13 is an illustration of the completed, lined, bridged lateral bore where the whipstock
has been removed.
GENERAL DESCRIPTION AND PREFERRED MODE FOR CARRYING OUT THE INVENTION
Referring now to Fig. 1, an existing primary well-bore, cased and cemented, a typical
down-hole well is illustrated. This embodiment is a vertical well, however, it should be understood that embodiments of the present invention work with well-bores that are not cased or lined, not cemented and not vertical. Embodiments of the present invention are designed for
application wherever a stress resistant, sealed junction is desired out of an existing primary well-
bore.
Fig. 1 generally describes an area where a lateral well is desired. The figure is illustrative of a well that is completed with steel casing 1 and cement 2 around well-bore 3. The manner of selection of an area to drill a lateral well-bore may be by any means common in the art, however, most typically the selected location is where an operator desires to drill a new well, drill to a new target. However, this list is not exhaustive and there are numerous other reasons an operator may
desire to drill a lateral well. The area selected for the lateral well is generally defined as
preselected location 6.
In a preferred embodiment of this invention, as illustrated by Fig. 2, an illustration of a
well-bore where the casing 1 has been removed at the pre-selected location 6, the well-bore 3 is
prepared for drilling a lateral well. A specific and usually predetermined length of casing has been milled out, thus exposing cement 2 or a formation along the area desired to drill the lateral
well-bore.
Section milling is common in the art. However, an exemplary section milling operation
will be described briefly. An embodiment of a section milling operation in an existing well-bore
3 may include the steps of lowering a drill string 7 into the well bore 3, the drill string 7 having a conventional section mill 8 operateably attached about the drill string 7. In a preferred embodiment, the section mill 8 will be stopped above the preselected location 6 and begin
downward section milling. The section milling may and should cause the section mill 8 to engage the casing 1 and destroy substantially all of the casing 1 about the pre-selected location
6. An operator may thus lower the drill string 7 to a point below the preselected point while keeping the section mill engaged thereby destroying or removing the casing from a point above the preselected location 6 to a point below the preselected location 6. After completion of the
section milling step, the operator should have removed substantially all of the casing along location 6.
Fig. 3b, an illustration of an embodiment of the prior art under-reaming operation,
demonstrates the enlarging of the well-bore width 13 to an under-reamed width 17. In one embodiment of the present invention, it is necessary to under-ream a well-bore to a diameter of about 3.5 times the diameter of the well-bore to enable a lateral well-bore to be drill off the primary well-bore 3. Embodiments of the present invention are designed for establishing a
lateral well-bore from any sized well-bore and under-reamed area. A preferred embodiment of
the present invention utilizes an under-reamed area that is only about two to 2.5 times the
diameter of the well-bore.
In Fig. 3a, an illustration of an embodiment of the present inventions under-reaming
operation, it may be observed that well -bore width 13 is only enlarged to under-reamed width 12.
It may be further observed that the ratio of under-reamed width 12 to borehole width 13 of Fig.
3a is smaller than the ratio of under-reamed width 17 to borehole width 13 of Fig. 3b. In a
preferred embodiment of the present invention, as depicted in Fig.3a, the ratio of under-reamed
width 12 to borehole width 13 is about 2.0 to 2.5 whereas prior art ratios and ratios of
embodiments of this invention, as depicted in Fig. 3b, of under-reamed ratio of width 17 to
borehole width 13 is about 3.5. Accordingly, embodiments of the present invention do not require as much of an under-reaming operation. As previously discussed, a large under-reaming
operation typically removes much of the formation about the borehole 3, as depicted in Fig.3b.
Accordingly, under the guidelines of embodiments of the present invention, the formation and
existing well-bore 3 will not have as much of the formation removed by an under-reaming
operation. The manner of achieving the reduced under-reaming is depicted in Fig. 3c and Fig.
3d and will be more succinctly described below.
The remainder of this description of apreferred embodiment of the method of the present
invention will utilize the under-reaming of Fig.3a where the ratio of under-reamed width 12 to
borehole width 13 is about two to 2.5.
Now referring to Fig. 4a, an illustration of pre-bent guide run into the well-bore at about
the preselected location, it may be observed that the pre-bent guide 26 is not straight along the path of well-bore 3, but rather is arcuate at about the preselected location 6, returning to about straight along the remaining path of well-bore 3 at the lower end of preselected location 6. In an
embodiment of the present invention a preselected guide is lowered into the well-bore 3 to
provide an arcuate guide at about the preselected location 6. However, embodiments of the
present invention may be used with a straight guide 27 running through well-bore 3 , as illustrated
in Fig. 4c. The guide 27 may extend through preselected location 6.
Now referring to Fig. 4b, an illustration of a pre-bent guide with an inflatable packer
element run into the well-bore at about the preselected under-reamed location, it may be observed
that the pre-bent guide 26 is surrounded by an inflatable packer element 18. Further, pre-bent guide 26 is not straight along the path of well -bore 3, but rather is arcuate at about the preselected
location 6, returning to about straight along the remaining path of well-bore 3 at the lower end of preselected location 6. In this embodiment of the present invention a preselected guide is
lowered into the well-bore 3 to provide an arcuate guide at about the preselected location 6. However, embodiments of the present invention may be used with a straight guide running through well-bore 3, as illustrated in Fig. 4d. In an embodiment with a straight guide 27, an
inflatable packer element 19 may also be utilized. ,
Now referring to Fig.5a, an illustration of an embodiment of the present invention where a cement 41 material has been injected into the well-bore to fill about the preselected location 6, it may be observed that a guide 26 still defines an arcuate path and the cement 41 has completely filled about the pre-bent guide. Another embodiment utilizes an epoxy cement material produced from apumpable material of epichlorohydrin and bisphenol that hardens after
injection into the well-bore 3. This epoxy resin and its derivatives are common in the art and are
known to provide a high degree of impermeability while providing flexibility for shifts in the formation, unlike conventional methods or conventional cement. Often, these epoxy resin
materials will include a liquid diluent containing a substance to allow the epoxy to have a sufficient viscosity to allow the epoxy material to be pumped into the well-bore 3 and completely fill about the preselected location 6. As well, another preferred embodiment of the present invention utilizes an additive within the material pumped to change the time of hardening of the
cement. The additive may either be a retardant to prevent premature hardening or setting up of
the material within the well-bore or an accelerator to hasten the hardening of the cement.
A most preferred embodiment of the present invention utilizes a pre-bent guide 26 (as
depicted in Fig. 4b) that is surrounded by an inflatable packer 18. The inflatable packer 18 is
typically constructed of an elastic substance such as rubber or an elastomer. However, any material may be used that stretches section milling four times the diameter of the packer element.
The inflatable packer 18 is preferably about the pre-bent guide 26 in the area of preselected
location 6 where the lateral well-bore is desired. After the under-reaming operation, the packer
may be inflated (not shown) such that the inflation completely fills the under-reamed area. Inflation of packers is common in the art and may be accomplished as known in the art. A
typical method of inflating a packer pumps cement or other substance into the packer to inflate, a preferred substance is an epoxy resin such as an armoured epoxy.
The use of inflatable packer 18 on the pre-bent guide 26 will ensure that upon inflation no contaminant from the formation will become mixed with the cement and reduce the hardening of the material and sealing effect about the junction and also will ensure that the under-reamed cavity is substantially filled with a cement or epoxy resin material.
Referring now to Fig.6a, an illustration of an embodiment of the present invention where
a path is drilled through the hardened cement 41 along the guide path with a pilot mill 37, it may
be observed that a path about the size of theprimarywell-bore is drilled through the epoxy at the
preselected location 6 along guide 26 to re-establish well-bore 3. Apparatuses and drill strings
are common in the art to drill along a curved path. Fig. 6b illustrates an embodiment of the
present invention drilling along a straight guide 27 with pilot mill 37 attached to drill string 36
to establish a sealed well-bore and re-establishprimarybore 3.
The remainder of the written description will illustrate embodiments of the present
invention utilizing the arcuate drill path 44. However, embodiments of the present invention may
utilize a straight drill path without any arcuate shape.
Referring now to Fig. 7, an illustration of a completed drill path through a preselected
location, it may be observed that a continuous path 44 can be drilled along the guide 26 of Fig.
4 in well-bore 3. The drill path 44 of Fig. 8 will be sealed in the cement 41 material and will
have a higher degree of strength and resiliency than the common cement methods because the cement was allowed to fill the entire area of the under-reamed section rather than filling in the
interstices of the well-bore 3. This complete fill of the under-reamed area ensures that the
junction may be machined down-hole through the filled under-reamed area.
Referring now to Fig. 8, an illustration of an orienting sleeve and whipstock in the drill path, it may be observed that a sleeve 47 and whipstock 46 may be aligned within the drill path 44 within the preselected location 6. In a preferred embodiment of the method, an orientation sleeve 47 is lowered,. oriented and anchored in well-bore 3 and a whipstock 46 is then placed about the sleeve 47 such that an angle 50 may be created away from the drill path 44. Angle 50
may be any angle that an operator desires according to the well plan.
Referring now to Fig. 9, an illustration of an embodiment of the present invention
whereby a lateral well-bore is drilled, it may be observed that the new or lateral well-bore 61 may be drilled without requiring excessive space to make the transition from the primary well-bore 3 to the lateral well-bore 61 because of the arcuate fashion of the drill path 44. Drill string 56
may be lowered to whipstock 57 where it will be deflected into cement 41 to begin drilling a
lateral well-bore 61. In a preferred embodiment of the method, lateral well-bore 61 may be
drilled out of preselected location 6 into a desired formation or payzone to begin regular drilling operations.
Referring now to Fig.3c, an illustration of a top side view of the under-reaming required
under embodiments of the present invention, the illustration of a cross-sectional cut 9 of Fig.3a,
it may be better seen that the area of under-reaming may be reduced to about two to 2.5 times the
diameter of the well-bore with use of embodiments of the present invention, primary well-bore
14 is shown as it extends above and below the cemented area of reduced under-reamed area 24.
The newprimarybore 15 is established after drilling along the pre-bent guide and the lateral well
61 is shown. The running of the pre-bent guide, as depicted in Fig. 4, allows the primary well-
bore 14 to be off-centered within the reduced under-reamed area 24 when the new primary bore
15 is re-established by shifting the path of the primary well-bore 3. Essentially, the arcuate pre-
bent guide shifts the well-bore from the general center of the under-reamed area towards the side.
This off-centering allows the new primary well-bore 15, when re-established, to make full use
of the reduced under-reamed area 24. Therefore, after the deflection is run, as depicted in Fig.
8, the lateral well-bore 61 may be established within the reduced under-reamed area 24.
However, embodiments of the present invention still achieve the many benefits of the invention
without a reduced under-reamed area.
Other embodiments of the present invention utilize various other under-reamed widths
as depicted in Fig. 3d. It may be observed that under-reaming area 25 is about 3.0 times the
diameter of primary well-bore 3. Typically, a straight guide (not shown) will be used to establish
the primary bore-hole .3 along the path of the previously existing well-bore. In such a
configuration, lateral well-bore 19 requires an under-reamed width of about 3.0 times the
diameter of the primary well-bore 3.
As well, embodiments of the present invention allow the lateral well 61 to be drilled to
a diameter that is substantially equivalent to the diameter of the primary well-bore 3. As such,
the lateral well 61 is compatible with conventional drilling methods and equipment and does not
jeapordize future operations.
Embodiments of the present invention are designed to be used with prior art drilling
operations, the drilling operations not requiring any special modifications before implementation.
Embodiments of the present invention produce a lateral well-bore that is substantially the same
size as that of the primary well-bore or the existing bore from which the lateral bore was drilled.
For a further understanding of the integration of the present invention into common well
plans, reference should be had to Fig. 10, Fig. 11, Fig. 12, and Fig. 13. Fig. 10 is an illustration
of a drilled lateral well 61 with the drill string removed. From this point, regular drilling
operations may begin. It is common in the art for a liner 65 to be hung in a lateral well 61 after
completion as shown in Fig. 11. Further, it is common in the art to employ a bridge 66 at the
liner as depicted in Fig. 12. Finally, as depicted in Fig. 13, the whipstock 46 may be retrieved.
This results in two selectively accessible well-bores whereby the lateral well bore's diameter is
of comparable size to the primary well-bore.. In a preferred embodiment, the orienting sleeve
47 is a pass through sleeve such that a drill string may pass through the sleeve 47 and enter the
primary well-bore 3.
It is noted that the embodiment of the Improved Method for Drilling Multi-Lateral Wells
and Related Device described herein in detail is only for exemplary purposes and is of course
subject to many different variations in structure, design, application and methodology. Because
many varying and different embodiments may be made within the scope of the inventive
concept(s) herein taught, and because many modifications may be made in the embodiment
herein detailed in accordance with the descriptive requirements of the law, it is to be understood
that the details herein are to be interpreted as illustrative and not in a limiting sense.