METHODS AND SYSTEMS FOR PERFORMANCE OF SUBTERRANEAN OPERATIONS
USING DUAL STRING PIPES
Background
Hydrocarbons, such as oil and gas, are commonly obtained from subterranean
formations. The development of subterranean operations and the processes involved in removing
hydrocarbons from a subterranean formation are complex. Typically, subterranean operations
involve a number of different steps such as, for example, drilling the wellbore at a desired well
site, treating the wellbore to optimize production of hydrocarbons, and performing the necessary
steps to produce and process the hydrocarbons from the subterranean formation.
In order to understand the formation testing process, it is important to understand
how hydrocarbons are stored in subterranean formations. Typically, hydrocarbons are stored in
small holes, or pores, within the subterranean formation. The ability of a formation to allow
hydrocarbons to flow between pores and consequently, into a wellbore, is referred to as
permeability. Additionally, hydrocarbons contained within a formation are typically stored under
pressure. It is therefore beneficial to determine the magnitude of that pressure in order to safely
and efficiently produce from the well.
Drilling operations play an important role when developing oil, gas or water wells
or when mining for minerals and the like. A drilling fluid ("mud") is typically injected into a
wellbore when performing drilling operations. The mud may be water, a water-based mud or an
oil-based mud. During the drilling operations, a drill bit passes through various layers of earth
strata as it descends to a desired depth. Drilling fluids are commonly employed during the
drilling operations and perform several important functions including, but not limited to,
removing the cuttings from the well to the surface, controlling formation pressures, sealing
permeable formations, minimizing formation damage, and cooling and lubricating the drill bit.
One of the methods used during drilling operations is the Reelwell Drilling
Method ("RDM") developed by Reelwell of Stavanger, Norway. In accordance with RDM, as
shown in Figure 1, a dual string drill pipe 102 comprising an inner pipe 104 and an outer pipe
106 is inserted into a wellbore 108 that passes through a formation of interest 110. The drilling
fluid may be directed downhole through the annular channel 112 of the drill string and exits the
dual string drill pipe 102 through a Bottom Hole Assembly ("BHA") 14. Return ports 116 are
provided above the standard BHA 114. The BHA 114 may include a number of components
such as, for example, the drill bit, the bit sub, a mud motor, stabilizers, drill collar, heavy weight
drillpipe, jarring devices and/or cross overs for various threadforms. The returning drilling fluid
(which contains the cuttings) is directed into the return ports 116 and flows through the inner
pipe 104 back to the surface. The return ports 116 of the RDM may be used to clean the wellbore
when performing drilling operations by facilitating removal of drill cuttings through the inner
pipe 104. Additionally, a piston 118 may be coupled to the outer pipe 106 to provide weight on
the drill bit. The piston 118 may push the dual string drill pipe 102 forward by putting hydraulic
pressure on the drill bit in the BHA 114. Additionally, the piston 118 may act as a barrier
preventing the loss of annular well fluids.
However, the typical RDM methods has a number of drawbacks. First, only a
portion of the dual string drill pipe 102 may be utilized for directing the drilling fluid downhole.
Specifically, the drilling fluid may be directed downhole through the annular channel 112
between the inner pipe 104 and the outer pipe 106 because the inner pipe is utilized for returning
the drilling fluid to the surface. This limits the rate at which drilling fluid can be delivered to the
drilling location. The limitation on the rate of delivery of drilling fluids may adversely impact
the drilling operations. Moreover, hydraulic motors relying on hydraulic pressure are often used
when performing drilling operations. Therefore, the limited rate of delivery of drilling fluids
results in less hydraulic pressure being available downhole for a hydraulic motor. Moreover, the
piston 118 that places weight on the drill bit 1 4 is fixed so when the section of liner or casing it
is in is reached, the drilling has to stop and the piston pulled to reposition it. Further, typically,
the piston 1 8 can not be easily removed or collapsed to facilitate extra flow area for cementing
operations. Finally, in order to perform drilling operations using the RDM, sections of the inner
pipe 104 and the outer pipe 106 need to be laid out on the surface and cut in predetermined
lengths to form matching pairs of inner and outer pipes that can form segments of the drillstring.
This process adds to the cost of performing the drilling operations and consumes valuable time.
Moreover, cementing operations are another part of performing subterranean
operations. For instance, it may be desirable to isolate section of the wellbore by forming one or
more cement plugs therebetween. During typical cementing operations, a cement mix is prepared
at the surface and pumped downhole to a desired location. When preparing the cement mix, it is
important to carry out accurate calculations to determine the setting time and pump the mix
downhole accordingly so that the cement mix cures at the perfect time at the particular location
of interest. Specifically, if the cement mix cures too early or too late it may not form the cement
plug at its intended location.
Brief Description of the Drawings
Figure 1 is a dual string drill pipe mechanism in accordance with the prior art.
Figure 2 is an improved dual string pipe mechanism in accordance with an
embodiment of the present disclosure.
Figure 3A is a closeup view of the diverter sub of the improved dual string pipe
mechanism configured to be in the closed position.
Figure 3B is a closeup view of the diverter sub of the improved dual string pipe
mechanism configured to be in the open position.
Figure 4 is a closeup view of the packer of the improved dual string pipe mechanism
in accordance with an embodiment of the present disclosure.
Figure 5 depicts an improved dual string pipe segment in accordance with an
embodiment of the present disclosure.
While embodiments of this disclosure have been depicted and described and are
defined by reference to exemplary embodiments of the disclosure, such references do not imply a
limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed
is capable of considerable modification, alteration, and equivalents in form and function, as will
occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted
and described embodiments of this disclosure are examples only, and are not exhaustive of the
scope of the disclosure.
Detailed Description
For purposes of this disclosure, an information handling system may include any
instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit,
receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or
utilize any form of information, intelligence, or data for business, scientific, control, or other
purposes. For example, an information handling system may be a personal computer, a network
storage device, or any other suitable device and may vary in size, shape, performance,
functionality, and price. The information handling system may include random access
memory (RAM), one or more processing resources such as a central processing unit (CPU) or
hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional
components of the information handling system may include one or more disk drives, one or
more network ports for communication with external devices as well as various input and
output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling
system may also include one or more buses operable to transmit communications between the
various hardware components.
For the purposes of this disclosure, computer-readable media may include any
instrumentality or aggregation of instrumentalities that may retain data and/or instructions for a
period of time. Computer-readable media may include, for example, without limitation, storage
media such as a direct access storage device (e.g., a hard disk drive or floppy disk drive), a
sequential access storage device (e.g., a tape disk drive), compact disk, CD-ROM, DVD, RAM,
ROM, electrically erasable programmable read-only memory (EEPROM), and/or flash memory;
as well as communications media such wires, optical fibers, microwaves, radio waves, and other
electromagnetic and/or optical carriers; and/or any combination of the foregoing.
The terms "couple" or "couples" as used herein are intended to mean either an
indirect or direct connection. Thus, if a first device couples to a second device, that connection
may be through a direct connection, or through an indirect mechanical or electrical connection
via other devices and connections. Similarly, the term "communicatively coupled" as used herein
is intended to mean either a direct or an indirect communication connection. Such connection
may be a wired or wireless connection such as, for example, Ethernet or LAN. Such wired and
wireless connections are well known to those of ordinary skill in the art and will therefore not be
discussed in detail herein. Thus, if a first device communicatively couples to a second device,
that connection may be through a direct connection, or through an indirect communication
connection via other devices and connections. Finally, the term "fluidically coupled" as used
herein is intended to mean that there is either a direct or an indirect fluid flow path between two
components.
The term "uphole" as used herein means along the drillstring or the wellbore hole
from the distal end towards the surface, and "downhole" as used herein means along the
drillstring or the wellbore hole from the surface towards the distal end.
Illustrative embodiments of the present invention are described in detail herein. In
the interest of clarity, not all features of an actual implementation may be described in this
specification. It will of course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions may be made to achieve the specific
implementation goals, which may vary from one implementation to another. Moreover, it will be
appreciated that such a development effort might be complex and time-consuming, but would
nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of
the present disclosure.
To facilitate a better understanding of the present invention, the following examples
of certain embodiments are given. In no way should the following examples be read to limit, or
define, the scope of the invention. Embodiments of the present disclosure may be applicable to
horizontal, vertical, deviated, or otherwise nonlinear wellbores in any type of subterranean
formation. Embodiments may be applicable to injection wells as well as production wells,
including hydrocarbon wells. Embodiments may be implemented using a tool that is made
suitable for testing, retrieval and sampling along sections of the formation. Embodiments may be
implemented with tools that, for example, may be conveyed through a flow passage in tubular
string or using a wireline, slickline, coiled tubing, downhole robot or the like. "Measurementwhile-
drilling" ("MWD") is the term generally used for measuring conditions downhole
concerning the movement and location of the drilling assembly while the drilling continues.
"Logging-while-drilling" ("LWD") is the term generally used for similar techniques that
concentrate more on formation parameter measurement. Devices and methods in accordance
with certain embodiments may be used in one or more of wireline, MWD and LWD operations.
The present application is directed to improving efficiency of subterranean
operations and more specifically, to a method and system for improving delivery and retrieval of
fluids to and from a downhole location.
Turning now to Figure 2, an improved dual string drilling system in accordance
with an embodiment of the present disclosure is denoted generally with reference numeral 200.
The improved dual string drilling system 200 includes an inner pipe 204 and an outer pipe 206.
A diverter sub 208 may be coupled to the dual string pipe 202. The fluid flowing through the
diverter sub 208 is directed to the BHA 210 and the return fluid is returned to return ports 212 of
the diverter sub 208. The diverter sub 208 permits selectively directing fluids downhole or
returning fluids uphole using the inner pipe 204. The operation of the diverter sub 208 will now
be discussed in more detail in conjunction with Figures 3A and 3B.
Figure 3A depicts an exemplary configuration of the diverter sub 208 in a closed
position. In the closed position, the diverter sub 208 facilitates delivery of drilling fluids to the
BHA 210 through both an annulus 205 between the inner pipe 204 and the outer pipe 206 and
the inner pipe 204 itself. As shown in Figure 3A, the diverter sub comprises a pair of return port
valves 302 that are operable to open and close the return ports 212. Additionally, the diverter sub
may comprise an inner pipe valve 304 that is configured to open and close an outlet at the end of
the inner pipe 204 proximate to the BHA 210. As shown in Figure 3, with the diverter sub 208 in
the closed position as shown in Figure 3A, the return ports 212 are closed, preventing return
fluids from flowing into the inner pipe 204. In contrast, when the diverter sub 208 is in the
closed position, the inner pipe valve 304 is positioned to permit delivery of fluids flowing
downhole through the inner pipe 204 to the BHA 210.
Figure 3B depicts the diverter sub 208 in an open position. In the open position,
the return port valves 302 are opened permitting fluid flow through the return ports 212 into the
inner pipe 204. At the same time, the inner pipe valve 304 closes off the bottom of the inner pipe
204, preventing fluid flow from the inner pipe 204 to the BHA 210. As would be appreciated by
those of ordinary skill in the art, with the benefit of this disclosure, the valves 302, 304 may be
any suitable valves, including, but not limited to, a flapper valve, plug (piston) valve, gate valve,
pinch valve, diaphragm valve, rotary valve such as a ball valve or butterfly valve. In certain
preferred embodiments, a piston or plug valve may be the best suited valve to seal with the given
geometries. Moreover, the valves 302, 304 may be communicatively coupled to an information
handling system (not shown) and may be controlled from the surface to selectively place the
diverter sub 208 in the open or the closed position. Specifically, computer-readable instructions
may be stored in a computer readable medium and be used by the information handling system
to control the diverter sub 208.
Returning now to Figure 2, the improved dual string drilling system 200 may be
utilized in two different modes of operation. In the first mode, referred to as the normal drilling
mode, the diverter sub 208 is in the closed position and a fluid may be directed downhole
through the inner pipe 204 from the surface to a desired location downhole along the wellbore
axis. Both the inner pipe 204 and the annulus 205 between the inner pipe 204 and the outer pipe
206 are utilized to provide a path for fluid flow from the surface to the BHA 210. In the second
mode, referred to as the high flow mode, the diverter sub 208 is in the open position.
Accordingly, the downward flow of the drilling fluid continues through the annulus 205 between
the inner pipe 204 and the outer pipe 206 to the BHA 210. With the diverter sub 208 in the open
position, the return ports 212 are fluidically coupled to the inner pipe 204. Accordingly, the
return fluid together with cuttings and other materials removed from the downhole location may
be directed to the return ports 212 and returned to surface through the inner pipe 204. In certain
embodiments, the diverter sub 208 may be cycled multiple times between its open and closed
positions when performing a subterranean operation to provide the high flow mode on demand.
As would be appreciated by those of ordinary skill in the art, with the benefit of this disclosure,
the high flow mode may be used in a clean out mode to perform clean out operations or in a
cementing mode to perform cementing operations.
In certain embodiments, the improved dual string drilling system 200 may include
one or more packers 214 positioned at different axial positions along the its length. In one
embodiment, the packers 214 may be inflatable packers. The packers 214 may bridge the
annulus 222 between a casing 216 (or the wellbore if the well is not cased) and the outer pipe
206. As shown in Figure 2, the outer pipe 204 may be positioned within the casing 216. In one
embodiment, the packers 214 may include a seal element 218 that does not rotate with the casing
216 but allows the dual string pipe 202 to rotate freely. The activation/deactivation of the
packers 214 may be powered and controlled by electrical commands from the surface which may
be directed downhole using a wired or wireless communication network. In certain
embodiments, an information handling system may be communicatively coupled to the packers
214 and control operations thereof.
The packers 214 may serve a number of functions. For instance, the packers may
be used to close the annulus 222 between the casing 216 (or the wellbore wall if not cased) and
the outer pipe 206 to prevent return of fluids to the surface. Moreover, in certain embodiments,
hydraulic pressure may be applied to an upper side of the packers 214 in order to exert a
downward pressure on the BHA 210 and the drill bit. Additionally, in certain embodiments, the
packers 214 may be utilized to inject fluids into the fluid flow stream provided by the dual string
drilling system 200.
Figure 4 depicts a cross sectional view of a packer 214 in accordance with one
exemplary embodiment of the present disclosure. In one embodiment, the packer 214 may be a
subassembly that is inserted between two sections of the dual string pipe 202. Accordingly, the
packer 214 may include a packer inner pipe 224 and a packer outer pipe 226 that are fluidically
coupled to the inner pipe 204 and the outer pipe 206, respectively. The packer 214 may further
include an inner pipe valve 220A and an outer pipe valve 220B that as discussed in more detail
below, are operable to fluidically couple the annulus 222 with the inner pipe 204 or the annulus
205. As would be appreciated by those of ordinary skill in the art, with the benefit of this
disclosure, the present invention is not limited to the specific arrangement of valves depicted in
Figure 4. For instance, more valves may be used to achieve different specific fluid flow
mechanisms without departing from the scope of the present disclosure.
The inner pipe valve 220A may control fluid flow from the annulus 222 between
the outer pipe 206 and the casing 216 (or the wellbore if not cased) into the packer 214 and into
the inner pipe 204. In contrast, the outer pipe valve 220B may control fluid flow from the
annulus 222 into the packer 214 and into the annulus 205 between the inner pipe 204 and the
outer pipe 206. As would be appreciated by those of ordinary skill in the art, with the benefit of
this disclosure, any suitable valves may be utilized in much the same way as the diverter valve,
such as, for example a flapper valve, plug (piston) valve, gate valve, pinch valve, diaphragm
valve, rotary valve such as a ball valve or butterfly valve. In certain preferred embodiments, a
piston or plug valve is optimal as it can be easily sealed with the given geometries.
In the normal drilling mode or the high flow mode, the valves 220A and 220B
may be closed and no fluid flows from the annulus 222 into either the inner pipe 204 or the
annulus 205 between the inner pipe 204 and the outer pipe 206. Accordingly, because the packer
inner pipe 224 and the packer outer pipe 226 are in fluid communication with the inner pipe 204
and the outer pipe 206, fluid flow through the dual string pipe 202 continues in the same manner
discussed above in conjunction with Figures 1-3. However, the valves 220A, 220B may be
selectively opened and closed to inject fluids into the fluid stream flowing through the inner pipe
204 and/or the annulus 205.
In certain embodiments, it may be desirable to inject a fluid into the downhole
fluid flow through the annulus 205 when in the normal drilling mode or in the high flow mode.
The outer pipe valve 220B may be opened and a fluid that is to be injected into the stream
flowing downhole through the annulus 205 may be directed to the annulus 205 through the
annulus 222 and the packer 214. Accordingly, fluids may be injected into the downward flow in
the annulus 205 from the surface at a controlled rate. Similarly, it may be desirable to inject a
fluid into the inner pipe 204 when in the normal drilling mode with the fluid flowing downhole
from the surface. Accordingly, the inner pipe valve 220A may be opened and the fluid may be
directed into the inner pipe 204 through the annulus 222 and the packer 214.
Moreover, in certain embodiments it may be desirable to inject a fluid into the
return fluid flow through the inner pipe 204 in the high flow mode. For instance, it may be
desirable to inject air, Nitrogen, or other appropriate fluids into the upward fluid flow through
the inner pipe 204 during the high flow mode in order to increase the annular velocity of the
return fluid and improve the hole cleaning operations. Accordingly, air, Nitrogen, or other
appropriate fluids may be directed to the fluid stream in the inner pipe through the annulus 222
and the packer 214 by opening the inner pipe valve 220A.
Returning now to Figure 2, the improved dual string pipe 202 of the present
disclosure may be used to perform cementing operations by providing a quick setting isolation
system. In accordance with an embodiment of the present disclosure a two part cement mix may
be prepared at the surface whereby the cement cures once the two parts come in contact with one
another. In one embodiment, the two part cement mix may comprise an epoxy component and a
hardner component. An improved dual string pipe 202 may be positioned in the wellbore with
the outlet of the dual string pipe 202 located proximate to a location where the cement plug is to
be formed. A first part of the two part cement mix may be directed downhole through the inner
pipe 204 and a second part may be directed downhole through the annulus 205 between the inner
pipe 204 and the outer pipe 206. Once the first part and the second part of the two part cement
mix exit the outlet of the dual string pipe 202 at the desired location and come in contact they
will create a cement plug. Accordingly, using the dual string pipe 202 to perform cementing
operations may obviate the need for utilizing resources to calculate the cement setting time in
detail and implement the pumping operations in a manner to ensure the cement mixture is
positioned at the right position downhole at its setting time.
In certain embodiments, as discussed above, the dual string pipe 202 may
comprise two or more segments of pipes with one or more subassemblies or components placed
therebetween. As shown in Figure 5, in accordance with an embodiment of the present
disclosure, the inner pipe 204 and the outer pipe 206 of the dual pipe string 202 may each
comprise a corrugated section 504 and 506, respectively. The corrugated sections 504, 506
permit the inner pipe 204 and the outer pipe 206 to be extended and/or retracted to a desired
length. Accordingly, because the inner pipe 204 and the outer pipe 206 now have a variable
length, there is no need to cut sections of inner pipe 204 to match the length of sections of the
outer pipe 206 when assembling the different drill pipe segments. The uses of inner pipe 204 and
outer pipe 206 with corrugated sections that need not be cut helps maintain the integrity of top
and bottom connections of the different drill pipe segments.
The present invention is therefore well-adapted to carry out the objects and attain
the ends mentioned, as well as those that are inherent therein. While the invention has been
depicted, described and is defined by references to examples of the invention, such a reference
does not imply a limitation on the invention, and no such limitation is to be inferred. The
invention is capable of considerable modification, alteration and equivalents in form and
function, as will occur to those ordinarily skilled in the art having the benefit of this disclosure.
The depicted and described examples are not exhaustive of the invention. Consequently, the
invention is intended to be limited only by the spirit and scope of the appended claims, giving
full cognizance to equivalents in all respects.

CLAIMS
What is claimed is:
1. A dual string pipe comprising:
an outer pipe;
an inner pipe positioned within the outer pipe;
a bottom hole assembly fluidically coupled to the outer pipe and the inner pipe;
a diverter sub coupled to the inner pipe,
wherein the diverter sub is selectively operable in a normal drilling mode
and a high flow mode,
wherein in the normal drilling mode a fluid is directed downhole through
the inner pipe, and
wherein in the high flow mode a return fluid is directed uphole through the
inner pipe.
2. The dual string pipe of claim 1, wherein the diverter sub comprises a return port, wherein
in the high flow mode the return fluid flows into the inner pipe through the return port.
3. The dual string pipe of claim 2, wherein the diverter sub comprises a return port valve,
wherein the return port valve selectively opens and closes the return port.
4. The dual string pipe of claim 3, wherein the diverter sub comprises an inner pipe valve,
wherein the inner pipe valve selectively opens and closes an outlet of the inner pipe.
5. The dual string pipe of claim 4, wherein in the normal drilling mode the return port valve
closes the return port and the inner pipe valve opens the outlet of the inner pipe.
6. The dual string pipe of claim 4, wherein in the high flow mode the return port valve
opens the return port and the inner pipe valve closes the outlet of the inner pipe.
7. The dual string pipe of claim 1, further comprising a packer coupled to at least one of the
inner pipe and the outer pipe.
8. The dual string pipe of claim 1, further comprising:
a casing, wherein the outer pipe is positioned within the casing;
a first annulus, wherein the first annulus is formed between the inner pipe and the
outer pipe;
a second annulus, wherein the second annulus is formed between the outer pipe
and the casing; and
a packer coupled to the outer pipe, wherein the packer extends into the second
annulus.
9. The dual string pipe of claim 8, wherein the packer comprises one or more valves,
wherein the one or more valves are operable to fluidically couple the second annulus with at
least one of the first annulus and the inner pipe.
10. The dual string pipe of claim 1, wherein at least one of the inner pipe and the outer pipe
is corrugated.
11. The dual string pipe of claim 1, wherein the high flow mode is selected from a group
consisting of a clean out mode and a cementing mode.
12. A method of selectively directing fluids between a surface location and a downhole
location comprising:
placing a dual string pipe in a wellbore,
wherein the dual string pipe comprises an inner pipe located within an
outer pipe;
coupling a diverter sub to the dual string pipe,
wherein the diverter sub comprises one or more valves; and
selectively controlling the diverter sub to at least one of direct a first fluid from
the surface location to the downhole location through the inner pipe and
direct a second fluid from the downhole location to the surface location
through the inner pipe.
13. The method of claim 12, wherein the diverter sub comprises a return port, wherein in
high flow mode the return fluid flows into the inner pipe through the return port.
14. The method of claim 12, wherein the diverter sub comprises a return port valve, wherein
the return port valve selectively opens and closes the return port.
15. The method of claim 12, wherein the diverter sub comprises an inner pipe valve, wherein
the inner pipe valve selectively opens and closes an outlet of the inner pipe.
16. The method of claim 12, wherein in the normal drilling mode the return port valve closes
the return port and the inner pipe valve opens the outlet of the inner pipe.
17. The method of claim 12, wherein in the high flow mode the return port valve opens the
return port and the inner pipe valve closes the outlet of the inner pipe.
18. The dual string pipe of claim 1, further comprising:
positioning an outer pipe within the casing;
wherein a first annulus is formed between the inner pipe and the outer
pipe;
wherein a second annulus is formed between the outer pipe and the casing;
and
wherein a packer is coupled to the outer pipe and the packer extends into
the second annulus.
19. The method of claim 18, wherein the packer comprises one or more valves, wherein the
one or more valves are operable to fluidically couple the second annulus with at least one of
the first annulus and the inner pipe.
20. The method of claim 12, wherein at least one of the inner pipe and the outer pipe is
corrugated.