PRESSURE PERFORATED WELL CASING SYSTEMS
Pressure perforated casing system has a plurality of grooves cut to an equal depth in an outer surface of a casing joint or a casing collar. Each groove has a bottom spaced from and internal surface of the casing joint or the casing collar. Sidewall bottom material in the groove ruptures at a predetermined fluid pressure below the burst pressure rating of the casing joint or casing collar.
This invention relates in general to hydrocarbon well casing systems and, in particular, to a novel well casing system that is pressure perforated after a casing string is assembled, inserted and cemented into a section of a recently drilled wellbore.
BACKGROUND OF THE INVENTIONWell casing is made up of casing joints and casing collars for connecting the casing joints together to assemble a casing string. Well casing is well known in the art and used to line recently drilled hydrocarbon wellbores to prevent borehole collapse and provide a smooth conduit for inserting tools required to complete the well for production and to produce hydrocarbon from the well. Most hydrocarbon wells drilled today are vertical bores extending down to proximity of a production zone and horizontal bores within the production zone. There are two ways commonly used to complete a horizontal bore, plug-and-perf (PNP) and openhole multistage (OHMS).
The openhole multistage system has external casing packers that provide a seal between a production casing and the horizontal bore. The production casing has dropped-ball actuated sliding sleeves. The sliding sleeves open ports through the production casing. The sliding sleeves are opened in succession from the toe to the heel of the horizontal bore. The dropped balls are graduated in size to pass through each sliding sleeve until they reach the sliding sleeve to be opened next. When a ball is caught by a sliding sleeve the fracture fluid pressure opens the sliding sleeve exposing the ports, and the ball provides a seal to prevent frac fluid from going downhole past the opened sliding sleeve. The permits OHMS systems to perform multiple fracture stimulations without the need to rig up wireline or set plugs to perforate new intervals. Casing perforation is unnecessary because communication between the cased borehole and the productive formation is afforded by each set of ports opened by the balls dropped to open the respective sliding sleeves. When the entire horizontal bore has been fractured the balls are captured at the surface during flow back of the fracturing fluid.
With plug-and-perf, after assembly and insertion of the casing in the open borehole, the casing is “cemented in” by circulating a cement slurry through the inside of the casing and out into the annulus through a casing shoe at the bottom of the casing string. The cement fills the annulus around the casing and hardens to prevent the migration of fluids between zones in the wellbore. Once cemented in, the casing is perforated in sections from toe to heel using a perforating gun system that is run into the well with wireline or completion tubing. The perforating guns are triggered from the surface to fire steel projectiles that penetrate the casing to let the hydrocarbon flow into the casing. After a section of casing has been perforated, the spent perforating guns are withdrawn and fracturing fluid is pumped down the casing to fracture the formation behind the perforations. When fracturing of that section is completed, a fiber plug is run into the well with the next perforating gun system. The fiber plug is set in the casing up hole from the fractured section, before the perforating guns are fired to perforate a new section of the casing. This process is repeated until the entire horizontal bore has been plugged, perforated and fractured. Thereafter, the fiber plugs are milled out to put the horizontal bore into production.
OHMS and PNP each have their advantages and disadvantages. OHMS is more expensive to install, but fracturing proceeds more quickly because the sliding sleeves are opened in succession and fracturing can be performed with virtually no interruptions. However, OHMS is much less flexible in that once installed it cannot be reconfigured or changed. OHMS also has shorter reach because the reach is restricted by the number of sliding sleeves that can be opened using a series of different sized balls that are pumped into the well. OHMS also severely restricts fracture fluid flow rates at the toe of the lateral well bore because of the ball seat size through which fracturing fluid must be pumped. OHMS bores are likewise more difficult to re-complete, and the service life of the sliding sleeves is known to be limited. A further hazard is that sliding sleeves are sometimes skipped because a wrong sized ball is dropped, a ball shatters before it can seat in the sliding sleeve, or one or more of the openhole packers provide an incomplete seal.
PNP offers complete flexibility because casing perforations can be located at any desired interval and the location can be dynamically determined as the production zone is being fractured. PNP also offers unlimited reach because newly available completion tubing can be pushed to the furthest extent that a horizontal bore can be drilled and cased. PNP is also secure because the casing is cemented in, so fracture fluid has no place to migrate except into the formation. PNP can also provide much more drainage area than OHMS, which can be advantageous. The disadvantage of PNP is the time required to run the perforating gun strings and to set the plugs in the cased well bore. While each run is being performed the fracturing crews sit idle. This adds significantly to expense.
A disadvantage of both systems is the fracturing pump horsepower required to complete the well. The interval fractured in OHMS systems is necessarily long even though the fracture fluid ports are concentrated in a very small area opened by the sliding sleeve, and the interval fractured in PNP is preferably long in order to minimize idle time. Consequently, both OHMS and PNP require a large number of high powered pump trucks, about 25,000 total horsepower, each with attendant crew. Those trucks must be scheduled, congregated and maintained onsite throughout the well completion. This requires long term planning, complex scheduling and significant expense.
Perforated casing is also known and is used for openhole completions in certain heavy oil reservoirs. However, perforated casing does not permit cementing or well stimulation and its use is therefore limited.
There therefore exists a need for a novel well casing system that is pressure perforated after it is assembled, inserted and cemented into a section of a recently drilled wellbore.
SUMMARY OF THE INVENTIONIt is therefore an object of the invention to overcome the disadvantages of prior art hydrocarbon well casing systems and provide a novel well casing system that is pressure perforated after it is assembled, inserted and cemented into a section of a recently drilled wellbore.
The invention therefore provides a pressure perforated well casing joint, comprising: a pipe having a sidewall with a first end, a second end, an inner surface, an outer surface and a burst pressure rating; an external tread on each of the first and second ends adapted to threadedly engage a casing collar, and a plurality of grooves cut in the outer surface, each groove extending inwardly from the outer surface to an extent less than a thickness of the sidewall, so there remains sidewall bottom material in each groove; whereby fluid pressure applied within the pressure perforated well casing will cause the sidewall bottom material in the grooves to rupture before the burst pressure rating of the pipe is reached, thereby opening a slot through the sidewall at each of the plurality of grooves subjected to the fluid pressure.
The invention further provides a pressure perforated well casing collar, comprising: a pipe having a sidewall with a first end, a second end, an inner surface, an outer surface and a burst pressure rating; an internal tread on each of the first and second ends adapted to threadedly engage an external thread on a casing joint; a plurality of grooves cut in the outer surface, each groove extending inwardly from the outer surface to an extent less than a thickness of the sidewall, so there remains sidewall bottom material in each groove; whereby fluid pressure applied within the pressure perforated well casing collar will cause the sidewall bottom material in the grooves to rupture before the burst pressure rating of the casing collar is reached, thereby opening a slot through the sidewall at each of the plurality of grooves.
The invention yet further provides a pressure perforated well casing system, comprising: a well casing joint and a well casing collar respectively having a plurality of grooves cut in an outer surface thereof, the grooves being cut to an equal depth in the outer surface, each groove having sidewall bottom material remaining in a bottom of the groove; whereby sufficient fluid pressure applied to the grooves cause the sidewall bottom material in the respective grooves to rupture before a burst pressure rating of the well casing joint or the well casing collar is reached, thereby opening slots through the sidewalls at each of the respective grooves under sufficient fluid pressure.
Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, in which:
The invention provides a pressure perforated well bore casing system that permits hydrocarbon wells to be completed and fractured with greater efficiency and at less expense than prior art casing and completion systems. The casing system in accordance with the invention eliminates the need for sliding sleeves, openhole packers, wirelines, perforating gun systems, plugs and plug mills. In one embodiment the casing system in accordance with the invention also reduces the pump horsepower requirement for completing a well by up to 60%, thus significantly reducing completion cost and simplifying job scheduling. The well casing system in accordance with invention also significantly reduces fracturing crew idle time while providing fracture location flexibility. The well casing system in accordance with invention may be used in vertical or horizontal well bores and is equally effective and efficient in either a vertical or a horizontal well bore.
In one embodiment, each groove 20 is about 0.375″-0.5″ (1-1.27 cm) wide and 1″-3″ (2.5-7.6 cm) long. As will be explained below with reference to
In one embodiment the number of grooves and the size of each of the grooves in each cluster 1-n opens slots through the sidewall 72 having a predetermined total area when the grooves in that cluster are ruptured using frac fluid pressure, that predetermined total area being an area through which fracturing fluid can be pumped at a constant rate by about 10,000 horsepower of pump capacity. This reduces the pump horsepower requirement for completing a well bore by about 60%, thus significantly reducing completion cost and simplifying job scheduling.
The casing collar 82 provides further flexibility to a well operator, who can assemble casing strings with plain casing joints and the pressure perforated casing collars 82, pressure perforated casing joints 10, 30, 50, 70 and plain casing collars, or pressure perforated casing joints 10, 30, 50, 70 and pressure perforated casing collars 82, in any combination, as will be described below in more detail with reference to
The thickness “B” may be calculated, for example, using a formula (Formula 1) described on page 16 and 17 of American Petroleum Institute Bulletin 5C3, Fifth Edition, July, 1989, incorporated herein by reference. The formula is:
Py=0.7854(Dz−dz)Yp (Formula 1)
where:
-
- Py=pipe body yield strength in pounds rounded to nearest 1000;
- Yp=Specified minimum yield strength for pipe, psi;
- D=specified outside diameter, inches;
- d=specified inside diameter, inches.
Table 1 shows examples of commonly used sizes and grades of well casing, and the sidewall bottom material thickness (SBT) for each to achieve a perforation rupture pressure of 4,000 psi (27,579 KPa) and 7,000 psi (48,263 KPa).
The explicit embodiments of the invention described above have been presented by way of example only. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.
Claims
1. (canceled)
2. The pressure perforated well casing joint as claimed in claim 4, wherein the grooves are arranged in at least one cluster, a total area of the at least one cluster being less than a total area of the outer surface between the external threads on the first and second ends of the pipe.
3. (canceled)
4. A pressure perforated well casing joint, comprising:
- a pipe having a sidewall with a first end, a second end, an inner surface, an outer surface and a burst pressure rating;
- an external thread on each of the first and second ends adapted to threadedly engage a casing collar; and
- a plurality of spaced apart grooves cut in the outer surface, each groove extending inwardly from the outer surface to an extent less than a thickness of the sidewall, so there remains sidewall bottom material in each groove and the grooves are cuts having ends that overlap;
- whereby fluid pressure applied within the pressure perforated well casing will cause the sidewall bottom material in the grooves to rupture before the burst pressure rating of the pipe is reached, thereby opening a slot through the sidewall at each of the plurality of grooves subjected to the fluid pressure.
5. The pressure perforated well casing joint as claimed in claim 4, wherein the grooves surround a narrow column of sidewall material designed to facilitate cement penetration when the sidewall bottom material in the grooves rupture.
6. The pressure perforated well casing joint as claimed in claim 4, wherein the grooves are filled with a coating material to protect machined surfaces while the casing joint is in storage and while the casing joint is being run into a recently drilled well bore.
7. The pressure perforated well casing joint as claimed in claim 4, wherein the grooves are grouped in at least two spaced apart clusters between the external thread on the respective first and second ends.
8. The pressure perforated well casing joint as claimed in claim 4, wherein the grooves are grouped in three equally spaced apart clusters between the external thread on the respective first and second ends.
9. The pressure perforated well casing joint as claimed in claim 4, further comprising a groove cut on the inside surface of each of the respective first and second ends to positively identify the perforated well casing joint in a well casing string comprising perforated well casing joints and plain casing joints connected together.
10. A pressure perforated well casing collar, comprising:
- a pipe having a sidewall with a first end, a second end, an inner surface, an outer surface and a burst pressure rating;
- an internal thread on each of the first and second ends adapted to threadedly engage an external thread on a casing joint;
- a plurality of spaced apart grooves respectively having overlapping ends cut in the outer surface, each groove extending inwardly from the outer surface to an extent less than a thickness of the sidewall, so there remains sidewall bottom material in each groove;
- whereby fluid pressure applied within the pressure perforated well casing collar will cause the sidewall bottom material in the grooves to rupture before the burst pressure rating of the casing collar is reached, thereby opening a slot through the sidewall at each of the plurality of grooves.
11. The pressure perforated well casing collar as claimed in claim 10, wherein the plurality of grooves are filled with a coating material to protect machined surfaces while the casing collar is in storage and while a casing string including the casing collar is being run into a recently drilled well bore.
12. (canceled)
13. The pressure perforated well casing system as claimed in claim 16 further comprising an interval on an outer surface of the well casing joint or the well casing collar without grooves.
14. The pressure perforated well casing system as claimed in claim 16 wherein the well casing joint comprises at least two clusters of grooves, each cluster of grooves being separated from the ends of the well casing joint and any other cluster of grooves by an outer surface of the well casing joint without grooves.
15. (canceled)
16. A pressure perforated well casing system, comprising:
- a well casing joint and a well casing collar respectively having a plurality of spaced apart if grooves cut in an outer surface thereof, the grooves being cut to an equal depth in the outer surface, each groove having sidewall bottom material remaining in a bottom of the groove the respective grooves having ends that overlap;
- whereby sufficient fluid pressure applied to the grooves cause the sidewall bottom material in the respective grooves to rupture before a burst pressure rating of the well casing joint or the well casing collar is reached, thereby opening slots through the sidewalls at each of the respective grooves under sufficient fluid pressure.
17. The pressure perforated well casing system as claimed in claim 16 wherein the grooves respectively surround a sidewall material designed to facilitate cement penetration when the sidewall bottom material in the grooves rupture.
18. The pressure perforated well casing system as claimed in claim 16, wherein the grooves are filled with a coating material to protect machined surfaces while the casing joint or the casing collar is in storage and while the casing joint or the casing collar is in a casing string being run into a recently drilled well bore.
19. A well casing string comprising the pressure perforated well casing joints claimed in claim 16.
20. A well casing string comprising the pressure perforated well casing collars claimed in claim 16.
Type: Application
Filed: Mar 27, 2017
Publication Date: Sep 27, 2018
Inventor: Lloyd Murray Dallas (Streetman, TX)
Application Number: 15/469,821