Patent Application
20120037373
In downhole industries, including hydrocarbon exploration and recovery, Carbon Dioxide Sequestration, etc., there is often an understanding that fracturing the earth formation in which a borehole is located will serve to enhance the operation being conducted.
In recent years many systems and apparatuses have been devised for fracturing the formation most of which utilize a pump at surface and any of a number of means to direct the pressure generated by the pump to the target area of interest.
While such methods are ubiquitously used they do require significant equipment resources especially with respect to pump horsepower to generate sufficient pressure to effect fracture. Alternative systems and methods of effecting fracturing will be welcomed by the art.
A system for fracturing a subterranean formation including a housing having one or more radially directed ports therein; a valve disposed within the housing proximate the one or more ports; and a seat member interactive with the valve to rapidly prevent or substantially retard fluid flow therethrough.
A method for initiating a fracture in a subterranean formation including flowing a fluid at a given pressure through a system having a capability of rapidly and substantially retarding fluidic momentum in the fluid adjacent one or more radially oriented ports; rapidly and substantially retarding fluidic momentum in the flowing fluid; and initiating the fracture with a pressure spike resulting from the rapid and substantial retardation in fluidic momentum of the flowing fluid.
A system for fracturing a subterranean formation including a housing having one of more radially directed ports therein; and a configuration within the housing capable of rapidly and substantially retarding fluidic momentum of a fluid flowing therethrough resulting in a pressure spike sufficient to initiate fracture formation in a subterranean formation.
Referring now to the drawings wherein like elements are numbered alike in the several Figures:
Referring to
System 10, in one embodiment, includes a valve 16 that may be configured as a flapper valve. The valve 16 is intended to provide for the rapid retardation of fluidic momentum or stoppage of the fluid. In the illustrated embodiment the fluid will be stopped entirely as the flapper 16 will slam closed at a prescribed time and instantly stop fluid flow therethrough. The flapper in the illustrated embodiment is mounted to a flapper seat member 18 that is slidably disposed within an outer housing 20 of the system 10. A seal 22 is provided between the housing 20 and the member 18. At an interior of the member 18 is a flow tube 24 that defines a shoulder 26 for interaction with a spring 28 and fluid drag feature 30. The flow tube 24 is in one embodiment releasably affixed to the member 18 at release member 32. In one embodiment the release member 32 may be one or more shear members such as shear screws. A stop tube 34 is positioned in spaced relationship with the seat member 18 with a spacing dimension that allows the flapper 16 in the open position to be held open by the tube 34. A shoulder 38 is provided to limit downstream travel of the seat member 18 after the release member(s) 32 release.
Having introduced the operable components of the system it will be appreciated that in
As the flapper 16 closes, a pressure spike is created that is related to a sudden retardation of fluidic momentum locally and the compressing force of the fluid column upstream that is still moving toward the source of fluid momentum retardation. In the illustrated case, this source is the closed flapper but it is to be understood that any fluid pathway closure, significant reduction in pathway dimensions or simply any other reason for flow to suddenly be significantly reduced will produce the pressure rise that is utilized in the invention. The ultimate pressure achieved by causing such a fluid retardation is several times (about three to about eight times) the initial pressure of the fluid.
Referring to
Fracture initiation requires the highest pressure of the entire fracturing operation as once fracture initiation has occurred; fracture propagation is maintainable at significantly lower pressures. Due to the pressure spike created by the concept disclosed herein, the pressure local to the system hereof is about three to about eight times the initial pressure of the flowing fluid. Beneficially, the horsepower required of a pump motor is much less than it has been previously as the only pressure required of the pump motor used in combination with the system and methods described herein is for fracture propagation. This represents a significant cost savings in equipment and operating expense.
At the same time that fracture initiation is occurring, the seat member 18 is being very heavily loaded against the flow tube 24 which cannot move farther downstream in view of the shoulder 42. At a point, which is set by the number of and resistance of the release member(s) 32, the release member(s) 32 will release and allow the seat member 18 to stroke downstream while the flow tube 24 remains stationary. The stroke of the seat member 18 is limited by the shoulder 38 to avoid unduly loading the pin (not separately numbered but within the torsion spring 36) in shear. The member 18 then is intended to land on the shoulder 38 only after the flow tube 24 lands on shoulder 42 and the release members 32 release. It is desirable to provide for stroke distance of the flow tube within the member 18 after the release members 32 release so that the flow tube 24 does not actually come into heavily loaded contact with the pressure closed flapper 16 but rather only more strongly contacts flapper 16 after pressure in the system is relieved and the spring 28 is the motive factor in control. Once the release members 32 are released the only thing resisting the spring 28 is the pressure from the fluid column. Upon relief of the pressure the flow tube 24 will move again to open flapper 16 under the influence of the spring 28, which as can be seen in
In view of the foregoing one of ordinary skill in the art will understand that the method for initiating a fracture in a subterranean formation includes operating a system capable of creating a pressure spike due to a rapid and substantial retardation of fluidic momentum in a fluid flowing through the system, the pressure spike occurring proximate one or more ports in a housing that is a part of the system. The method includes causing fracture initiation with the pressure spike. The method further includes one or more of the steps inherent in using the system components discussed above.
There are many factors that can affect the magnitude of the pressure spike including flow rate, fluid density, tubing string stiffness, etc. Each of these can be manipulated to fit a particular application. The greatest factor on the magnitude of the pressure spike is however the speed at which the flow can be stopped since the more gradual the stoppage of fluid flow, the less ultimate compression of the local fluid is achieved.
While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.
