Wells – Processes – Placing fluid into the formation
Reexamination Certificate
1999-09-21
2001-02-13
Neuder, William (Department: 3672)
Wells
Processes
Placing fluid into the formation
C166S177500
Reexamination Certificate
active
06186236
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to fracturing zones in a well, and more particularly, to a method and apparatus which allows multiple zones to be treated with one trip of the apparatus into the hole and which does not require hydraulic fracturing to be removed from each zone separately.
2. Description of the Prior Art
Hydraulic fracturing is the parting of a desired section of a well formation or zone by an application of hydraulic pressure. A fracture made in this manner may be extended from the wellbore by continued pumping. Extended distance will depend on several factors such as injection rates, formation or zone characteristics, fracturing fluid properties and injected volume of fluid.
Selected particles, added to the fracturing fluid, are transported into the fracture. These act as propping agents to hold the fracture open when the applied pressure is dissipated, thus leaving a channel of high flow capacity connected to the wellbore.
Initially, fracturing was applied primarily to old wells, but now a majority of the treatments performed are on new ones. Many new fields and field extensions have resulted from the application of this production stimulation technique.
Research dealing with theory, methods and materials has resulted in a wide selection of fracturing fluids, additives and equipment to satisfy the many well conditions encountered.
Procedures have been developed to enhance the possibility of obtaining additional fractures during a single treatment of a well. These techniques are known as Multi-Frac. They are especially applicable on wells having multiple pay zones or long producing zones.
Any of a variety of known fracturing fluids may be employed to produce a fracture in the well. Then, that fracture is bridged or sealed. Additional fracturing fluid is then diverted to other parts of the zone, or to other zones, to produce another fracture. Repetition of this procedure has made varied numbers of fractures, as indicated by surveys conducted before and after the treatment. Granular type materials of specific size and characteristics have proven to be very effective for quick sealing and bridging fractures, thus diverting the fluid to other portions of the formation. These are called bridging agents.
The assignee of the present invention has developed a multiple-stage fracturing system which reduces elapsed times between stages, thus allowing operators to reduce rig time, completion time and expense. The system utilizes one or more tubing or casing baffles positioned in the completion string between the zones to be stimulated. Each zone may be perforated, fractured and then temporarily isolated with a bridging ball while a shallower zone is being completed in like manner. Thus, a two-, three-, four- or five-stage fracturing operation usually can be completed in a semi-continuous manner allowing for the short time delay required to perforate each zone before treatment.
Casing or tubing baffles installed between zones in the completion string have graduated internal openings. Sealing balls are selected and mated with the baffles so that the smaller diameter balls or plugs will pass through the larger ID baffles that are installed at the more shallow depths. Some of the balls are of such density that they usually are expelled from the tubing with the flow of fluids and gas when the well is opened to test or production.
Other, more conventional methods utilize setting a plug below a zone and positioning a fracturing tool thereabove which includes a packer. The tool is then removed from the wellbore and another bridge plug positioned below the next higher zone, and the tool utilized again to fracture the formation. This can be repeated as many times as necessary. This system has the disadvantage of having to remove the fracturing tool at each formation so that another plug can be set.
The apparatus of the present invention solves these problems by providing a tool which can be utilized to fracture multiple zones without requiring that the tool be removed from each zone separately. Rather, it can be used to fracture multiple zones in a single trip.
SUMMARY OF THE INVENTION
The present invention includes both methods and apparatus for fracturing a plurality of zones in a well with a single trip of the apparatus into the wellbore. The invention is designed for use in a well having a plurality of vertically spaced formations or zones of interest.
A preferred embodiment of the method of fracturing a plurality of zones in a well comprises the steps of closing the well below a first one of the zones, positioning a first big bore casing packer between the first and second zones, positioning a second big bore casing packer above the second zone, and providing a tool assembly for carrying out the fracturing operation. The tool assembly comprises a tool packer, a crossover positioned above the tool packer, and a concentric wash pipe positioned below the tool packer and having an inner wash pipe portion and an outer wash pipe portion. The method further comprises positioning the tool assembly through the first and second big bore casing packers such that a lower end of the tool assembly is adjacent of the first zone, fracturing the first zone by pumping a fracturing fluid through the tool assembly and monitoring the progress of the fracturing operation at the surface, repositioning the tool assembly such that a lower end of the tool is adjacent to the second zone, and fracturing the second zone by pumping a fracturing fluid through the tool and monitoring progress of the fracturing operation of the surface. These steps may be completed for progressively higher zones.
The step of fracturing may comprise pumping fracturing fluid down the inner wash pipe and flowing fluid up the outer wash pipe such that well conditions at the zone being fractured may be monitored at the surface of the well. The apparatus may further comprise placing a sand cap on each zone after fracturing thereof.
The invention also includes an apparatus for fracturing a plurality of zones in a well. The apparatus comprises a big bore casing packer adapted for positioning in the well adjacent to one of the zones and a tool string adapted for positioning through the big bore casing packer. The tool string comprises a crossover having a first portion adapted for connection to, and communication with, a length of tubing and a second portion adapted for communication with a well annulus, a tool packer connected to the crossover adapted for sealing engagement with the wellbore below the crossover, and a concentric wash pipe extending below the tool packer. The packer has a central passageway in communication with the first portion of the crossover and the inner wash pipe, and an outer passageway in communication with the second portion of the crossover and the outer wash pipe. The concentric wash pipe comprises an inner wash pipe in communication with the first portion of the crossover and an outer wash pipe in communication with the second portion of the crossover.
The big bore casing packer has a bore adapted for receiving the tool string therethrough and is adapted for sealing engagement with an outer surface of the tool string when the big bore casing packer is positioned in an operating position sealingly engaged with the wellbore. This outer surface of the tool string is preferably an outer surface of the outer wash pipe.
In the preferred embodiment, the tool packer is a mechanical packer settable by rotation. However, other types of packers could be utilized.
The apparatus further comprises a screen attached to the outer wash pipe.
Numerous objects and advantages of the invention will become apparent as the following detailed description of the preferred embodiment in read in conjunction with the drawings which illustrate such embodiment.
REFERENCES:
patent: 3090436 (1963-05-01), Briggs, Jr.
patent: 3289762 (1966-12-01), Schell et al.
patent: 4850431 (1989-07-01), Austin et al.
patent: 5265678 (1993-11-01), Grundmann
patent: 5361843 (1994-11-01), Shy et al.
patent:
Halliburton Energy Service,s Inc.
Kennedy Neal R.
Kent Robert A.
Neuder William
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