Wells – Processes – Graveling or filter forming
Reexamination Certificate
1999-06-09
2001-05-29
Schoeppel, Roger (Department: 3672)
Wells
Processes
Graveling or filter forming
C166S051000, C166S134000, C166S212000, C166S187000, C175S061000
Reexamination Certificate
active
06237687
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The apparatus of the present invention relates to downhole oil well tools, and more particularly relates to an improved method and apparatus for setting a gravel pack in a downhole oil and gas well environment.
2. General Background of the Invention
There are a number of applications in the oil and gas well drilling industry where it is desirable to install a packer in an oil and gas well whose “annulus” or internal diameter is restricted by existing equipment. One downhole oil and gas well delivery system is known in the industry as a “coil tubing” unit. By using a coil tubing unit, it is possible to run a tool in a well that is very restricted in diameter because of existing equipment. However, there are many oil and gas well drilling operations that are not feasible heretofore with the small diameter coil tubing units.
Gravel packing is a mechanical means of preventing sand flow from unconsolidated formations in a producing well. If the sand flow is not controlled, serious and costly problems, such as, loss of production due to sand bridging, failure of casing or liners from removal of surrounding formation, compaction, erosion and disposal of produced materials. U.S. Patents that relate to gravel packs include U.S. Pat. Nos. 5,620,050 and 5,377,749 issued to Phil Barbee, applicant herein, each hereby incorporated herein by reference.
The purpose of a screen in gravel packs is to hold the gravel in place. The slot width or wire spacing should be smaller than the smallest gravel used. The outside diameter of the screen should provide maximum radial clearance of the casing wall while maintaining an adequate internal diameter for anticipated production rates. Screen sections should provide five feet of minimum overlap above and below the perforated interval to compensate for depth measurement inaccuracies. If the gravel is to be circulated into place, the screen may extend further above the perforated interval to develop a higher column of compacted gravel above the completion interval.
Two commonly used techniques for the placement of gravel are the “squeeze technique” and the “one trip circulating technique”.
The squeeze technique is primarily used for gravel packing short intervals. Gravel is squeezed through the perforations to pack outside the casing and in the screen annulus without circulation. If the squeeze technique is used in longer intervals, variations of the formation permeability may cause all the slurry to go into the highest permeable section of the interval. Although longer intervals have been successfully squeezed, it is recommended that this technique be limited to shorter intervals.
A squeeze packer with a crossover tool is used to place the gravel pack. The screen and the blank pipe are run in the hole and positioned across the productive interval. The packer is set and the crossover opened. The slurry is then “bullheaded” down a workstring, through crossover tool, into the screen-casing annulus, and through the perforations in the casing. Pumping is continued until a pre-determined pressure increase or “sandout” pressure occurs, indicating that no more gravel can be “squeezed” outside of the casing or into the annulus. Once a “sandout” is achieved, pumping is discontinued and treatment pressures are vented before physically pulling the crossover tool to the “upper” circulating position. After the upper circulating position has been accomplished, pumping is resumed to circulate any excess gravel remaining in the workstring to surface.
The one trip circulating technique is typically better suited for longer intervals than the squeeze technique, but can be used for any length interval. A washpipe is positioned inside and extending through the screen to accommodate the circulation of fluids and gravel to the bottom of the screen. A gravel slurry is circulated down the tubing, through a crossover tool, down the screen-casing annulus, through the screen, up the washpipe, through the crossover tool and returns up the workstring-casing annulus. Gravel contained in the slurry is separated out of the circulating fluid as it passes through the screen.
As the screen is covered with gravel, the circulation pressure increases, forcing gravel into the perforations. Pumping is continued until a pre-determined pressure increase or “sandout” occurs indicating that no more gravel can be circulated outside of the casing or into the annulus. Once a “sandout” is achieved, pumping is discontinued and treatment pressures are vented before pulling the crossover tool to the “upper” circulating position. After the upper circulating position is accomplished, pumping is resumed to circulate out any excess gravel remaining in the workstring.
Slurry rates may vary as low as 0.25 bbl/min to in excess of 16.0 bbl/min depending on workstring or tubular diameters and the well configuration. Higher rates result in higher treating pressures which generally promote tighter packing of gravel. At higher placement rates, friction pressure is incurred due to pumping the slurry down relatively long lengths of tubing. These friction pressures tend to “mask” the actual down-hole differential pressure from the screen exterior to the screen interior during a “sandout”.
BRIEF SUMMARY OF THE INVENTION
The present invention features a sliding sleeve, type pressure activated bypass valve. Once in the “lower” circulating position, the hydraulic pressure, incurred as a result of achieving a predetermined “sandout” pressure, shifts the sleeve-type valve to an open position. Once the valve is open, a flow path or by-pass for the excess slurry is exposed allowing the gravel pack media to be circulated back to surface.
A pre-determined “sandout” pressure can be accurately controlled by the adjustable shear value for activation (opening) of the crossover tool by-pass valve. The crossover tool by-pass valve allows for a non-stop pumping operation. The continuous pumping eliminates the opportunity for gravel to settle out of static fluid that may inhibit crossover tool movement or removal from the packer bore. The excess gravel is totally evacuated from the packer/crossover tool vicinity prior to repositioning or removing the crossover tool from the packer bore.
The present invention provides an improved oil and gas well downhole packer apparatus for use in well casing below the wellhead, and can be used in combination with a coil tubing unit having an elongated coil tubing portion, a reel portion for coiling the tubing thereupon, and a free end portion of the tubing that can be transmitted into the well casing below the wellhead area.
In the preferred embodiment, the apparatus includes a tool body having a central, longitudinally extending hollow tool body bore, an upper end portion and a lower end portion. Threads at the top end portion of the tool body assembly are provided for forming a connection between the tool body assembly and the lowermost free end portion of the coil tubing. In this fashion, as coil tubing is unwound from the reel, the coil tubing pays out and the free end portion of the coil tubing lowers into the well with the tool body attached.
The coil tubing provides a bore that can be used to transmit pressurized fluid to the tool body during use. The hydraulic pressure transmitted to the tool body via the coil tubing unit is used to activate the tool body such as, for example, in setting of the packer. Further, the bore of the coil tubing unit is used to transmit coarse sand or gravel from the wellhead area to the tool body for use in gravel packing operation.
The tool body includes an elongated tubular inner mandrel having a polished inner bore, a hydraulic piston that is movably disposed upon the mandrel between a first running position and a second setting position. An external sleeve portion of the tool body surrounds the mandrel and the piston and can b
Barbee, Jr. John Phillip
Red John Tims
Trudeau Roger
Eclipse Packer Company
Garvey, Smith, Nehrbass & Doody LLC
Schoeppel Roger
LandOfFree
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