Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
2002-06-21
2004-04-20
Tsay, Frank (Department: 3672)
Wells
Processes
Cementing, plugging or consolidating
C166S207000, C166S293000
Reexamination Certificate
active
06722433
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and compressible sealant compositions for sealing expandable pipe in well bores.
2. Description of the Prior Art
A new well completion practice has been developed whereby casings and liners are expanded diametrically after they are placed in well bores. Prior to the expansion, a sealing composition is placed in the annulus between the walls of the well bore and the unexpanded casing or liner. A problem which can be encountered involves the use of hydraulic cement compositions as the sealing composition. Hydraulic cement compositions are non-compressible and tend to resists the expansion of the casing or liner making the expansion more difficult. In addition, if the cement composition gels or sets prior to when the expansion is accomplished, the cement composition is crushed in the annular space between the walls of the well bore and the expandable casing or liner whereby it does not function to seal the expanded casing or liner in the well bore.
Thus, there are needs for improved sealant compositions for sealing expandable casings or liners in well bores which are compressible and maintain the properties required to provide a seal between the walls of the well bore and the expanded casings or liners.
SUMMARY OF THE INVENTION
The present invention provides methods of sealing expandable casings and liners in well bores and compressible sealant compositions. A method of the present invention for sealing an expandable pipe or pipe string such as a casing or liner in a well bore is basically comprised of the following steps. The expandable pipe or pipe string is placed in the well bore. A compressible hydraulic cement sealant composition which remains competent when compressed is placed in the annulus between the well bore and the pipe or pipe string. The sealant composition is allowed to harden into an impermeable mass and thereafter, the expandable pipe or pipe string is expanded whereby the hardened sealant composition is compressed.
Another method of the invention for sealing expandable pipe or pipe strings is basically comprised of the following steps. A compressible foamed sealant composition is provided comprised of a hydraulic cement, a rubber latex, a rubber latex stabilizer, a gas and a mixture of foaming and foam stabilizing surfactants. An expandable pipe or pipe string is placed in the well bore and the compressible foamed sealant composition is placed in the annulus between the well bore and the expandable pipe or pipe string. The foamed sealant composition is allowed to harden into an impermeable mass, and thereafter, the expandable pipe or pipe string is expanded whereby the hardened foamed sealant composition is compressed.
The compressible foamed sealant compositions of this invention which remain competent when compressed are basically comprised of a hydraulic cement, a rubber latex, a rubber latex stabilizer, a gas and a mixture of foaming and foam stabilizing surfactants.
The amount of gas included in the compressible foamed sealant composition is such that the gas volume is substantially equal to the expansion volume of the expandable casings or liners. This allows the hardened sealant composition to be compressed while maintaining its integrity and sealant properties.
The objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides compressible hydraulic cement sealant compositions which remain competent when compressed. That is, when a compressible hydraulic cement composition of this invention is used for sealing an expandable pipe or pipe string in a well bore, the composition is placed in the annulus between the expandable pipe and the well bore, it is allowed to harden therein and when the expandable pipe is expanded, the sealant composition is compressed and retains its competency, i.e., continues to support and seal the pipe. Methods of using the compositions are also provided.
The compressible sealant compositions of this invention are basically comprised of a hydraulic cement, a rubber latex, a rubber latex stabilizer, a gas and a mixture of foaming and foam stabilizing surfactants. The compressible foamed sealant compositions are compressible after hardening to the extent that the compositions contain gas. Thus, the volume of gas utilized in the sealant compositions are substantially equal to the volume reduction of the annular space containing the sealant composition.
Examples of the hydraulic cement that can be utilized in accordance with this invention, include, but are not limited to, calcium aluminate cement, Portland cement, and Portland blast furnace cement. Of these, calcium aluminate cement is preferred.
A variety of well known rubber latexes can be utilized in accordance with the present invention such as styrene/butadiene copolymer latex emulsion, polychloroprene emulsion, polyisoprene emulsion and acrylonitrilibutadiene emulsion. Of these, styrene/butadiene latex emulsion is preferred. The styrene/butadiene latex emulsion can include in the range of from about 40% to about 70% water by weight of the latex. The weight ratio of styrene to butadiene in the latex can range from about 10%:90% to about 90%:10%. A preferred styrene/butadiene aqueous latex for use in accordance with the present invention contains water in an amount of about 50% by weight of the latex and has a weight ratio of styrene to butadiene in the latex of about 25%:75%. A latex of this type is commercially available from Halliburton Energy Services, Inc. of Duncan, Okla. under the trade designation “LATEX 2000™.” The rubber latex utilized is included in the foamed sealant composition of this invention in an amount in the range of from about 80% to about 300% by weight of the calcium aluminate cement therein.
In order to prevent the aqueous latex from prematurely coagulating and increasing the viscosity of the foamed sealant composition, an effective amount of a latex stabilizing surfactant is included in the composition. Latex stabilizing surfactants which are suitable for use in accordance with this invention are surfactants having the formula R—Ph—O(OCH
2
CH
2
)
m
OH wherein R is an alkyl group having from about 5 to about 30 carbon atoms, Ph is phenyl and m is an integer of from about 5 to about 50. A preferred surfactant in the above defined group is ethoxylated nonylphenyl containing in the range of from about 20 to about 30 moles of ethylene oxide.
Another suitable surfactant is a salt having the formula R
1
(R
2
O)
n
SO
3
X wherein R
1
is an alkyl group having from about 5 to about 20 carbon atoms, R
2
is the group —CH
2
—CH
2
—, n is an integer from about 10 to about 40 and X is a cation. A particularly preferred surfactant of this type is the sodium salt of a sulfonated compound derived by reacting a C
12-15
alcohol with about 15 moles of ethylene oxide having the formula H(CH
2
)
12-15
(CH
2
CH
2
O)
15
SO
3
Na which is commercially available under the trade designation name “AVANEL S150™” from PPG Mazer, Mazer Chemicals, a Division of PPG Industries, Inc. of Gurnee, Ill.
The latex stabilizing surfactant utilized is included in the foamed sealant composition in an amount in the range of from about 3% to about 6% by weight of the rubber latex in the foamed sealant composition, preferably in an amount of 4%.
The gas in the compressible foamed sealant composition can be air or nitrogen with nitrogen being preferred. The gas is present in the foamed sealant composition in an amount in the range of from about 5% to about 35% by volume of the non-foamed sealant composition. As mentioned above, the volume of gas used in the foamed sealant composition is generally substantially equal to the volume of decrease in the annulus between the walls of the well bore and the expandable pipe when the expandable pipe is expanded.
Various mixtures of foaming and foam stabilizing surfactants can be
Brothers Lance E.
Palmer Anthony V.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Roddy Craig W.
Tsay Frank
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