Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2000-03-08
2001-05-15
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S790000, C106S791000
Reexamination Certificate
active
06231664
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to well sealing compositions and methods, and more particularly, but not by way of limitation, to such compositions and methods for performing sealing operations in wells.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized in oil, gas and water well sealing applications during completion and remedial operations. For example, hydraulic cement compositions are used in primary cementing procedures whereby pipes such as casing are cemented in well bores. In performing primary cementing, a hydraulic cement composition is pumped into the annular space between the walls of a well bore and the exterior of a pipe disposed therein. The cement composition is permitted to set in the annular space thereby forming an annular sheath of hardened substantial impermeable cement therein. The cement sheath physically supports and positions the pipe in the well bore and seals the pipe to the walls of the well bore whereby the undesirable migration of fluids between zones or formations penetrated by the well bore is prevented.
Hydraulic sealing compositions used for sealing subterranean formations or zones in wells must have particular properties. For example, the sealing compositions must be capable of being mixed and pumped without prematurely gelling, have sufficiently long pumping times to be placed in subterranean formations or zones, have high compressive and tensile strengths and have a high degree of resiliency after setting or hardening.
The American Petroleum Institute (API) has set standards for different classes for oil well cements to insure that the cement slurries formed with them have required properties. The API cements are Portland cements and because of the strict requirements placed on them, they are generally more difficult to produce and more expensive than other sealing compositions such as slag cement compositions.
Slag cement has heretofore been utilized to form hydraulic cement slurries used for cementing subterranean formations or zones in wells. Slag cement is produced from slag which is formed in the manufacture of iron. The iron is produced from iron ore and limestone flux in a blast furnace and slag is a by-product therefrom. The essential components of slag are the same oxides that are present in Portland cement, e.g., lime, silica and alumina, but their proportions are different. The slag comes from the blast furnace as a molten stream at a temperature of about 1400° F. to 1500° F. The slag is chilled very rapidly either by pouring it into a large excess of water or by contacting it with jets of water or a mixture of air and water. The quenching prevents the slag from rapidly crystallizing and causes it to solidify as a glassy material. Simultaneously, the quenching breaks up the material into small particles or grains. Granulated slag cement alone has a negligible cementing action until an alkaline activator is present, e.g. hydrated lime.
While a slag cement composition has substantial compressive strength after it sets, it generally includes extensive microcracks which decrease its flexural strength and causes it to be permeable to gasses and water. It has been shown that the hydration products of alkali activated slag contain an unstable gel phase which causes shrinking during setting and the formation of microcracks. That is, the alkali activated slag consists of two principal phases during hydration, one of which is calcium silicate hydrate. The other phase is rich in silica and has properties similar to silica gel. The silica phase is unstable and expels water resulting in irreversible shrinkage during setting. This shrinking produces the microcracks which in turn cause increased permeability and decreased tensile strength in the set slag cement.
Thus, there is a need for improved well sealing compositions and methods of using the compositions which are formed of relatively inexpensive slag cement, but which do not shrink and form micro cracks upon setting.
SUMMARY OF THE INVENTION
The present invention provides improved well sealing compositions and methods which meet the need described above and overcome the deficiencies of the prior art. That is, the well sealing compositions of this invention are formed of slag cement but do not shrink and form microcracks upon setting.
The well sealing compositions of this invention are basically comprised of slag cement, water, a slag cement set activator, a hardenable epoxide containing material and an epoxide containing material hardening agent. Upon setting and hardening, the sealing compositions do not contain microcracks, are essentially impermeable, have good compressive and tensile strengths and are resilient.
The methods of the present invention for sealing a subterranean zone penetrated by a well bore basically comprises the steps of preparing a sealing composition as described above, placing the sealing composition in the subterranean zone to be sealed and then allowing the slag cement to set and the epoxide containing material to harden.
It is, therefore, a general object of the present invention to provide improved well sealing compositions and methods.
Other and further 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 improved slag cement well sealing compositions which set into substantially impermeable masses without the formation of microcracks.
The sealing compositions are basically comprised of slag cement, water, a slag cement set activator, a hardenable epoxide containing material and an epoxide containing material hardening agent. The inclusion of the hardenable epoxide containing material and a hardening agent for the material in the sealing compositions reduces or eliminates cracking of the compositions during setting and hardening, decreases or eliminates shrinking upon setting, produces a set and hardened sealing composition which is substantially impermeable and significantly increases the tensile and flexural strengths of the sealing composition as compared to the heretofore utilized slag cement compositions.
The slag cement used in accordance with the present invention is a granulated blast furnace by-product formed in the production of iron and is broadly comprised of the oxidized impurities found in iron ore. During the operation of a blast furnace to remove iron from iron ore, a molten waste slag product is formed. By preventing the molten product from crystallizing and thereby losing its energy of crystallization, a non-crystalline glassy material is formed. The non-crystalline, glassy material, which has also been described as a vitreous substance free from crystalline materials, is capable of exhibiting some hydraulic activity upon being reduced in size by grinding to a fine particle size in the range of from about 1 to about 100 microns.
As mentioned, the molten blast furnace slag is prevented from crystallizing by rapid chilling. The rapid chilling can be accomplished by spraying the molten slag with jets of water which causes solidification and the formation of a water slurry of small slag grains. The water is removed from the slurry and the slag grains are ground to a fine particle size having a Blaine fineness in the range of from about 5,000 to about 7,000, most preferably from about 5,200 to about 6,000 square centimeters per gram.
One or more slag cement set activators are added to the slag cement which provide increased hydraulic activity to the slag cement. Such activators include, but are not limited to, hydrated lime, sodium hydroxide, sodium carbonate, sodium silicate, alkali metal sulfates such as sodium sulfate, Portland cement, magnesia and mixtures of the foregoing activators. The activator or activators used are generally combined with the slag cement in an amount in the range of from about 8% to about 20% by weight of the slag cement, preferably in an
Chatterji Jiten
Cromwell Roger S.
King Bobby J.
Onan David D.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Marcantoni Paul
Roddy Craig W.
LandOfFree
Well sealing compositions and methods does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Well sealing compositions and methods, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Well sealing compositions and methods will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2567465