Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2002-02-28
2003-05-13
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S716000, C106S737000, C106S814000
Reexamination Certificate
active
06562122
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to lightweight well cement compositions and methods of cementing subterranean zones penetrated by well bores using the compositions.
2. Description of the Prior Art
In carrying out completion operations in oil, gas and water wells, hydraulic cement compositions are commonly utilized. For example, hydraulic cement compositions are used in primary cementing operations whereby pipe is cemented in the well bore. That is, a hydraulic cement composition is pumped into the annular space between the walls of the 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 impermeable cement therein. The objective of the cement sheath is to physically support and position the pipe in the well bore and bond 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.
Recently the need for better economics, higher productivity, environment protection and more efficient well operations has brought about new well drilling and completing techniques. Examples of such new techniques include the reduction of the well bore diameter (referred to as a slim hole) and extending the reservoir penetration by drilling small lateral well bores which are completed using small diameter pipe such as coiled tubing to increase the productivity of the reservoir. The performance of primary cementing operations in the smaller annular spaces in the well bores requires improved lightweight cement compositions having low viscosities so that the cement compositions can be accurately placed. In addition, the cement compositions must have good static gel strength, low rheology, high compressive strength, low fluid loss, low permeability, good chemical resistance and a broad operating temperature range. That is, the cement compositions must be suitable for use at temperatures in the range of from about 45° F. to 270° F.
Thus, there are needs for improved lightweight cement compositions and methods of using the compositions for cementing pipe in well bores.
SUMMARY OF THE INVENTION
The present invention provides improved lightweight cement compositions and methods of cementing subterranean zones utilizing the compositions which meet the needs described above and overcome the deficiencies of the prior art. The lightweight cement compositions of the invention are basically comprised of a coarse particulate hydraulic cement; an ultrafine particulate hydraulic cement mixture comprised of slag cement and a Portland or equivalent cement present in an amount in the range of from about 50% to about 150% by weight of the coarse particulate hydraulic cement in the composition; fly ash present in an amount in the range of from about 50% to about 150% by weight of the coarse particulate hydraulic cement in the composition; fumed silica present in an amount in the range of from about 20% to about 60% by weight of the coarse particulate hydraulic cement in the composition; hollow glass spheres present in an amount sufficient to impart a density to the cement composition in the range of from about 9 to about 13 pounds per gallon; and water present in an amount sufficient to form a slurry. The cement compositions also preferably include a fluid loss control additive present in an amount in the range of from about 0.2% to about 8% by weight of the coarse particulate hydraulic cement in the composition.
The coarse particulate hydraulic cement has a particle size no greater than about 118 microns and a specific surface area no less than about 2800 square centimeters per gram. The slag cement and Portland or equivalent cement in the ultrafine cement mixture has a particle size no greater than about 30 microns, a mean particle size of 6 microns and a specific surface area no less than about 6000 centimeters per gram.
The methods of the present invention for cementing a subterranean zone penetrated by a well bore are comprised of the following steps. A lightweight cement composition of the invention is prepared comprised of a coarse particulate hydraulic cement, an ultrafine particulate hydraulic cement mixture of slag cement and Portland or equivalent cement, fly ash, fumed silica, hollow glass spheres, sufficient water to form a slurry and optionally, a fluid loss control additive. After preparation, the cement composition is placed in the subterranean zone to be cemented and the cement composition is allowed to set into a hard impermeable mass.
When the subterranean zone to be cemented has a temperature in the range of from about 45° F. to about 100° F., a cement composition set accelerator is included in the cement composition. When the subterranean zone has a temperature in the range of from about 100° F. to about 270° F., a set accelerator and a dispersing agent are included in the cement composition. When the subterranean zone has a temperature in the range of from about 230° F. to about 270° F., a cement composition set retarder and silica flour are included in the cement composition. The silica flour functions to prevent set cement strength retrogression.
It is, therefore, an object of the present invention to provide improved lightweight well cementing 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 THE PREFERRED EMBODIMENTS
The present invention provides universal non-foamed lightweight cement compositions and methods of using the compositions for cementing subterranean zones penetrated by well bores. The lightweight cement compositions can be used over a broad temperature range, i.e., from about 45° F. to about 270° F. at densities in the range of from about 9 to about 13 pounds per gallon. The cement compositions have excellent properties including high static gel strengths, low rheologies, low fluid loss, high compressive strength upon setting, low permeability upon setting and resistance to chemical deterioration and failure due to sulfate degradation or the like.
The lightweight cement compositions of this invention are basically comprised of a coarse particulate hydraulic cement; an ultrafine particulate hydraulic cement mixture comprised of slag cement and a Portland or equivalent cement, fly ash, fumed silica, hollow glass spheres, water present in an amount sufficient to form a slurry and optionally, a fluid loss control additive.
The coarse particulate hydraulic cement can be any of a variety of hydraulic cements having a maximum particle size of about 118 microns and a specific surface area of about 2800 square centimeters per gram. Portland cement is generally preferred, and the coarse cement can be, for example, one or more of the various Portland cements designated as API Classes A-H cements. These cements are identified and defined in the
API Specification For Materials And Testing For Well Cements,
API Specification 10, 5
th
Edition, dated Jul. 1, 1990 of the American Petroleum Institute. API Portland cements generally have a maximum particle size of about 90 microns and a specific surface of about 3900 square centimeters per gram. When an API Portland cement is utilized as the coarse hydraulic cement in accordance with this invention, it is preferably API Class G cement. Other hydraulic cements which are more coarse than API Portland cement can also be used up to the maximum particle size set forth above. When more coarse cements are used, they preferably have properties which are the same or similar as API Class G cement.
The ultrafine particulate hydraulic cement mixture comprised of slag cement and a Portland or equivalent cement has a particle size no greater than about 30 microns, a mean particle size of 6 microns and a specific surface area no less than about 6,000 centimeters per gram. Preferably the ultrafine particulate hydraulic ce
Dao Bach
Noik Christine
Ravi Krishna M.
Rivereau Alain
Vijn Jan Pieter
Dougherty, Jr. C. Clark
Marcantoni Paul
Roddy Craig W.
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