Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1999-08-19
2001-08-07
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S725000, C106S823000
Reexamination Certificate
active
06270565
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to improved methods and compositions for cementing pipe in well bores.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized in primary sealing operations whereby strings of pipe such as casing and liners are sealed in well bores. In performing primary cementing, a hydraulic cement composition is pumped into the annular space between the walls of the well bore and the exterior surfaces of the pipe desposed therein. The cement composition is permitted to set in the annular space thereby forming an annular sheath of hardened substantially impermeable cement therein. The sheath physically supports and positions the pipe in the well bore and is intended to bond the exterior surfaces of 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.
In a deep, high temperature well bore penetrating weak formations, the cementing of a pipe string in the well bore is often difficult and characterized by lost circulation during cementing and gas migration through the resulting cement sheath. These problems are principally caused by the use of a cement slurry having insufficient fluid loss control and using an aqueous spacer between the drilling fluid and the cement slurry which does not adequately remove drilling fluid from the pipe surfaces and the walls of the well bore. Further, at the high temperatures encountered, when an oil based drilling fluid is used and the aqueous spacer mixes with oil on the walls of the well bore, solidification of the mixture often results. The presence of drilling fluid and/or solidified oil-water mixtures in the well bore prevents the cement slurry from adequately bonding to the pipe and walls of the well bore, and as a consequence, costly remedial cementing procedures are required.
Thus, there are needs for improved methods and compositions for cementing pipe strings in well bores drilled using oil based drilling fluids.
SUMMARY OF THE INVENTION
The present invention provides methods and compositions for cementing pipe in well bores which meet the needs described above and overcome the deficiencies of the prior art. The methods of the invention basically comprise the steps of preparing a cement composition comprised of hydraulic cement, water, an in situ foam generating additive and a water-wetting foam stabilizing surfactant; placing the cement composition in the annulus between the exterior surfaces of a pipe string and the walls of the well bore whereby the surfactant causes drilling fluid in the well bore to be displaced therefrom and causes the pipe surfaces and walls of the well bore to be water-wetted whereby the cement composition will readily bond thereto; and then allowing the cement composition to foam and set in the annulus. The surfactant in the cement composition also facilitates and stabilizes the foaming of the cement composition which in turn helps prevent the migration of gas into and through the cement composition.
The compositions of this invention are basically comprised of a hydraulic cement, water in an amount sufficient to form a pumpable slurry, an in situ foam generating additive and a water-wetting foam stabilizing surfactant. The in situ foam generating additive causes a gas to be formed within the cement compositions which foams the compositions prior to when they set and, as mentioned, the surfactant in the cement compositions water wets the pipe and well bore surfaces, facilitates the formation of foam and stabilizes the foam.
It is, therefore, a general object of the present invention to provide improved methods and compositions for cementing pipe strings in well bores.
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 methods and compositions for cementing a pipe string in a well bore, and particularly in such a well bore which is deep, has a high bottom hole temperature, penetrates weak formations having high potential for gas flow into the well bore and was drilled using an oil based drilling fluid.
In accordance with the methods of the present invention, a cement composition is prepared comprised of hydraulic cement, water, an in situ foam generating additive and a water-wetting foam stabilizing surfactant. The cement composition is placed in the annulus between the exterior surfaces of a pipe string and the walls of a well bore in which the pipe string is disposed, and the cement composition is allowed to foam and set therein.
The in situ foam, generating additive in the cement composition produces a gas which foams the cement composition during and after its placement in the annulus. The water-wetting foam stabilizing surfactant in the cement composition facilitates the generation of the foam and stabilizes it. In addition, the surfactant functions to cause oil on the pipe surfaces and the walls of the well bore to be removed and the surfaces and walls to be made water-wet whereby good bonding between the cement composition and the surfaces and walls results.
A variety of hydraulic cements can be utilized in accordance with the present invention including those comprised of calcium, aluminum, silicon, oxygen and/or sulfur which set and harden by reaction with water. Such hydraulic cements include Portland cements, pozzolana cements, gypsum cements, high alumina content cements, silica cements and high alkalinity cements. Portland cements are generally preferred for use in accordance with the present invention, and Portland cements of the types defined and described in
API Specification For Materials And Testing For Well Cements
, API Specification 10, 5th Edition, dated Jul. 1, 1990 of the American Petroleum Institute are particularly preferred. API Portland cements include classes A, B, C, G and H, with API classes G and H being more preferred and class H being the most preferred.
The water utilized in the compositions of this invention can be from any source provided it does not contain an excess of compounds that adversely affect other components in the cement compositions. For example, the water can contain various salts such as sodium, potassium, calcium chloride or the like. Generally, the water is present in a cement composition of this invention in an amount sufficient to form a pumpable slurry. More particularly, the water is generally present in the cement compositions of this invention in an amount in the range of from about 35% to about 55% by weight of hydraulic sement therein (from about 4 to about 6.2 gallons per sack).
While various in situ foam generating additives can be utilized, aluminum powder or aluminum powder coated with a dispersing surfactant is preferably utilized. When added to an aqueous cement composition, aluminum powder delayedly generates hydrogen gas in the cement composition which causes it to foam during and after placement. The foam generating agent is included in the cement compositions of this invention in a general amount in the range of from about 0.1% to about 1% by weight of hydraulic cement in the composition (about 0.1 pounds per sack to about 1 pound per sack), preferably in the range of from about 0.2% to about 0.7% (about 0.2 pounds per sack to about 0.66 pounds per sack), and more preferably about 0.5% (about 0.47 pounds per sack).
While various surfactants can be included in the cement compositions of the present invention for facilitating the removal of water based and oil based drilling fluids and filter cake from pipe and well bore and leaving them water wet surfaces and/or for facilitating and stabilizing the in situ foam formed in the cement composition, a single water-wetting foam stabilizing surfactant is preferably utilized. Such a surfactant which is preferred for use in accordance with the present invention is an anion
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Marcantoni Paul
Roddy Craig W.
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