Wells – Processes – Cementing – plugging or consolidating
Reexamination Certificate
2002-06-20
2004-04-06
Swann, J. J. (Department: 3677)
Wells
Processes
Cementing, plugging or consolidating
C523S130000, C166S295000
Reexamination Certificate
active
06715552
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to well cementing methods and compositions.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized in the construction and repair of oil and gas wells. For example, hydraulic cement compositions are used in primary cementing operations whereby strings of pipe such as casing or liners 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 surfaces of a pipe string disposed therein. The cement composition is permitted to set in the annular space thereby forming an annular sheath of hardened substantially impermeable cement therein. The cement sheath physically supports and positions the pipe string in the well bore and bonds the exterior surfaces of the pipe string 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 cement compositions are also commonly used to plug lost circulation and other undesirable fluid inflow and outflow zones in wells, to plug cracks or holes in pipe strings cemented therein and to accomplish other required remedial well operations.
In order for such well cementing operations to be successful, the cement compositions utilized must include a fluid loss control additive to reduce the loss of fluid, i.e., water, from the cement compositions when they contact permeable subterranean formations or zones. Excessive fluid loss causes a cement composition to be prematurely dehydrated which limits the amount of cement composition that can be pumped, decreases the compressive strength of the cement composition and prevents or reduces bond strength between the set cement composition and a subterranean zone, the walls of pipe and/or the walls of the well bore.
Heretofore polymers and copolymers have been utilized as fluid loss control additives for well cements. A particularly suitable copolymer which has been utilized as a cement composition fluid loss control additive is a copolymer of 2-acrylamido-2-methyl propane sulfonic acid and N,N-dimethylacrylamide having mole ratios of 2-acrylamido-2-methyl propane sulfonic acid to N,N-dimethylacrylamide of between 1:4 and 4:1 respectively, and having an average molecular weight of between about 75,000 and 3,000,000. While the above described copolymer well cement fluid loss control additive has achieved commercial success, there is a continuing need for improved polymer fluid loss control additives which achieve better fluid loss control in well cement compositions.
SUMMARY OF THE INVENTION
The present invention provides well cementing methods and compositions which include improved liquid fluid loss control additives comprised of water soluble polymers which meet the need described above and overcome the deficiencies of the prior art. The water soluble fluid loss control polymer additives which are useful in accordance with this invention are comprised of the following monomers:
a) 5 to 93 weight % of monomers of the formula (Ia) or (Ib) or both
wherein
R
1
is hydrogen or C
1
-C
5
alkyl,
R
2
is C
1
-C
20
alkylene, carboxy C
1
-C
20
alkylene, carboamido C
1
-C
20
alkylene or phenylene,
M is hydrogen, ammonium or a metal cation in the oxidation state +I, +II or +III and
x is 1 to 3;
b) 1 to 50 weight % of monomers of the formula (IIa) or (IIb) or both
wherein
R
3
and R
4
are —COO
−
(M
x
+
)
1/x
or
R
5
is —COO
−
(M
x
+
)
1/x
,
M is hydrogen, ammonium or a metal cation in the oxidation state +I, +II or +III and
x is 1 to 3;
c) 5 to 93 weight % of a monomer of the formula (III)
wherein
R
6
is hydrogen or C
1
-C
5
alkyl,
R
7
and R
8
are hydrogen, C
1
-C
10
alkyl or —(CH
2
)
y
— and
y is 3 to 7; and
d) 1 to 25 weight % of monomers of the formula (IVa) or (IVb) or both
wherein
R
9
is hydrogen or C
1
-C
5
alkyl,
R
10
is C
1
-C
10
alkyl, C
1
-C
10
aminoalkyl, C
1
-C
20
hydroxyalkyl, C
1
-C
4
alkyl or hydroxyl terminated mono- or poly-C
2
-C
3
alkylenoxy (with 1 to 400 alkylenoxy units), C
7
-C
20
alkylaryl, C
7
-C
20
hydroxyalkylaryl, C
6
-C
10
aryl or C
6
-C
10
hydroxyaryl,
R
11
, R
12
and R
13
are hydrogen or C
1
-C
5
alkyl and
R
14
is hydrogen, C
1
-C
20
alkyl, C
1
-C
10
aminoalkyl, C
1
-C
20
hydroxyalkyl, C
1
-C
4
alkyl- or hydroxyl terminated mono- or poly-C
2
-C
3
alkylenoxy (with 1 to 400 alkylenoxy units), C
7
-C
20
alkylaryl, C
7
-C
20
hydroxyalkylaryl, C
6
-C
10
aryl, C
6
-C
10
hydroxyaryl or with hydroxyl substituted C
1
-C
20
alkylensulfonic acids and their ammonium, alkali metal or alkaline earth metal salts; and
wherein the monomers a) to d) add up to 100 weight %.
The methods of this invention for cementing a subterranean zone penetrated by a well bore are basically comprised of the following steps. A cement composition is provided comprised of a hydraulic cement, sufficient water to form a pumpable slurry and a fluid loss control polymer additive as described above. The composition is placed into the subterranean zone to be cemented and then allowed to set into an impermeable solid mass therein.
The cement compositions of this invention are basically comprised of a hydraulic cement, sufficient water to form a pumpable slurry and a fluid loss control polymer additive as described above.
A preferred fluid loss control polymer additive useful in this invention is a polymer containing the calcium salt of 2-acrylamido-2-methyl propane sulfonic acid in an amount of about 69 weight %, the calcium salt of maleic acid in an amount of about 14 weight %, N-vinyl caprolactam in an amount of about 14 weight % and 4-hydroxybutyl vinyl ether in an amount of about 3 weight %. The polymer additive has a molecular weight of about 250,000.
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 methods of the present invention for cementing a subterranean zone penetrated by a well bore are basically comprised of the following steps. A cement composition is provided comprised of a hydraulic cement, sufficient water to form a pumpable slurry and a fluid loss control polymer additive. The cement composition is placed in the zone to be cemented and thereafter the cement composition is allowed to set into an impermeable solid mass therein. The placement of the cement composition is usually accomplished by pumping the cement composition through the well bore and into the zone to be cemented.
The cement compositions of this invention are basically comprised of hydraulic cement, sufficient water to form a pumpable slurry and a fluid loss control polymer additive.
A variety of hydraulic cements can be utilized in accordance with the present invention including, but not limited to, Portland cements, pozzolana cements, gypsum cements, aluminous cements and silica cements. Portland cements are generally preferred with the types defined and described in
API Specification For Materials And Testing For Well Cements
, API Specification 10, 5
th
Edition, dated Jul. 1, 1990 of the American Petroleum Institute being particularly suitable. Preferred such API Portland cements include classes A, B, C, G and H with API classes G and H being more preferred.
The water in the cement compositions can be fresh water or salt water. The term “salt water” includes unsaturated salt solutions and saturated salt solutions including brines and seawater. Generally, any water can be utilized so long as it does not adversely affect components of the well cement composition. The water is generally present in a cement composition of this invention in an amount sufficient to form a pumpable slurry, i.e., in an amount in the range of from about 30% to about 120% by weight of cement in the composition. The water is generally present in the cement composi
Eoff Larry S.
Keener Krista L.
Dougherty, Jr. C. clark
Mitchell Katherine
Roddy Craig W.
Swann J. J.
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