Appeal No. 2005-2446 Page 5
Application No. 09/951,099
Discussion
The examiner rejected claims 1, 3-5 and 7-10 under 35 U.S.C. § 103 as
unpatentable over Dawson1 in view of Segel.2 In addition, the examiner rejected claims
1-5 and 7-10 under 35 U.S.C. § 103 as unpatentable over Dawson and Segel, and
further in view of Christgau.3 Because we consider the examiner’s proposed
combination of Dawson and Segel to be central to both rejections, we will discuss the
rejections together.
Dawson describes “a gellable fracturing fluid [ ] formulated by blending together
an aqueous fluid, a hydratable polymer, a suitable crosslinking agent . . . and an enzyme
breaker which is effective to degrade the polymer gel at temperatures below about 140-
150 F within a time period less than about 24 hours. In order to provide a controlled
break, the pH of the fracturing fluid is initially raised above about 9.0, whereby the
enzyme breaker is inert. A pH regulating substance is also incorporated in the fracturing
fluid which slowly hydrolyzes to produce a Bronsted acid, thereby dropping the pH of the
fracturing fluid. As the pH . . . drops, the enzyme breaker is activated to attack the
polymer” (Dawson, column 2, line 56 to column 3, line 2). “Propping agents are typically
added to the base fluid prior to addition of the crosslinking agent” (id., column 4, lines 52-
54).
1 Dawson, U.S. Patent 5,067,566, issued November 26, 1991.
2 Segel, I.H., in Biochemical Calculations, John Wiley & Sons, New York, Appendix IV, pp. 403-406 (1976).
3 Christgau et al., U.S. Patent 5,795,764, issued August 18, 1998.
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