"Fragile Gel" Indefinite for Failure to Distinguish from Prior Art

In Halliburton Energy Svcs. v. M-I (January 25, 2008) the Federal Circuit concluded that since neither Halliburton’s proposed definition, nor any other possible construction, resolved the ambiguity in the scope of the term "fragile gel," then the claims containing that term were indefinite. (The issue of whether additional limitations in the dependent claims rendered them sufficiently definite was not raised.) Professor Wegner describes the The lengthy opinion of the court’s Chief Judge as providing "a tutorial in line with the increasingly stringent attitude the court is taking against sloppy claim drafting."

The claims of U.S. Patent No. 6,887,832 recited certain fragile gel drilling fluids for which Claim 1 read:

1. A method for conducting a drilling operation in a subterranean formation using a fragile gel drilling fluid comprising:

(a) an invert emulsion base;
(b) one or more thinners;
(c) one or more emulsifiers; and
(d) one or more weighting agents, wherein said operation includes running casing in a
borehole.

During prosecution, Halliburton distinguished the claims of the ’832 patent from prior art fluids by stating that the claims were "limited to" a "fragile gel" drilling fluid or the method of using a "fragile gel" drilling fluid. Thus, although the term "fragile gel" appears only in the preamble of the asserted independent claims, Halliburton conceded that the claimed drilling fluids are limited to those that are "fragile gels."


Halliburton then argued that "fragile gel" as used in the asserted claims is definite and had a three-part definition:

1. A gel that easily transitions to a liquid state upon the introduction of force (e.g., when drilling starts) and returns to a gel when the force is removed (e.g., when drilling stops); and


2. At rest, is capable of suspending drill cuttings and weighting materials; and


3. Contains no organophilic clay or organophilic lignite or can contain low amounts of organophilic clay or lignite individually or in combination so that the fragile gel can still easily transition between a gel and liquid state and suspend drill cuttings and weighting materials.

On third third point, the court concluded that "fragile gels" that have no or low organophilic clay or lignite are merely preferred embodiments of the invention covered by certain dependent claims, and thus "fragile gel" as used in the independent claims is not limited to those embodiments.

The, on the first two points, Chief Circuit Judge Michel wrote that the court,

. . . reject[ed] Halliburton’s assertion that a "fragile gel" can be defined by an L-shaped curve [above] alone because the specification does not distinguish how the "fragile gels" claimed in the ’832 patent performed differently than the disclosed prior art—how much more quickly the gels broke when stress was imposed or how much more quickly the gels reformed when stress was removed. Halliburton’s failure to distinguish the fragileness of the drilling fluids of the invention from the close prior art (the 12.1 SF fluid that exhibited the L-shaped curve behavior) is fatal. Amgen, Inc. v. Chugai Pharm. Co., Ltd., 927 F.2d 1200, 1218 (Fed. Cir. 1991) (holding that the term "at least about" was indefinite because the patent provided no guidance as to where the line should be drawn between the numerical value of the prior art cited in the prosecution history and the close numerical value in the patent); see also Verve, LLC v. Crane Cams, Inc., 311 F.3d 1116, 1119-20 (Fed. Cir. 2002) (recognizing that guidance as to measurement of a term of degree can come from the intrinsic record or from the knowledge of a person of ordinary skill in the art).

Even if the ’832 patent distinguished "fragile gels" of the invention from those of the prior art, it did not place any limit on the scope of what was invented beyond the prior art. By Halliburton’s own admission, drilling fluids which included an invert emulsion base, a thinner, an emulsifier, and a weighting agent were known in the prior art, and independent claims 1-3 and 5 are distinguishable from the prior art only because they are "fragile gels." By failing to identify the degree of the fragility of its invention, Halliburton’s proposed definition would allow the claims to cover not only that which it invented that was superior to the prior art, but also all future improvements to the gel’s fragility. While patentees are allowed to claim their inventions broadly, they must do so in a way that distinctly identifies the boundaries of their claims. The fluids of the ’832 invention may provide less resistance to shear (i.e., break more quickly) than the prior art fluids, but the degree of improved speed remains ambiguous. Thus, it is unclear whether a person of ordinary skill in the art would have interpreted this claim as having an upper bound of fragility.

. . . The second part of Halliburton’s definition (i.e., the fragile gel is capable of suspending drill cuttings and weighting materials at rest) fares no better because nothing in the record suggests what degree of such capability is sufficient. Halliburton argues that a person of ordinary skill would know how to measure the quantity of drill cuttings suspended in a fluid (either through laboratory measurements or in the field for example by measuring weight (or density) of the fluid when entering the borehole and when exiting the borehole), and would also know how to determine when the fluid no longer exhibited the L-shaped curve behavior when tested with a Brookfield viscometer. The fact that an artisan would know how to perform these measurements and tests, however, says nothing about whether the artisan would also know which fluids were "fragile gels" as that term is used in the claims of the ’832 patent.

Assuming a person of ordinary skill would add solids incrementally, determining the effect of each addition by observing whether the fluid still maintains its fragile gel characteristics (the L-shaped curve), as Halliburton suggests, this testing protocol still does not answer the fundamental question: what quantity, weight, size and/or volume of cuttings must be suspended? Halliburton does not attempt to resolve this ambiguity, instead arguing that this limitation merely means adequate for the circumstances.

. . . We also note that the two parts of Halliburton’s proposed definition discussed above (ability of the fluid to transition quickly from gel to liquid, and the ability of the fluid to suspend drill cuttings at rest) are functional, i.e., the fluid is defined "by what it does rather than what it is."

. . . When a claim limitation is defined in purely functional terms, the task of determining whether that limitation is sufficiently definite is a difficult one that is highly dependent on context (e.g., the disclosure in the specification and the knowledge of a person of ordinary skill in the relevant art area). We note that the patent drafter is in the best position to resolve the ambiguity in the patent claims, and it is highly desirable that patent examiners demand that applicants do so in appropriate circumstances so that the patent can be amended during prosecution rather than attempting to resolve the ambiguity in litigation.

A patent drafter could resolve the ambiguities of a functional limitation in a number of ways.6 For example, the ambiguity might be resolved by using a quantitative metric (e.g., numeric limitation as to a physical property) rather than a qualitative functional feature. The claim term might also be sufficiently definite if the specification provided a formula for calculating a property along with examples that meet the claim limitation and examples that do not. See Oakley, Inc. v. Sunglass Hut Int’l, 316 F.3d 1331, 1341 (Fed. Cir. 2003) (holding that, at the preliminary injunction stage, the accused infringer had not shown a substantial question of indefiniteness, where the claims and specification linked the claim term "vivid colored appearance" to a calculation for differential effect and then provided examples of when differential effect values were and were not sufficient for a "vivid colored appearance"); see also In re Marosi, 710 F.2d 799, 803 (Fed. Cir. 1983) (finding claims definite where the applicant’s disclosure provided "a general guideline and examples sufficient" to teach an artisan when the claim limitation was satisfied).

In this case, Halliburton differentiated its invention from the prior art because it was a "fragile gel." As discussed above, Halliburton’s proposed definition of that term is not sufficiently definite because it does not adequately distinguish the fragileness of the invention from disclosed prior art, it is ambiguous as to whether an upper bound of fragileness is contemplated, and it is ambiguous as to its requisite ability to suspend drill cuttings. In other words, Halliburton’s proposed construction of "fragile gel" as used in the claims of the ’832 patent is indefinite because it is ambiguous as to the requisite degree of the fragileness of the gel, the ability of the gel to suspend drill cuttings (i.e., gel strength), and/or some combination of the two. We discern no other construction that can properly be adopted that would render the claims definite.

Thus, we hold that M-I did provide clear and convincing evidence that the term "fragile gel" was indefinite, and that the district court correctly held the claims invalid on that basis.