IP Law Daily, PATENT—Fed. Cir.: Oilfield tool infringement, validity verdicts vacated over claim-construction errors, (Sep 16, 2026)

By Ravindra Kumar Singh, B.L.

The district court improperly construed two limitations of a patented casing-flotation tool, while an earlier sale and use of a competing device qualified as prior art.

The U.S. Court of Appeals for the Federal Circuit has vacated infringement, non-invalidity, and damages judgments involving a patented oilfield casing-flotation tool and ordered a new trial. In a precedential decision, the court held that the district court incorrectly construed “internal diameter” and improperly imposed a 4.5-inch size qualification on “casing string.” It also held that an earlier competing tool was prior art as a matter of law because the patent owner’s preceding private sale did not qualify as a public disclosure shielding the later sale from prior-art treatment (NCS Multistage Inc. v. Nine Energy Service, Inc., No. 25-1000 (Fed. Cir. Sep. 14, 2026)).

Casing-flotation technology. NCS Multistage Inc. and NCS Multistage LLC provide technology and services for oil and gas well completions. Nine Energy Service, Inc. provides completion and production services to oil and gas operators. NCS accused Nine’s BreakThru Casing Flotation Device of infringing U.S. Patent No. 10,465,445 (the ’445 patent).

The patent addresses difficulties encountered when inserting a long casing string into a wellbore. Friction between the casing and wellbore can create substantial drag, particularly in horizontal or deviated wells. Earlier flotation techniques reduced that drag by plugging a portion of the casing and filling it with low-density fluid, but the plugs later had to be drilled out. The ’445 patent instead describes a rupture-disc assembly that permits the casing to be floated into position before the disc is ruptured to restore the fluid passageway.

A Western District of Texas jury found that Nine directly infringed claims 28 and 29 and induced infringement of claims 36, 39, 50–52 and 55–57. It also found the asserted claims not invalid. The district court denied Nine’s post-trial motions and entered judgment for NCS, including damages.

“Internal diameter.” The Federal Circuit first rejected the district court’s construction allowing “internal diameter” to mean both an inner surface and a measured diameter. Nine maintained that the term meant a measured diameter across the casing string.

Claim terms appearing in different portions of claims are presumptively given the same meaning unless the specification and prosecution history clearly demonstrate otherwise, the court explained, relying on Paragon Solutions, LLC v. Timex Corp., 566 F.3d 1075 (Fed. Cir. 2009).

Nothing in the intrinsic record overcame that presumption. Although NCS argued that certain uses of “internal diameter” necessarily referred to an inner surface, Nine’s construction could consistently apply a measured line across the casing string. The prosecution history likewise did not establish two meanings. During prosecution, NCS distinguished Gano, U.S. Patent No. 5,479,986, which describes an oilfield tool containing a disc attached to a sloped region of a tubular member. But that distinction remained consistent with treating “internal diameter” as a measured diameter.

The Federal Circuit therefore construed “internal diameter” as a measured diameter across the casing string’s width. It declined, however, to enter judgment of noninfringement for Nine. As illustrated by the court’s annotations of the BreakThru devices, portions of the surface where the rupture disc potentially attached could be parallel to the measured diameter. That factual question belonged to a jury under the corrected construction, requiring a new infringement trial.

No 4.5-inch limitation. The district court also erred by construing “casing string” as pipe “customarily ≥ 4.5 inches in outer diameter” intended to line a drilled well.

The patent repeatedly described casing strings without imposing a particular size. Where it discussed dimensions, it expressly indicated that other sizes were possible. Although NCS relied on industry evidence showing that casing of at least 4.5 inches was common, extrinsic evidence could not override the intrinsic record. Under Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005) (en banc), claim construction must remain grounded principally in the patent’s intrinsic evidence.

The erroneous construction also mattered to validity. At trial, NCS relied partly on the 4.5-inch distinction to argue that an earlier TDP-PO device was a tubing tool rather than a casing tool. The construction therefore risked improperly influencing the jury’s assessment of whether that device satisfied the patent’s limitations.

Earlier device was prior art. Nine additionally argued that TCO Group AS sold a TDP-PO tool to Apache in August 2012 and that Apache subsequently used it before the ’445 patent’s effective filing date. NCS sought to remove that activity as prior art under 35 U.S.C. § 102(b)(1)(B), contending that its own July 2012 sale of an AirLock device to Tundra constituted an earlier public disclosure of the subject matter.

The Federal Circuit disagreed. Applying Sanho Corp. v. Kaijet Technology International Ltd., 108 F.4th 1376 (Fed. Cir. 2024), it explained that a commercial sale does not necessarily “publicly disclose” an invention for purposes of the statutory safe harbor. The relevant question is whether the disclosure made the invention available to the public so that the public could learn its relevant features.

NCS privately sold the AirLock to a single customer. The device was delivered in a sealed black tube that had to be cut open, and technical documents supplied by NCS were marked confidential. There was no evidence of widespread distribution or that members of the public could learn the claimed rupture-disc features from the device. The AirLock transaction therefore was not a public disclosure.

Consequently, TCO’s subsequent sale of the TDP-PO tool to Apache and Apache’s use of that device constituted prior art to the ’445 patent as a matter of law. Whether that prior art ultimately invalidates the asserted claims remains for the new trial because NCS preserved additional arguments against invalidity that the Federal Circuit did not resolve.

The court separately upheld the exclusion of evidence concerning potential TCO sales to another customer because Nine obtained and disclosed the material only two days before fact discovery closed despite having known much earlier that the TDP-PO device was relevant.

The Federal Circuit accordingly vacated the judgments of infringement and no invalidity. Because the infringement judgment was vacated, the damages award also fell. The case was remanded for a new trial under the corrected claim constructions and with the TDP-PO sale and use treated as prior art. Costs were awarded to Nine.

The Case is No. 25-1000.

Judge: Cunningham, T.

Attorneys: Domingo M. Llagostera (Blank Rome LLP) for NCS Multistage Inc. Hilary L. Preston (Vinson & Elkins LLP) for Nine Energy Service, Inc.

Companies: NCS Multistage Inc.; Nine Energy Service, Inc.

Cases: Patent FedCirNews