The dataset's leading assignee holds 36 of the 519 records in scope, well ahead of the fifth-place figure of 20 and the tenth-place figure of 9. The ranking is dominated by large national oil companies and their oilfield engineering subsidiaries, several of which file jointly with their own research institutes rather than with outside partners. Because the top 5 assignees together account for 26.4% of all records and the top 10 for 39.3%, the field is concentrated at the top but still leaves the majority of filings spread across a long tail of smaller entrants.

Filing volume rose from 19 records in 2017 to a peak of 48 in 2024, but the 2022 midpoint of 41 was already close to that peak, indicating the growth curve has flattened rather than accelerated. Several of the largest assignees show zero filings in the most recent tracked year, which is consistent with a maturing filing wave. Recent-year counts are always understated because publication lags filing by roughly 18 months, so the true 2025-2026 picture will not be clear until later data cuts.

Water and wastewater treatment claims (IPC class C02F) appear in 80.7% of the 519 records, and separation-process claims (B01D) appear in 25.6%, making these the two most heavily claimed areas. Earth and rock drilling claims (E21B), tied to wellbore-side reinjection equipment, appear in 10.8% of records. Smaller classes covering catalysis, hydrocarbon refining, mixing, specialty materials and cyclone separation each sit under 3%, marking comparatively open ground for new filings that avoid the core treatment-and-separation claim space.

CA2917959A1 describes a settling oil removal tank for produced water treatment, with a central tubular column, water distribution chamber, oil collecting groove and a bottom sludge discharge device. It was filed by a Xinjiang oilfield engineering entity in 2017 and is representative of tank-and-internals design claims common among Chinese national-oil-company filers in this dataset. Anyone designing gravity-settling or tank-based deoiling equipment for produced water should review its specific internals configuration — the sealed lower end of the central column and the water collecting pipeline arrangement — before finalizing a similar mechanical layout.

The classes furthest below the dominant C02F and B01D categories — cyclone separation (B04C) at 1.2%, mixing and stirring (B01F) at 1.5%, and specialty materials (C09K) at 1.5% — carry the least claim density in the dataset. Combined with the flat filing trend since 2022, this suggests mechanically distinct approaches like cyclone-based deoiling skids or biocide-dosing systems targeting bacteria control face less crowded prior art than another incremental treatment-train claim. A first filing in these areas should tie the mechanical or chemical novelty explicitly to injectivity decline or reinjection economics, since those problem statements appear in the search scope but are thin in the class breakdown.