The dataset shows a small cluster of oil majors and equipment specialists holding the densest filing positions, including 沙特阿拉伯石油公司, 雪佛龙美国公司, 林德股份公司 and 国际壳牌研究有限公司. Behind this group sits a long tail of single- or few-filing entrants, which is typical of a mature, method-heavy patent space. None of these named leaders shows filings in the most recent tracked year, though that is partly explained by publication lag rather than an actual halt in R&D.

No — filing peaked at 64 families in 2019 and has declined since, sitting at 22 by the 2022 midpoint and falling further toward the most recent year. This is a flat-to-declining trajectory rather than an emerging technology curve. The apparent drop in the final year or two should be read cautiously, since publication typically lags actual filing by around 18 months.

Method claims, tagged under IPC E21B, cover the physical well configuration: injection well placement, horizontal drilling paths and completion hardware. Chemistry claims, tagged under C09K, cover the injection fluids, additives or materials used during recovery. In this dataset the two are frequently combined — more than half of E21B records also carry a C09K tag — so many patents are best understood as a specific fluid used with a specific wellbore method, not a pure hardware or pure chemistry claim.

The core injection-well and horizontal-drilling methods are densely claimed, but several adjacent branches show comparatively thin filing: microbial or fermentation-based recovery approaches, produced-fluid separation hardware, and water-treatment tie-ins connected to recovery operations. These sit at the edges of the search's IPC scope with only a couple dozen records each, versus 889 for the core drilling subclass, suggesting room for narrowly scoped claims that combine core recovery methods with these secondary processes.

Not necessarily. Citation counts accumulate over time within a searched corpus, so older patents such as the in-situ combustion and radiant-tube-heater families in this dataset naturally show higher citation totals simply because they have existed longer and had more opportunity to be cited. High citation counts are better read as a signal of historical influence on how later patents were drafted, not as evidence that the underlying technology is still the commercial standard today.