The field is concentrated: the leading assignee holds 15 of the 102 records in scope, and the top 5 assignees combined account for 60.8% of all records. Several of the highest-ranked names are related Schlumberger entities with strong co-assignee overlap, which means the visible concentration partly reflects one filing programme spread across corporate names rather than several unrelated competitors. Anyone assessing freedom to operate should resolve corporate relationships before treating the ranking as a simple competitive map.

Filing peaked at 7 records in 2018 and has eased since, with the most recent year showing 0 recorded filings. That figure is understated because publication typically lags filing by around 18 months, so the last one to two years in any trend will always look lighter than the eventual total. A firm growth rate is not computable here because there are fewer than four complete years once that lag is accounted for, but the visible direction since the 2018 peak is a cooling one.

US10711551B2, assigned to Saudi Arabian Oil Company and published 2020-07-14, covers a milling downhole tubulars assembly built around a central shaft with an internal flow path positioned inside a washover pipe. A lead tapered mill centres the tool and continues that flow path, milling blades with tungsten-carbide hardened faces and soft steel bodies carry the milling load while allowing fluid flow, and a junk basket completes the assembly. It is a useful reference point for washover-pipe and milling-blade claim structure even for filers outside the operator segment.