US 6585061

Patent Overview — US 6,585,061 B2

Title: Calculating directional drilling tool face offsets

Source: https://patents.google.com/patent/US6585061/en

Bibliographic data (from supplied text): Application US09/976,129; priority/filing date 2001-10-15; publication date 2003-07-01; legal status "Expired – Lifetime" (anticipated expiration 2021-10-15). Inventors: Paul E. Radzinski, Michael L. Larronde, Jian-qun Wu. Original assignee: Precision Drilling Technology Services Group Inc.; current assignee listed as Weatherford Technology Holdings LLC. Other versions: US20030070844A1; GB2381022B; CA2407541C. Classification: E21B7/067 (adjustable bent sub).

Purpose: The invention relates generally to directional drilling of wells and, in particular, to a method and apparatus for "more efficient and accurate determination of an angular offset between a directional sensor reference point and the high side of a bent sub." One stated object is to eliminate error that may be made in measuring and applying the angular difference used to determine bent sub orientation, and to implement equipment for achieving same.

Plain-language scope: In directional drilling, a downhole motor assembly includes a bent sub that offsets the bit a slight angle (usually about three degrees) from the drill string axis. To steer, the operator must know the bent sub's orientation, derived from the directional sensor tool face plus a "tool face offset"—the angular difference between the sensor reference point and the bent sub. Conventional practice uses a scribe line and a chalk line measured with a protractor, requiring the operator to decide whether to add or subtract the difference. In the described approach, a locater (e.g., a circumferential groove) marks the approximate midpoint of the magnetometer in the instrument housing; the tools are suspended vertically; a chalk line is drawn from the bent sub high side to that groove; and magnetic field measurements ("B before") are taken via a probe and electrical lead to the surface instrument panel.

What the excerpt does not establish: It is truncated ("[Excerpt only; consult the source for omitted text.]"). It does not provide the full claims, the complete measurement/computation method, how the offset is finally calculated, any drawings' content, or the remaining description. No litigation, ownership-transfer analysis, validity, or prior-art assessment is made here.