1. . []

Abbreviation for the now-defunct "Oil Company Materials Association," an organization that for years set standards based primarily on what oil companies operating in the Middle East wanted in mud materials. Suppliers had little voice in OCMA. OCMA's specifications for bentonite clay were modified and taken over by API/ISO.

See: montmorillonitepeptized clay

2. . []

Pertaining to a drilling-grade bentonite clay with API/ISO specifications. API specifications for this clay are similar to those of OCMA.