1. . 
Abbreviation for the US oilfield unit of concentration, pounds per barrel, more correctly written as lbm/bbl. One lbm/bbl is the equivalent of one pound of additive in 42 US gallons of mud. The "m" is used to denote mass to avoid possible confusion with pounds force (denoted by "lbf"). In SI units, the conversion factor is one pound per barrel equals 2.85 kilograms per cubic meter. For example, 10 lbm/bbl = 28.5 kg/m3.
See: barrel equivalent