Updated from 10:25 a.m. EDT
U.S. oil service firms were mixed in Monday trading.
lost 0.2% at $37.67,
advanced 4% at $15.72 a share,
National Oilwell Varco
gained 4.1% at $25.96 a share,
was 2.2% higher at $27.17 a share, and
was 2.8% higher at $10.60 a share.
Oil Services HOLDRs
, an exchange-traded fund that is mostly comprised of U.S. oil service firms, was recently climbing 0.7% at $69.27 a share.