Oil prices, notoriously vulnerable to political events, spiked as high as $40 a barrel during the Gulf War in 1991.
Natural gas production will become more efficient than oil production.
( z1 become :ARG1 ( z2 produce :ARG1 ( z3 gas :ARG1-of ( z4 natural ) ) ) :ARG2 ( z5 have-degree :ARG1 z2 :ARG2 ( z6 efficient :ARG1 z2 ) :ARG3 ( z7 more ) :ARG4 ( z8 produce :ARG1 ( z9 oil ) ) ) )