OPEC oil producers will need to invest $60 billion by 2010 in order to meet world oil demand, according to figures released by the group. To maintain its 1995 production level and make its proportionate share of the additional amounts, OPEC needs to invest about $60 billion by the year 2010 and another $250 billion by 2020, officials said. World oil demand, which was about 70 million bpd in 1995, is expected to be over 90 million bpd in 2010 and over 100 million bpd in 2020.