About half the funding would come from a rights issue to shareholders with the balance raised in the form of debt.
The expansion plan follows the collapse in March of merger talks between Enterprise and Lasmo, and Lasmo's subsequent pounds 710m takeover of Monument Oil & Gas.
The two areas where Enterprise is keenest to boost its portfolio are the UK North Sea and the Gulf of Mexico where it believes mature assets will come up for sale as a result of the wave of mega-mergers sweeping the oil industry.
A rights issue would allow Enterprise to capitalise on its rising share price, which has increased by more than a third since the failure of the Lasmo talks on the back of strengthening oil prices. The shares now stand at 482.5p, just below their high for the year.
Pierre Jungels, the chief executive of Enterprise, has briefed institutional shareholders on the group's expansion plans. He said he had received a favourable response to the idea of a capital raising exercise provided any asset purchase adds value to the group. Enterprise is valued at pounds 2.4bn against Lasmo's market capitalisation of pounds 2.23bn. A pounds 300m rights issue would lift Enterprise comfortably ahead of its rival.
Mr Jungels believes there is scope for deals in the Gulf of Mexico, pointing to the recent $700m purchase of some of Shell Oil's interest in the area by the independent US oil exploration company Apache.
Enterprise executives emphasised, however, that a rights issue was not imminent, and said the focus of the group's activities in the short term would be to increase the level of reserves in its existing fields. Capital expenditure this year will be pounds 380m including pounds 90m on exploration and appraisal.
Enterprise hopes to be able to book an extra 500 million barrels of oil from its interests in the Llano field in the Gulf of Mexico, Corrib in Ireland and Skarv in Norway. This would take the group's proven and probable reserves up to 1.7 billion barrels of oil equivalent.
The group is also optimistic about the prospects for its low-cost Italian fields where the cost of production is just $6 a barrel. Output is expected to rise from 9,000 barrels a day at present to 150,000 barrels by 2002.