The two Iranian F4 fighter-bombers came howling up the Tigris Rivers from the south with Baghdad's Dora oil refinery clearly in their sight.

But before the two low-flying jets could reach it, a volcano of Iraqi antiaircraft fire erupted over the riverside refinery. Choosing not to risk the flak, the two Iranian jets jettisoned their bombs prematurely on an oil tank farm just south of the refinery and darted up the Tigris through the heart of the Iraqi capital before veering east toward home unscathed.

Though the jets missed the Baghdad oil installation -- he last refinery in Iraq still not hit by the Iranians -- the twin columns of black smoke that welled up in the pale blue autumn sky earlier this week were grim reminders of how the 25-day-old conflict with Iran has become a war against oil installations more than a war between armies in the field.

The broad strategic design behind Iraq's relentless drive toward Abadan -- one that crops up in conversations with Iraqi officials here and closer to the scene in Basra -- seems to be a desire to cripple Iran as a gulf oil power and put the economy down long enough for President Saddam Hussein to consolidate his leadership position in the area.

Behind that aim is an old score that Iraq wants to settle with Iran's Persians over sovereignty in the Shatt-al-Arab waterway that is vital to both nations and an urge to humiliate Ayatollah Ruhollah Khomeini's government and its pretentions to paramountcy in the gulf.

Getting control of the Shatt-al-Arab and regaining border territory given to Iran in a 1975 Iranian-Iraqi treaty were important Iraqi objectives at the outset of the war. But to outside observers, it looks like Hussein achieved these goals in the first three weeks of fighting. Now he appears intent on gaining enough of a bargaining advantage to make forceful claims on the gulf islands of Abu Musa and the Greater and Lesser Tumbs, which once belonged to Arab gulf states but were occupied by Iran in 1971.

The ambitious Iraqi leader also can be expected to seek at least partial autonomy for the ethnic Arabs of Iran's oil-rich Khuzestan Province. Occupying large parts of the province, therefore, is bound to strengthen his hand on that issue. And striking at Iran's oil pipelines and refineries seems from this vantage point to be the least costly way of making that possible.

The trouble is that Iranian strikes against Iraqi oil treasures also seem in Tehran to be the least costly way of preventing it. When the war began last month, conventional wisdom was that the two countries, aware of the mutual vulnerability of the oil economies on which their futures depend, would refrain from attacking oil installations. But no sooner had the Iraqi and Iranian air forces exchange raids on air bases than they turned to the easier game of raiding oil refineries, pumping stations, pipelines and loading terminals.

Now the real cost, and implication, of this oil war will probably take years to assess.

Overnight the oil-hungry industrial world has been deprived of almost 4 million barrels of oil a day -- 2.8 million from Iraq, OPEC's second-largest exporter, and just under 1 million from Iran. The loss to the industrial world, however, has been nowhere near as great as that to the two belligerent OPEC partners, which, for the duration of the war and into the future, have lost their national incomes.

For Iraq, the loss has come to $84 million a day, or $3.5 million an hour. Iran, whose once vast oil production has shrunk drastically since the mullahs' revolution, is losing just over $20 million a day, a price its already shattered economy can ill afford.

Although it is unclear who struck the first blow against the oil industries, Khomeini's armed forces were clearly the most determined to smash their rival's oil economy the first week of the war. Iranian jets. U.S.-made F4 Phantoms and F5 Tigers, first hit the Shueiba refinery outside Basra, Iraq's largest such installation. They raided petrochemical plants and oil storage tanks nearby, as well as vast tank farms at A1 Faw, where oil is stored for exports through the gulf. Behind each raid, huge boiling clouds of black smoke were left smudging the sky.

More devastating to Iraq than the raids around Basra -- or later bombing attacks of oil fields and pumping installations at Kirkuk and Mosul in the north -- as Iran's attack on the third day of the war against the vulnerable oil export terminals of Khor al-Amaya and Mina al-Bakr perched on steel stilts far out in the gulf.

Instead of using planes, the Iranians launched their Navy against the two terminals, which pipe 2 million barrels a day to the outside world. Iranian gunboats blasted the terminals with surface-to-surface missiles, sending their crews jumping into the sea in water ablaze with burning oil.

Attacking oil installations, however, is a game that two can play and Iraq has played the game just as destructively as Iran.

Iran's mammoth oil complex at Abadan, on the exposed and disputed Shatt-al-Arab, was Iraq's first oil target, lying as it did in the immediate way of the Army moving into Iran. In 24 days of relentless artillery pounding, large parts of the refinery have been left a blazing inferno. Production has been lost for years to come. When coupled with possible losses from the other major Iranian refineries bombed at Tehran, Isfahan and Tabriz, the Abadan destruction has left Iran facing a cruel winter of heating oil and gasoline shortages.

In addition, the advancing Iraqi Army has tried to blow up the pipeline that normally carries crude oil north to Tehran, further mortgaging Iran's ability to get fuel for its Army and the residents of Tehran.

But Iran's worst long-term loss, experts here say, has been that of its huge, computerized oil loading terminal at Kharg Island, once able to ship 6 million barrels of oil a day to the outside world. It was hit by Iraqi bombers a day after Iran knocked out Iran's export terminals at Al Bakr and Al Amaya.

The big question being asked by oil experts now is just how serious the long-term damage to the oil installations is.

The air strikes have been dramatic, matched only by the shooting columns of fire and smoke that followed in their wake. But surprisingly, in Iraq at least, the damage seems to be somewhat less than meets the eye.

In most cases the Iranian raids have missed, either on purpose or by sheer ineptitude, the main cracking plants of the refineries they have tried to bomb, setting off spectacular by not overly damaging fires only in storage tank areas that can be quickly repaired.

There has been damage to pumping stations in Kirkuk and Mosul, but that is considered also easily reparable once the hostilities end. And the oil wells themselves are basically bomb-proof, so once the war ends, they can be brought back on stream.

Estimates about how long it will take to repair Iraq's oil installations vary. The most bullish predict say it will be a matter of weeks, though more realistic assessments tend toward three to six months. No one here, however, is prepared to be so optimistic about Iran.

Iraq also has a comfortable foreign exchange cushion of about $35 billion, according to Western economists. That will certainly allow it to weather the oil dislocations, even if they last a year, which is the most pessimistic estimate. Iran, with its reserves depleted, is not so lucky, and its economic recovery is expected to be much slower and more painful.