John Hofmeister, president of Shell, remarked that "as repetitive and uninteresting as it may sound, the fundamental laws of supply and demand are at work".
However, Democratic members of the committee said this explanation did not suffice and prices needed to be controlled.
"We need to get prices under control ... we can only conclude that the oil markets have failed," said Herbert Kohl, a senator for Wisconsin, said.
Republican senators also condemned the companies' profits, with Arlen Specter of Pennsylvania noting that Exxon's annual profits increased in the past five years from $11.5bn to $40.6bn.
Specter said there was no explanation for "why profits have gone up so high when the consumer is suffering so much".
J Stephen Simon, executive vice-president of Exxon Mobil, said profits have been huge "in absolute terms'' but must be viewed in the context of the large scale of the industry.
He said high earnings are needed "in the current up cycle'' to pay for investments in the long term when profits will be down.
The companies, also including Chevron and BP, earned a combined total of $36bn in the first quarter of 2008.
During the hearings some Democratic senators tied the companies' record profits to the Bush administration's support of the oil industry.
"The president once boasted that with his pals in the oil industry, he would be able to keep prices low," said Patrick Leahy, senator for Vermont and chairman of the judiciary committee.
"Instead, it is his pals in the oil industry who have benefited."
Earlier this month, Democratic congress members unveiled a new energy package that would revoke $17bn in tax breaks extended to big oil companies.
It would also impose a 25 per cent windfall profits tax on firms that do not invest in new energy sources.
Oil executives criticised the proposals as "counterproductive".
"We urge you not to pass measures ... such as tax increases that diminish our investment capabilities, reduce the attractiveness of high-cost domestic production, or disadvantage US oil and gas companies," said John Lowe, executive vice-president of ConocoPhillips.
Oil companies also asked the committee for an expansion of their rights to explore US lands and offshore regions for oil, a move strongly condemned by environmental activists.
Oil prices have soared in recent years following rising demand in China and other emerging economies.
Last week, Saudi Arabia rejected a US appeal to increase oil production, saying they had already done so by an extra 300,000 barrels per day and were meeting existing demand.