Mexico’s oil regulator voted Aug. 4 to sweeten rules for the second phase of the country’s historic oil field auction, such as lowering a required corporate guarantee to lure more bidders and boost lagging crude output.

In the first concrete step of a sweeping energy sector overhaul, last month’s inaugural oil auction covering 14 shallow-water exploration blocks failed to meet the government’s modest expectations when only two were awarded.

The auction’s next phase consists of five shallow-water production-sharing contracts that cover blocks containing proven reserves and are set to be awarded on Sept. 30.

A corporate guarantee—money a consortium has to put up in case of an accident—was set at 18 times the value of each contract’s minimum work commitment.

That translates to about $2 billion, Juan Carlos Zepeda, president of oil regulator CNH told Reuters, well below the $6 billion required by the earlier version of the rules.

Companies can still satisfy the corporate guarantee requirement via an open-ended parent company guarantee, an option available in the earlier version.

The changes are aimed at luring more bidders and several were made to address perceived flaws in the July auction.

“We are presenting new alternatives, a package of guarantees that is more open, with new instruments that seek flexibility,” Zepeda said shortly before the new rules were formally adopted by the seven-member CNH.

The commission also tweaked a $2.5 million bid security guarantee which can now be applied to all blocks a bidder wins rather than just one.

The contract's adjustment mechanism was also modified to allow oil companies a higher upside if the contract’s profitability rises.

If a contract is revoked for willful misconduct, the updated rules specify that companies can keep assets like a mobile jackup rig that were not previously claimed as recoverable expenses, Zepeda said.

The CNH also added a required insurance policy to each contract of at least $1 billion to cover possible spills or other industrial accidents per activity, like the drilling of a new well.

Companies must also have a service provider specialized in spill containment for each block.

Consortia will also be allowed to restructure as late as one week before the September auction, if the group's operator pulls out.

Final contract and bidding terms will be published on Aug. 21.