U.S. to stop 33 exploratory rigs for 6 months

* 33 exploratory wells will stop operations for 6 months

* Affected companies may include Chevron, Shell, BP

* Plan calls for new blow out preventer, cementing rules

WASHINGTON, May 28 (Reuters) - Deepwater exploratory rigs affected by the Obama Administration’s crackdown on offshore drilling must halt operations soon and stay out of action for six months, according to government documents and officials.

The U.S. Interior Department released a 44-page safety report late Thursday with more technical details about the six-month ban in the wake of the BP oil spill.

The ban stops issuance of new exploratory drilling permits in deep water for six months and effectively idles operations of 33 deepwater exploratory rigs for the same period.

“Drilling operations should cease as soon as safely practicable for a six-month period,” the report said. Interior officials said they expect industry to move quickly to shut down the rigs safely.

Big offshore operators in the Gulf include BP Plc BP.L, Chevron CVX.N, Royal Dutch Shell RDSa.L and Petrobras PETR4.SA. Contractors that operate deepwater rigs in the Gulf of Mexico include Transocean RIG.N, Diamond Offshore DO.N, Ensco ESV.N and Noble Corp NE.N. For a factbox on contractors and operators of rigs in the Gulf of Mexico, please click on [ID:nN20182158]

BP, which has been struggling to plug the ruptured well gushing thousands of barrels of oil into the Gulf for weeks, is involved with at least four of these deepwater exploratory rigs.

Interior's drilling ban does not affect platforms beyond the exploration stage and already producing. BP's doomed Deepwater Horizon semi submersible, leased from Transocean Ltd RIGN.S, was an exploratory rig.

Operations on the Gulf’s deep sea exploratory rigs will cease pending findings and recommendations of the commission set up by U.S. President Barack Obama to determine the cause of the Gulf spill.

The six-month moratorium will block any new exploratory drilling permits in water depths more than 500 feet.

Any delays to future offshore development could have consequences for U.S. oil output, however. Energy consultants Wood Mackenzie previously estimated a six-month extension of the ban would delay 80,000 barrels a day in U.S. oil production that was expected in 2011.

In addition to the deepwater drilling ban, the report also outlined a number of potentially costly new safety standards companies will be required meet.

In particular, blow-out preventers on floating drilling operations will have to be certified and include two sets of blind shear rams. There will also be new design requirements for casing and cementing on wells.