(Adds details on Mainline bidding, throughput, gas line explosion)
Aug 2 (Reuters) - Canadian pipeline company Enbridge Inc said on Friday it would invite bids for contracted space on its Mainline system, in the face of opposition from some oil shippers who worry the changes could disadvantage small producers.
The Mainline ships 2.85 million barrels per day of crude from Alberta in Canada to the United States, making it Canada's biggest network of export pipelines.
Currently, shippers nominate barrels on a monthly basis, but Enbridge is proposing to switch to a system in which shippers sign up for long-term fixed volume contracts for up to 20 years.
Producers, midstream companies and refiners will be able to bid for capacity. But some shippers are concerned that smaller Canadian producers will be elbowed out by large refiners like BP Plc and ExxonMobil in the U.S. Midwest as they snap up the bulk of space.
Separately, the company said its adjusted earnings rose to C$1.35 billion ($1.02 billion), or 67 Canadian cents per share, in the second quarter ended June 30 from C$1.09 billion, or 65 Canadian cents per share, a year earlier.
Analysts on average were expecting 59 Canadian cents per share, according to IBES data from Refinitiv.
The company said it transported 2.66 million barrels per day through its Mainline system in the second quarter, up from 2.64 million barrels per day a year earlier.
It also said an explosion at one of its natural gas lines in Moreland, a community about 40 miles (65 km) south of Lexington, Kentucky, which killed one and ignited homes, will not be returned to service until it is "absolutely safe".
($1 = 1.3220 Canadian dollars) (Reporting by Debroop Roy in Bengaluru and Nia Williams in Calgary; Editing by Arun Koyyur)