Nigerian oil company NNPC is asking investors to bid to fix pipelines and depots serving its oil refineries, according to a document posted on its website on Tuesday.

Built in the 1970s, the pipeline network is crucial to getting crude oil to NNPC’s three refinery complexes, and moving the finished fuels to consumers.

But years of what NNPC described as “incessant” theft and vandalism, as well as simple ageing, have left the pipelines in need of extensive repairs.

The refineries themselves have run only sporadically, and NNPC shut them down earlier this year while they await repairs and upgrades. It said on Tuesday that those projects would be handled separately.

Nigeria, Africa’s largest oil exporter, has made producing its own fuels a core priority for years, but several efforts in recent years to revamp the refineries have failed, leaving it almost wholly reliant on imports.

Bidders for the projects would have to finance them independently and operate them for a “defined period” while they recovered investment costs, and were compensated for their work, with throughput tariffs, the document said.

It added that the new pipelines would need “intrusion detection” systems, in addition to deep burial, to stymie theft or vandalism. Submissions are due by Sept. 18.(Text, excluding headline, courtesy Reuters)