"petroleum reservoirs" refers to underground areas or rocks that contain oil or natural gas. These reservoirs are like storage spaces where these fossil fuels are trapped and can be extracted for use. Full definition
Getting more oil out of the ground, in the Jilin or Shengli petroleum reservoirs for example, could help defray the cost. (scientificamerican.com)
Taxonomic study of aerobic thermophilic bacilli: descriptions of Geobacillus subterraneus gen. nov, sp. nov. and Geobacillus uzenensis sp. nov. from petroleum reservoirs and transfer of Bacillus stearothermophilus, Bacillus thermocatenulatus, Bacillus thermoleovorans, Bacillus kaustophilus, Bacillus thermodenitrificans to Geobacillus as the new combinations G. stearothermophilus, G. thermocatenulatus, G. thermoleovorans, G. kaustophilus, G. thermoglucosidasius and G. thermodenitrificans. (jgenomics.com)
Oil platforms over major petroleum reservoirs may house hundreds of staff members who live and work on the rig for weeks or months at a time. (waterencyclopedia.com)