Oil refinery at Baku (1890). In 1806, the Russian empire occupied Baku Khanate and took monopolistic control of oil production. Later exclusive rights to produce oil were given to individuals, thereby creating the Persian otkupchina lease system.The main oil-producing regions were located near Baku at Sabunchy, Surakhany and Bibi-Heybat. Until the beginning of the 20th century, the Sabunchi region produced 35% of Baku's oil, and the Bibi-Heybat region produced 28%, followed by the Romany and the Balakhany regions. Most oil production came from oil gushers in the early days, although this was a very uneconomical and environmentally-harmful process. However, the share of blowout production in the total decreased as the equipment improved. In 1887 blowouts had accounted for 42% of recovered oil, but by 1890 their prevalence decreased to 10.5%.