The BTC pipeline is used to export oil from the Azeri, Chirag and Guneshli (ACG) oilfields operated by BP.
Azerbaijan's total oil exports during the January-May period totalled 16.536 million tonnes, 81.1% of which was exported through the BTC.
Azerbaijan also exports oil via Russia through the Baku-Novorossiisk pipeline and via Georgia by rail and through the Baku-Supsa pipeline.
Oil from Kazakhstan, Turkmenistan and Russia is also exported through the BTC pipeline, although Turkmenistan diverted its flows through the BTC to a Russian port earlier this year.
Azeri oil exports via the BTC rose 0.2% in 2018 to 33.827 million tonnes.
Azerbaijan's total oil exports last year amounted to 41.490 million tonnes.