Complex sentence: Guneshli offshore oil fields, which supplies 80% of the country's oil production, and the Shah Deniz gas field, and develops the Shafag-Asiman complex of offshore geological structures.
Split into simpler sentences: Guneshli offshore oil fields, which supplies 80% of the country's oil production, and the Shah Deniz gas field. It also and develops the Shafag-Asiman complex of offshore geological structures.