Abstract: Aiming at the complicated phase distribution of Ordovician reservoirs in Fault F$_{\rm{{Ⅱ}}}$21 of Tazhong Uplift, we make a comprehensive analysis of tectonic analytical geochemistry, and find out that the plane distribution of oil and gas physical properties such as oil density, gas drying coefficient, gas oil ratio, etc. is closely related to strike-slip fault segment structure, that condensate gas reservoir develops in the north of the wing tail structure zone, and that volatile oil reservoir and crude oil reservoir develop successively in the south area. The crude oil in the F$_{\rm{{Ⅱ}}}$21 fault is the same as that of the northern depression Fuman and Shunbei areas, mainly from Lower Cambrian source rocks. The maturity of crude oil decreases from north to south along the fault zone. Natural gas in the north of the fault zone is mainly crude oil cracking gas, and in the central and southern parts mainly kerogen cracking gas. The Ordovician reservoir in the F$_{\rm{{Ⅱ}}}$21 fault zone underwent multi-stage oil and gas injection, and the wing tail graben site was a favorable filling point for oil and gas, and the strong charging and transformation of pre-salt crude oil cracking gas in the Himalayan period was an important reason for the formation of condensate gas reservoir in the northern part of the fault zone. Affected by the paleostructural, the oil resources generated in the Late Caledonian and Late Hercynian periods were mainly accumulated in the southern nose uplift area of the wing tail graben structure.

Key words: oil and gas reservoir phase, strike-slip fault, wing tail structure, evaporative fractionation, Ordovician, Tazhong Uplift