Oil and gas shows are common in the Ordovician carbonates in Tarim Basin

but few oil and gas fields (reservoirs) have been found. Based on the current Ordovician oil and gas fields (reservoirs)in Tarim Basin

summarizing the hydrocarbon accumulation patterns and main controlling factors of enrichment is helpful to identify potential exploration target areas. According to the analysis of the Ordovician geology conditions

reservoir types

sealing conditions and petro-leum system (source rocks

the main hydrocarbon generation and expulsion period

petroleum system division)

we analyzed the areal and lateral distribution characteristics of the Ordovician reservoirs. The results show that fractured-vuggy carbonate reservoir is the main reservoir type of the Ordovician in Tarim Basin

which are characterized by large scale continuous distribution or zonal distribution. In combination with the previous understandings

we summarized the regularity of the Ordovician carbonate reservoirs in Tarim Basin: fractured-vuggy karst reservoirs that matched well with hydrocarbon generation and expulsion period and were development on paleo-uplifts and paleo-slopes

and/or fractured-vuggy carbonate reservoirs of multiple origins that were controlled by deep faults are characterized by large scale hydrocarbon enrichment and the development of reservoirs is the key factor controlling differential hydrocarbon accumulation. It is proposed to understand the hydrocarbon accumulation process from a dynamic perspective and to identify carbonate exploration targets via dialectical thinking. According to the comprehensive analysis

the deep interval of the Ordovician in Tahe oilfield and the Ordovician in south Shunnan-Gulong area are the most favorable target for discovering large and medium sized gas fields (reservoir).