Abstract:

The characterization of faulted-karst reservoirs in the Shunbei area demonstrates well the important role played by strike slip faults in hydrocarbon accumulation.Based on the identification and division of the crystallization stages of the calcite veins in the Ordovician reservoirs at the north section of the Shunbei 5 fault belt, the hydrocarbon accumulation stages are determined through fluid inclusion analyses and the effect of strike-slip faults on hydrocarbon accumulation stages is revealed by fault zone activity analyses.The results show that there are three phases of calcite vein generation in the Ordovician reservoirs, of which the second phase was formed during the late Silurian.The development characteristics of bitumen and fluid inclusions in the reservoirs reveal two stages of oil charge, with the first stage presumably occurring (before the second phase of the calcite generation) in the late Caledonian and being destroyed later in the early Hercynian.The second stage from the late Hercynian to Indosinian (ca.260-230 Ma) is the main stage for hydrocarbon accumulation in the Ordovician faulted-karst.Fault zone activity analyses of the Shunbei 5 fault belt show a good correspondence between the activity times and the hydrocarbon charge and destruction stages, indicating that the strike-slip fault activities in the Shunbei area is the main factor controlling the hydrocarbon accumulation.

Key words: fluid inclusion, hydrocarbon accumulation stage, faulted karst, Shunbei area, Tarim Basin