The characteristics and distribution of the hydrocarbon reservoirs in the Carboniferous Karashayi Formation, Tahe Oil Field, Xinjiang

The Carboniferous hydrocarbon reservoirs in the Tahe Oil Field, Xinjiang are arranged into the interbedded sandstone and mudstone horizons in the Karashayi Formation. The hydrocarbon reservoirs are characterized by deep burial, small thickness of individual beds, and laterally discontinuous and disconnected strata. The sandstone and mudstone horizons in the Carboniferous Karashayi Formation may be divided, from top to bottom, into five oil formations, which have recorded a complete transgression-regression cycle:the Ⅴ and Ⅳ oil formations were developed during the early transgressions, followed by Ⅲ, Ⅰ and Ⅱ oil formations during the later regressions.The spatial distribution of the oil reservoirs indicates that the oil and gas accumulations are mostly controlled by faults and structural-lithologic traps and concentrated in the structural highs and composite structural-lithologic traps below unconformities.