塔西南地区石炭系卡拉沙依组成藏主控因素、成藏模式及区带评价OA

The Carboniferous Kalashayi Formation in the southwestern Tarim Basin is a key target for Paleozoic hydrocarbon exploration in the Tarim Basin.Exploration results currently show marked spatial differences.Several sizable hydrocarbon reservoirs have been discovered in the Bachu Uplift,demonstrating favorable exploration results,whereas only limited exploration breakthroughs have been achieved on the Maigaiti Slope,where explora-tion has reached a bottleneck.To clarify the mechanisms responsible for the differences in hydrocarbon accumula-tion conditions between the two areas and identify directions for future exploration,a systematic study of the accumulation conditions and play evaluation of the Kalashayi Formation was conducted.Source-rock analytical data from 12 wells,drilling,well-log,and mud-logging data from more than 30 wells,3D seismic interpretation results,and geochemical test data were integrated.The main factors controlling hydrocarbon accumulation were analyzed in terms of five aspects:source rocks,reservoirs,carrier systems,traps,and tectonic movements.Differentiated hydrocarbon accumulation models were established,and a multi-index evaluation system with block-specific weights was constructed to delineate favorable zones.Detailed seismic interpretation was also used to delineate traps and select favorable exploration targets.As indicated by the research results,hydrocarbon accu-mulation in the Kalashayi Formation is jointly controlled by source-rock supply,reservoir development,carrier systems,trap matching,and tectonic movements,and shows distinct spatial differences.Against the background of inherited paleo-uplift development,the Bachu Uplift is characterized by a structural-trap accumulation model involving a single phase of hydrocarbon generation and multistage tectonic adjustment.The Maigaiti Slope is con-trolled by secondary hydrocarbon generation and source-reservoir coexistence and is characterized by a near-source accumulation model in low-relief lithologic or structural-lithologic traps.The differentiated evaluation indi-cates that the area where the Yubei Fault Zone overlaps tidal-channel sand bodies in the eastern Maigaiti Slope is a Class Ⅰ favorable zone.Its overall score is 0.84 and decreases to 0.80 after barrel-effect correction.The eastern Bachu Uplift is a Class Ⅱ favorable zone,with an overall score of 0.76.A total of 13 favorable traps,covering an area of 147.85 km2,were delineated in the Yubei 3D seismic survey area,and three Class Ⅰ targets were selected.