Differential Fault Control Characteristics in Y Region of Xihu Sag in the East China Sea Basin
To systematically analyze the spatial-temporal differences in fault activity and its control on hydrocarbon accumulation in Block Y of the Xihu Depression,relied on detailed interpretation of three-dimensional seismic data.The area was divided into zones based on structural characteristics.Techniques such as balanced cross-section and fault activity rate methods were employed,combining qualitative and quantitative approaches to explore the differential evolutionary characteristics of the fault system.This led to an analysis of the spatial-temporal arrangement of faults relative to hydrocarbon accumulation,identifying areas with a higher potential for oil and gas enrichment.The results indicate that the Neogene fault system on the western slope of the Xihu Depression is characterized by deep and shallow stratification,as well as north-south zonal differences.Block Y extensively develops four groups of extensional faults,with deep faults being larger but fewer,and shallow faults being smaller but denser.The northern K structure is primarily defined by step faults,exhibiting a simpler structural style,whereas the southern W structure is more complex,characterized by fault troughs interspersed with low-convex boundary faults.The fault evolution underwent a rift phase,rift-thrust transition phase,and sag-reversal phase,with the rift phase showing the most intense fault activity,reaching maximum rates of 38.7 m/Ma.Overall,the evolution displays early strength diminishing over time,stronger activity in the east than the west,and stronger in the south than the north.Massive development of high-quality hydrocarbon source rocks in the Gem and Pinghu formations within Block Y,combined with short-distance convergent ridges and long-term active NNE-oriented faults,leads to hydrocarbon accumulation in various fault-related traps.Based on this,it suggests that the advantageous convergent ridges and NEE-oriented fault zones,which possess early intense activity and lateral sealing in the later stages at the nose and fault-lithology traps,are considered prime enrichment areas.The east side of the W structure's low rise near the depression zone is identified as the most favorable production area.
the East China Sea Basinstretch fracturefracture characteristicsdifferential evolutionfracture control cacheconverging ridges
万方数据
维普
