四川盆地龙马溪组上部气层页岩气差异富集主控因素OA

The upper gas layer of the Longmaxi Formation in the Sichuan Basin represents a crucial strategic replacement field for shale gas exploration.Based on biostratigraphic methods,through systematic fine correlation of graptolite-bearing shale intervals and analysis of drilling results from typical wells,the main controlling factors for the differential enrichment and the distribution patterns of favorable areas of the upper Longmaxi gas layer have been clarified.The results show that:(1)The development of the Aeronian LM7-LM8 graptolite zones and their associated high TOC shale is a prerequisite for the enrichment of the upper Longmaxi gas layer.In the Jiaoshiba area,successful wells are predominantly located in structural highs where this specific shale unit,characterized by relatively high TOC,porosity,and gas content,is developed.In contrast,poorer results in areas like Changning and Weiyuan are primarily due to the absence or inferior quality of this shale unit.(2)Structural morphology exerts a significant control on the enrichment of shale gas in the upper gas layer.Due to higher horizontal permeability compared to vertical permeability,gas tends to migrate updip.This leads to higher enrichment degrees in structural highs of anticlines(e.g.,Jiaoshiba),while synclines(e.g.,Wulong)and anticlinal limbs show lower enrichment levels and generally poorer exploration results.Based on the identified controls,it is recommended to enhance research on the development characteristics of the LM7-LM8 organic-rich shale,and conduct systematic evaluation and target optimization for the upper gas layer integrating actual drilling results.These findings provide a geological basis for optimizing favorable areas and exploration deployment of the upper Longmaxi gas layer in the Sichuan Basin.