江汉盆地沙市组蒸发岩沉积充填与成藏特征

由于构造和气候因素的差异，江汉盆地沙市组的上段和下段具有不同的沉积充填特征。沙市沉积早期为弱断陷构造背景，湖盆彼此分隔闭塞，受中、亚热带干旱气候影响，在断陷区形成盐湖相蒸发岩充填，表现为浓缩型沉积序列特征；沙市晚期为拗陷型构造背景，盆地持续下降，湖盆范围扩大，湖水逐渐淡化，形成三角洲—咸水湖相充填，表现为淡化型沉积序列特征。盆地的沉积充填特征控制了蒸发岩地层生、储、盖等成藏要素的差异，表现为不同的油气成藏模式。浓缩型沉积序列的蒸发岩及盐间泥岩提供了烃源岩条件，盐间的膏岩、泥岩提供储层条件，蒸发岩提供盖层条件，为盐间非砂岩油气成藏模式；淡化型沉积序列的湖相泥岩及前三角洲泥岩提供烃源岩条件，三角洲前缘各微相砂体提供储层条件，蒸发岩提供盖层条件，为盐下砂岩油气成藏模式。

SEDIMENTARY FILLING CHARACTERS AND RESERVOIR PATTERN OF THE SHASHI FORMATION IN JIANGHAN EVAPORATE BASIN

Different sedimentary filling characters generated by the differences in tectonic evolution and climatic condition between upper and lower member in Shashi Formation，Jianghan Basin.Under weak fault depression tectonic condition and arid subtropical climate during depositional period of the lower member，evaporites were deposited in separated salt-lake and presented a concentrated sedimentary sequence.However，under depression tectonic condition during the depositional period of the upper member，sedimentation of delta-lake facies filled the enlarged basin and presented a desalted sedimentary sequence，which led to different source-reservoir-seal combinations and hydrocarbon accumulation modes.In concentrated sedimentary sequence，evaporate rocks and mudstone within salt-layers provide source condition，the gypsum rocks and mudstone within salt-layers provide reservoir condition，and the evaporate rocks provide seal condition.In desalted sedimentary sequence，mudstone in lacustrine facies and pro-delta micro-facies provide source condition，the different channel sandstone provide reservoir condition，and the evaporite rocks provide seal condition.