济阳坳陷东营凹陷北带丰深1井区深层沙四下古油藏与天然气成因

A fossil oil-reservoir and the gas origin in the Lower Sha-4 Member of the Well Fengshen-1 area,the North Dongying zone of the Jiyang Depression

李延钧 宋国奇 李文涛 郭瑞超 杨显成 陈义才 罗文军

LI Yan-Jun SONG Guo-Qi LI Wen-Tao GUO Rui-Chao YANG Xian-Cheng CHEN Yi-Cai LUO Wen-Jun-

济阳坳陷东营凹陷北带丰深1井区深层古近系沙四段下亚段以产出凝析油气为特征。根据天然气烃类气体组成、氮气含量、气体碳同位素、储层显微荧光薄片观察与测试结果以及热模拟实验结果综合分析,丰深1井区天然气属于原油裂解气,且储层孔隙大量分布热蚀变焦沥青。结合储层地温史和烃源岩生烃史,证实该区深层沙四下砂砾岩体存在古近纪末期(Es1末)古油藏,并在新近纪明化镇组沉积期至今(Nm—Q)因热力作用发生裂解,形成现今的深层凝析气藏。同时发现,在古油藏边缘,如丰深3井区存在源岩干酪根裂解与原油裂解成因的混合气;储层大量微观泄压缝的存在是凝析气藏保持正常压力系统的主要原因。

The deep interval of Lower Sha-Member 4 is characterized by producing condensate oil and gas in the Well Fengshen-1 area,the North Dongying zone,Bohai bay Basin.According to a comprehensive analysis of hydrocarbon gas composition,nitrogen content,gas carbon isotope,microfluorometric reservoir section and thermal simulation experiment,it is revealed that the gas in this area belongs to a type of crude-cracked gas,and that pyrobitumen generated by thermal alteration occurs widely in the reservoir pores.In combination with the geothermal history of the reservoir rocks and hydrocarbon generation history of the source rocks,it can be verified that a latest Paleogene(Es1)fossil oil-reservoir existed in the deep Sha-Member 4 sandstone-conglomerate body,the oil in which was thermally cracked from Neogene Minghuazhen to the present time(Nm-Q),resulting in the formation of a deep condensate gas reservoir.It is also found that a type of gas mixed by source-kerogen-cracked gas and oil-cracked gas occurs along the fossil oil-reservoir margin,such as the Well Fengshen-3 area,and that a lot of releasing microfractures in the reservoir rocks are the main factor to maintain a normal pressure system in the condensate gas reservoir.

10.11743/ogg20100206