四川盆地蓬莱地区灯影组二段输导层古孔隙度演化及成藏期分布特征

Paleo-porosity evolution and its distribution in carrier bed of the second member of Dengying Formation during hydrocarbon accumulation stages, Penglai area, Sichuan Basin

油气成藏过程是地质历史时期的事件之一,恢复输导层在关键成藏阶段的孔隙度可以帮助定量恢复成藏期的地质条件,更好地认识油气成藏过程。综合利用薄片鉴定、矿物微区U-Pb测年、流体包裹体分析及岩石物性测试等多种技术方法,建立了四川盆地蓬莱地区灯影组二段输导层成岩演化序列,并以“成岩作用演化序列—油气成藏期”时间耦合关系为条件,利用输导层岩石相孔隙反演回剥的方法恢复了各关键成藏阶段灯二段输导层的古孔隙度特征。利用丰富的岩心实测孔隙度数据来标定测井孔隙度,而后根据波阻抗与孔隙度关系,通过三维地震波阻抗反演结果转化为现今孔隙度值,并利用古孔隙度与现今孔隙度关系恢复灯二上亚段输导层各关键成藏期古孔隙分布特征,以明确输导层在关键成藏阶段的输导能力。古油藏期和裂解成气期的输导层古孔隙度比现今孔隙度略有增大,第一次调整期和第二次调整期与现今孔隙度基本一致。在各个关键成藏期,灯二上亚段3小层的储集空间发育程度最高,高孔隙度分布范围大,油气输导性能好,有利于油气大规模聚集成藏。灯二上亚段2小层的储集空间欠发育,高孔隙度呈零星分布,油气输导性能下降,不利于油气大规模聚集成藏。

The hydrocarbon accumulation processes an event in geological history,and restoring the porosity of the carrier formation in key stages of accumulation can help quantitatively restore the geological conditions during the accumulation period and better understand the process of oil and gas accumulation.By comprehensively utilizing various technical methods such as thin section identification,micro area U-Pb dating,fluid-inclusion analysis,and rock property testing,the diagenetic evolution sequence of the second member of Dengying Formation(Deng 2 Member)carrier formation in the Penglai area has been established.Based on the time coupling relationship between the“diagenetic evolution sequence and hydrocarbon accumulation period”,the paleoporosity characteristics of the Deng 2 Member carrier formation at each key accumulation stage have been restored using the method of pore inversion and stripping.By using abundant core measured porosity data to calibrate logging porosity,and then based on the relationship between wave impedance and porosity,the 3D seismic wave impedance inversion results are converted into the current reservoir porosity values,and the relationship between paleo-porosity and current porosity is used to restore the distribution characteristics of ancient pores in each key reservoir formation stage of the upper member of the Deng 2 Member,in order to clarify the transport capacity of the carrier formation in the key reservoir formation stage.The porosity of the paleo oil reservoir period and the cracking gas generation period slightly increased compared to the current period,and the first and second adjustment periods were basically consistent with the current porosity.In each key reservoir formation period,the porosity in the upper and middle parts of the Deng 2 Member is developed,with a large distribution range of high porosity and good oil and gas transport performance,which is conducive to large-scale oil and gas accumulation and accumulation.The porosity in the lower part of the upper section of Deng 2 Member is underdeveloped,and high porosity is scattered,resulting in a decrease in oil and gas transport performance,which is not conducive to large-scale hydrocarbon accumulation.