塔中4油田石炭系各油组油气性质差异及成因机制

Property differences and genetic mechanisms of hydrocarbon in each oil unit of the Carboniferous in Tazhong-4 oilfield

姜振学 杨俊 庞雄奇 杨海军 李卓

Jiang Zhenxue Yang Jun Pang Xiongqi Yang Haijun Li Zhuo

塔中4油田石炭系3个油组表现为上、下油,中间气的特征.塔中4石炭系油气藏以两期成藏为主,早期以油充注为主,晚期以天然气充注为主.通过分析不同时期泥岩抗张强度、流体剩余压力和断面正压力大小及其相互关系,结合油气充注时间认为:晚海西期沟通石炭系3个油组的断裂具有开启性,油气主要充注在C和C油组;喜马拉雅期C油组剩余压力大于断面正压力,使得后期充注的天然气主要充注到C油组,同时由于C油组上部泥岩厚度较大,调整到C油组的天然气不能突破断裂向上调整到C油组.在塔中4石炭系成藏过程分析的基础上,预测塔中中央断垒带西段是寻找C和C调整型油藏的有利区.

The three oil units of the Carboniferous in Tazhong-4 oilfield feature in a hydrocarbon distribution of gas-bearing formation being clipped between oil-bearing formations.The Carboniferous reservoirs in Tazhong-4 oilfield were formed mainly in two stages,the earlier oil-charging stage and the later gas-charging stage.By combining the oil and gas charging times with the analysis of mudstone compressive strength,fluid residual pressure and normal pressure on fault surface in different periods,and the relationship among these three parameters,it is suggested that the fault cutting through the three units were open in the late Hercynian,leading to accumulation of oil and gas in the Unit C and C;while in the Himalayan period,fluid residual pressure of Unit C was greater than the normal pressure on fault surface,resulting in late accumulation of gas in the Unit C rather than Unit C.Moreover,the gas charged in C unit could not migrate upward through the fault into Unit C due to the large thickness of the upper shale interval.The analysis of the whole process of the pooling in the Carbonife-rous reservoirs in Tazhong-4 oilfield indicates that the western section of the central fault-horst zone is favorable for finding secondary oil pools in Unit C and C.

10.11743/ogg20080202