北羌塘凹陷重力地震联合反演预测深部油藏  

Seismic-gravity Inverse Modeling and Deep Oil-reservoir Prediction of Northern Qiangtang Depression

作　　者：吴珍汉[1] 宋洋[1] 赵珍[1] WU Zhen-han;SONG Yang;ZHAO Zhen(Chinese Academy of Geological Sciences,Beijing 100037)

机构地区：[1]中国地质科学院,北京100037

出　　处：《地球学报》2021年第1期1-8,共8页Acta Geoscientica Sinica

基　　金：中国地质调查局地质调查项目“羌塘盆地油气地质构造保存条件研究”(编号:1212011221111)和“中国大地构造演化和国际亚洲大地构造图编制”(编号:DD20190367)联合资助。

摘　　要：羌塘盆地北部布格重力异常对深部结构和密度变化反应敏感,密度较低的深部油储能够导致布格重力显著减小,密度较高的深部玄武岩能够引起布格重力明显增加。基于野外观测和钻探标定形成二维地震反射解释剖面,以岩石地层的几何参数和密度为约束,建立羌塘盆地北部正反演模拟初始模型;采用Model Vision软件,通过人机交互反复试算,拟合布格重力异常,进行重力-地震联合反演。结果表明,北羌塘凹陷南部龙尾错—阿木错布格重力低值异常区,中侏罗统布曲组中上部发育厚层油储,平均埋深~1700 m,厚度~480 m,密度2.48 g/cm^3,含油率~10%,对应布格重力变化为-8 mGal;白滩湖地区三叠系顶部发育透镜体状玄武岩,埋深5800~6300 m,对应布格重力变化变化为+2 mGal。根据布格重力异常及重力-地震联合反演,预测北羌塘凹陷龙尾错—阿木错地区深部发育厚达数百米的油藏,具有发现超大型油田的勘探前景。Bouguer gravity anomaly is sensitive to deep structure and density change in northern Qiangtang basin.Deep oil reservoir of lower density may reduce Bouguer gravity,and deep basalt of higher density may increase Bouguer gravity.The initial model was constructed for northern Qiangtang basin by geological interpretation of the 2-D seismic reflection profile after field mapping and deep drilling,which was further constrained by geometric parameter and density of strata and rocks.Numerical simulation and progressive fitting of gravity data in a human-computer interaction mode were carried out by using the software Model Vision.It is revealed that the Bouguer gravity anomaly from Longweico to Amuco is most likely derived from deep oil storage as thick as 480 m of the Middle Jurassic Buqu Formation in Northern Qiangtang Depression(NQD).The density,oil content and average depth of the oil storage are 2.48 g/cm^3,~10%and~1700 m,respectively.Such a deep oil storage leads to Bouguer gravity anomaly of-8 mGal in southern NQD,and Upper Triassic basalt at the depths of 5800~6300 m yielded Bouguer gravity anomaly of+2 mGal in Baitanhu area,northern NQD.It is further predicted that a deep oil reservoir with thickness of hundreds of meters exists in the Longweico–Amuco area,and super-large scale oil fields might be discovered in southern NQD.

关 键 词：重力异常 联合反演 深部油储 油藏预测 羌塘盆地 

分 类 号：P631.8[天文地球—地质矿产勘探]