海拉尔盆地贝尔凹陷埋藏沉降史

为揭示贝尔凹陷内的沉降抬升差异,利用该地区钻井取得的地层厚度、时代、岩性、密度、孔隙度等信息,根据其次级凹陷构造特征,选取五口代表井进行回剥分析,绘制贝尔凹陷砂岩孔隙度与深度关系曲线,并给出沉降史。结果表明：贝尔凹陷砂岩原始孔隙度为50%,压实系数为0.78 m-1。五口井共性显示,贝尔凹陷沉降史整体可分为n1、n2、d1和d2的快速沉降期（140.0～125.0 Ma）、尹敏组的持续沉降期（125.0～105.0 Ma）、抬升剥蚀期（105.0～99.0 Ma）和青元岗组的缓慢沉降期（70.6～65.0 Ma）四个阶段。贝尔凹陷整体底界的古构造演化具有相似性和继承性。五口井差异性显示,贝尔凹陷中西部含油气多、沉降速率大,其他地区含油气少、沉降速率小,沉降速率是影响油气富集的因素之一。该研究为进一步分析凹陷内油气富集条件提供了依据。

Burial and subsidence history of Beier Depression in Hailaer Basin

Aimed at revealing uplift and subsidence differences occurring in Beier Depression, this paper describes the backstripping analysis of 5 typical wells located in Beier Depression, based on the in- formation, such as the stratigraphic thickness, ages, lithosphere, porosity, and seismic section, presents the relation curves of porosity changing with depth, and provides the sedimentary and subsidence history. Beier Depression has the primary porosity of 50% and compacting factor of sandstone 0.78 m-~. The subsidence history of Beier Depression falls generally into four stages： quick subsidence （140. 0 - 125.0 Ma）, continued subsidence（ 125.0 - 105.0 Ma）, uplift erosion （ 105.0 - 99.0 Ma） and slow subsidence（70.6 ~ 65.0 Ma）. The whole lower boundary tectonic evolution of Beier Depression shows the similarity and inheritance. The differences among 5 wells show that Beier Depression is marked by central western areas rich in oil and gas and vulnerable to more rapid subsidence, and punctuated by other areas found to have less oil and gas and show a slower subsidence. It follows that settlement rate is one of the factors influencing the oil and gas enrichment. The study provides a basis for the further research on con- ditions for oil enrichment.