基于三维地震解释资料,对尼日尔三角洲东部M区块AE斜向背斜的形成机制和生长过程及其伴生断裂系统的形成演化过程进行剖析。研究表明,中新世中后期的H4—H6地层沉积时期为初始褶皱逆冲阶段,AE背斜区为斜向伸展断层控制的半地堑,其成因主要是局部的初始差异褶皱逆冲作用下形成的斜向伸展变换构造。该时期的差异滑动也控制了撕裂断层的形成。在中新世晚期到上新世的H1—H4地层沉积时期,大规模褶皱逆冲作用下的收缩变形强度差异导致先存伸展半地堑发生斜向构造反转而形成背斜,背斜在持续生长过程中规模逐渐变大,顶部也逐渐发生迁移。形成的断裂系统有差异逆冲伴生的少量撕裂正断层和由背斜翼部斜坡倾角诱导重力驱动的多米诺正断层。在更新世到全新世的H0—H1地层沉积时期,背斜生长停止,进入后褶皱逆冲演化阶段,局部重力回返垮塌、局部差异滑动与再活动的先存正反转断层耦合控制共轭断层的形成与分布。斜向背斜的反转成因机制及相关断裂系统演化的研究可为揭示其油气富集和油水分布规律提供指导。图10参32
Based on the three-dimensional seismic interpretation data, this paper analyzed the formation mechanism and the growth process of the oblique anticline AE of the M region of the eastern Niger Delta, as well as the evolution process of the associated fault systems. The study results show that the stratigraphic sedimentary period between reflector H4-H6 of the middle and late Miocene was the initial fold-thrust stage, the anticline AE was a half-graben controlled by oblique extensional faults derived from the oblique extensional transfer structure formed by local initial differential fold-thrusting. At the same time the tear faults developed as a result of the differential sliding. During the stratigraphic sedimentary period between reflector H1-H4 of the late Miocene to Pliocene, the large-scale folding and thrusting occurred, differential contractional deformation resulted in the pre-existing extensional half-graben became AE anticline by oblique tectonic inversion, then the anticline grew continually and the crest of the anticline migrated gradually. The newly formed fault systems consist of a small number of associated tear-normal faults caused by differential thrusting and gravity-driven domino normal faults predominantly induced by the slope inclination of the anticline limb. During the stratigraphic sedimentary period between reflector H0-H1 of the Pleistocene to Holocene, as the growth of the anticline ceased, the area entered post-fold thrusting stage. The formation and distribution of conjugated faults were controlled by the local gravity return collapse, local differential sliding and reactivation of pre-existing positive inversion faults jointly. The research results of genetic mechanism of the oblique inversion anticline and evolution of associated faults are helpful to reveal the key factors controlling the accumulation and distribution of oil and gas.
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