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龙门山中段山前构造三角楔变形特征及迁移规律
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Abstract:
龙门山位于青藏高原东缘与川西前陆盆地之间，其构造活动的复杂性、继承性和长期性使得龙门山山前油气勘探面临诸多挑战：山前地震资料信噪比低，构造圈闭落实差；冲断带内多期构造复合叠加，晚期构造对早期变形改造强烈；构造变形迁移规律复杂，这些都严重制约了龙门山山前勘探的进展。本文依据二、三维地震数据，钻、测井数据，遥感解译及地面地质调查数据，对重点剖面开展断层相关褶皱精细几何学分析，建立了龙门山中段山前构造新样式，并探讨其侧向变形迁移规律。龙门山中段山前带从北西向南东依次可以划分为三个构造变形特征带：北川–映秀断层上盘推覆构造变形带；通济场与关口断层之间的三角楔断块构造带；山前隐伏褶皱带。山前隐伏褶皱带又分为三排斜列构造：大邑背斜构造；彭州向斜构造；金马–鸭子河背斜构造，三排斜列的构造之间具有明显的构造侧向和前陆方向的迁移特征，控制各主要构造形成的断层之间存在明显的横向位移传递和转移；龙门山前构造样式和侧向迁移是多方向性物源的主控因素，把握其规律对山前带油气预测具有重要的指导意义。
Longmenshan is located between the eastern margin of Qinghai-Tibet Plateau and the foreland basin of western Sichuan. The complexity, inheritance and long-term nature of tectonic activity make the exploration of gas and gas in front of Longmen Mountain face many challenges: low signal-to-noise ratio (SNR) of seismic data, poor reliability of structural traps, multi-stage deformation superposition, strong reworking of early deformation, complex characteristic of tectonic deformation and migration, which seriously restrict the progress of exploration in front of Longmen Mountain. Based on petroleum industry seismic data, drilling and logging data, remote sensing interpretation and ground geological survey data, this paper analyzes the geometry of faults and folds in key sections, establishes a new style of structure deformation in the middle section of Longmen Mountain, and discusses its lateral deformation and migration characteristic. The middle section of Longmen Mountain front can be divided into three structural deformation characteristic zones from north west to south east: the upper nappe plate west of Beichuan-Yingxiu fault, the triangular wedge fault structure zone between Tongji field and Guankou fault, and Hidden fold belt in front of mountain. The hidden fold belt is divided into three rows of oblique structures: Dayi anticline structure; Pengzhou syncline structure; Jinma-Yazihe River anticline structure. There are obvious lateral and foreland deformation migration characteristics between the three rows of oblique structures, which control the lateral displacement transfer between the faults. Longmen Mountain front structure style and lateral migration are the main control factors of multi-directional sedimentary source, and it is important to grasp its law for oil and gas exploration in the mountain front zone.
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