川西北地区关键井埋藏特征及其沉降机制

Burial characteristics and its subsidence mechanism of key wells in Northwest Sichuan Province

为了更好认识川西北地区地层埋藏特征、深入探讨其沉降机制,为成岩、成藏作用和构造—沉积耦合作用研究提供有利地质的依据,选取该区3口关键井地层模型,在区域地质分析、剥蚀量恢复基础上,经压实校正和古水深校正,建立埋藏史模型,再经逐层回剥分析后,得到各期的沉降曲线,进行沉降机制分析。研究表明:川西北地区加里东期经历了两期埋藏—抬升半旋回,分别对应于兴凯地裂沉降和桐湾抬升、加里东抬升机制;海西期早期经历克拉通抬升、西部边缘埋藏,而后整个地区持续埋藏,归因于峨眉地裂持续沉降机制;印支期—燕山期西部和北部依次褶皱冲断隆升,东部斜坡形成,中部持续埋藏,形成了中间深两侧浅的埋藏格局,源于印支—燕山前陆褶皱冲断隆升—沉降作用;喜山期,全区持续抬升,受控于印藏碰撞隆升的裙带效应,盆山系统调整改造最终定型。

In order to ascertain the burial characteristics and subsidence mechanism of the sedimentary rock sequence within Northwest Sichuan Province and to further provide the valuable geological evidence for the analysis of diagenesis,hydrocarbon accumulation and the coupling of structural-sedimentary interaction,depth of strata from three key wells were examined.The burial and subsidence history were obtained from quantitative stratigraphic back-stripping,through compaction and paleo-water-depth correction based on regional geological settings and denudation restoration.The investigation revealed that: the study area experienced two burial-uplift sub-cycles in the Caledonian phase,corresponding to the Xingkai Taphrogenic subsidence and,the Tongwai and Caledonian uplift mechanism.the study area also experienced uplifting in the craton and subsidence in the western margin during the early stage,and then subsidence in the entire zone,all of which was attributed to on-going subsidence of E' mei Taphrogenesis.The burial pattern,deep within the interior zone and shallow on both sides,was closely related to the uplift-subsidence mechanism of the foreland thrusting and folding in the Indosinian and Yanshanian periods which caused the west and the north to thrust and fold,the east to tilt with the middle sustaining subsidence.The Himalayan experienced an overall uplift as a result of the skirting effect of India-Tibet collision,causing the basin-mountain system to adjust and reconstruct structural patterns and eventually resulting in its formation.