绵阳-长宁拉张槽北段构造-沉积特征  

Tectonic and sedimentary features of the northern Mianyang-Changning intracratonic sag,Sichuan,China

作　　者：刘树根[1] 刘殊[2] 孙玮[1] 宋金民[1] 冉波[1] 钟勇 叶玥豪[1] 蒋能春 夏国栋[1] 

机构地区：[1]油气藏地质及开发工程国家重点实验室(成都理工大学),成都610059 [2]中国石化西南油气分公司研究院,成都610041 [3]中国石油川庆钻探有限公司地球物理勘探公司,成都610213

出　　处：《成都理工大学学报（自然科学版）》2018年第1期1-13,共13页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金："十三五"国家科技重大专项(2017ZX05005003-007);中国石化前导性项目(P16109)

摘　　要：绵阳-长宁拉张槽北段(川西地区)震旦系-下古生界埋藏深,研究程度低。本文利用川西高精度地震资料、综合钻探资料和野外露头资料,探讨绵阳-长宁拉张槽北段的构造与沉积特征,并对烃源岩特征进行分析。研究表明:拉张槽边界有2个明显的陡坎;拉张槽西侧边界大致垂直于原特提斯洋,其东侧边界分布在射洪-三台-元坝-剑阁一带。拉张断层沿着拉张槽两侧对称分布,在陡坎下方发育一系列的拉张断层。拉张槽两侧,震旦系灯影组厚度大,上覆的下寒武统厚度小,甚至缺失;在拉张槽内,灯影组厚度减小,而下寒武统厚度明显加大。拉张槽内麦地坪组属于斜坡-盆地相,广泛分布着浊流或碎屑流沉积的钙屑(磷屑)岩屑砂岩,可能是绵阳-长宁拉张槽在拉张初期的沉积记录;拉张槽外麦地坪组发育不完整,属台地相沉积。拉张槽内筇竹寺组+麦地坪组烃源岩厚度大、品质好、成熟度高。拉张槽北段(川西地区)的下寒武统烃源岩无论是厚度还是品质均明显高于中段(川中地区),是下寒武统重要的生(供)烃中心。拉张槽北段(川西地区)具有中段(川中地区)的构造-沉积特征和原始油气地质条件,其海相油气具有较大的勘探前景。Sinian(Ediacaran)-Lower Paleozoic strata are deeply buried and less studied in the northern Mianyang-Changning intracratonic sag(western Sichuan Basin).Based on the high-precision seismicdata,integrated with drilling well and outcrop data,the tectonic-sedimentary features of the northern Mianyang-Changning intracratonic sag are investigated,and the features of the Lower Cambrian sources rocks in the sag are analyzed.There are two distinct scarps in the boundaries of the intracratonic sag.The western boundary of the intracratonic sag is approximately perpendicular to the proto-Tethys Ocean,and the eastern boundary occurs in Shehong-Santai-Yuanba-Jiange.Extensional faults symmetrically distributed along both sides of the intracratonic sag.Outside the intracratonic sag,Sinian Dengying Formation is extremely thick while the thickness of Lower Cambrian strata are thin or even missed.However,inside the intracratonic sag,Dengying Formation is thin and the Lower Cambrian strata are thick.Inside the intracratonic sag,Maidiping Formation belongs to slopebasin facies with wide distribution of the turbidity flow or debris flow deposition of the Calcarenaceous(phosphorus)lithic sandstone,which may be a depositional record during the initial extensional movement.Outside the intracratonic sag,Maidiping Formation is poorly developed and belongs to platform facies.The source rocks of Maidiping Formation and Qiongzhusi Formation in the intracratonic sag are characteristic of large thickness,good quality and high maturity;and the thickness and quality of Lower Cambrian source rocks in the northern intracratonic sag are significantly better than those in the middle intracratonic sag.It reveals that the northern intracratonic sag(western Sichuan Basin)has the similar tectonic-sedimentary features and original geologic conditions of oil and gas to the middle intracratonic sag(central Sichuan Basin),and therefore,has large exploration prospect of marine oil and gas.

关 键 词：拉张槽 筇竹寺组 麦地坪组 海相油气 下寒武统 四川盆地 

分 类 号：P54[天文地球—构造地质学] TE121[天文地球—地质学]