四川盆地中二叠世广元—巴中拉张槽的发现及其油气地质意义  

The discovery of Middle Permian Guangyuan-Bazhong extensional trough in the Sichuan Basin and its petroleum geological significance

作　　者：张玺华[1] 陈聪[1] 黄婕 文龙[1] 谢忱 徐诗薇 高兆龙 Zhang Xihua;Chen Cong;Huang Jie;Wen Long;Xie Chen;Xu Shiwei;Gao Zhaolong(Research Institute of Exploration and Development,PetroChina Southwest Oil&Gasfield Company;Project Cost Center,PetroChina Southwest Oil&Gasfield Company)

机构地区：[1]中国石油西南油气田公司勘探开发研究院 [2]中国石油西南油气田公司工程项目造价中心

出　　处：《中国石油勘探》2019年第4期466-475,共10页China Petroleum Exploration

基　　金：国家科技重大专项“四川盆地二叠系—中三叠统大型气田富集规律与目标评价”(2016ZX05007-004)

摘　　要：利用野外、钻井和地震资料综合研究,在四川盆地广元—巴中地区发现中二叠世的槽谷,为上扬子西北缘受海西期拉张作用形成的拉张槽。拉张槽的地质—地震特征明显,呈北西向展布,宽度为70~120km,面积约为2×104km2,根据其中线展布将其命名为广元—巴中拉张槽。拉张槽控制着中二叠统的烃源岩展布,拉张槽内为深水欠补偿沉积,充填10~30m的深水陆棚相泥质岩,TOC为2%~9%,为优质烃源岩。该拉张槽还控制着中二叠统茅口组台缘带优质储层的形成与展布,拉张槽两侧发育台地边缘滩相沉积,三维地震资料解释表明,台缘带宽度为8~10km,面积达3000km^2,受岩溶等成岩作用改造,可形成规模优质储层。广元—巴中拉张槽的发现改变了四川盆地二叠纪构造沉积分异形成于长兴期的传统认识,拉张槽内部优质烃源岩与其周缘规模滩相储层构成旁生侧储的源储配置关系,为有利成藏组合,是茅口组重要勘探方向。Based on the comprehensive analysis of outcrop,drilling and seismic data,a Middle Permian trough is discovered in the Guangyuan-Bazhong area of the Sichuan Basin.And it is an extensional trough which is formed under the effect of Hercynian tension along the northwestern margin of Upper Yangtze,and its geological-seismic characteristics are obvious.It is extended in the direction of northwest,with a width of 70-120 km and an area of about 2x10^4 km^2.According to the distribution of its central line,it is named as Guangyuan-Bazhong extensional trough.This extensional trough controls the distribution of the Middle Permian hydrocarbon source rocks.Inside the extensional trough are deepwater undercompensation sediments.It is filled with argillaceous rocks of deepwater shelf facies with the thickness of 10-30 m and its TOC ranges from 2%to 9%,so it is classified as high-quality hydrocarbon source rock.It also controls the formation and distribution of high-quality reservoirs in the platform margin belt of Maokou Formation,Middle Permian.The sediments of platform margin beach facies are developed on both sides of the extensional trough.It is indicated from the 3D seismic data interpretation that the platform margin belt covers an area of 3000 km2 with a width of 8-10 km.Owing to the diagenetic reformation(such as karstification),large-scale high-quality reservoirs can be formed.The discovery of Guangyuan-Bazhong extensional trough changes the traditional understanding that the Permian tectonic sedimentary differentiation in the Sichuan Basin is formed in the Changxing Period.The high-quality source rocks inside the extensional trough and the large-scale reservoirs of beach facies in the periphery constitute the source-reservoir configuration relation of side generation and lateral preservation,they are the favorable reservoir-forming assemblages and the importation exploration direction of the Maokou Formation.

关 键 词：构造沉积分异 广元-巴中拉张槽 深水陆棚相泥质岩 茅口组台缘带 成藏组合 

分 类 号：TE122.1[石油与天然气工程—油气勘探]