1、第 35 卷 第 2 期2023 年 3 月岩性油气藏LITHOLOGIC RESERVOIRSVol.35 No.2Mar.2023方锐等:川东北五宝场地区侏罗系沙溪庙组沉积特征收稿日期:2022-05-10;修回日期:2022-05-23;网络发表日期:2022-09-16基金项目:重庆市自然科学基金面上项目“基于成岩系统剖析的致密砂岩储层差异致密化机理及渗流差异响应研究”(编号:cstc2021jcyj-msxmX0897)资助。第一作者:方锐(1995),男,西南石油大学在读博士研究生,研究方向为地震沉积学。地址:(610500)四川省成都市新都区新都大道 8 号西南石油大学。Emai
2、l:。文章编号:1673-8926(2023)02-0047-12DOI:10.12108/yxyqc.20230205引用:方锐,蒋裕强,陈沁,等.川东北五宝场地区侏罗系沙溪庙组沉积特征 J.岩性油气藏,2023,35(2):47-58.Cite:FANG Rui,JIANG Yuqiang,CHEN Qin,et al.Sedimentary characteristics of Jurassic Shaximiao Formation in Wubaochangarea,northeastern Sichuan Basin J.Lithologic Reservoirs,2023,35(
3、2):47-58.川东北五宝场地区侏罗系沙溪庙组沉积特征方锐1,蒋裕强1,陈沁2,曾令平2,罗宇卓2,周亚东1,杜磊2,杨广广3(1.西南石油大学 地球科学与技术学院,成都 610500;2.中国石油西南油气田公司 川东北气矿,四川 达州 635000;3.中国石油西南油气田公司 勘探开发研究院,成都 610000)摘要:根据基准面旋回变化原理,利用野外露头、钻井、测井和地震地层切片等资料,对川东北五宝场地区侏罗系沙溪庙组二段开展了层序结构分析和不同可容空间下河道构成特征及河型转换模式等方面的研究。研究结果表明:川东北五宝场地区侏罗系沙溪庙组二段主要发育1个三级及3个四级基准面旋回,各四级层序
4、在低可容空间下为厚层、叠置箱形砂体,随着基准面上升,可容空间增大,到层序顶部过渡为相对孤立的砂体沉积;沙二段沉积时期,研究区气候干燥,砂岩粒度大、成熟度低,发育强水动力构造,地震剖面上为平行反射,河流相沉积特征明显,发育多个低可容空间下的间断正韵律相互叠置的辫状河沉积体系及高可容空间下具“二元”结构的曲流河沉积体系;沙二段河流相地层自下而上具有“辫曲”转换特征,低可容空间下,砂体大面积展布,地震地貌上表现为相互叠置的辫状河河道,当基准面迅速上升时,可容空间增大,地震地貌上表现为相对孤立的曲流河河道;研究区可容空间和沉积物供给比值(A/S)主要受大巴山物源区强烈的构造活动及温暖潮湿向炎热干旱的气
5、候变化影响。关键词:A/S;河流相;基准面旋回;地层切片;沙溪庙组;侏罗系;五宝场地区;川东北中图分类号:TE121;P539.2文献标志码:ASedimentary characteristics of Jurassic Shaximiao Formation inWubaochang area,northeastern Sichuan BasinFANG Rui1,JIANG Yuqiang1,CHEN Qin2,ZENG Lingping2,LUO Yuzhuo2,ZHOU Yadong1,DU Lei2,YANG Guangguang3(1.School of Geoscience a
6、nd Technology,Southwest Petroleum University,Chengdu 610500,China;2.Northeast SichuanGas Field,PetroChina Southwest Oil&Gas Field Company,Dazhou 635000,Sichuan,China;3.Research Institute ofExploration and Development,PetroChina Southwest Oil&Gas Field Company,Chengdu 610000,China)Abstract:Based on t
7、he principle of base level cycle change,the data of field outcrop,drilling,logging and seismicstratigraphic slice were used to analyze the sequence structure,river channel composition characteristics underdifferent accommodation spaces and river type conversion model of the second member of Jurassic
8、 ShaximiaoFormation in Wubaochang area of northeastern Sichuan Basin.The results show that:(1)There are mainly onethird-order and three fourth-order base level cycles developed in the second member of Jurassic Shaximiao Forma-48岩性油气藏第 35 卷第 2 期tion in Wubaochang area of northeastern Sichuan Basin.Ea
9、ch fourth-order sequence is a thick layered stacked boxtype sand body under the low accommodation space.With the base level rising,the accommodation space increases,and it transits to a relatively isolated sand body deposition at the top of the sequence.(2)The paleoclimate of thesecond member of Sha
10、ximiao Formation was dry.Due to the near provenance deposition,the sandstone wascoarse and the maturity was low,the strong hydrodynamic structure was developed,it was parallel reflection onseismic profile,and the fluvial facies characteristics were obvious.There are many braided river sedimentary sy
11、stemswith discontinuous positive rhythms superimposed on each other in low accommodation space and meanderingriver sedimentary systems with binary structure in high accommodation space.(3)The fluvial facies strata of thesecond member of Shaximiao Formation have a“braid curve”transformation law from
12、bottom to top,which isspecifically shown as follows:under the low accommodation space,sand bodies are distributed in a large area,and the seismic geomorphology is shown as mutually overlapping braided river channels.When the base level risesrapidly,the accommodation space increases,and the seismic g
13、eomorphology shows a relatively isolated meanderingriver channel.(4)The accommodation space and sediment supply ratio(A/S)is mainly affected by strong tectonic activity and change from warm and humid to hot and dry climate in Daba Mountain provenance area.Key words:accommodation space and sediment s
14、upply ratio;fluvial facies;base level cycle;stratal slice;Shaxi-miao Formation;Jurassic;Wubaochang area;northeastern Sichuan Basin0引言随着河流相沉积体系研究的不断深入,国内外学者1-3认识到不同河流体系在时空上可发生转换,辫状河与曲流河并不是独立存在于某个地质时期,而是会随着地质历史的发展而发生相互转换。学者们意识到了河型时空转换的重要性并进行了相关研究,同时分析了不同河型演化过程的主控因素。王随继等4-5参照现代地表冲积河型的空间转化模式解释了古代河型的空间分布
15、特征,总结出 6类主要河型演化模式。李胜利等6、谭程鹏等7、唐武等8基于野外露头对河流相转换模式进行了研究,总结出基准面旋回、物源供给、地形坡度及古气候等 4 个河型转换控制因素,但由于很难找到规模巨大的理想剖面,所以无法通过露头剖面来揭示其转化模式。王航等9、白振华等10基于可容空间变化对河流相演化模式进行了研究,在不同体系域地震属性上明确了不同河型的平面展布,基本阐明了河流相的沉积演化。河型转化过程的相关研究对明确河流沉积体系演变具有重要意义,但以往的研究成果主要依托于钻井曲线或野外露头来识别不同河流相类型,对认识河流相砂体展布及空间演化规律仍有不足。近年来,地震沉积学理论和方法在河道砂体
16、精细刻画研究方面受到了高度重视,其利用三维地震资料平面属性优选11-13、分频地层切片处理14-16等手段,在纵向上识别薄层砂体并在横向上刻画砂体展布17-18,结合古地貌恢复结果,可直观表征河流相沉积体系的演化19-20。川东北五宝场地区沙溪庙组二段气藏累产天然气 4.574108m3,凝析油 115 t,开发效果较好,但对该区沙溪庙组的河流相沉积学研究尚不深入,对于沉积体系的厘定存在分歧,对沉积规律认识的不足,制约了河道砂体的开发优选。此外,研究区井位主要集中于五宝场构造主体内,分布极不均匀,总体井控程度较低,仅通过钻井信息开展沉积相展布研究不太现实。本次研究拟采用地震沉积学理论对沙溪庙组沉积体系及砂体空间演化规律进行研究。在建立沙二段等时地层格架基础上,综合利用岩心测井及地震资料,通过分析辫状河和曲流河沉积特征,利用地震地层切片识别出不同演化阶段河道砂体的分布及砂体空间展布特征,进一步分析辫状河转化至曲流河的沉积过程及河型演化控制因素,以期为陆相河流体系的沉积特征和演化提供新的实例,并为其他陆相河流相的研究提供一定参考。1地质概况川东北五宝场地区位于四川盆地川东高陡断褶带,北接大