鄂尔多斯盆地二叠系盒8段河流扇沉积模式及勘探意义  

Sedimentary model of fluvial fan of Permian He-8 member in Ordos Basin and its exploration significance

作　　者：王宏波[1] 张雷[2] 曹茜 张建伍[2] 潘星[2] WANG Hongbo;ZHANG Lei;CAO Qian;ZHANG Jianwu;PAN Xing(PetroChina Research Institute of Petroleum Exploration&Development-Northwest,Lanzhou 730020,China;Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi’an 710018,China)

机构地区：[1]中国石油勘探开发研究院西北分院,兰州730020 [2]中国石油长庆油田公司勘探开发研究院,西安710018

出　　处：《岩性油气藏》2024年第3期117-126,共10页Lithologic Reservoirs

基　　金：中国石油天然气股份有限公司“十四五”前瞻性基础性重大科技项目“致密气新区新领域资源潜力与富集规律研究”(编号:2021DJ2101)资助。

摘　　要：根据野外露头及岩心的分析化验资料,在源-汇系统分析的基础上,对鄂尔多斯盆地二叠系盒8段的古气候环境及沉积相特征进行了详细研究。研究结果表明:(1)鄂尔多斯盆地二叠系盒8段Sr/Cu的值多大于10,V/Cr值多小于2.0,地层厚度差小于30 m,未出现明显的突变,古沉积坡度为0.5°~1.0°,古地貌开阔平缓且无明显坡折带,沉积水体较浅,是在古气候干旱、古地形平缓的背景下,受阶段性洪水作用主导的事件沉积。(2)盒8段沉积期,盆地不存在大面积汇水区,沉积体系中河流并未进入湖泊水体,而是向东南流出盆地或是消失在内陆干旱地区,全盆地以洪泛平原沉积为主,表现为河道与泛滥平原交互分布的沉积格局,形成了河流扇沉积模式。(3)湖水进退往复,洪水期与枯水期间歇发育,洪水期多期次决口河道接力搬运使得粗粒级砂岩向湖盆长距离延伸,枯水期发育厚层泥质沉积可作为区域性盖层,形成了良好的储盖组合,勘探潜力大。Based on the analysis and laboratory data of field outcrops and drilling cores,combined with sourcesink system analysis,the paleoclimatic environment and sedimentary facies characteristics of the eighth member of Permian Shihezi Formation(He-8 member)in Ordos Basin were studied.The results show that:(1)The Sr/Cu values of Permian He-8 member in Ordos Basin are mostly greater than 10,and the V/Cr values are mostly less than 2.0.The thickness difference of the strata is less than 30 m,and there is no obvious sudden change.The ancient sedimentary slope is 0.5°-1.0°,the paleotopography is open and flat without obvious slope breaks,and the sedimentary water is shallow.It is an event deposit dominated by flood transportation under the background of arid ancient climate and gentle paleotopography.(2)During the sedimentary period of He-8 member,there was no large catchment area in the basin,and the rivers in the sedimentary system did not enter the lake water body.Instead,they flowed out of the basin to the southeast or disappeared in inland arid areas.The entire basin was dominated by floodplain sedimentation,manifested as a sedimentation pattern of alternating distribution of rivers and floodplains,forming afluvial fan sedimentary model.(3)The lake water flows back and forth,with intermittent development in flood season and dry season.In flood season,the relay transport of multi-stage crevasses makes the coarse-grained sandstone extend to the lake basin for a long distance,while in dry season,thick muddy deposits can be used as regional caprocks,forming a good reservoir-cap assemblage with great exploration potential.

关 键 词：河流扇 干旱气候 事件沉积 洪泛平原 洪水期 枯水期 源-汇系统 盒8段 二叠系 鄂尔多斯盆地 

分 类 号：TE121.3[石油与天然气工程—油气勘探] P618.13[天文地球—矿床学]