摘要
渤海海域辽西凹陷北部古近系沙河街组二段(沙二段)广泛发育滩坝砂体,油气测试获得高产,表明沙二段滩坝砂体勘探潜力巨大。但是,有关滩坝沉积的机制依然认识不清,严重制约了该类沉积的勘探评价,因此从源-汇系统理论出发进行滩坝沉积控制因素分析十分必要。利用岩心、录井、测井、粒度及铸体薄片等资料,结合三维地震和区域地质资料,对辽西凹陷北部沙二段源-汇系统及其对滩坝沉积的控制进行了研究。结果表明:①研究区沙二段沉积时期,燕山隆起的兴城河水系和月亮河水系为辫状河三角洲沉积提供物源,辫状河三角洲进一步为滩坝沉积提供了物源。由于兴城河水系和月亮河水系汇水区面积相对较小,主河流长度较短,形成的辫状河三角洲规模相对较小,小规模的辫状河三角洲为滩坝沉积提供物源的能力较弱。②辽西凹陷北部发育宽缓的古隆起,为滩坝沉积提供了有利的沉积古地貌条件。③水体较浅,物源供源能力较弱,波浪携带辫状河三角洲前缘砂体向湖盆方向搬运,受古隆起带较高地貌的阻挡,砂体在古隆起带沉积并形成细粒砂质滩坝,岩性以细砂岩与粉砂岩为主。随着湖平面的逐渐上升,滩坝发育程度逐渐减弱。④燕山隆起、兴城河-月亮河水系、凹中古隆起及湖平面共同控制了滩坝沉积的岩性和规模,是该地区取得油气勘探突破的关键要素。本次研究为渤海海域古近系油气勘探中滩坝砂体的预测提供借鉴。
The beach-bar deposits developed in the 2nd member of the Paleogene Shahejie Formation(Sha 2 Member,Es2)in the northern Liaoxi Sag,have great exploration potential as proved by the testing results of exploratory wells.However,there is little insight obtained on the mechanism of beach-bar deposition,seriously restricting the exploration and evaluation of this kind of deposits.Therefore,it is necessary to analyze the controlling factors of beach-bar sand deposition from the perspective of source-to-sink system.The source-to-sink system of the Es2 in the northern Liaoxi Sag and its control on beach-bar deposition are studied by integrating the data of core observation,logging,grain size and casting thin section,combined with 3D seismic and regional geological data.The results are shown as follows.First,during the deposition of the Es2 in the study area,the Xingchenghe river system and the Yuehe river system in the Yanshan uplift transported sediments to the braided river deltas,which in turn served to supply sediments for the beach bar.Because the relatively small catchment area of the two river systems together with the shorter length of main river,the braided river deltas formed are relatively small in scale,and their capability to provide sediments for beach bars is thereby relatively weak.Second,during the deposition of Es2,a wide and gentle palaeo-uplift was developed in the northern Liaoxi Sag,providing favorable sedimentary palaeo-geomorphic conditions for beach bar deposition.Third,during the same period,the study area was characterized by shallow water body and weak sediment supply capacity,resulting in the transportation of sand from the braided river delta front towards the lacustrine basin with waves.Blocked by the higher landform of the palaeo-uplift zone,the sand bodies deposited in the palaeo-uplift zone and formed fine-grained sandy beach bars,dominated by fine-grained sandstone and siltstone.As the lake level gradually rises,the development of the beach bars gets weakened.Fourth,Yanshan uplift,Xingchenghe-Yuehe river systems,palaeo-uplift in the central Liaoxi Sag and lake level fluctuation jointly control the lithology and scale of beach-bar sands,and they are the key factors in making breakthrough in hydrocarbon exploration in the study area.The understanding obtained in the study is of referential significance to the prediction of beach-bar sandstone reservoirs in the Paleogene hydrocarbon exploration in the Bohai Sea.
作者
杜晓峰
庞小军
黄晓波
王冰洁
DU Xiaogfeng;PANG Xiaojun;HUANG Xiaobo;WANG Bingjie(CNOOC Research Institute,Beijing 100028,China;Tianjin Branch of CNOOC,Tianjin 300459,China)
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2023年第3期662-674,共13页
Oil & Gas Geology
基金
中海油“十四五”重大科技项目(KJGG2022-0303)
中国海洋石油有限公司科技项目(KJZH-2023-2104)。
关键词
物源
母岩
水系
滩坝砂体
源-汇系统
古近系
辽西凹陷
渤海海域
provenance
parent rock
river system
beach-bar sandstone
source-to-sink system
Paleogene
Liaoxi Sag
Bohai Sea
