摘要
二连盆地由为数众多的早白垩世小型断陷湖盆组成,其缓坡带普遍发育的高位三角洲体系与特定的构造背景配置可形成多种类型的成藏组合,发育多个有利的油气成藏区带,构成立体含油、叠加连片的态势。以二连盆地吉尔嘎朗图凹陷为例,以层序地层分析为基础,在缓坡带的湖泊层序高位体系域识别出了扇三角洲、辫状河三角洲等两种粗碎屑三角洲体系。根据储层发育的层位和不同类型圈闭在缓坡带的分布特征,结合已发现的油藏类型,划分出了3个与高位三角洲体系密切相关的成藏组合。按照不同成藏组合在平面上的分布特点,指出缓坡内带是岩性地层油藏形成的有利成藏区带,而缓坡中、外带构成了构造油藏的有利成藏区带。不同成藏组合和成藏区带在缓坡带纵、横向上的分布规律,为缓坡带实施油气整体评价和立体勘探提供了科学依据。目前,以缓坡带高位三角洲体系为主要勘探目的层,在缓坡内带、中带和外带已经发现了规模整装储量,取得了良好的勘探成效。
In the past more than ten years,distribution and prediction of lowstand sandbodies of LST had been put too much emphasis on during sequence stratigraphy research and petroleum exploration in continental faulted basins.However,the questions about petroleum reservoirs formation of highstand sandbodies of HST were rarely studied.As a result,petroleum exploration of highstand sandbodies of HST was directly restricted.Erlian Basin is located in the north-midland of Inner Mongolia Autonomous Region of China and is composed of many small faulted lacustrine basins of early Crataceous.In general,highstand delta system is well developed and formed the main sandstone reservoir in the gentle slop of faulted lacustrine basins.The petroleum exploration practice shows that highstand delta system that developed widely in gentle slopes,together with specific structural settings,can made many types of play and favorable petroleum accumulation zone.As a result,there is a good prospect that different reservoirs in the gentle slop overlap vertically each other and distribute laterally in a large area.The paper takes an example of Jiergalangtu Sag,which is one of the most representative faulted sags in Erlian Basin,to discuss thoroughly the depositional characteristics and petroleum reservoirs formation conditions of highstand delta system. The Lower Crataceous in the gentle of Jiergalangtu Sag can be divided into five third-order sequences that are,respectively,named as SQ1,SQ2,SQ3,SQ4 and SQ5 from bottom to top.SQ1,SQ2,SQ3 and SQ4 are lacustrine sequence and the highstand sandbodies of HST of three sequence such as SQ1,SQ2 and SQ3 are the most oil-bearing reservoir.Based on sequence stratigraphy analysis of early Crataceous,according to the result of characteristics of borehole lithology and log,cores observation,sedimentary facies of single well and seismic facies analysis,and so on.two types of coarse clastic highstand delta system that consist of fan delta and braided delta are divided in lacustrine sequence.The fan delta system is mainly distributed in HST of SQ1 and its sedimentary facies belts are imperfect.Its main part is the fan delta front subfacies,while the fan delta plain subfacies is difficult to be preserved because of latter erosion of the top strata of SQ1.The braided delta system is well formed in HST of SQ2 and SQ3.Its sedimentary facies belts,including braided delta plain,braided delta front and pre-braided delta subfacies,are completely developed.Two different types of the highstand delta system of above have characteristics of multiphasic and inherited formation.In the end,there are two sandbodies concentrating areas in the neighborhood of Well Ji 45 and Well Ji 36 that located respectively in the north and south of the gentle slop. After more than twenty years of exploration,two types and eight kinds of oil pools,including structural reservoir,lithologic and stratigraphic reservoir,have been discovered in the gentle slop.According to the stratigraphic position of reservoirs and the distribution character of different traps in gentle slope,and combing with types of oil pools that have been discovered,three plays that are closely associated with hightstand delta system have been respectively divided.In the vertical direction,they are named as SQ1 play of stratigraphic traps,SQ2 play of lithologic traps and SQ3 play of structural and complex traps.On the basis of distribution character of the plays,petroleum accumulation zones in different domains such as structural reservoir,lithologic and stratigraphic reservoir,etc.are finally predicted.It advances that the inner belt of the gentle slope is favorable petroleum accumulation zone of lithologic and stratigraphic reservoir,while the center and outer belts of the gentle slope are favorable petroleum accumulation zone of structural reservoir.Vertically and laterally,the distribution laws of the plays and petroleum accumulation zones provide scientific reference for evaluation and exploration on the whole.Now,through petroleum exploration that regard the highstand delta systems as the main targets,reserves have been discovered on a large scale and a good effect have been made in the inner,center and outer belts of the gentle slope.This example encourages increased focus on petroleum exploration potential of the highstand sandbodies of HST in faulted lacustrine basins and provides useful reference for petroleum exploration of numerous similar faulted basins in the east of China.
出处
《沉积学报》
CAS
CSCD
北大核心
2011年第4期783-792,共10页
Acta Sedimentologica Sinica
基金
中石油重大科研攻关项目"渤海湾盆地精细勘探与滩海大油气田分布规律研究"(编号:2008B-0300)
"渤海湾盆地油气预探研究"(编号:2008D-0702)联合资助
关键词
二连盆地
吉尔嘎朗图凹陷
缓坡带
高位三角洲
成藏组合
成藏区带
Erlian Basin
Jiergalangtu Sag
gentle slope
highstand delta system
play
petroleum accumulation zone
