准噶尔盆地西北缘同沉积构造坡折对层序建造和岩性油气藏富集带的控制

准噶尔盆地西北缘是该盆地油气最富集的区带，岩性地层油气藏是其主要的勘探领域，同沉积构造坡折对层序建造和岩性油气藏富集带具有控制作用。应用地震、钻井和测井资料，按照构造层序分析的方法，对该区同沉积构造坡折特征及其控制的层序建造进行了系统研究。结果表明：该区发育的同沉积构造坡折按成因可划分为同沉积逆断裂坡折和隐伏断裂挠曲坡折。前者是同期发育的逆断层活动造成的湖底坡度梯度变化带，后者是深部隐伏断裂活动造成的湖底坡度梯度变化带。中-晚二叠世，该区属于断坳转换幕，发育同沉积逆断层坡折及其控制的层序建造。三叠纪以后盆地处于挤压坳陷阶段，发育同沉积逆断裂坡折和隐伏断裂挠曲坡折及其控制的层序建造。同沉积逆断裂坡折控制的层序建造向岸一侧低位域发育冲积扇到辫状河道砾岩，向湖一侧发育辫状河三角洲沉积；湖扩展体系域坡折向岸一侧发育薄层泛滥平原、浅湖及退积型三角洲沉积，向湖一侧发育泛滥平原或半深湖沉积；高位域发育河流、三角洲前缘，其可越过坡折向湖进积。挠曲坡折控制的层序建造低位域坡折向岸一侧发育辫状下切水道充填，向湖一侧发育由滨浅湖滩坝砂体或低位辫状三角洲砂体构成的低位楔；湖扩展体系域坡折向岸一侧发育滨浅湖，向湖一侧发育半深湖沉积；高位域发育河流三角洲及滨浅湖沉积。同沉积构造坡折控制的层序低位域砂砾岩体储层，如冲积扇、辫状河道、低位三角洲及滨浅湖砂体、湖底扇砂体，若有断裂和不整合面与风城组油源沟通，能形成良好成藏条件，有利于岩性油气藏发育。

Controls of syndepotitional structural slope-break zones on sequence architecture and enrichment zones of lithologic reservoirs in northwestern margin of Junggar Basin

The western margin of Jungger Basin is a petroliferous structural belt,and lithostratigraphic reser-voirs are dominant exploring targets. Syndepositional structural slope-break zone has a strong control effect on sequence architecture and enrichment zones of lithologic reservoirs. On the basis of seismic,drilling and logging data,according to the method of structural sequence analysis,the characteristics of syndepositional structural slope-break zones in the study area and its controlled sequence architecture were studied. The results show that the syndepositional slope-break zones developed in the study area can be divided into two types,namely,the slope-break zone controlled by syndepositional reverse faults and flexure slope-break zone controlled by buried fault,according to the origin. The former is the gradient abrupt zone of lake bed caused by syndepositional reverse fault movement,while the later is the gradient abrupt zone of lake bed resulted by seated-reverse-faults. During Middle to Late Permian period,the study area was in the transition stage from rifted basin to down-warped basin, slope break zones controlled by syndepositional reverse faults and sequence architecture controlled by them were developed. Since Triassic to Paleogene period,the study area was in the compressional down-warped stage, slopebreak zones controlled by syndepositional reverse faults,flexural slop-break zones controlled by buried fault,and sequence architecture controlled by them,were developed. The sequence architecture controlled by syndepositional reverse faults slop-break zone shows that the lowstand systems tract is composed of alluvial fans and braided river deposited at the upward of the zone,and the braided deltas developed at the downward of the zone,the expanding systems tract consists of floodplain,shallow lake and retrogradational deltaic sediments at the upward of the zone,shallow to deep lake deposits at the downward of the zone,and highstand systems tract comprises of fluvial deltas. The sequence architecture controlled by flexural slope break zone is characterized by incised infills deposited at the upward of the flexural slope break zone and shallow lake or lowstand braided deltas deposited at the downward of the zone within lowstand systems tract,shallow to half deep lake developed in expanding systems tract,and fluvial deltaic and shore to shallow lake deposited within highstand systems tracts. Lowstand conglomerate bodies and sand bodies in sequences,such as alluvial fans,deltas of lowstand and sand bodies of shore and shallow lake,have good conditions for hydrocarbon accumulation and are favorable for enrichment of lithologic reservoirs.