塔中北部奥陶系层序地层模型的建立

Establishment of Ordovician Sequence Stratigraphic Models in Northern Tazhong Area

塔中坡折带是油气勘探的重点区块,但层序划分及坡折带之下的研究程度很低。在塔中29井划分出83m相当于良里塔格组沉积时期的地层,重新建立起塔中北部奥陶系层序地层模型;对地震相进行了研究,塔中北部斜坡奥陶系良里塔格组发育3个地震相,从南到北是"平行连续反射相"、"杂乱丘状反射相"、"连续强反射相",分别代表碳酸盐岩台地、台缘礁滩复合体、密集段沉积;重新厘定了地震解释方案,对重点地震剖面进行了解释,认为晚奥陶世良里塔格组沉积之后,塔中北部斜坡主要遭受风化剥蚀,坡折带之下则接受了巨厚的"黑被子"中下部沉积。在塔中42井以东地区,良里塔格组坡折带前缘"三角带"是礁滩体的一部分,溶蚀孔洞发育,是值得探索的一个新领域。

TZ-1 slope break is an important area for oil and gas exploration.However,research on the sequence division and the lower slope break is not so advanced.The strata about 83 meters thick are distinguished in Tazhong 29 well,equivalent to the deposition of Lianglitark formation.Models of the Ordovician sequence strata in northern Tazhong area are reestablished,as well as research on seismic facies is conducted.Three seismic facies developed in Ordovician Lianglitark formation on the northern slope of Tazhong area,i.e.,the continuous parallel reflection facies,the chaotic hummocky reflection facies,and the continuous strong reflection facies from south to north.They respectively represent the carbonate platform,the platform edge reef-shoal complex,and the deposit of condensed sections.Seismic interpretation is redefined,as well as key seismic profiles are interpreted.It is considered that the northern slope of Tazhong area is mainly exposed to weathering and denudation after the sedimentation of late Ordovician Lianglitark formation. However,there is a deposit called'black quilt'of a great thickness in the lower slope break.In the east of Tazhong 42 well,the'triangular belt'in the front of the slope break in Lianglitark formation is one part of the reef-shoal complex.With abundant denudation pores,the belt is a new area worth exploring.