准噶尔盆地玛中地区二叠系-三叠系叠合成藏特征及主控因素

Characteristics and main controlling factors of Permian-Triassic superimposed reservoirs in central Mahu Sag,Junggar Basin

玛湖凹陷是准噶尔盆地目前已发现油气富集程度最高的生烃凹陷,其中二叠系—三叠系具有较大的勘探潜力。为了研究其叠合成藏特征及主控因素,开展了录井、测井、岩心分析化验及试油资料分析,并进行了三维地震资料解释。结果表明:①玛中地区发育二叠系下乌尔禾组和三叠系百口泉组2套优质储层,扇三角洲前缘亚相是研究区油气富集的有利相带;在湖侵背景下,砂体多期叠置连片,具备形成大面积岩性圈闭群的地质条件。②研究区储盖组合配置较好,砂体纵向上相互叠置,侧面的断裂和上覆的三角洲平原亚相泥岩可为油气成藏提供遮挡。③研究区发育高角度走滑断层及一系列伴生构造,深层断裂沟通油源,浅层断裂控制圈闭和油藏,与不整合面一起共同构成了高效的输导体系,是多层系叠合成藏的重要控制因素。该研究成果对玛中地区中深层油气勘探具有借鉴意义。

Mahu Sag is a hydrocarbon generation deperession with the highest hydrocarbon accumulation degree in Junggar Basin,and Permian-Triassic has great exploration potential.In order to study the characteristics and main controlling factors of its superimposed reservoirs,a large number of analyses of mud-logging,well logging,core analysis and oil test data were carried out,and 3D seismic data was interpreted.The results show that:(1)There are two sets of high-quality reservoirs developed in central Mahu Sag,including Permian lower Urho Formation and Triassic Baikouquan Formation.The front edge of fan delta is a favorable belt for oil and gas enrichment.Under the background of lacustrine transgression,sand bodies are superimposed and connected in many stages,which has geological conditions for forming large lithologic trap group.(2)The reservoir-cap assemblage is well configured,sand bodies are vertically overlapped,and lateral faults and overlying delta plain subfacies mudstone can provide shelter for hydrocarbon accumulation.(3)High-angle strike-slip faults and a series of associated structures are developed in the study area.Deep faults communicate with oil sources,and shallow faults control traps and reservoirs,together with unconformities,they form a highly efficient transport system,which is an important controlling factor for multi-layer superimposed reservoirs.The research results have reference significance for mid-deep oil and gas exploration in central Mahu Sag.