塔里木轮南油田寒武系坡折带的层序和储层

STRATIGRAPHIC SEQUENCES AND RESERVOIRS ALONG THE CAMBRIAN SLOPEBREAK BELT,LUNNAN,NORTHERN TARIM,XINJIANG

寒武纪西高东低的海底地貌显著控制着塔里木板块轮南区的岩相差异。轮南寒武系可划分为6个层序,每个层序的地震反射总体上显示较弱,从西到东可划分出3种地震相并分别对应3个沉积带:平行连续地震相指示碳酸盐岩台地、杂乱丘状地震相指示台缘高能带、斜交连续地震相指示斜坡。不同层序在坡折带附近相互叠置,从下到上显示为台地有西向东迁移的趋势,平面上呈南北向展布。坡折带规模大,与轮南隆起巨型台背斜构造配置好,紧邻寒武系油源区,白云岩储层发育,溶蚀孔洞、裂逢、晶间孔综合构成主要储集空间,台地相低能带致密碳酸盐岩可作为盖层,这些因素优化坡折带为油气勘探的最好靶区。

The Tarim Basin deepened eastward during the Cambrian, and this paleotopographic feature controlled the lithological differentiation of the Lunnan region, Xinjiang. In the Lunnan region, six sequences can be recognized from the Cambrian System, whose seismic reflections are generally weak. Three seismic facies can be distinguished from west to east, which correspond to three sedimentary environments respectively. The parallel continuous reflection facies indicates carbona＇te platform; the irregular hummocky reflection facies indicates high-energy platform margin, and the continuous oblique reflection facies indicates slope. Different sequences superimpose on one another within the slope-break region. Throughout the sequences, however, platform migrated basinward to the east, resulting in a horizontally spread along the belt from the north to the south. The slope break is big in size, matching the tremendous anticline tectonically and close to the source rock spatially. Dolomite within the slope-break is an ideal reservoir with dissolution porosity, fissures and inter-crystal pores. Moreover, the fine-grained carbonate rock of the low-energy platform facies can be a cap. These features are favorable for further oil-gas exploration in the slope-break belt of the Tarim Basin.