塔里木盆地塔河油田主体区海西早期岩溶台面划分及洞穴层对比*

在现代岩溶地质考察中,岩溶区因多期次幕式构造抬升运动而形成多级岩溶台面,每级岩溶台面的排泄基准面(潜水面)控制一期洞穴发育。塔河油田海西早期形成了复杂的碳酸盐岩岩溶洞穴系统,纵向上呈现多层性特征,是油气勘探的重点。因此,为了深入认识和阐述洞穴层发育机制,以现代岩溶理论为指导,基于三维地震资料,采用水系汇流点法、侵蚀阶地法、上超终止法并结合地貌特征,对塔河油田主体区海西早期岩溶台面进行划分,并在岩溶台面约束下进行洞穴层对比。研究结果表明:(1)塔河油田主体区发育4级岩溶台面。岩溶台面1形成时代最早,台面3面积最大。(2)主要发育3套洞穴层,具有明显的层状分布特征,台面3的洞穴层规模最大。3套洞穴层在垂向上并不构成大范围重叠,仅台面3控制的洞穴溯源侵蚀穿越台面向上游发育,说明洞穴层形成时的构造稳定期长。其他台面洞穴层并未穿跨台面发育,说明洞穴层形成时的构造稳定期短,潜水面控制下洞穴溯源侵蚀范围比较有限。

Division of karst platform architecture and cave levels correlation in the early Hercynian,Tahe Oilfield,Tarim Basin

Multi-levels of karst platforms are generally formed in karst regions due to multi-stage tectonic movements,and one phase of caves will be generated by a drainage base level corresponding to a karst platform,which are observed in modern karst geological surveys. A complex karst cave system,marked by multi-layer architecture in vertical and acted as an important exploration target,was created in early Hercynian,Tahe Oilfield, Tarim Basin. In order to better understand the mechanism of cave development,modern karst theories,3-D seismic data and three different methods,namely river terraces,flow concentration and onlap termination,were utilized to subdivide karst platform architecture. Moreover,cave levels correlation constrained by karst platform was carried out. This study result demonstrated that:(1)karst platforms in Tahe Oilfield can be subdivided into 4 levels,and platform I was first formed,while the area of platform Ⅲ was the maximum; (2)three cave levels were identified,distributing to be layered,and the scale of the cave level controlled by platform Ⅲ was the largest. Actually,this three cave levels are not overlapped in vertical except some part of the cave level controlled by platform Ⅲ extending to platform Ⅱ. This feature above proved that the cave level controlled by platform Ⅲ was resulted from a long stable tectonic stage,while the other two cave levels were created in a relatively restricted tectonic stage, and the headward￣erosion scale controlled by ground water level was limited.