不整合面剥蚀量恢复及其构造意义——以贝南凹陷T_(22)不整合面为例

Erosion amount build-up of unconformity and its structural significance:Taking Cretaceous T_(22) unconformity in southern Beier Depression as an example

文中综合应用声波时差法和地震反射结构外延法对T22不整合面进行剥蚀趋势恢复,进而探讨其构造活动强度及对油气运移和成藏的影响。研究表明,剥蚀厚度沿主干断裂边缘及古隆起斜坡带呈NE—SW向分布,最大剥蚀厚度位于南部苏德尔特断隆东缘,可达900 m,紧邻斜坡的低洼处剥蚀较小,约150 m。剥蚀量大小和分布形态与区域构造活动密切相关,南屯组末期,由于受来自NW—SE方向挤压应力作用,造成先存的同沉积断裂发生构造反转。反转断裂沟通底部油源向上运移,在断隆高部位,由于剥蚀较大而造成早期油气散失,而斜坡部位则由于反转适度,有利于油气的保存,其中贝8、贝3等5口井出现工业油流,其余4口亦出现良好的油气显示。因此,预测贝南斜坡带是下一步油气勘探的重要区带。

This paper built up the erusion estimates of T22 unconfnrmity boundal7 and discussed the effects caused by erosion on the migration and accumulation of hydrocarbon by using the method of interval transit time and the charaeteristies of seismic reflection, The results show that the erosion thickness mostly distributes along the edge of main fauhs and the slope of ancient uplift, oriented in NE-SW trending, The maximum thickness of 900 m is sited on the rim of Sudeerte Fault, while the minimum thickness is about 150 m in the low-lying position close to the slope. The amount and the distribution patterns of erosion are closely related to regional tectonic activities. In the final sedimentary stage of Nantun Formation, compressed by NW-SE trending stress the pre-existing synsedimentary faulting was reversed. The hydrocarbon migrated upward bec, ause of reverse fault. In the high position of fault uplift, the oil and gas dissipated due to the early erosion, while the slope was conducive to the preservation of hydrocarbon owing to proper reversing, There were commereial oil flows in some wells such as B8 and B3, etc. There were oil and gas shows in the other wells in the slope position. So it is predicted that the slope zone is an important target for next oil and gas exploration.