伸展盆地的转换斜坡:控制储层发育与烃类运聚的重要构造单元

Relay Ramp in Extensional Basins:An Important Structure of Reservoir Deposition and Hydrocarbon Migration or Accumulation

转换斜坡是指两条倾向相同并在走向上叠覆的正断层之间的强烈旋转地带。此定义自20世纪50年代提出以来,尤其是在20世纪90年代后得到了深入的研究。转换斜坡是伸展盆地中传递带的一种类型,对储层沉积和烃类运聚具有重要意义。基于正断层的生长机制形成的转换斜坡具有显著的位移和演化特征,虽成因相似但规模悬殊。由于转换斜坡部位较小的构造沉降速率和对沉积物的输导作用,其控制下发育的沉积体的层序地层学特征为扇体,主要以进积的准层序组叠置而成;受转换斜坡演化的控制,沉积体的沉积学特征为前期扇体随断层叠覆程度加深而增大,后期随转换斜坡的破坏水系被重新定位从而导致扇体废弃。针对转换斜坡的特征,总结了前人对其研究的思路和方法。方法包括实验模拟研究和地质研究,其中,地质研究包括断层的定量分析、地层厚度和高程分析及层序地层学方法和沉积学分析。最后归纳了转换斜坡及其在油气储层研究中的应用与发展,并认为该领域在国内颇具研究前景。

To understand comprehensively the role of relay ramp in extensional basins,and to introduce research methods,we refer plenty of documents about relay ramp since it was proposed and sum up the conclusions and approaches.The relay ramp is defined as ＂a volume of rotation between two normal fault segments that overstep along the strike in the same dip direction＂ proposed in 1950s,and researched in depth since 1990s.Relay ramps are one kind of transfer zones in extensional basins where they can be significant for reservoir deposition and hydrocarbon migration or accumulation.The fault growth results in relay ramp with characteristic displacement profiles and various scales.The sequence stratigraphy in relay ramp area is the strongly progradational pattern of deltas due to the low subsidence rate and high sediment supply,while the sedimentology is the delta being drowned resulted from redirection of sediment efflux due to the evolution of relay ramp.This paper has summarized previous research methods of relay ramp including experimentation and field investigation as well as the quantitative analysis of faults,stratigraphic thickness and elevation analysis,sequence stratigraphy and sedimentology.It is suggested that the study of relay ramp should have a possible future development in our country.