南海北部坡折带的识别及油气地质意义

RECOGNITION OF SLOPE BREAK BELTS AND ITS HYDROCARBON GEOLOGICAL SIGNIFICANCE

当坡折带被引入层序地层学理论以后,并作为层序地层学理论核心的内容之一,其概念的内涵和外延都发生了明显的变化,应该说此时坡折带已经不仅仅是一个单纯的地貌学概念,而在其中赋予了更多的沉积学含义,从单一的地貌起伏面转化为沉积地质体。坡折带的存在制约影响着层序界面的识别、地层叠加样式和层序内体系域构成分析及层序地层模式的建立,同时对地层岩性油气藏勘探开发具有重要作用。笔者从地质及地球物理方法出发,对珠江口盆地所存在的沉积坡折及地貌坡折进行了识别,认为沉积坡折发育于惠州凹陷南侧,而地貌坡折主要存在于白云凹陷北坡,但坡折带不是固定不变的,随着盆地的演化,其分布位置不断变动。最后总结了坡折带识别在珠江口盆地岩性油气藏勘探开发重点现实意义,并形成了坡折带识别方法体系及研究工作流程,对于相关盆地坡折带识别具有一定的指导意义。

The intension and extension of the concept of slope break belts have changed obviously after its introduction as a key concept into sequence stratigraphy.Nowadays,the slope break belt is not only a term for a kind of geomorphological feature,but also a concept with more sedimentological meanings,that is from a topographic relief to a sedimentary body.The recognition and identification of a slope break belt affect the identification of sequence boundaries,the analysis of strata stacking pattern,the architectural analysis of systems tract,and the establishment of sequence stratigraphic model,and thus play an important role in the exploration and development of stratigraphic/lithologic oil and gas reservoirs.The authors have recently identified the depositional slope break belt and physiographical slope break belt in the Pearl River Mouth Basin using integrated geological and geophysical methods.The depositional slope break belt is developed in the south of Huizhou sag,and the physiographical slope break belt mainly developed on the north slope of Baiyun Sag.The type and place of slope break belt is variable with the evolution of the basin.Finally,the practical significance of the identification of slope break zone is concluded in the exploration and development of lithologic oil and gas reservoirs in the Pearl River Mouth Basin.Meanwhile,the identification method and the work flow of the slope break belt are proposed,which has a certain guiding significance to the identification of slope break belt in related basins.