鄂尔多斯盆地华庆油田延长组长6油层组深水沉积组合特征

Deepwater sedimentary association of Chang 6 oil bearing formation,Yanchang Formation of Huaqing Oilfield in Ordos Basin

华庆地区位于晚三叠世鄂尔多斯盆地湖盆沉积中心,长6油层组沉积复杂,具有多物源控制、深水沉积的特征。主要沉积类型可划分为半深湖—深湖沉积、重力流沉积及深水三角洲沉积。不同流态的流体在不同阶段和位置可以相互转化、相伴出现。在湖退背景下长6发育厚层砂体,成因复杂,主要包括深水三角洲砂体、滑塌砂体、砂质碎屑流砂体和浊积砂体等类型。其中三角洲砂体发育各种交错层理;滑塌砂体多顶底突变,发育滑动面;砂质碎屑流沉积颗粒大小混杂,含泥岩撕裂屑;浊积砂体通常为正粒序,或呈块状。从平面上分析,东北物源控制区主要为进积的三角洲砂体、滑塌砂体夹浊积砂体;西部、西南物源影响区主要为浊积砂体、滑塌和砂质碎屑流砂体;混源区和东北物源体系的前端主要为砂质碎屑流砂体、滑塌砂体和浊积砂体。

Located in the depositional central of Ordos Basin in Late Triassic, the sedimentary of Chang 6 oil bearing formation in Huaqing area is characterized by mixed sources and deepwater deposition association which can be divided into three types,i, e semi-deep lake and deep lake sediment,gravity current sediment and deepwater delta sediment. In different areas and stages, flow state will develop and transform one another. Delta sediment is featured by plentiful cross- beddings. Slump is marked by slide plan, with sudden lithologic contact relationship with overlying and underlying strata at top and bottom generally. Debrite in the study area is featured by development of different sized mud debris and turbidite presents normal grading. In the context of early lake regression, thick sandbody well developed in the central of Ordos Basin. Deposition controlled by northeast provenance is constitute of slump and progradation sand body of delta with thin layers of turbidite,and the deposition,controlled by southwest and west provenances,is constitute of turbidite,debrite and slump. In the mixed-provenance area, sediment is made up of debrite,turbidite and slump.