火山活动背景下优质储层发育机制-以海拉尔盆地贝中地区为例

Sequence-stratigraphic framework through Beizhong Area has been established on the analysis of combined lithologic, well-log, and 3D seismic data. Based on previous stratigraphic classification and correlation, it is proposed in this paper that the key sequence in Beizhong Area response characteristics of volcanic activity are analyzed. On the basis of third-order sequence framework, the high resolution sequence framework of Nantun Fm in Beizhong oilfields is established, sand-controlling patterns of tectonic slop break and sedimentary response characteristics of volcanic activity are analyzed. Then establish the model of sequence stratigraphic filling patterns coupled with lake basin subsidence. Through the study of reservoir development features on the background of volcanic activity, the high-quality reservoir genetic mechanism is analyzed . The favorable conditions for the development of high-quality reservoir include : acid liquid produced and discharged by source rock; favorable sedimentary types dominated by fan delta front subaqueous distributary channel; easily dissolved components supplied by volcanic activity, such as analcime, albite et al. Meanwhile it helps to promote the sequence stratigraphy filling patterns study of fault depression and the research of high-quality reservoir developmental mechanism on the background of volcanic activity.

以层序地层学及储层沉积学等理论为指导，分析贝中地区关键级层序界面与火山活动的波动关系，建立不同火山活动阶段，构造活动控制下的多种与湖盆沉降作用耦合的层序地层充填样式，探讨不同级别层序形成的主控因素。进而开展沉积砂体展布和演变研究，构建不同类型构造坡折带－砂体响应模式，并着重探讨火山活动的沉积响应，以显示其对储层储集条件的影响。在明确富含火山物质的碎屑岩储层储集空间类型及微观孔隙结构特征和成岩作用类型的基础上，重点分析火山活动所提供易溶蚀物质如方沸石、钠长石，对储层储集性能的影响，并划分成岩储集相。最终从优质储层的发育的多个有利条件出发，包括①酸性流体介质、②有利沉积类型、③ 火山活动所提供的易溶组分④碎屑岩沉积动力机制类型、⑤ A/S值条件以及层序所处位置对于优质储层形成的影响、⑥ 层序界面附近古大气水淋滤作用等，建立火山活动背景下多因素复合影响下的优质储层发育模式。

本课题以层序地层学及沉积学等理论为指导，从建立贝尔－南贝尔－塔南凹陷层序格架出发，将贝尔凹陷铜钵庙－南屯组划分为4个三级层序，其形成严格受构造活动的控制，表现出三种与湖盆沉降作用耦合的层序地层充填样式。进一步在贝尔凹陷构建了5种类型构造坡折带－砂体响应模式：① 陡坡断崖型坡折带－近岸水下扇砂体模式；② 陡坡断阶型坡折带－扇三角洲、近岸水下扇和远岸湖底扇砂体模式；③ 断阶型缓坡坡折带－扇三角洲砂体模式；④ 盆内坡折带－远岸水下扇砂体模式；⑤ 断坡式坡折带－扇三角洲及远岸水下扇砂体模式。同时，分析火山作用沉积响应特征，如贝26井“龟裂状”砂岩的形成过程，显示了火山活动对于储层储集条件的影响：一方面，以脉状充填的凝灰质使得储层非均质性极大加强；另一方面，重新注入的易溶火山碎屑为次生孔隙的形成提供了物质基础。贝中油田优质储层发育的最有利条件主要有：① 烃源岩生成并排放的酸性流体介质；② 以扇三角洲前缘水下分支河道为主的有利沉积类型；③ 火山活动所提供的易溶组分，如方沸石、钠长石等。最终从优质储层的发育的多个有利条件出发，建立了火山活动背景下多因素复合影响下的优质储层发育模式。