基于叠覆朵体模式的厚层三角洲前缘砂体精细刻画——以大庆油田杏六中区PⅠ油层组为例

Fine characterization of thick delta front sand body based on overlapping lobe model:a case study of PⅠoil layers in Xing 6 middle area,Daqing Oilfield

为了厘清大庆油田杏六中区PⅠ油层组厚层三角洲前缘砂体的内部结构特征,为剩余油开发提供地质支撑,文中针对按照水下分流河道模式无法精细刻画目标砂体的问题,引入叠覆朵体模式,提出六步剖析法,依据密井网资料,对目标砂体的内部结构进行了精细刻画。结果表明:1)按照叠覆朵体模式,能够较清楚地刻画目标砂体的内部结构特征。2)运用六步剖析法(即确定标志层,划分等时地层单元;进行底拉平处理,认识等时地层单元内砂体的内部结构特征;识别较大的沉积界面,区分并追踪复合朵体;在复合朵体内识别单朵体,刻画其分布;分析朵体间接触关系,确定朵体间连通性;结合生产动态资料,验证剖析结果的正确性),对目标砂体的刻画结果打破了三角洲前缘砂体呈层状结构的传统认识。3)目标砂体内部可以以进积、退积特征划分为一系列的沉积复合朵体和单朵体。按照叠覆朵体模式,运用六步剖析法对砂体内部结构的刻画结果,避免了传统的基于相带的砂体结构剖析法中跨沉积时间单元所造成的对砂体内部结构认识的偏差,为剩余油分析提供了可靠的依据。

In order to clarify the internal structural characteristics of the thick delta front sand body of PⅠoil layers in Xing 6 middle area,Daqing Oilfield,and to provide geological support for the development of remaining oil,this paper addressed the issue of the inability of the underwater distributary channel model to fine-characterize the target sand body,introduced the overlapping lobe model,proposed the six-step analysis method to conduct fine characterization of the internal structure of the target sand body according to dense well pattern data.The results are as follows.Firstly,following the overlapping lobe model,the internal structural characteristics of the target sand body can be clearly characterized.Secondly,with the use of the six-step analysis method(namely determining marker layer and dividing isochronous stratigraphic units,conducting bottom flattening and understanding the internal structural characteristics of sand bodies in isochronous stratigraphic units,identifying larger sedi-mentary interfaces and distinguishing and tracing composite lobes,identifying single lobes in composite lobes and characterizing their distribution,analyzing the contact relationship between lobes and determining the connectivity between lobes,verify-ing the correctness of analytical results combined with pro-duction dynamic data),the characterization results of the target sand body breaks the traditional understanding that the delta front sand body has layered structures.Thirdly,the internal of the target sand body can be divided into a set of sedimentary composite lobes and single lobes according to prograding and retrograding characteristics.According to the overlapping lobe model and using the six-step analysis method,the internal structure of sand body is characterized.The characterization results avoid the the deviation of understanding the internal structure of sand body caused by crossing sedimentary time units,which resulted from the traditional sand body structure analysis method based on facies belts,and provide reliable basis for remaining oil analysis.