利用不确定性高精度反演数据表征曲流河储层构型

Architecture pattern characterization of meandering river reservoirs based on high-resolution geostatistics inversion

由于曲流河储层构型横向岩性变化快、储层空间变化复杂、单砂体厚度小,而海上油田井距大、井网稀疏,因此采用陆上密井网条件下的多井预测方法很难准确表征曲流河储层构型;地震解释方法受常规地震资料及常规反演资料纵向分辨率的限制,只能识别厚度为10~20m的大套厚层砂体,无法识别薄互层小砂体,也不能满足曲流河储层构型分析的精度要求。为此,在曲流河砂体沉积模式的指导下,以不确定性高精度反演数据为基础,结合测井数据分析,采用"垂向分期、横向定边、三维定型"的方法对渤海W油田明化镇组下段Ⅱ油组3小层(N_(2m)~LⅡ-3)的R23砂层组的曲流河砂体构型进行层次分析。根据测井曲线形态差异和反演地震数据特征将R23砂层组在垂向上划分为R23-1和R23-2两个沉积单元,在R23-1和R23-2两期复合河道中识别出6条近SN向展布的单一河道,且在单一河道内识别出多个规模不等的复合点坝,在海上油田稀疏井网条件下精细识别了不同级次曲流河砂体构型边界,有效提高了复合河道、单河道及点坝体的识别精度。

Meandering river reservoirs are characterized by quick lithology change on lateral,complicated reservoir space,and thin sand body.So it is difficult to accurately characterize meandering river reservoir architectures with the multi-well prediction method which is usually used in onshore oilfields with dense well pattern,because offshore oilfields always have a much larger well spacing.Due to the vertical resolution limitation of conventional 3D seismic and conventional inversion data,only thick sand bodies(larger than 10m)can be recognized and thin sand bodies cannot be identified.An accurate analysis in meandering river reservoir architecture cannot be conducted.Therefore we propose an approach to solve the problem.It is composed of 3 steps:'vertically timing,lateral boundary identification,and shape identification with 3D information'based on sedimentary models,geostatistics inversion,and logging data analysis.This approach is applied to sand bodies R23 of the 2nd member of Minghuazhen Formation in Oilfield M,Bohai Bay.Based on well logs and seismic inversion data characteristics,R23 can be divided into 2 sedimentary units in the vertical direction,R23-1 and R23-2.In the R23-1 and R23-2 composite channels,six channels with the direction SN are respectively recognized,and moreover,a few composite bars on these channels are also identified.Our experience shows that the proposed approach is practical and efficient in the condition of large well spacing in offshore oilfields.