主流线叠合法在分流河道演化特征分析中的应用

Application of Main Streamline Superimposition in Distributary Channel Evolution Analysis

大牛地气田二叠系下统山西组三角洲平原分流河道分支多、迁移快、河道窄,单期河道迁移演化及规模的量化成为高效挖潜的关键技术。为了实现分流河道单砂体沉积演化特征的定量描述,通过岩心与测井资料对比分析,建立了砂体沉积微相与测井曲线形态的关系模式,在密井网对比、水平井实钻资料对比和测井相分析等基础上,采用"垂向分期、曲线定位、侧向划界"进行小层级单期河道规模的解剖,识别储层内部期次与叠置关系,提出并采用"主流线叠合法"重建河道的平面迁移规律与沉积演化过程。研究表明:山21层内垂向上共发育2期河道砂体,晚期河道整体规模变小;单期河道宽度约为1 000~1 500 m,厚度约为3~7 m,顺河道方向的砂体连续性好;平面上呈现由东北向西南方向逐渐迁移的特征。现场实践表明,以多期河道砂体迁移演化与叠置特征为地质导向,部署设计调整井,可保障井眼轨迹的钻遇效果,提高钻井的成功率。研究方法对薄窄分流河道储层的有效开发调整具有较好的指导意义。

The Permian Shanxi Formation delta plain distributary channels in the Daniudi Gasfield are characterized by multiple branches,fast migration and small channel width,and the single-phase channel migration evolution and scale quantification have become a key technology for efficient recovery. In order to quantitatively characterize the sedimentary evolution of single-sandbody in the distributary channel,the relationship between sandbody sedimentary microfacies and well logging morphology was established through comparative analysis of core and logging data. The"vertical phase separation,curve positioning and lateral demarcation were used to dissect the subzone-level single-phase channels and recognize the internal phase and superimposition pattern based on the comparison of dense well pattern and horizontal well drilling data,and logging facies analysis,etc. The"main streamline superimposition"method was proposed to reconstruct the lateral migration pattern and sedimentary evolution process.Research indicates that 2-phase channel sandbodies developed along the longitudinal direction in the Shan21 bed,and the late channel integrally shows a relatively small scale. The single-phase channel width is about 1 000~1 500 m,the thickness is about 3~7 m,and the sandbodies along the channel show a better continuity. Laterally,it gradually migrated from northeast to southwest. Field practice illustrates that the adjustment well deployment based on the multi-phase sandbody migration and evolution and superimposition patterns could ensure the drilling performance of wellbore trajectory and improve drilling success rate. This research could provide certain guidance for the effective development and adjustment of thin-narrow distributary channel reservoirs.