四川盆地五百梯地区长兴组古地貌恢复及地震预测

四川盆地五百梯地区长兴组地层分布范围广、勘探潜力大, 但存在礁滩储层厚度薄、礁滩体刻画难、演化规律不明显、非均质性强等问题, 增加了储层预测的多解性。对此, 从生物礁岩石学特征及储层特征研究出发, 提出了生物礁储层的纵向发育规律和部位, 并利用生物礁储层的地震异常特征, 刻画礁滩体优质储层横向展布特征, 并重点分析了古地貌对礁滩储层发育特征的关键性控制作用, 最后结合古地貌恢复及储层反演等方法, 对礁滩储层进行综合评价, 并总结形成了长兴组礁滩体储层地震识别模式, 降低了礁滩储层预测的多解性。研究发现, 长兴组沉积前已形成了海槽雏形, 长兴组早中期形成了台缘及台内二排礁区域高地貌基本格局, 到长兴组沉积末期海槽特征明显, 古地貌高部位是储层发育的最有利区域, 优势储层主要集中在台缘外带及台内二排礁局部区域, 该认识为四川盆地长兴组台内礁勘探提供了重要的依据及借鉴意义。

The Permian Changxing Formation in the Wubaiti area of the Sichuan Basin is widely distributed and has a great potential for exploration.However, there are also difficulties, such as the thickness of reef-bank reservoirs, difficult characterization of reef-beach bodies, unobvious evolution rules, and strong heterogeneity, which increase the ambiguity of reservoir prediction.In this study, the seismic anomaly of the reef-bank was described macroscopically and a seismic identification model of the reef-bank reservoir in the Changxing Formation was established.The vertical and horizontal development positions of high-quality reef-bank reservoirs were excavated, and the controlling effect of paleogeomorphology on the vertical and horizontal development characteristics of the reef-bank reservoirs was analyzed.Finally, the reef-bank reservoir was comprehensively evaluated by combining paleogeomorphology and reservoir inversion methods, which reduced the multiplicity of the reef-bank reservoir predictions.This study found that the trough prototype was formed before the deposition of the Changxing Formation, and the basic pattern of high landforms in the platform margin and second row of reefs in the platform were formed in the early and middle stages of the Changxing Formation.By the end of the deposition of the Changxing Formation, the characteristics of the trough were evident and the high part of the paleogeomorphology was the most favorable area for reservoir development.The dominant reservoirs were mainly concentrated in the outer belt of the platform margin and the local area of the second row of reefs on the platform, providing an important basis and reference for reef exploration in the Changxing Formation of the Sichuan Basin.