川东地区长兴组生物礁发育特征与迁移规律

Development characteristics and migration law of Changxing Formation reefs in eastern Sichuan Basin

川东地区长兴组生物礁是四川盆地礁滩相油气勘探的重要目标。文中结合野外露头、钻井、地震等资料,对川东地区长兴组生物礁发育特征与迁移规律进行了研究。结果表明:长兴组生物礁主要发育在台地边缘和台内缓坡沉积相带,可划分为台地缘边礁、斜坡礁、台内礁三大类。台地边缘礁绝大多数发育于长二期,消亡于长三期;而台内礁发育时间较早,多在长一期和长二早期。台地边缘礁多为单套巨厚礁滩体;而台内礁主要为多套薄储层的垂向叠置。总体上,台地边缘礁在发育规模、发育厚度及横向展布等方面均优于台内礁。台地边缘礁在陡坡时多以垂向加积为主,伴随一定程度的侧向迁移,在缓坡时多呈垂向加积和侧向迁移并进的模式;而台内礁以垂向加积为主。在开江—梁平海槽东侧温泉井和五百梯地区,生物礁具有从台内向台缘迁移和层位“爬升”的特征。研究成果为该区长兴组生物礁下一步的油气勘探指明了方向。

The Changxing Formation reefs in the eastern Sichuan Basin are the main targets of oil and gas exploration of reef-shoal facies in the Sichuan Basin.Based on outcrop,drilling and seismic data,the development characteristics and migration law of reefs in the Changxing Formation in eastern Sichuan Basin are studied in this paper.The results show that the Changxing Formation reefs are mainly developed in platform margins and intra-platform ramp facies,which can be divided into three types such as platform marginal reefs,slope reefs,and intra-platform reefs.Most of the platform marginal reefs developed in the Chang 2 stage and disappeared in the Chang 3 stage.The intra-platform reefs developed earlier,and mostly grew in the Chang 1 stage and early Chang 2 stage.Platform marginal reefs are dominated by a single set of huge thick reef shoals,while the intra-platform reefs are mainly vertically overlaid with multiple sets of thin reservoirs.On the whole,the platform marginal reefs are superior to the intra-platform reefs in terms of development scale,development thickness and lateral distribution.The platform marginal reefs are mainly vertical accretion on steep slopes,accompanied by a certain lateral migration.On gentle slopes,vertical accretion and lateral migration are both developed,while intra-platform reefs are mainly vertical accretion.In the WenquanJing and Wubaiti area on the east side of the Kaijiang-Liangping trough,the reefs migrated from the intra-platform to the platform edge,and the layers have an ascending tendency.The research indicates the direction for further oil and gas exploration of Changxing Formation reefs in this area.