This study deciphers the origin and distribution of multiphase carbonate cementations and assesses their implications for reservoir quality of the Eocene delta hydrocarbon sandstones in the Bohai Bay Basin. Petrographic observation and stable isotopic analysis identified two phases of carbonate cementations: (1) eodiagenetic phase including non-ferroan calcite cement precipitated at 25–42 °C (δ¹³C_VPDB: 1.0‰ to +5.7‰ and δ¹⁸O_VPDB: 10.7‰ to −7.5‰); and (2) mesodiagenetic phase which includes ferroan calcite cement (δ¹³C_VPDB: 11.8‰ to −5.7‰ and δ¹⁸O_VPDB: 17.0‰ to −12.6‰) and ankerite cement (δ¹³C_VPDB: 13.7‰ to −5.9‰ and δ¹⁸O_VPDB: 17.1‰ to −12.4‰) precipitated at 90–134 °C. The eodiagenetic non-ferroan calcite cement that is mainly sourced from microbial methanogenesis of organic matter in adjoining mudrocks, extensively cemented at or near sandstone-mudstone contact. Mesodiagenetic ferroan carbonate cements are derived from predominantly thermal decarboxylation of organic acids and subordinate dissolution of eodiagenetic calcite cements in sandstones. These ferroan carbonates are preferentially concentrated at distances of 0.5–1.0 m from sandstone-mudstone contacts. Kinetic modelling reproduces evolution pathways of different diagenetic minerals in the Es4s sandstones (the upper part of the fourth member of the Eocene Shahejie Formation). More importantly, results of modelling reveal that the dissolution of non-ferroan calcite cements would not enhance total reservoir quality due to the precipitation of more stable ferroan calcite and ankerite cements. Therefore, the occurrence of multi-phase carbonate cementations at different sections of sandstones leads to significant destruction of porosity and reservoir heterogeneity during progressive diagenesis.

这项研究破译了多相碳酸盐胶结物的起源和分布，并评估了它们对渤海湾盆地始新世三角洲烃砂岩储层质量的影响。岩相学观察和稳定同位素分析鉴定碳酸盐胶结的两个阶段：（1）相eodiagenetic包括非含铁方解石水泥在25-42℃（沉淀δ ¹³ Ç _VPDB：1.0‰至+ 5.7‰和δ ¹⁸ ö _VPDB：10.7 ‰至-7.5‰）；和（2）相mesodiagenetic包括含铁方解石水泥（δ ¹³ Ç _VPDB：11.8‰至-5.7‰和δ ¹⁸ ö _VPDB：17.0‰至-12.6‰）和铁白云石水泥（δ ¹³ C ^_VPDB：13.7‰至-5.9‰和δ ¹⁸ ö _VPDB：17.1‰至-12.4‰）在90–134°C时析出。成岩非铁方解石水泥主要来自于相邻泥岩中有机物的微生物甲烷化作用，在砂岩-泥岩接触处或附近广泛胶结。中成岩碳酸亚铁水泥主要来自有机酸的热脱羧作用和成岩方解石水泥在砂岩中的次要溶解。这些碳酸亚铁优先集中在距砂岩-泥岩接触点0.5-1.0 m的位置。动力学模拟再现了Es4s砂岩（始新世沙河街组第四段的上部）中不同成岩矿物的演化途径。更重要的是，建模结果表明，由于更稳定的方解石铁矿和方铁石水泥的沉淀，非铁方解石水泥的溶解不会提高总储层质量。因此，在渐进的成岩过程中，在砂岩的不同断面发生的多相碳酸盐胶结作用导致孔隙度和储层非均质性的显着破坏。