Full
ZAN Chunjing,born in 1997,is a Ph.D. candidate. She is mainly engaged in research on geology. E-mail: chunjing_zan@outlook.com.
Outline
The continuous discovery of giant hydrocarbon reservoirs in continental rift basins has highlighted bioclastic dolomite reservoirs as a promising new exploration frontier. This study integrates petrography,geochemistry,and in-situ isotopic techniques to investigate the genesis and pore evolution of bioclastic dolomite reservoirs in the Member 2 of Shahejie Formation in eastern Shijiutuo uplift of Bohai Bay Basin. The results reveal the following: (1)Three sets of bioclastic dolomite reservoirs are developed,and four types of replacive dolomites are identified—micritic envelope dolomite(ME),micritic-fine crystalline matrix dolomite(MD),early fibrous dolomite cement(CD1),and late mosaic dolomite cement(CD2). (2)Two dolomitization mechanisms are proposed: reflux and burial dolomitization,elucidating the genesis of different dolomite types. ME,MD,and early CD1 formed under hypersaline reflux conditions in hot,semi-saline,lacustrine shallow shoals. (3)In the high-temperature,closed diagenetic environment of the shallow burial stage,organic acids generated from kerogen thermal decomposition promoted the dissolution-reprecipitation of MD and CD1 to form CD2. Concurrently,pore fluids rich in Mg2+ released by compaction,together with retained connate water,facilitated CD2 cementation,filling intergranular pores. (4)During the synsedimentary stage,meteoric freshwater leaching selectively dissolved aragonite and high-Mg calcite,forming early secondary pores such as moldic and intrabioclastic cavities. In the middle to late burial stage,abundant organic acid production and hydrocarbon charging led to non-selective dissolution and microfracture development. However,reservoir space remains dominated by primary intergranular pores and early secondary pores. By coupling in-situ isotopic temperature reconstruction with multi-stage dolomitization mechanisms,this study refines previous models focused solely on reflux and mixing-zone dolomitization and provides a theoretical framework and predictive approach for reservoir quality enhancement and efficient hydrocarbon development in bioclastic dolomite reservoirs.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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