Deep burial dissolution of Lower Palaeozoic carbonates and the role of compacted released water from Palaeogene strata in the Zhuanghai area, Jiyang Depression, Bohai Bay Basin, NE China

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• 作者：Shumei Xu ; Haiming Bi ; Sanzhong Li ; Ian Somerville ; Qing Ye ; Huaiwei Feng and Meng Li
• 刊名：Geological Journal
• 出版年：2017
• 出版时间：January/February 2017
• 年：2017
• 卷：52
• 期：1
• 页码：30-44
• 全文大小：2351K
• ISSN：1099-1034

文摘

The Zhuanghai area is located in the northern part of the Jiyang Depression, Bohai Bay Basin, which is a superimposed basin. In this basin, there are very thick Cenozoic sediments that unconformably overlie Lower Palaeozoic rocks, which form buried hills (topographic highs). Through core description and microscopic observations, the diagenetic characters, pore types, reservoir quality and the dissolution characteristics of the Lower Palaeozoic strata have been investigated in the study area. Organic and inorganic gas–liquid bi-phase inclusions with bright orange-yellow fluorescence are evidence of the dissolution of the compacted released water enriched in organic matter released from Palaeogene strata into the Lower Palaeozoic strata. The relatively high homogenization temperatures of fluid inclusions can help explain the temperature condition of secondary low-temperature hydrothermal minerals and the effects of dissolution of the compacted released water on the Lower Palaeozoic carbonates and hydrocarbons within the buried hills. The δ¹³C values of crystalline calcite in the high-angle fractures of Lower Palaeozoic rocks range from −0.08‰ to −3.5‰, well above those of primary carbonates of the Lower Palaeozoic. The very high values of δ¹³C of crystalline calcite suggest the effects of dissolution of the compacted released water on the Lower Palaeozoic carbonates. The paper analyses the effects of dissolution of the compacted released water and the character of the reservoir space of the Zhuanggu-10 well in the Zhuangxi Buried Hill and suggests that the Ordovician Majiagou Formation underwent significant dissolution because of the introduction of compacted released water and formed various secondary pores acting as a primary reservoir. The compacted released water that corroded the Lower Palaeozoic carbonates comes from the Palaeogene sediments in the adjacent Zhuangxi Sag. It migrated along the boundary fault of the sag to the Zhuangxi Buried Hill, modified the Lower Palaeozoic carbonates and caused the formation of deeply buried dissolution pores. The dissolution mode of the down-dip faulted block seepage as recognized in the Chengbei 305 to 307 wells is proposed to explain the pore distribution patterns of the buried hills in the research area. Copyright