Influence of hydrothermal activity on the Maokou Formation dolostone in the central and western Sichuan Basin

被引：0
|
作者：
Li T. [1 ,2 ]
Zhu D. [1 ,2 ]
Yang M. [1 ,2 ]
Li P. [1 ,2 ]
Zou H. [1 ,2 ]
机构：
[1] College of Geosciences, China University of Petroleum (Beijing), Beijing
[2] State Key Laboratory of Petroleum Resource and Prospecting, Beijing
来源：
Oil and Gas Geology | 2021年 / 42卷 / 03期
关键词：
Hydrothermal fluid; Laminar dolostone; Maokou Formation; Patchy dolostone; Recrystallization; Sichuan Basin;
D O I：
10.11743/ogg20210310
中图分类号：
学科分类号：
摘要：
The hydrothermal dolostone in the Permain Maokou Formation of Sichuan Basin has been targeted frequently for natural gas during the past few years.Though quite common in the formation as a result of the Emeishan flood basalt eruption, hydrothermal activities and their effect on dolostone reservoirs are not sufficiently understood.Based on observation of outcrops, cores, and thin sections along with analysis of cathodoluminescence, homogenization temperature of fluid inclusions and geochemistry, we reached the following conclusions.Firstly, dolostone in the Maokou Formation can be divided into laminar dolostone and patchy dolostone.The former, the dominant type, can be further subdivided into very fine to fine-crystallized dolostone (D1) and fine to medium-crystallized dolostone (D2).The latter is composed of medium to coarse-crystallized dolomite (D3).Secondly, D2, mainly developed in D1 as patches, shows inequigranular texture and develops hydrothermal-related structures and minerals.Compared with D1, D2 has higher Fe and Mn content, stronger cathodoluminescence, higher homogenization temperature of fluid inclusions, higher 87Sr/86Sr, and more negative δ18 OPDB value, indicating that D2 is generated by recrystallization of D1 under the influence of hydrothermal fluids.Thirdly, hydrothermal process can be both constructive and destructive to the development of Maokou Formation dolostone reservoirs.It is constructive in that hydrothermal activities led to the formation of rupture system and breccia, hydrothermal dissolution to dissolved pores and cavities, and hydrothermal metasomasis to dolomitization of limestone.It is destructive in that the physical properties of dolostone were affected by mineral sedimentation that plugged previously formed pores, ruptures, and cavities and by recrystallization that added more Mg2+ and CO32- to the system.Lastly, the main driving force for the formation of reservoir space in the Maokou Formation is an early-stage meteoric freshwater dissolution, and the footprint of hydrothermal fluid can be seen as a clue to potential dolostone reservoirs.Therefore, importance shall be attached to shoal with early-stage dissolution during the exploration of Maokou Formation reservoirs in Sichuan. © 2021, OIL & GAS GEOLOGY Editorial Board. All right reserved.
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页码：639 / 651
页数：12
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