LI Dan,born in 1994,is an engineer of Sinopec Star Petroleum Co.,Ltd.,China. She is mainly engaged in geothermal geology research. E-mail: lid9194.xxsy@sinopec.com.
BAN Shuyue,born in 1997,China University of Petroleum(Beijing). She is mainly engaged in carbonate sedimentology and reservoir geology. E-mail: lillianknow@gmail.com.
Karstified carbonate geothermal reservoirs,characterized by high porosity-permeability and substantial development potential,represent a key target in deep geothermal exploration. The thick and strongly karstified Middle-Upper Cambrian carbonates of the Yuncheng Basin provide an ideal setting for investigating the genesis of deep karst reservoirs;however,the controlling mechanisms of reservoir development under multiphase tectonic-karst overprinting remain insufficiently constrained. In this study,outcrop observations,seismic data,cores,wireline logs,and casting thin sections,integrated with regional tectonic evolution and paleogeomorphic reconstruction,are used to systematically investigate lithologic and reservoir characteristics,diagenetic processes,karst types,and karstification stages of the Middle-Upper Cambrian carbonate succession. The results indicate that: (1)dominant lithologies include oolitic limestone,bioclastic limestone,stromatolitic and argillaceous limestone,and micro-to fine-crystalline dolostone,with reservoir space mainly comprising selective dissolution pores,bedding-parallel dissolution belts,and structural fractures;(2)three genetic categories of karstification and five major evolutionary stages are recognized,controlled by multiphase tectonic uplift,among which large exposure surfaces formed during the Huaiyuan,Late Caledonian,and Yanshanian events served as key loci for epigenetic karstification;(3)the karst reservoir initiated by synsedimentary to early diagenetic dissolution,significantly enlarged through three phases of superimposed epigenetic karstification,and was further modified by fracture-controlled burial dissolution,ultimately forming a composite system characterized by high porosity and strong connectivity. These results clarify the formation mechanisms of the Middle-Upper Cambrian karst geothermal reservoir in the Yuncheng Basin under multiphase karstification and tectonic evolution,and provide a robust theoretical basis for the prediction and evaluation of carbonate geothermal system. The findings also have important implications for geothermal exploration in North China and in analogous fault-depression basins.
| 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 |