The study of fractures in karst reservoirs is a hot spot in the field of geosciences. In this article, we conducted a systematic study on the characteristics, influencing factors, and prediction methods of karst reservoir fractures of the Ordovician Majiagou Formation in the Daniudi Gas Field, China. Both weathering and tectonic fractures are mainly developed in the Ma 5 member of the Majiagou Formation. The former is categorized into surface weathering, steep wall tensile and karst collapse fractures, and the latter is made of tensile and shear fractures. The palaeo‐temperatures of the fracture filling inclusions range from 90 to 140°C, peaking at 111–120°C, which are derived from oxygen isotopes of −7.9 to −17.5‰, with average −14.1‰ from the same filling inclusions. Integrations of regional tectonic activities, inclusion tests, and stable isotope analysis recognizes four formation periods of fractures since the Caledonian. The factors controlling the development degree of the karst reservoir fractures include lithology, petrophysical properties, rock layer thickness, structural deformation strength, and karst palaeomorphology. The buckling thin plate simulation results show a good positive correlation between the maximum principal stress and tensile fracture density. The same positive correlation is also observed between the shear stress and fracture density. The ancient karst landforms have strongly affected the distribution of weathering fractures. Surficial weathering fractures occur typically in the weathered residual monadnocks, while steep wall tension ruptures in areas near geomorphic steep ridges, and karst collapse fractures in karst residual monadnocks and karst pit areas.

中文翻译：

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风化壳岩溶储集层的特征，影响因素及裂缝预测-以鄂尔多斯盆地大牛地气田奥陶系马家沟组为例

岩溶储层裂缝的研究是地球科学领域的一个热点。本文对大牛地气田奥陶系马家沟组岩溶储层裂缝的特征，影响因素及预测方法进行了系统的研究。风化裂缝和构造裂缝都主要发生在马家沟组的马五段。前者分为表面风化，陡壁拉伸和岩溶塌陷裂缝，而后者则由拉伸和剪切裂缝组成。裂缝填充夹杂物的古温度范围为90至140°C，在111-120°C达到峰值，这是从-7.9至-17.5‰的氧同位素得出的，平均温度为-14.1‰。区域构造活动的整合，纳入测试，稳定的同位素分析可以识别自古苏格兰以来的四个裂缝形成时期。控制岩溶储集层裂缝发育程度的因素包括岩性，岩石物性，岩层厚度，结构变形强度和岩溶古地貌。屈曲薄板模拟结果表明最大主应力与拉伸断裂密度之间具有良好的正相关性。在剪切应力和断裂密度之间也观察到相同的正相关。古代喀斯特地貌强烈影响了风化裂缝的分布。表面风化裂缝通常发生在风化后的残余单峰中，而陡峭的壁张力在地貌陡峭的山脊附近区域破裂，