The characteristics, formation time, and origin of the sucrosic dolomite reservoirs in the Permian Qixia Formation of northwestern Sichuan Basin are analyzed. Core and outcrop description and microscopic analysis of the sucrosic dolomite samples are carried out. It is found that the dolomite has typical features different from other kinds of dolomites: (1) This dolomite is generally medium-coarse in crystal size, and often associated with very finely to finely crystalline dolomite and cave-filling dolomite. (2) Typical identification marks of eogenetic karstification are developed at the top of the upward-shallowing sequence. (3) The medium-coarse crystalline sucrosic dolomite is cut by the early diagenetic karst fabric, and is characterized by dolomite with dissolution edge, dolomite vadose silt in pores, and transgression clay filling between the medium-coarse dolomite crystals. The medium-coarse crystalline sucrosic dolomite was formed earlier than the eogenetic karstification. The sucrosic dolomite with occasional cloudy core and clear rim has bright cathodoluminescence, high inclusions temperature, significant negative skewness carbon and oxygen isotopic compositions, and rare-earth element (REE) pattern similar to seawater, indicating it experienced two periods of dolomitization, evaporative concentration reflux-infiltration and penecontemporaneous seawater circulation hydrothermal fluid dolomitization. The study results not only update the understanding on the dolomitization time of Qixia Formation, demonstrate that the sucrosic dolomite can be formed in the penecontemporaneous stage when seawater reflux superimposed with hydrothermal fluid effects, but also show that the taphorogenesis in the Dongwu period began in the Early Permian. Moreover, the dolomite controlled by the grain bank migration and terrain in the slope break appears in bands of large scale, this knowledge provides basis for expanding the exploration field of this type of reservoirs.

分析了川西北地区二叠系栖霞组的共统白云岩储层的特征，形成时间和成因。对阴囊白云岩样品进行岩心和露头描述以及显微分析。发现白云石具有与其他种类的白云岩不同的典型特征：（1）该白云石通常具有中等粗大的晶体尺寸，并且通常与非常细至微细的结晶白云石和填满洞穴的白云石相关。（2）上岩化序列顶部形成了典型的岩溶岩溶识别标志。（3）中等成岩型的sucrosic白云岩被早期成岩岩溶岩层切割而成，其特征是白云岩具有溶蚀边缘，白云石渗流在孔隙中淤积，在中等粗度白云岩晶体之间填充海侵粘土。中粗晶系的白云岩早于生代岩溶作用形成。丘陵白云岩芯部偶有混浊，边缘清晰，具有明亮的阴极发光，高夹杂物温度，明显的负偏斜碳和氧同位素组成以及类似于海水的稀土元素（REE）模式，表明它经历了两个白云石化，蒸发浓缩的时期。回流入渗和近现代海水循环热液白云石化作用。研究结果不仅更新了对栖霞组白云石化时间的认识，这表明，在海水回流与热液作用叠加的同时期，就可以在阴前期形成阴积白云岩，而且还表明东吴期的造山作用始于二叠纪。而且，受坡度突变影响的粮库迁移和地形控制的白云岩大量出现，为扩展这类储层勘探领域提供了依据。