Abstract The Mina del Carmen, Bajo Barreal and Canadon Seco Formations bear the most important Cretaceous reservoirs in the southern flank of the Golfo de San Jorge Basin, in which the porosity is mainly secondary in origin. Primary porosity is about 4% in average and can be divided in intergranular and intercrystalline porosity, the former is better preserved where chlorite rim cement is abundant, and the second occurs among crystals of the clay cement (main kaolinite). Secondary porosity comprises dissolution of feldspar, ductile fragments, clay cements, lithic grains, and carbonate-zeolite cements. Dissolution of feldspar produces the formation of authigenic kaolinite and secondary porosity; this mechanism dominates in the western area of the southern flank due to sandstones show higher amounts of plagioclase grains, which were very reactive to diagenetic dissolution. Ductile fragments, composed of tuffaceous mudstones (probably of intrabasinal origin), were strongly deformed during the compaction reducing the primary porosity and closing the pore system. Nevertheless, in sandstones containing similar proportions of intrabasinal and extrabasinal clasts, some ductile grains suffered massive dissolution increasing the secondary porosity. Another source of secondary porosity comprises the dissolution of tuff fragments, and locally, carbonate and zeolite cements. The secondary porosity includes the types redistributional (RDS) and pervasive (PVS). This division can be related to previous diagenetic model for the Bajo Barreal Formation. In this way, redistributional secondary porosity is linked to the first and the second events of diagenetic dissolution, while the pervasive secondary porosity to the third dissolution event, which likely had a telogenetic origin.

中文翻译：

---

阿根廷巴塔哥尼亚 Golfo de San Jorge 盆地南翼 Chubut 群上部生产储层中孔隙度的模式和成因

摘要 Mina del Carmen组、Bajo Barreal组和Canadon Seco组是Golfo de San Jorge盆地南翼最重要的白垩系储层，其中孔隙以次生为主。原生孔隙度平均为4%左右，可分为晶间孔隙和晶间孔隙，前者在绿泥石环胶结物丰富的地方保存较好，其次出现在粘土胶结物（主高岭石）的晶体中。次生孔隙包括长石、韧性碎片、粘土胶结物、岩屑颗粒和碳酸盐-沸石胶结物的溶解。长石溶解形成自生高岭石和次生孔隙；这种机制在南翼的西部地区占主导地位，因为砂岩显示出更多的斜长石颗粒，它们对成岩溶解非常敏感。由凝灰质泥岩（可能起源于盆地内）组成的韧性碎片在压实过程中发生强烈变形，从而降低了原生孔隙度并关闭了孔隙系统。然而，在含有相似比例的盆内和盆外碎屑的砂岩中，一些韧性颗粒遭受大量溶解，增加了次生孔隙度。次生孔隙的另一个来源包括凝灰岩碎片的溶解，以及局部碳酸盐和沸石胶结物的溶解。次生孔隙度包括再分布型（RDS）和普遍型（PVS）。这种划分可能与之前 Bajo Barreal 组的成岩模型有关。这样，重新分布的次生孔隙度与第一次和第二次成岩溶解事件有关，