鄂尔多斯盆地姬塬地区堡子湾长4＋5储渗成因分析

Analysing Genesis of Chang4＋5 Reservoir Permeability in Buziwan of Jiyuan Area, Ordos Basin

姬塬地区堡子湾延长组长4＋5为短暂湖侵背景下形成的三角洲前缘沉积，主要发育水下分流河道和河口坝沉积微相。砂岩粒度细，填隙物含量高，主要以铁方解石和高岭石为主，受酸性成岩环境控制，次生溶蚀作用较强，主要发育长石溶孔。成岩相研究表明，该区发育碳酸盐胶结相、绿泥石薄膜胶结相和长石溶蚀＋绿泥石薄膜胶结相三种成岩相带，长石溶蚀＋绿泥石薄膜胶结相是有利的成岩相带。另外，裂缝及微裂隙的发育，有效地改善了储层的渗透性。

Chang4＋5 sandstone reservoirs of Yanchang Formation in Buziwan block of Jiyuan area are delta front deposits formed under the background of short period lake invasion. Underwater distributary channel and river mouth bar sedimentary micro-facies is mainly developed in the reservoirs. The granularity of sandstone is fine. Content of pore-filling matters is high, with ferrous calcite and kaolinite remaining dominant. Controlled by the sour diagenetic background, secondary erosion is strong, mainly with dissolved pores instead of feldspar developed. Diagenetic facies study shows that three sorts of diagenetic facies belts of carbonate cementation facies, chlorite film cementation facies, and feldspar erosion adding to chorite film cementation facies are developed in the area. The feldspar erosion adding to chlorite film cementation facies are favorable diagenetic facies belts. In addition, development of fractures and micro-fissures improves effectively the permeability of the reservoirs.