Application of mapping and dating techniques in the study of ancient carbonate reservoirs: A case study of Sinian Qigebrak Formation in northwestern Tarim Basin, NW China

YANG Hanxuan,HU Anping,ZHENG Jianfeng,LIANG Feng,LUO Xianying,FENG Yuexing,SHEN Anjiang

Fig. 2. Petrographic characteristics of dolomite cements in Qigebrak Formation, northwestern Tarim Basin. (a) Lace structure, 13m below the unconformity at the Qigebrak Formation top; (b) fibrous isopachous dolomite, multi-layers in alternate light and dark colors, under plane polarized light; (c) bladed dolomite, perpendicular to the edge of dissolved fissure, under plane polarized light; (d) powder-fine crystalline dolomite, precipitated between dark thrombolite, under plane polarized light; (e) medium crystalline dolomite, precipitated in dissolved fissure, under plane polarized light; (f) saddle-shape dolomite filling between breccia with wavy extinction, under cross-polarized light.