Fracture, Dissolution, and Cementation Events in Ordovician Carbonate Reservoirs, Tarim Basin, NW China

Figure 8

(a, b) Hand specimen of the Yijianfang Formation showing S1a, S1b, and S2 stylolites and V3 and V4 dissolution vugs. (c) Plane light optical photomicrograph showing a V3 lined by Cc3a calcite cement and bitumen. (d) Plane light optical photomicrograph showing a V6 vug filled with blocky Cc6. (e, f) Hand specimens and (g) plane light optical photomicrograph of the Yijianfang Formation showing an association between F3a, S1a, and dark mottles. (h) Plane light optical photomicrograph showing V3 vugs occurring within a dark mottle. Bitumen-infilled vugs and interparticle porosity within mottle fabrics. (i) Plane light optical photomicrograph showing pyrite mineralization and an F4a fracture enlarged by secondary dissolution. (j) Panchromatic SEM-CL photomosaic showing corroded Cc4 and precipitation of kaolinite into dissolved voids.

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