Diagenetic Heterogeneity of Deep Sandstones and Its Relationship to Oil Emplacement: A Case Study from the Middle Jurassic Toutunhe Formation in the Fukang Sag, Central Junggar Basin (NW China)

Figure 8

SEM BSE images of sandstones. (a) Sample 4514.65 m, well D-7: calcite postdating grain-coating chlorite and quartz overgrowths. (b) Sample 4514.65 m, well D-7: chlorite coats and authigenic albite engulfed by barite. (c) Sample 4837.5 m, well D-1: authigenic albite or feldspar overgrowths postdating hematite rims in contact with detrital grains and engulfed by calcite and anhydrite that are possibly synchronous with barite. (d) Sample 4837.5 m, well D-1: calcite possibly simultaneous with anhydrite. (e) Sample 3970.9 m, well D-6: analcime filling intergranular pores. (f) Sample 5299.52 m, well D-1: pyrite filling intergranular pores and replacing detrital grains locally. (g) Calcite having homogeneous almost 100% CaCO₃; the location refers to Figure 9(a). (h) Calcite containing Mn; the location refers to Figure 8(c). Cement: calcite (Cal), chlorite coat (Chl-c), analcime (Anl), anhydrite (Adr), barite (Brt), quartz overgrowth (Qtz-o), feldspar overgrowth (Fs-o), albite (Ab), pyrite (Py), and hematite (Hem).

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)