The Relationship between Diagenetic Evolution and Hydrocarbon Charge in Deep Tight Reservoirs: A Case Study from Kepingtage Formation of S9 Well Block in Tarim Basin

Figure 6

Optical photomicrographs of sandstones (pore space is indicated in blue). (a) Sample 5583.47, well S9: the reservoir is dominated by primary pores, note there are some metamorphic rock fragments which are extruded and deformed under compaction, blocking the primary pores. (b) Sample 5580.36, well S903: partially dissolution of feldspar grain forming secondary porosity, note the quartz overgrowths are occupying primary pores. (c, d) Sample 5516.07, well S901, plane-polarized light and cross-polarized light, respectively: the quartz overgrowth is located in adjacent rock fragment dissolution pore and then partially replaced by later calcite cement. (e) Sample 5580.36, well S903: chlorite developed as grain coating rims and engulfed by quartz overgrowths. (f) Sample 5692.86, well S10, two phases of quartz overgrowths. (g) Sample 5528.79, well S902H: lattice defect of quartz overgrowth can be seen due to the calcite cement preoccupied the pore space. (h) Sample 5516.07, well S901: intense quartz overgrowth and no visible thin section porosity is observed. (i, j) Sample 5580.1, well S9, plane-polarized light and cross-polarized light, respectively: the grains are distributed directionally under strong compaction, and some ductile grains are squeezed into the pores to form pseudomatrix. Key: quartz (Qtz), metamorphic rock fragment (MRF), quartz overgrowth (Qtz-o), Calcite (Ca), Chlorite (Chl), primary porosity (PP), secondary porosity (SP).

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