Grading evaluation and prediction of fracture-cavity reservoirs in Cambrian Longwangmiao Formation of Moxi area, Sichuan Basin, SW China

WANG Bei,LIU Xiangjun,SIMA Liqiang

Fig. 2. Lithology and reservoir space photographs of all types of gas reservoirs in Longwangmiao Formation of Moxi area. (a) Well MX13, brown-gray micritic-powder crystal vug dolomite, 4 621.93-4 622.10 m, vugs partially filled with dolomite, occasional quartz, asphalt migration traces in the vugs, vug diameter: 1-50 mm; (b) Well MX204, deep-gray doloarenite, 4 651.23-4 651.36 m, rich in vugs of 2-5 mm; (c) Well MX202, gray graniphyric aplitic-powder crystal vug dolomite, 4 647.85-4 647.97 m, with dissolved pores in irregular distribution; (d) Well MX13, brown-gray powder crystal dolomite, 4 610.64-4 610.89 m, with reticulated fissures, vugs of 0.5-12.0 mm in diameter and surface porosity of 11%; (e) Well MX12, brown powder crystal dolomite, 4 639.34-4 639.50 m, with a high-angle fracture and sporadic vugs, a maximum vug diameter of 0.7 cm and a surface porosity of 3%; (f) Well MX13, residual aplitic doloarenite, 4 614.58 m, with abundant vugs partially filled by bitumen and dolomite, cast thin section, plane polarized light; (g) Well MX12, brown residual aplitic doloarenite, 4 648.43 m, with abundant intergranular dissolved pores filled by bitumen in the edge, cast thin section, plane polarized light; (h) Well MX12, brown gray fine-medium crystalline residual doloarenite, 4 639.13 m, with intergranular dissolved pores, intracrystalline pores and intracrystalline dissolved pores, cast thin section, plane polarized light; (i) Well MX12, brown aplitic residual doloarenite, 4 638.18 m, with reticulated microfractures filled by asphalt, cast thin section, plane polarized light.