Characteristics of "Guangyuan-Wangcang" trough during Late Middle Permian and its petroleum geological significance in northern Sichuan Basin, SW China

WANG Xingzhi,LI Bo,YANG Xiyan,WEN Long,XU Liang,XIE Shengyang,DU Yao,FENG Mingyou,YANG Xuefei,WANG Yaping,PEI Senqi

Fig. 5. Lithological characteristics of platform margin in the south of the trough. (a) Well YB7, 6991.54 m, calcsparite bioclastic limestone, with many visceral pores and dissolution pores, biological detritus mainly composed of spines and forams etc. The forams have visceral pores preserved, and dissolution occurs locally, forming dissolution enlarged pores filled with fine-grained dolomite and asphalt, with a surface porosity of about 3%, cast thin section, plane polarized light. (b) Well ST12, 6768.00 m, fine-medium crystalline dolomite, dolomite crystals in subhedral-heteromorphic shape and mosaic contact, and a small amount of unfilled intergranular dissolution pores, cuttings photo, plane polarized light.