Characteristics and formation mechanism of low porosity-low permeability reservoirs of the Triassic Xujiahe Formation in Jiannan area, eastern Sichuan Basin
Xie Qingbin1, Li Na1,2, Liu Haotian3, He Wenbin3, Wang Zhifang1
1 College of Geosciences, China University of Petroleum(Beijing),Beijing 102249 2 China Academy Land and Resources of Economic,Sanhe 065201,Hebei 3 Jianghan Oilfield Exploration and Development Research Institute, SINOPEC,Wuhan 430000,Hubei
Abstract：Triassic Xujiahe Formation,in Jiannan area of Sichuan Basin,was deposited in a braided river deltaic-lacustrine depositional system. The rock types of reservoirs are lithic sandstone,feldspathic-lithic sandstone and lithic-quartz sandstone,which were developed in braided river delta. The reservoirs in this area are characterized in low porosity and low permeability, with the average values of 5.96％ and 0.044×10-3μm2 respectively, which is mainly caused by sedimentary environment and diagenesis. The reservoirs of Xujiahe Formation were mainly formed in deltaic-braided channel depositional system,and the braided channel changed frequently in side-direction. Thus the sandstone and mud poorly sorted and poorly rounded grains, and low compositional maturity and low texture maturity of sandstone,which was not in favor of the development of primary pores. During early diagenesis process,compaction caused 60%～85% primary porosity loss, while the following cementation further decreased the porosity of 12％～18％ which made the sandstone denser. In addition,the Xujiahe Formation of research area was lack of soluble substances,the content of feldspar and carbonate cement were low,which weakened the dissolution in the later stage. The dissolution increased porosity with an average of 1％,and maximum of 2.5％.
Xie Qingbin,Li Na,Liu Haotian et al. Characteristics and formation mechanism of low porosity-low permeability reservoirs of the Triassic Xujiahe Formation in Jiannan area, eastern Sichuan Basin[J]. JOPC, 2014, 16(1): 89-102.
