Abstract:

The Permian Shangshihezi formation in the Jiyang depression has rich oil and gas resources. To understand the diagenesis and pore evolution of the sandstone reservoir, many means like core observation, thin section identification, scanning electron microscope, cathodoluminescence, electron probe and porosity and permeability test are used. The results show that the sandstone reservoir of the Permian Shangshihezi formation in Yihezhuang-Dawangzhuang area in the Jiyang depression is of low porosity and low permeability. The compaction and cementation to the reservoir is medium to strong, which have been confirmed by quantitative study on the diagenesis in the study area. Generally, compaction is the primary factor in destructing the reservoir pores and cementation is the secondary factor. Analysis of the difference in the reservoir pore evolution divides the reservoirs generally into two types. The first type is the reservoir which was “first destroyed and then dissolved”. The second type is the reservoir which is “destroyed but not dissolved”. The reservoir of the first type has better physical properties and sweet spot intervals are found in the Permian sandstone reservoirs in the Yihezhuang-Dawangzhuang area of the Jiyang depression due to extensively developed fractures, dissolved tuffaceous matrix and well-preserved secondary pores. In comparison, the reservoir of the second type has worse physical properties shown as less fractures, not dissolved soluble matrix, and poorly developed secondary pores.

Key words: Jiyang depression, Permian, Shangshihezi formation, dissolved tuffaceous matrix, diagenesis, compaction, cementation, pore evolution