Abstract:

The physical property of Chang 6 reservoir was poor with strong heterogeneity in Yanchang Formation, Huaqing area, Ordos Basin. In this paper, casting thin sections, SEM, Xray diffraction, physical properties, high pressure mercury injection and other analytical testing methods were used to analyze the diagenesis, diagenetic facies and micropore structure of the low permeability reservoir deeply. The results showed that: main reservior diagenetic facies were the hydromica cementationintegranular pore and feldspar dissolution diagenetic facies, feldspar dissolution and hydromica cementationintegranular pore facies, feldspar dissolution and chlorite cementationintegranular pore facies. The features of microscopic pore structures of various types of diagenetic phases were different. And the porethroat ratio and coordination number with mercury injection saturation and mercury withdrawal efficiency had a good correspondence. That is, the smaller the porethroat ratio was, the greater the coordination number was, and the greater the mercury injection saturation and mercury withdrawal efficiency were, such as the hydromica cementationintegranular pore and feldspar dissolution diagenetic facies; otherwise, the greater the porethroat ratio was, the smaller the coordination number was, and the smaller the mercury injection saturation and mercury withdrawal efficiency were, such as the feldspar dissolution and chlorite cementationintegranular pore facies.

Key words: Huaqing area, Yanchang Formation, Chang 6 reservoir, diagenetic facies, micropore structure；Ordos Basin