地质科技通报 (Jan 2023)
Investigation of pore structure and permeability estimation models of Kongdian Formation glutenites in the Bozhong 19-6 Gasfield
Abstract
The pore structure of glutenite in Bozhong 19-6 Gasfield is complicated. In order to improve the estimation accuracy of permeability, it is necessary to start with the pore structure and find the pore structure factor with the best correlation with permeability. Taking the pore structure and permeability of 43 Kongdian Formation glutenites as the research object, using rock casting thin slices to determine the pore types, and obtaining pore-throat size distribution characteristics and pore structure parameters through high-pressure mercury intrusion. Combining pore types and pore structure parameters to analyze the relationship between pore structure and permeability, a permeability evaluation model based on pore structure parameters was established. Studies have shown that there are differences in the pore structure between different types of dissolved pores. The pore structure of dissolved pores in the grain is the best, and the pore structure of dissolved pores in the cement is the worst. The physical properties of glutenite with different types of dissolution pores vary greatly. The rock samples with intragranular dissolution pores and no cement dissolution pores have the best physical properties. Different pore structure factors have inconsistent degrees of permeability control. Among them, the permeability model which based on pore throat size, connectivity, ratio and shape has the highest accuracy. The large pore throat radius and good connectivity of the dissolved pores in the glutenite grains of the Kongdian Formation of BZ19-6 Gasfield are the main reasons for the good reservoir and seepage capacity of this kind of rocks. The average pore throat radius, mercury removal efficiency, average pore throat volume ratio and fractal dimension are suitable for estimating the permeability of glutenite reservoirs with complex pore structures and (extremely) low porosity and permeability, in order to provide technical support for the permeability evaluation of glutenite reservoirs inBozhong Depression, Bohai Bay Basin.
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