Abstract:

In recent years, a large number of porous carbonate reservoirs have been explored and developed in overseas blocks. Due to the complex lithologies and pore types, the pore structure is very complicated. Therefore, it is difficult to accurately calculate the reservoir parameters and evaluate oil and gas reserves. In order to accurately evaluate carbonate reservoirs, firstly, the influential factors of pore structure are analyzed based on the deposition and the diagenesis. As a result, in different lithologies, the difference between pore types is the main reason for a large difference between pore structures. In the same lithology, the increase in clay content can reduce the quality of pore structure. In addition, the diagenesis has a large impact on the rock with the larger particle size. Secondly, the quantitative evaluation of reservoir parameters is discussed. Due to the coexistence of different types of pore, the reservoir parameters including the permeability and the saturation are quite different while the porosity is similar. In order to solve this problem, the NMR and imaging logging data can be applied to characterizing the numerical distribution of different pore types. Additionally, the three-dimensional imaging technique can be used to show the spatial distribution of different pore types. This study laid a foundation for the accurate calculation of reservoir parameters and objective evaluation of oil and gas reserves.

Key words:  carbonate, pore structure, deposition, diagenesis, reservoir parameter, hydrocarbon evaluation