Study on the permeability calculation method of carboniferous carbonate reservoirs in the Coastal Caspian Basin based on the characteristics of pore-throat combination

Permeability is a key parameter for finding effective reservoirs and evaluating reservoir production capacity, but accurate evaluation of permeability in carbonate reservoirs has always been a challenge. This study proposes a new method for calculating the permeability of carbonate reservoirs. This study focuses on the Carboniferous carbonate reservoirs in the Pre-Caspian Sea Basin and uses high-pressure mercury injection experiments to measure the micropore structure of the reservoirs. According to the distribution of pore throats, it is divided into macropores, mesopores, small pores, and nanopores. Based on Multi-Resolution Graph-based Clustering, a reservoir permeability calculation model is established. The following understandings were obtained: (1) The pore throat radius of small pore is 0.27 μm, and the contribution rate to permeability is 13.8%; (2) The pore throat radius of mesopores is 0.83 μm and a contribution rate of 28.9% to permeability; (3) The pore throat radius of macropore was 3.78 μm, and the contribution rate to permeability was 57.4%; and (4) The model established using MRGC method has good performance. The innovation of this article is to propose a new permeability modeling method for carbonate reservoirs, which can be used for calculating the permeability of reservoirs in other regions.

渗透率（Permeability）是识别有效储层并评价储层产能的关键参数，但碳酸盐岩储层的渗透率精准评价长期以来都是行业难题。本研究提出了一种全新的碳酸盐岩储层渗透率计算方法。研究聚焦于前里海盆地的石炭系碳酸盐岩储层，采用高压压汞实验测定储层的微孔结构，并依据孔喉分布将其划分为大孔、中孔、小孔与纳米孔。基于多分辨率图聚类（Multi-Resolution Graph-based Clustering，MRGC）方法构建储层渗透率计算模型。经研究得到如下认识：（1）小孔的孔喉半径为0.27μm，对渗透率的贡献占比为13.8%；（2）中孔的孔喉半径为0.83μm，对渗透率的贡献占比为28.9%；（3）大孔的孔喉半径为3.78μm，对渗透率的贡献占比为57.4%；（4）采用MRGC方法构建的模型性能表现优异。本文的创新之处在于提出了一种适用于碳酸盐岩储层的新型渗透率建模方法，该方法可用于其他区域储层的渗透率计算。