Impact of clay minerals on reservoir sandstone properties: comparative study in Colombian eastern cordillera and middle Magdalena valley basins

The aim of this study is to examine how mineralogy influences the petrophysical properties, particularly porosity and permeability, of potential sandstone reservoirs in Colombia. It seeks to comprehensively understand how the presence of clay minerals impacts the overall quality of hydrocarbon reservoirs in the country. Samples of sandstones from reservoirs at various outcrops in the Eastern Cordillera and Middle Magdalena Valley basins were collected. Detailed analysis of mineralogy and petrographic characteristics of the samples was conducted through various analytical techniques such as transmitted light microscopy, X-ray diffraction, and scanning electron microscopy. Porosity and permeability were measured using automated permeametry and porosimetry equipment. The predominant composition of the analyzed reservoir rocks comprises quartz (45-50%), feldspar (35-40%), and clays (10-20%). These rocks were categorized into two distinct groups based on their permeability (K) and porosity (Φ), ranging from 0.009 to 29.220 mD and 1.88 to 20.75%, respectively. The presence of illite correlated with a reduction in both porosity and permeability, highlighting its negative impact on reservoir quality. Conversely, an elevated concentration of kaolinite was associated with favorable porosity and permeability. Samples with feldspar sericitization demonstrated inferior hydrocarbon storage quality. This study provides a deeper understanding of how mineralogy affects the petrophysical properties of sandstone reservoirs in Colombia. These findings are crucial for guiding exploration and production strategies in the Colombian oil industry, especially in challenging geological environments like those studied.