Reservoir Characterization and Modelling with Diagenetic Trends of Carbonates of the Kawagarh Formation: A Section Exposed in the Kala-Chitta Range, Pakistan

Abstract

Present study is focused on the diagenetic studies and reservoir characterization of the Cretaceous Kawagarh Formation exposed in the Gandab village, Kala-Chitta range, north-western Himalayan Fold-and-Thrust belt, Pakistan. The formation is composed of argillaceous limestone and dark grey marls. A total of thirty-three representative carbonate rock samples were collected at equal intervals of three meters. Various diagenetic features including cementation, micritization, pyrite precipitation, neomorphism, fracturing, sparitization and stylolitization were observed in the studied rocks which occur in the marine, meteoric and deep burial diagenetic environments respectively. Such diagenetic features control the reservoir quality of the rock unit. Porosity types include mostly vuggy and fracture, while minor stylolitic porosity were noted with quantity ranging from 2.66% to 3.88%. The carbonates of Kawagarh Formation are highly fractured, but the filling of these fractures due to precipitation of calcite or micritic mud has greatly reduced its reservoir potential, while some unfilled fractures, stylolites and vuggs are the dominant factors that enhance the reservoir potentiality of the Kawagarh Formation. However, the porosity values still do not mark the level of reservoir rock. These diagenetic studies revealed very less chances for hydrocarbon accumulation as no significant porosity values have been observed and overall reservoir potential is characterized as poor.