Abstract

To recognize the significance of high gamma markers within Pasarlapudi Formation in Krishna Godavari Basin, laboratory investigations were undertaken to understand the relationship of high gamma signature with mineralogy, organic matter, and depositional environments. The content of U, Th, and K were determined using Natural Gamma Spectroscopy. Amongst U and Th, the latter is present in abundance. The relationship between GR value and Th has a correlation coefficient of 0.92, followed by U (0.80) and K (0.41). There is also a good correlation between the presence of organic matter and GR (0.45). Based on these analyses, it is inferred that Th followed by U is contributing to the high gamma-ray signature. A quantitative examination of clay minerals indicates that chlorite followed by kaolinite is the dominant clay minerals along with montmorillonite and illite. The formation of high gamma shales present in Pasarlapudi Formation was due to intermittent basinal scale transgressive episodes of sea-level changes.