Study of subsoil radon anomaly using LR-115 (II) nuclear track detectors in and around the Geleki oilfield, Assam Shelf

Abstract

The subsoil radon gas anomaly in and around the anticlinal structure of the Geleki oilfield, Assam Shelf was studied using LR-115 (II) nuclear track detectors following a grid-sampling pattern. The present study was undertaken to understand the variability of the soil-gas radon concentrations with reference to the oil-wells, drilling activities and local geology. From the alpha-tracks formed on the detectors, the soil-gas radon concentrations were determined using a Spark Counter. The results showed that the natural background soil-gas radon radiation levels in the Geleki oilfield ranged from 1 to 5 kBq/m3 over the subsurface reservoir with anomaly of enhanced values of 12–13 kBq/m3 around the periphery of the oilfield. It has been concluded from the observed soil-gas radon distribution patterns that drilling beyond the extent of the northwestern and eastern corners of the oilfield may yield potential subsurface oil accumulations.