RESUMEN
Present study was aimed to investigate trace elemental composition and possible elemental correlation with depth of some Pakistani wells. Exploratory oil wells of Toot oilfield from Potwar region of upper Indus basin were selected for this purpose. Samples of well cuttings and soil sections were collected with the assistance of Oil and Gas Development Company Limited. Elemental analyses were performed using instrumental neutron activation analysis. This study is the first of its kind to report detailed elemental profile of Toot oilfield, Attock, Punjab, Pakistan, via instrumental neutron activation analysis (INAA). Source formation of Toot oilfield is characterized by Jurassic Datta formation. Around 19-26 elements were identified by INAA. Major, minor and trace elemental concentrations varied with depths along the sampling lines. Data analysis was performed by the application of principal component analysis (PCA). PCA was useful in differentiating between surface and depth samples. Elemental volumes of different wells were established through bi-plots. In extension, naturally occurring radioactive materials and technologically enhanced naturally occurring radioactive materials were also determined for the wells of Toot oilfield. Annual dose rates and activity levels were calculated in oil well formations. Measurements of annual dose rates fall within safe limits, indicating anodyne atmosphere. Contamination indices, such as enrichment factor with respect to Al, geo accumulation index (Igeo), pollution index and integrated pollution index, were also determined. Cr and Zn were found to cross the safe limits, which may be due to the local industrial and anthropogenic activities.