Abstract

The occurrence of hydrocarbons in Girujan formation of North Shelf of Assam & Assam Arakan Basin is known since long, yet identification and their realistic evaluation has remained elusive to log analysts till date. Non availability of sufficient logs especially reliable porosity log against this formation has been biggest constraint. The present paper, based on analysis of more than 500 wells in this area, suggests suitable interpretation technique for such reservoirs with limited logging suit. The study of well log data integrated with available testing results in twenty wells has helped in formulating suitable criteria for identifying hydrocarbon bearing sands. The log signatures of different sands have been compared with known water bearing sands to arrive at qualitative as well as quantitative evaluations. More than 330 hydrocarbon bearing sands in 120 wells have been identified. The study also established the special characteristics of sands developed within Girujan Formation such as limited aerial extent, high clay content and poor permeability of sands in spite of their good porosity which will be useful in exploitation of their potential.