Exploration drilling optimisation using geostatistics: a case in Jharia Coalfield, India

Abstract

Drill hole optimisation using geostatistics has been used in many parts of the world in respect of various mineral deposits including coal. The present paper is an attempt to provide a means to maximise the information to cost ratio for optimisation of exploration drilling in the Jharia coalfield, which is the only source of prime coking coal in India. Exploration in Jharia Coalfield that has led to the generation of a huge exploration database has been carried out by various governmental and non-governmental agencies. But because of lack of importance and an obvious application towards exploration modelling, the database had not been utilised to its fullest extent. In the present study, an attempt has been made to derive geostatistical models of various proximate coal constituents of selected seams in respect of nine opencast mine blocks of the coalfield. This experimental study, employing geostatistical volume–variance relationships, revealed that an exploration grid density of 16 drill holes per square kilometre with a grid spacing of 300 × 300 m within an exploration area of 1 × 1 km is adequate for maximisation of information in respect of the Jharia Coalfield. Until now, the density of exploration drilling in the coalfield has been considered as per Indian Standard Procedure (ISP) norms solely based on past experience and proposed mining methods. The present study of exploration drill hole optimisation using the concept of kriging variance is associated with an objectively defined mathematical basis and therefore may be applied for exploration optimisation in other coalfields in India and other countries, which occur in similar geological settings.