Estimation of ash content in Tabas Parvadeh IV coal mine using universal kriging and proposing additional drillings

Parvadeh coalfield which located in 85 km south-west of Tabas, South Khorasan province, is the largest coal reserve of Iran. This mine is producing 1.5 million tons of coking coal annually. Largest sub-region of Parvadeh coalfield is Parvadeh IV. 168 drill holes were drilled in Parvadeh IV to obtain core samples. Ash content of coal is the most important qualitative parameter in explorations and concentrate production. This study concentrates on estimation and modeling of ash content in B2 seam using geostatistical approach. An exploration database was made based on data gathered from 154 drill holes which crossed B2 seam. Basic statistical studies were carried out. Directional semi-variograms used to analyze and interpret the spatial heterogeneity of ash content. Due to trend existence in spatial raw data of ash content, universal kriging method was applied in order to removing the trend. As the result, ash content modeled and estimated for every 100×100m exploitation block using block kriging. Estimation results presents that ash content varies from 13.0% to 41.6% with an average of 28.0%. This estimation which has minimum errors, establishes a manner for exploitation and blending plans. Besides, the uncertainty map was generated and locations of proposed additional drillings were specified.