Coal occurrence in the Jurassic Dhruma Formation in Saudi Arabia: Inferences on its gas and surface mining potential

• We report on coal occurrence in the Jurassic Dhruma Formation in central Saudi Arabia
• The coal was neither analyzed nor studied in detail and was mentioned only in few local reports
• The coal is humic in origin and has low thermal maturity
• The coal exists at shallow intervals under the sand dunes with high surface mining potential
• Future work will focus on coal in deeper basin for (biogenic and/or thermogenic) coal gas potential

Coal occurrence in central Saudi Arabia was previously noted in government internal reports, but apparently was neither analyzed nor studied in detail.In the present study, a coal sample collected from a water-well drilled in the Az Zilfi area of Central Saudi Arabia was available for analysis to characterize the coal and define its potential to generate gas. The sample was obtained from a silty–sandy mudstone unit in the upper part of the Middle Jurassic Dhruma Formation, at a depth of 70 m below the ground surface. Organic geochemical (Rock Eval, TOC) and organic petrographic analyses of the sample have confirmed the occurrence of low maturity coal in the Dhruma Formation in the Az Zilfi area, which has potential for surface coal mining as well as for microbial gas generation.Regional geologic data highlights the potential for higher maturity coal occurrence at depths suitable for thermogenic gas generation. Deep and shallow well drilling programs would provide essential data to assess both the coal gas and surface mining potential.