At our coal bed methane operations at Raniganj in West Bengal, so-called “produced water” is water trapped in underground formations that is brought to the surface during oil and gas exploration and production. In traditional oil and gas wells, produced water is brought to the surface along with oil or gas. In CBM production, wells are drilled into coal seams, and the water located there is pumped to the surface in order to allow gas to be released from the coal seams. Because the water has been in contact with the hydrocarbon-bearing formation for centuries, it has some of the chemical characteristics of the formation and the hydrocarbon itself. However, the produced water may be put to beneficial use taking into account the chemical characteristics, geographical considerations and the cost of pre-treatment.
At Essar Oil’s CBM Raniganj project, the depth of de-watering from the reservoir ranges from a 600m to 1600m. The ground water table level is at a depth of 300m which is much higher than the reservoir water level. The produced water is within an impermeable rock structure so there is no interconnectivity of the reservoir water with the ground water.
Essar Oil installed a reverse osmosis plant for treating the produced water and using the treated water for CBM processes such as hydro fracturing, workover and drilling which otherwise would have required large quantities of freshwater. In the last year, 332,584 scm of produced water was generated and used for various processes as mentioned above.