Cold-frac Technology in Tight Gas Reservoirs

For the fracturing processes several frac fluids were presented, described by their properties and behavior in the reservoir formation and the practical experiences in using. Energized fluids such as CO2-foam or commingled CO2 fluids are predominantly used for the optimization of the backflow and the aimed proppant transport. Cold fracturing fluids have strong cooling effect in fracturing process mainly in rock-stress reduction, however these kinds of fluids should be investigate precisely, in terms of thermal stress effect, cleanup process and proppant movement. Cold water fluid has been tested successfully in geothermal reservoirs. This stimulation technique is successful in these fields but not in TGRs. The use of liquid CO2 as a fracturing fluid offers a viable method of stimulation. The successful application of these fluids to a variety of formations in USA was shown. The process has proven be an economical alternative to conventional stimulation fluids. Liquid N2 has also been used in limited cases. From this results it can be concluded, that liquid CO2 seems to be the most efficient frac fluid for future Tight Gas stimulations. The coupling of the cold frac technology with underground CO2 capture and storage (CCS) seems to be a future possibility.