Research and Field Application of Quasi-Dry CO2 Fracturing Technology in Ji Dong Oilfield

Tight sandstone gas reservoirs are generally characterized by poor reservoir physical properties, fine pore and throat volume and high clay content. Most of the tight reservoirs are water-sensitive. Conventional hydraulic fracturing using water based fracturing fluid may cause formation damage such as clay swelling and water blocking, and affect stimulation effect. Research on non-aqueous fracturing technologies have been carried on recent years. Quasi-dry CO2 fracturing is a waterless fracturing technology which uses a highly viscous mixture of emulsion that contains 100% liquid CO2 and a small amount of water-based fracturing fluid to avoid damage to water-sensitive reservoir, and no solid residue during flowback process. The main characteristics of the quasi-dry CO2 technology including fluid composition and sand-carrying capacity were studied, temperature and shear resistance of quasi-dry CO2 fracturing fluid were tested. The new fluid system has less formation damage, excellent fracture making ability and sand carrying capacity that can meet all the requirements of large scale fracturing construction. Meanwhile, using carbon dioxide as fracturing fluid have more economic and environmental significance. Pilot test was conducted in a deep tight sandstone gas reservoir of Nanpu No.5 structure in Ji dong oilfield. The fracturing operation was successful indicating that quasi-dry CO2 technology is operationally feasible. After fracturing, the pilot well achieved excellent stimulation effect with the daily oil and gas production increased 2.5 times and 8.6 times respectively, which has instructive significance to the development of similar reservoirs.