After three years of technological breakthrough and field practices, a complete set of patented waterless fracturing operation technology and supporting equipment with independent intellectual property rights have been invented. Obvious oil production increase effect has been observed in multiple field tests on tight sandstone oil reservoir. In this paper, the latest development of Chinese liquid CO2 fracturing technique is introduced through a case study of typical well.
The target depth of operating well is 1730.8m-1757m, with a daily fluid production of 1.6t and oil production of 0.5t, indicating that the displacement relationship has not been effectively established. The fracturing treatment was carried out using the independently developed equipment system, which has treatment capability of available pump rates up to 12 m3/min, sand transportation of 27 m3 and CO2 injection of 1000 m3. During this operation, 860m3 liquid CO2 was injected at a displacement of 5-6m3/min. and 23m3 proppant was preloaded and totally pumped into reservoirs with maximum instantaneous proppant concentration of 12%.
After the fracturing, the daily fluid production increased from 1.9t to 3.9t, the daily oil production increased from 0.7t to 2.3t and the water cut decreased from 63.2% to 41.0%, achieving a significant increase in production. In addition, the oil pressure of one adjacent well increased from 0.5Mpa to 12.4Mpa and the daily oil production of four adjacent wells increased by 0.7-1.1t through the energy enhancement and miscibility of CO2.
The field test shows that liquid CO2 fracturing technology has a significant effects of energy storage and stimulation, adjusts the injection-production relationship effectively, and greatly enhances the single well production. It is expected to become the key technology of the development of tight sandstone oil resources.