Experimental Study on Hydraulic Fracturing in Shale and its Application in Chinese Shale Gas Development(PPT)

摘要

Shale gas development has been booming in China in the last few years, but it is still far beyond expectations although some breakthroughs have been made in some individual shale gas wells. As a successful development technique, staged hydraulic fracturing of horizontal wells has been widely used in shale gas development especially in North America. In order to investigate hydraulic fractures initiation and propagation in shale, physical experiments were done with shale outcrops. The tests were done in a heavy load frame with cubic specimen(300mmX300mmX300mm) and fractures propagation were monitored using acoustic sensors installed on different location of cubic surfaces. Fracture propagation was then verified with fracture path from dyed fracturing fluid and CT scan after the test. The impact of stress difference, fluid viscosity and pumping rate on fracture propagation and the complexity was evaluated for hydraulic fracturing design improvement. Those measures in hydraulic fracturing design include slick water as fracturing fluid for brittle formations, combination of slick water and gel for formations with minor stress difference to avoid premature fracture diversion so as to increase stimulated reservoir volume, and varied pumping rate for formations with developed beddings to achieve fracture extension in all those beddings. Improved fracturing design resulted in stimulation success in shale gas development in Sichuan basin and gas production for one well reached 112,000 cubic meters per day.