Study on fracture propagation of fractured tight oil reservoirs in Ordos Basin

Abstract The recovery efficiency in a fractured reservoirs of Ordos Basin with small molecule hydrocarbons has many drawbacks, such as great difficulty in production, difficulty in fracture expansion, and it is a great significance to improving an obvious energy recovery rate in the Ordos Basin for exploring a fracture propagation behavior of unconventional tight oil reservoirs. This study constructs a fracture propagation model suitable for unconventional reservoirs according to the basic reservoir conditions of Ordos Basin, which can analyze an significant effects of different reservoir conditions and working fluid parameters on geological parameters such as length or width of rock fractures. In addition, the mechanism of rock initiation and damage of tight reservoirs can also be revealed and evaluated. The research results indicate that a 100 mPa·s of working fluid showed a crack width of 6 mm as well as the crack length of 25 m, which is much larger than the crack width of 4 mm as well as the crack length of 20 m while a 80 mPa·s of working fluid is showed. In addition, a steering angle of reservoirs fracture can also significantly affect the crack opening law of Ordos tight reservoirs. A larger steering angle will reduce the fracture propagation capacity from 21m at 45° to 18m at 60°. Simultaneously, driving speed of fracturing fluid and geological conditions are also significant elements changing the crack expansion capacity of tight reservoirs. The relevant data analysis can construct necessary data support for a utilization as well as exploitation of the Ordos reservoir and the oil recovery.