Study and Application of Intermittent Volume Fracturing Technology for Tight Reservoirs

Due to the dense physical properties, low brittleness index, large horizontal stress difference, low development of natural fractures of the Triassic Period reservoirs in the Ordos Basin, the conventional volume fracturing technology is difficult to form complex fractures, and then the single well production is low. For this reason, an intermittent volume fracturing technology has been proposed in this paper. Through the study of the friction characteristics of tight sandstone and the law of the subcritical fracture propagation at the fracture tip under the action of fluid, combined with the model experiments, the technical idea of intermittent volume fracturing is put forward for increasing well production. The field test by using the intermittent volume fracturing technical idea is also carried out. This technology provides a new method for the effective development of tight reservoirs. In the process of this technology, a cyclic fracturing method is adopted. The reservoir is first fractured and then stopped. After a certain interval of time, the main fracturing is carried out again. On the one hand, the use of intermittent stopping time promotes the formation pressure diffusion, reduces the difference of horizontal stress, and promotes the interaction between the main fracture and the natural fracture to improve the fracture complexity. On the other hand, after the fracturing fluid is injected into the reservoir, the aftereffect of “rock fluid chemical action” is used to promote the formation of micro fractures and realize the fracture network fracturing. This technology was applied to two wells in Changqing Oilfield. The average fracturing scale of the two wells is equivalent to the conventional mixture water fracturing, but the fracturing displacement is only half of the conventional mixed water fracturing, and the increase of the pressure can be achieved in multiple seams. Compared with contrast wells, the effective stimulated volume of the two wells increased by 30%, and the oil daily production of the single well is increased by 1.5t. It is indicated that the intermittent volume fracturing technology has obvious effect of increasing production for tight reservoirs.