Research on multi-stage propped fracturing for ultra-low permeability and thick reservoir

The reservoir with big thickness and no obvious interbed could not be produced sufficiently in longitudinal direction with the conventional fracturing technology because of proppant settlement, and long fractures are hard to be produced because of the big reservoir thickness and excessive vertical extension. To improve fracturing in thick oil reservoir, learning from the fracturing principle that the fracture height is controlled by sinking agents, starting from the optimization of some parameters like injection grade, fracturing scale, and injection displacement, a multi-stage propped fracturing technology is developed. The total amount of proppant is deployed by multi-stage injection, as well as the propped fracture of previous stage provides stress shielding, fracture length and propped height can be further increased, and then, effective drainage area is enlarged. In the past two years, multi-stage propped fracturing experiment has been conducted on 242 wells in L oil reservoir in Huaqing Oilfield, the average incremental oil was 0.4 to 1.8 t for single well. It is proved that the new technolgy could better stimulate the production of ultra-low permeability and thick oil reservoir.