Fracture diagnosis method for low-yield horizontal well in tight oil reservoir of AN block

In the AN block of the Ordos Basin, the long-term fracture creation in low-yield horizontal wells in tight oil reservoir can not be effectively evaluated by conventional testing techniques. In order to accurately learn the key information of fractures before stimulation in low-yield horizontal wells, the compression type double-sealing single-stick string was designed to obtain the sectional variable displacement squeeze pressure and shut-in drawdown data of horizontal wells. Then, fracture squeeze index curve, instantaneous pump off pressure and fracture diffusion pressure were used to conduct integrated evaluation on the primary reformation sufficiency and perforation blockage situations of horizontal wells, and thus obtain the sectional reservoir pressure and output of horizontal wells.Test and analysis were conducted in horizontal wells in tight oil reservoir, the AN block, showing that this fracture diagnosis method can be used to discriminate the primary reformation level of sectional fractures and the perforation blockage situations. Furthermore,the calculation results of the 3 kinds of reservoir pressure analysis methods are basically the same, which can be mutually verified. The diagnostic results have provided directions for the screening of potential stimulation section, the technology optimization and the parameter optimization. Repeated stimulation was implemented in 4 low-yield horizontal wells in tight oil reservoir, where diagnostic test had been carried out, and the single well output was increased by 70% than the stimulated horizontal well that had not been tested. This method can provide reference to the pre-stimulation fracture diagnosis of low-yield horizontal wells in other unconventional reservoirs.