Down-hole working condition diagnostic method and device for hydraulic drive screw pump system

The invention provides a down-hole working condition diagnostic method for a hydraulic drive screw pump system and belongs to the technical field of malfunction diagnosis. According to the high-pressure water injection pressure and the low-pressure water injection pressure, the actual pressurization value of a screw pump, the actual pressure-reduction value of a screw motor and actual working efficiency of the crew pump can be obtained; then according to the characteristic curve of the screw pump and the pipeline characteristic curve of the hydraulic drive screw pump system, largest theoretical efficiency of the screw pump is determined; and finally, according to the largest theoretical efficiency of the screw pump and actual working efficiency of the screw pump, down-hole working conditions of the hydraulic drive screw pump system are determined, so that the problem of down-hole working condition diagnosis of the hydraulic drive screw pump system is solved, the theoretical basis is supplied to matching adapt