CBM drilling technical parameter optimization methodology and software development: a case study of LUAN mining area.

Based on the leakage of the coalbed methane (CBM) drilling engineering practice of Luan mining area in China, the author determines the safe drilling fluid density range for the stable borehole wall based on borehole wall collapse and fracture pressure. Such parameters as the drilling fluid hydraulic parameters (including pump pressure, pump power and displacement, nozzle diameter, bit pressure drop, bit hydraulic horsepower, circulation pressure drop, impact force and jet velocity) and drilling parameters (including weight-on-bit, drilling rotary speed, bit tooth wear) in each borehole section are optimized. Taking the lowest drilling cost as the controlling target, the drilling parameter optimization model is designed and solved by the genetic algorithm.

Weld quality inspection of small-diameter thin-walled pipes by a laser ultrasonic method.

Defect inspection of small-diameter thin-walled pipes is a difficult problem in the field of nondestructive testing. In this paper, a new detection method based on laser ultrasonics and guided circumferential wave technology is proposed and used to inspect the defects in pipes. First, a theoretical model based on the theory of acoustic propagation in solids is proposed for the small-diameter thin-walled pipes.