Experimental study on wormhole distribution and etching pattern in naturally-fractured carbonate formation

The main control factor of acid loss during acid fracturing treatment is acid loss through acid wormhole. Acid excessive loss seriously restrained the propagation of hydraulic fracture, which diminished the chance to connect the cave-cleft system and the effectiveness of acid fracturing. This thesis utilizes the long core plate flow experiment, which modeling two dimension flowing and reaction of acid in fracture. The experiment indicates that the number and scale of acid wormhole is determined by acid flow rate, while the acid wormhole place is controlled by the distribution of natural fracture. Through the way of changing the aperture of fracture modeling the etching patterns of core with different aperture of fracture find that mainly etching patterns include: 1 mm aperture fracture corresponding to whole rock beam homogeneous etching; and 1 mm~0.5 mm aperture fracture corresponding to heterogeneous etching of most rock beam; and when the aperture of crack is around 0.1 mm the etching pattern is correspond to local deep and narrow dissolution channel. The test outcome has a guiding significance for adapting loss control measures in acid fracturing treatment.