关键词: 裂缝, 裂缝重构技术, 应力敏感性, 酸蚀, 有限元

Abstract: Carbonate rocks are highly brittle and stress sensitivity test will lead irreversible damage to the cores, resulting in the inability to evaluate the difference in stress sensitivity before and after acid erosion with the same cores and the poor comparability of evaluation results. To address this challenge, a method to evaluate the effect of acid erosion on stress sensitivity of carbonate rocks was established based on fracture reconstruction technology, the fracture surfaces before and after acid erosion were characteristically scanned and reconstructed, the finite element method was applied to study the fracture closure pattern under effective stress, and the effect of acid erosion on fracture seepage under effective stress was simulated to evaluate the variation in fracture permeability. It was found in the study that the difference in mineral components on the fracture face leads to non-uniform acid erosion on the fracture surface, making the fracture surface more rough and resulting in greater difference in the fractal dimension between the fracture surfaces; under the effective stress of 40 MPa, before the acid erosion, the fracture width decreased by more than 55% and the permeability damage rate was greater than 90%; however, after the acid erosion, the fracture width decreased by less than 40%, the permeability damage rate was less than 75%, and the stress sensitive damage decreased. In other words, acid fracturing and pickling are conducive to improving the permeability of artificial fractures and prevent fracture closure. This study can provide a reference for the evaluation of stress sensitivity damage of fractured tight sandstone and shale reservoirs.

Key words: fracture, fracture reconstruction technology, stress sensitivity, acid erosion, finite element