Study on the mechanism of reactive acid transport in fractured two-mineral carbonate rocks

Abstract

Centering on the mechanism of reactive acid transport in fractured two-mineral carbonate rocks, this paper established a two-mineral model for fractured media with the extended finite element method based on the two-scale continuum model. A series of examples are presented with the numerical model, the numerical results show that the variation of volume fraction of dolomite, the surface reaction constant of dolomite as well as the diffusion coefficient can alter the dissolution morphology and dissolution performance. As the volume fraction of dolomite increases or surface reaction constant of dolomite decreases, the dissolution patterns would transform form wormhole to uniform dissolution. And the bedding distribution and porphyritic distribution of dolomite will cause a fragmentation phenomenon for the dissolution morphology. Besides, the bedded dolomite can bring about an increased acid consumption. It can be inferred that the reaction rate difference between limestone and dolomite is the key factor that affects the dissolution morphology, and the retarded acid with a low reaction rate in dolomite rocks does not perform well.