Description Of Wormhole For Self-diverting Acid And Dynamic Simulation Study

Acidizing as a common stimulation method is widely used in many oil field.Acidizing could be divided into carbonate acidizing and sandstone acidizing through the difference type of reservoir.Because of the higher reaction intensity of carbonate acidizing,the highlighted difference for acid treatment between carbonate reservoir and sandstone reservoir is the existence of wormhole during the carbonate acidizing.As the predominant channel,the wormhole could increase the effect radius effectively.For fractured and vuggy type reservoir and strong anisotropism reservoir,the self-diverting acid could be used to modify the treatment profile to guarantee a good treatment result.Basing on the wormhole extending model,a semiempirical model for conventional acid,a two-scale model for conventional acid and a two-scale model for self-diverting acid are introduced.Box-counting method is used to get the final fractal dimension after acidizing.The result,that fractal dimension equal 1.365,suggest the wormhole hold a stronger fractal character than face dissolution and uniform dissolution.For the twoscale model,a detail solving process using finite difference is provided.The two scale model could simulate three typical dissolution pattern and show the growth process of wormhole during treatment clearly.Based on the two-scale model of conventional acidizing model,a twoscale model of self-diverting acidizing model is proposed.Finally,the diverting capacity test is carried out between conventional acid and self-diverting acid in an area with two permeability.It turns out that both the conventional acid and self-diverting acid could not divert from the area with high permeability.But the self-diverting acid show a tendency to uniform dissolution so that self-diverting acid could complete the mission of diverting to some extent.