A Parametric Study of Sandstone Acidizing Using a Fine-Scale Simulator

Sandstone acidizing is a group of complex chemical reactions process. Some of previous researches express that it is possible to generate wormhole in sandstone. If the optimal conditions for sandstone wormholing is found, the success rate of sandstone acid treatment will be largely improved from the current success rate which is about 50%-70%. A fine-scale sandstone acidizing simulator was developed to simulate the heterogeneity of properties in sandstone. To make the wormholing analysis easily and clearly, a 3D Visualization Program (UT3DVIS) is used to display a 3D image for numerical acidizing results. The parametric study demonstrate that to generate wormholes in sandstone, mineral heterogeneity is the most important factor. High temperature and high HF concentration are also helpful for wormholing. Low acid injection rate is advantage to wormholing for heterogeneous sandstone. However, too low an injection rate can cause face dissolution, and increase the operation cost. There is an optimal Damkohler number to generate channels or wormholes for a sandstone acidizing case. Precipitation will cause heavy damage in sandstone acidizing treatments if the acidizing reaction front is uniform in the core. However, if there is a main acid flow channel in the core, the precipitates will block the other parts of the core, and force more acid to converge into the channel. Therefore, precipitation is helpful to generate wormholes or high permeability channels in heterogeneous sandstone rather than being a solely negative factor in sandstone matrix acidizing.