Mechanism of wormholing and its optimal conditions: A fundamental explanation Academic Article uri icon


  • 2018 Elsevier B.V. Acid stimulation is commonly used in carbonate reservoirs, which can be either matrix acidizing or acid fracturing. In both treatments, wormholes can form. In matrix acidizing, wormholing is favorable because the damaged region can be bypassed. In acid fracturing, wormholing is not desired because it can increase fluid loss, which can limit conductive fracture length. Three major processes are involved for wormholing: convection, diffusion and surface reaction. A thorough understanding of these processes is necessary for engineering design. In this paper, we fundamentally explore wormholing mechanisms starting from pore growth. A wormhole forms when larger pores grow in cross-sectional area at a rate that greatly exceeds the growth rate of smaller pores due to surface reaction. This happens when pore growth follows a particular mechanism, which is discussed in this paper. We developed a model to predict wormhole growth behavior. The model uses the mode-size pore in a pore size distribution - the pore size that appears most frequently in a distribution - to predict the growth of the pore. By controlling the acid velocity inside of it, we can make larger pores grow much faster than other smaller pores, thus reaching the most favorable condition for wormholing. This also results in a balance between overall acid/rock reaction and acid flow. By understanding the wormholing mechanism, engineers can select proper treatment fluids and pumping rate for acid stimulation design.

published proceedings


author list (cited authors)

  • Dong, K., Zhu, D., & Hill, A. D.

citation count

  • 14

complete list of authors

  • Dong, Kai||Zhu, Ding||Hill, A Daniel

publication date

  • January 2018