Simulation study of wormhole formation and propagation during matrix acidizing of carbonate reservoirs using a novel in-situ generated hydrochloric acid

Abstract

Optimum acid selection based on reservoir condition is one of the key elements in achieving a successful treatment in carbonate matrix acidizing. High reaction and corrosion rate of regular hydrochloric acid especially in tight reservoirs with high temperatures is considered as a limitation of this acid. One alternative in a high-temperature reservoir is to use insitu generated hydrochloric. The objective of this study is to simulate acidizing treatment using both regular hydrochloric and in-situ generated hydrochloric acid. A continuum twoscale model for linear and radial flow geometry was used to simulate dissolution pattern. A finite-volume method with an implicit backward Euler scheme was used to solve the governing equations. The results of the simulation in a linear system showed that, due to low face dissolution, the in-situ generated hydrochloric at low injection rates could create longer wormholes with less pore volume to breakthrough. The results also proved that using the in-situ generated hydrochloric acid could lead to less face dissolution and deeper penetration of acid into the reservoir. This acidizing system is very suitable in situations where a low injection rate is needed and regular hydrochloric cannot be used due to higher pore volume to breakthrough and high corrosion rate.