Matrix acidizing is a common well stimulation technique in which acid is injected into
the producing reservoir. The main purpose of the process is to remove wellbore formation
damage and/or dissolve a portion of the rock and hence, enhance the permeability in the
near well-bore region. It is however, important to optimize many treatment parameters to
execute an efficient acidizing job.
This study are undertaken to investigate the influences of acid injection rate, acid
concentration, variation of rock permeability, and acid volume injected on the recovery of
damaged rock permeability using matrix acidizing of oil carbonate reservoirs.
Nine core flood experiments are undertaken to investigate the above-mentioned effects
on matrix acidizing process using actual cores and reservoir liquids. Every core sample
was cleansed, evacuated, saturated with brine, flooded with crude oil, and damaged with
bentonite water-base mud. Then, the designed acidizing run was carried out. The rock
permeability was measured before and after acidizing to quantify the success of the
process and to identify the effect of every factor. Models of prediction for permeability
damaged factor and permeability improvement factor were developed.
The results of the study indicated that the increase of acid concentration and/or the flow
rate increases the recovery of damaged permeability. Furthermore, initial rock
permeability has minor effect on permeability enhancement by matrix acidizing of
damaged carbonate oil reservoir rocks. The increase of acid injection rate increases the
required acid volume injected regardless of the reservoir temperature under acidizing.