Carbonate acidizing is one of the main techniques for improving the production and injectivity in oil and gas fields. Various studies and field stimulation results were analyzed to develop a fit-for-purpose acid stimulation treatment design placed with coiled tubing in which diversion is achieved by using in-situ gelation, emulsified diverting acid, degradable fibers, or combinations of these methods.

The lack of downhole fluid placement control during the pumping of stimulation treatments may cause these jobs to not achieve the maximum stimulation effect or even fail, which may eventually call for more costly solutions.

An innovative stimulation approach was applied on a sour gas injector well in a carbonate oil field in the Caspian region. The field is characterized as a naturally fractured, thick, and prolific carbonate formation with high H2S content. To dispose of H2S and improve oil recovery, the produced sour gas is injected back into the reservoir through injector wells. An innovative method using fiber optic technology for acquiring distributed temperature survey (DTS) measurements and a real-time downhole sensor tool providing pressure and temperature measurements and casing collar location were used in this well to improve its injection potential.

DTS technology was utilized to better understand the movement of stimulation fluids into the reservoir through real-time monitoring, thus providing the capability to optimize the acid injection along the target zone. The DTS analysis during the post-acid injection stage identified crossflow and provided good correlation between acid reaction with carbonates and proportional warm-back trends along the formation.

The adoption of the technique enabled increased overall confidence in decision making during treatment execution, which allowed an improved placement strategy, resulting in increased stimulation effectiveness. This technology has the potential to become the next important step in the evolution of acid stimulation strategies in the Caspian region.

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