Industry continues to struggle with acid distribution and penetration. Most papers, therefore, continue to focus on these themes. Other than recommendations for further reading, a few other papers are worthy of mention and may provide some useful tools for the practicing engineer.

Paper SPE 214416 describes a novel technique that could perhaps be developed further. The concept is built around running a tool on wireline across the zone of interest, which, upon activation, generates hot acid vapor. The procedure is simple, bearing a low cost with no associated environmental hazards. Engineers desperately need an alternative to acid placement through pipe, coiled tubing, or bullheading. For example, propellants have been around for years; however, their performance has not quite met the hype. Nevertheless, several case histories have been authored to suggest their efficacy; historically, some treatments have even been wildly successful. The point is, more effort is needed to mature techniques such as these as an alternative to conventional stimulation.

In paper URTEC 3818857, an oxidizer is introduced as a preflush to improve near-wellbore conductivity without adding significant cost and operational complexity. The oxidizer was effective in removing biological debris and biofilms, thereby improving acid penetration. Paper SPE 215664 examines the use of biodegradable particles and fibers to divert in naturally fractured carbonates. Size distribution was the key to achieving temporary isolation with a minimal amount of material. In fact, the paper showcases successful treatments with less than one barrel of this material. Furthermore, no material was recovered during flowback, indicating complete degradation.

Lastly, SPE 216144 introduces a novel automated framework that relies on smart sampling and tests multiple scenarios to arrive at an optimal stimulation design. The process is intelligent and entirely Web-based.

Acid stimulation is indispensable, and the understanding of fluid systems, and the placement thereof, continues to evolve.

Recommended additional reading at OnePetro:

SPE 218353 From Zero to Hero: A New Breakthrough of Stimulation Method by Combining Acidizing and Cyclic Extended Breakdown in Sawah Field by Ilfi, PT Pertamina, et al.

SPE 214821 How Downhole Conditions Impact Acidizing Performance in Carbonate Reservoirs by M.A. Sayed, Saudi Aramco, et al.

SPE 215332 Novel Single-Phase Retarded Acid System for Effective Stimulation of Limestone Reservoirs by Mohammed Qamruzzaman, ONGC, et al.

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