Experimental Evaluation of the Shielded Temporary Plugging System Composed of Calcium Carbonate and Acid-Soluble Preformed Particle Gels (ASPPG) for Petroleum Drilling

To protect oil and gas reservoirs during drilling, shielded temporary plugging technology has long been the key to oil and gas well drilling operations. Hard ultrafine calcium carbonate (CaCO3) has been widely used to effectively plug the storage, and to remove the plugging in time after drilling and completion effectively. Ultrafine calcium carbonate has the advantages of high strength, adjustable particle size, excellent bridging and plugging effect, and rapid and full reaction with acid. However, the bridging effect of hard particles usually cannot achieve complete sealing. This study intended to use acid-soluble preformed particle gels (ASPPG) as a collaborative plugging material. ASPPG is a soft material that can form deformation filling and self-decomposition. The research results show that the "superfine calcium carbonate + ASPPG" synergistic plugging system can significantly improve the plugging strength of the drilling fluid. In addition, the system can completely react or self-degrade in the process of hydrochloric acid plugging removal, causing very little damage to the formation. Besides, as the ASPPG particle concentration increases or the particle size decreases, the plugging strength will gradually increase. Moreover, the system can also be applied to high temperature (90 °C) formation conditions. The above experimental research results can provide a research foundation for the pilot application of the shielded temporary plugging drilling fluid technology based on the "hard particles + soft particles" synergistic plugging effect.