Plugging Efficiency in Fractured Carbonate Gas Reservoirs Using Fuzzy-Ball Fluids Combined with Solid Plugging Agents

Loss encountered during workover operation is a common challenge in the development of fractured carbonate gas reservoirs. Fuzzy-ball fluid, a non-solid phase plugging material developed based on Fuzzy Sealaplugging Theory, has been widely used in killing the well. However, in the plugging of fractured carbonate gas reservoirs, a substantial volume of Fuzzy-ball fluid is required and the pressurization process is time-consuming, which greatly impairs its application. In this study, solid plugging agents including calcium carbonate and fibers are introduced into Fuzzy-ball fluids to improve the plugging efficiency of large-scale macro-fractures. In particular, the plugging performance was evaluated by the indoor plugging of a synthetic core containing a 5 mm wide wedge-shaped fracture, as well as by field trials in two wells. The results show that the plugging ability of the new fluid increases as the concentration of calcium carbonate or fiber increases. Moreover, a more significant enhancement of plugging efficiency was achieved by fibers. In field applications, the use of Fuzzy-ball fluids with calcium carbonate or fibers reduced the volume of fluid consumed by 33~74% and decreased the pressurization time by 33~69%. Therefore, by combining solid plugging agents with Fuzzy-ball fluids, the dual demand for plugging efficiency and cost-effectiveness for fractured carbonate gas reservoirs is achieved simultaneously, which provides an alternative technique for addressing fluid loss in fractured carbonate gas reservoirs.