Microstructural analysis applied to carbonate matrix acidizing: An overview and a case study.

Carbonate formations constitute the primary source of hydrocarbon reservoirs worldwide, highlighting the importance of gaining a deeper understanding of matrix acidizing phenomena to enhance well productivity in these formations. Microstructural analysis of acidified cores is a key method to assess acidizing systems in carbonate rock samples. X-ray computed microtomography (Micro-CT) has significantly contributed to this field, primarily focusing on the qualitative and quantitative characterization of the profiles of carbonate mineral dissolution, also known as wormholes, created during matrix acidizing. This non-destructive evaluation technique allows the internal analysis of a sample without altering its internal structure or chemical composition. This work focuses on a comprehensive review of the research studies and the main applications of micro-CT for evaluating and characterizing matrix acidizing in carbonates. First, an overview of the fundamentals of micro-CT and acid stimulation in carbonates is provided. Next, the applications of micro-CT are discussed and grouped into microstructural characteristics of wormholes, dynamic in-situ experiments, and pore-scale modeling topics. A case study is presented with a methodology based on micro-CT analysis for matrix acidizing. Finally, future work and current challenges, such as 4D CT and CT-based acidizing models, are discussed.