Matrix Acidizing in Dolomitic Rocks: Wormhole Development and Injection Performance Analysis

Matrix acidizing is widely used to improve the productivity of carbonate reservoirs, particularly those with significant dolomitic content, which account for a substantial fraction of global hydrocarbon reserves. In this study, the pore volume to breakthrough (PV_bt) behavior of a dolomitic rock was investigated during acidizing with 15 wt % HCl containing commercial additives, namely a corrosion inhibitor (0.5% v/v) and an emulsion preventer (0.2% v/v). Eight core flooding experiments were conducted at 60 °C under a confining pressure of 2000 psi, a backpressure of 1200 psi, and an axial stress of 500 psi, with injection flow rates ranging from 0.4 to 4.0 mL/min. The samples exhibited porosities from 13.99% to 14.94% and permeabilities between 0.28 and 2.47 mD. The PV_bt curve followed the dissolution trend described by the Buijse and Glasbergen model, with an optimum PV_bt of 2.03 at 2.0 mL/min, corresponding to the most efficient stimulation condition and the formation of a dominant wormhole requiring the minimum acid volume for breakthrough. X-ray microcomputed tomography images revealed three main dissolution patterns: face dissolution and/or conical wormholes at low flow rates, dominant wormholes with branched structures under optimal conditions, and highly branched wormhole networks at high flow rates. The results demonstrate the strong influence of dolomite dissolution kinetics on acidizing efficiency and highlight the importance of selecting an appropriate injection rate for the stimulation fluid under investigation. This study provides new insights into reactive transport and wormhole development in dolomitic rocks and supports the optimization of acid stimulation treatments in dolomitic carbonate reservoirs.