Optimization of Reservoir Stimulation Technologie and Efficient Development Strategies for Ultra-Low Permeability Carbonate Reservoirs: A Case Study of the S Reservoir in Iraq H Oilfield

As a critical development layer in Iraq H Oilfield, the S reservoir is characterized by medium-high porosity, ultra-low permeability, complex pore structure, and strong reservoir heterogeneity. These features lead to rapid decline in single-well production and short duration of fracturing effects. To address these challenges, this study aims to optimize reservoir stimulation technologies and explore efficient development strategies suitable for the S reservoir, thereby enhancing well productivity and reservoir recovery. An integrated geology-engineering-reservoir approach was adopted, combining reservoir characteristic analysis, physical simulation experiments, sweet spot evaluation, and numerical modeling. By comparing the effects of hydraulic fracturing, acid fracturing, and slickwater fracturing, parameters such as reservoir brittleness index, bidirectional stress difference, and fracture toughness were analyzed. A graded sweet spot classification model was established, and fracturing parameter design was optimized. The S reservoir exhibits high brittleness, making it suitable for hydraulic fracturing. Slickwater fracturing outperformed traditional gel-based and acid fracturing due to its low reservoir damage and high flow conductivity. Through sweet spot classification, the required fracturing fluid and proppant volumes for fracture generation in different reservoir zones were clarified. Additionally, the impact of fracturing scale on well productivity was identified. Predictive results demonstrate that optimized fracturing significantly improves initial well productivity and extends stable production periods. This study provides technical support for the efficient development of the S reservoir. By optimizing reservoir stimulation technologies, it markedly enhances well production and economic benefits. The findings are applicable not only to the S reservoir but also offer valuable insights for similar ultra-low permeability carbonate reservoirs, demonstrating both theoretical and practical significance.