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The economic development of tight carbonate reservoirs requires hydraulic or acid fracturing stimulation. Acid fracturing better activates natural fractures, resulting in increased stimulated reservoir volume and improving oil and gas flowability. In order to solve the problem of excessive acid-rock reaction due to high temperature, this paper screened four kinds of solid forms of acid with the maximum quantity of acid and reaction rate as the index and formed a high temperature-resistant mixed solid acid system with solid organic acid as the main part and inorganic solid acid as the auxiliary part. The maximum quantity of acid produced and effective acid concentration of the system were greater than 50%, and no residue was precipitated after the complete reaction. Dynamic acid-rock rate tests were performed on different types of retarded acid at 140 °C. The test results show that the solid acid dissolves to form a low-viscosity acid solution, and the reaction rate is one order of magnitude lower than that of gelled and cross-linked acids at the same hydrogen ion concentration, and it is little affected by temperature. Moreover, the paper compares the treatment effect of micro-proppants and solid acids on micro-fractures. The results show that the core permeability improvement multiples up to 900 times under low dissolution of solid acid and the formation of oil and gas flow channels with the same scale as micro-proppants. The experimental results demonstrated the ability of solid delayed acid to transport the fracture leading edge at high temperatures and effectively activate micro-fractures. [ABSTRACT FROM AUTHOR]

The Lower Paleozoic Ordovician strata within the Ordos Basin harbor dolomite gas reservoirs are characterized by low porosity (0.98% to 14.2%) and low permeability (0.001 mD to 2.8 mD). Gas extraction from these reservoirs is frequently impeded by water lock due to the intrusion of water-based drilling fluids and the accumulation of formation water, which increase water saturation near the wellbore and significantly decrease gas permeability. This research is pivotal in elucidating water-lock mechanisms and developing water-unlocking strategies for such tight gas reservoirs. Comprehensive analysis through wettability tests, spontaneous imbibition, high-speed centrifugal drainage, and nuclear magnetic resonance (NMR) revealed that Jingbian gas field rocks are predominantly water-wet with a spontaneous imbibition water saturation of 60% to 80%, indicating a high propensity for water lock. The pore structure, mainly within the 200 to 300 nm range, presents challenges as high-speed centrifugation achieves only 70% to 80% water saturation displacement, with a drainage rate of about 20% to 30% and a drastic decline in gas permeability by several orders of magnitude. This study identifies the surfactant sodium dodecyl benzene sulfonate (SDBS) as an optimal agent for enhancing water displacement and gas production. At a 0.1% concentration, SDBS improves drainage rate and permeability by 58.5% and 69.42%, respectively, demonstrating its efficacy in mitigating water lock and enhancing recoverability in tight dolomite reservoirs. These findings serve as a scientific guide for augmenting production in similar geological settings. [ABSTRACT FROM AUTHOR]