Shale reservoirs have emerged as potential targets for geological carbon sequestration, particularly in scenarios involving the co-injection of acidic gases like CO2 and H2S. This study employs molecular simulations to investigate the competitive adsorption behavior of CH4, CO2, and H2S within graphite and quartz nanopores, representative of organic and inorganic pore environments in shale formations, finding a stronger adsorption affinity of organic pore surfaces. The confinement effect analysis quantified the competitive adsorption strengths, revealing the order H2S > CO2 > CH4, with H2S and CO2 exhibiting advantageous positions. By employing the competitive Langmuir adsorption model, the maximum adsorption capacities were determined for each gas in different nanopore types. Quartz nanopores exhibited lower adsorption capacities but higher CO2 selectivity, and graphite nanopores displayed high maximum adsorption capacities and adsorption affinities for all three gases, rendering them favorable for acid gas co-sequestration in shale reservoirs.