二连盆地油气勘探以石油为主，天然气勘探程度较低，主要在二叠系、侏罗系、白垩系发现天然气。基于天然气组分、碳同位素组成等地球化学分析，将二连盆地天然气按成因分为生物气、油型气、煤型气及非烃气4种类型。烃源岩评价、天然气成熟度判别、气源对比揭示二连盆地发育多套气源岩，包括白垩系浅层赛汉塔拉组未成熟—低成熟煤层及暗色泥岩、白垩系中深层阿尔善组成熟—高成熟暗色泥岩、侏罗系低成熟—高成熟煤系源岩及石炭系—二叠系成熟—过成熟暗色泥岩。煤层厚度小、分布较广，暗色泥岩厚度近千米、在盆地内广泛发育，有机质类型为Ⅱ₂-Ⅲ型，具备形成天然气的烃源基础。天然气在近源构造高部位成藏聚集，主要有5套常规气储盖组合，据此建立浅层生物气、中深层油气、深层天然气的成藏模式。采用成因法及类比法开展天然气资源评价，计算得到石炭系—二叠系天然气原地资源量为2 411×10⁸ m³，侏罗系天然气原地资源量为2 311×10⁸ m³，白垩系阿尔善组4个洼槽区天然气原地资源量为707×10⁸ m³，白垩系赛汉塔拉组和腾二段天然气原地资源量为1 425×10⁸ m³。洼槽区成熟度高的白垩系阿尔善组近源构造高部位，白垩系赛汉塔拉组、腾二段的浅层生物气圈闭是勘探有利目标；东部凹陷区的石炭系—二叠系，洪浩尔舒特、阿其图乌拉、高力罕等继承性凹陷的侏罗系具有较好的勘探前景。

The Erlian Basin is mainly focused on oil exploration, with a relatively low degree of natural gas exploration. Natural gas has been discovered in the Permian, Jurassic and Cretaceous strata. Based on geochemical analysis of the gas components and carbon isotopic compositions, the natural gas in the Erlian Basin can be classified into four genetic types: biogenic gas, oil-type gas, coal-type gas, and non-hydrocarbon gas. Gas maturity assessments and gas-source correlations reveal that the basin hosts multiple sets of gas-prone source rocks, including immature to low-mature coal and dark mudstone in the shallow Saihantala Formation of the Cretaceous, mature to high-mature dark mudstone in the middle-deep Arshan Formation of the Cretaceous, low-mature to high-mature coal-measure source rocks of the Jurassic, and mature to over-mature dark mudstone of the Carboniferous-Permian. The coal seams are thin but widely distributed, while the dark mudstones are nearly 1 000 m thick and extensively developed in the basin, with organic matter types of II₂-III, providing a source rock foundation for natural gas generation. Natural gas accumulates in near-source structural highs, and there are five main favorable reservoir-seal assemblages, based on which accumulation models for shallow biogenic gas, mid-deep oil and gas, and deep natural gas are established. Using the genetic method and analogy method, the natural gas resources are evaluated. The calculated in-place resources are 2 411×10⁸ m³ for the Carboniferous-Permian, 2 311×10⁸ m³ for the Jurassic, 707×10⁸ m³ for the Cretaceous Arshan Formation in four sags, and 1 425×10⁸ m³ for the Cretaceous Saihantala Formation and Teng-2 member. Overall, favorable exploration targets include the near-source structural highs of the mature Arshan Formation in the sags, and the shallow biogenic gas traps of the Cretaceous Saihantala Formation and Teng-2 member. The Carboniferous-Permian in the eastern sags, and the Jurassic in inherited sags such as Honghaorshute, Aqituwula, and Gaolihan, have good exploration prospects.