Organic-rich mudstone, whose formation and accumulation are strongly related to the depositional environment, is a potential source of natural gas. Here, geochemical tests (including total organic carbon (TOC), rock pyrolysis, X-ray diffraction (XRD), and main and trace element analyses) were carried out on mudstone samples from two boreholes in the Jixi Basin to reveal the paleoenvironment and its control on organic matter enrichment. The results show that type III kerogen dominated and that all samples entered the maturity stage with good hydrocarbon generation potential. Generally, the TOC content tended to increase with increasing depth, and the mudstone in the middle (K₁ch₂) and lower (K₁ch₁) segments of the Chengzihe Formation was characterized by good quality with TOC > 2.5%. In the Jixi Basin, two common types of mudstones (silica-dominated mudstone and silica-rich argillaceous mudstone) were mainly composed of quartz and clay minerals. These mudstones were rich in Na₂O, MnO and several trace elements (e.g., Zn, Mo, and Bi) and depleted in other elements (e.g., MgO, CaO, Cr, Co, and Ni). The rare earth element and yttrium (REY) distribution patterns normalized by North American shale compositions (NASC) were flat, with slight negative Ce and Eu anomalies. The ratios of Sr/Cu, Rb/Sr, Sr/Ba and V/(V + Ni) in mudstones indicated a warm-humid paleoclimate, a suboxic environment and a marine-continental transitional fresh-brackish water mass. From the K₁ch₁ to Muling Formation (K₁m), although the paleoclimate was more arid and paleosalinity increased gradually, depositional environments were in fresh-brackish water. The paleoclimate and clastic influx are the keys to controlling the enrichment of organic matter. The paleoclimate indirectly affects the preservation of organic matter by influencing the aquatic environment and controlling the level of paleoproductivity, while the strong clastic influx rate directly dilutes organic matter preservation.

富含有机质泥岩的形成和聚集与沉积环境密切相关，是天然气的潜在来源。在这里，对鸡西盆地两个钻孔的泥岩样品进行了地球化学测试（包括总有机碳（TOC）、岩石热解、X射线衍射（XRD）以及主微量元素分析），以揭示古环境及其古环境。控制有机质富集。结果表明，以Ⅲ型干酪根为主，所有样品均进入成熟期，具有良好的生烃潜力。TOC含量总体上随着深度的增加而增加，中部（K ₁ ch ₂）和下部（K ₁ ch ₁) 的城子河组段的特征是TOC > 2.5% 的质量好。鸡西盆地常见的两种泥岩（硅质为主的泥岩和富硅质的泥质泥岩）主要由石英和粘土矿物组成。这些泥岩富含Na ₂ O、MnO 和几种微量元素（如Zn、Mo 和Bi），而其他元素（如MgO、CaO、Cr、Co 和Ni）贫化。由北美页岩成分 (NASC) 归一化的稀土元素和钇 (REY) 分布模式是平坦的，具有轻微的负 Ce 和 Eu 异常。泥岩中Sr/Cu、Rb/Sr、Sr/Ba和V/(V+Ni)比值表明古气候为暖湿古气候、低氧环境和海-陆过渡性淡水-微咸水体。从 K ₁ ch ₁至穆岭组（K ₁ m），虽然古气候更加干旱，古盐度逐渐增加，但沉积环境为淡咸水。古气候和碎屑流入是控制有机质富集的关键。古气候通过影响水生环境和控制古生产力水平间接影响有机质的保存，而强烈的碎屑流入速率则直接稀释有机质的保存。