Crude oil samples from surface seeps in the Douala Basin (southern Cameroon) and from producing fields in the nearby Rio del Rey and Kribi‐Campo sub‐basins were analysed for bulk and molecular geochemical parameters by inductively coupled plasma – mass spectrometry (ICP‐MS), gas chromatography – mass spectrometry (GC‐MS) and isotope ratio mass spectrometry (IRMS). The aims of the study were to assess the composition of the oils, to evaluate the relationship between the seep oils and the oils from producing fields, and to highlight the significance of the data for oil exploration in the region. Chromatograms of the saturate fractions of the oils exhibit biodegradation ranging from very light (PM1 on the scale of Peters and Moldowan, 1993) in oil from the offshore Lokele field in the Rio del Rey sub‐basin, to severe (PM 6+) for seep oils from the Douala Basin. A plot of Pr/n‐C₁₇ (1.3– 5.0) versus Ph/n‐C₁₈ (0.8–2.6) for the samples further supports mild biodegradation in some samples (Lokele, Kole, Ebome), and demonstrates that the oils from the Lokele and Kole fields (Rio Del Rey sub‐basin) and from Ebome field (Kribi‐Campo sub‐basin) originated from mixed organic matter with a dominant marine contribution. The Pr/Ph ratio (1.8–2.3) for the Lokele, Kole and Ebome oil samples, and the V/(V+Ni) ratios (< 0.5) for the seep oils (Douala Basin) and the oils from the Lokele, Kole and Ebome fields, indicate derivation from source rocks deposited in oxic – dysoxic environments. The CPI (1.0–1.1) demonstrates that the Lokele and Ebome oils originated from mature source rocks, with the ratios of C₃₁ 22S/(S+R) (0.57 to 0.63) and C₃₀‐βαH/C₃₀‐αβH (0.18–0.23) for the Lokele, Kole and Moudi samples indicating early oil window maturity. Both V/(V+Ni) ratios (0.06–0.22) and δ¹³C (‐26.96 to ‐24.89 ‰) were used for correlation of the oils, with the seep oils from the Douala Basin showing the closest relationship to the oil from the Lokele field. The presence of mature Type II / III source rocks in different basins in southern Cameroon suggests significant potential for oil exploration in the region.

中文翻译：

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喀麦隆南部产油样品的地球化学

通过电感耦合等离子体质谱法（ICP-MS）分析了杜阿拉盆地（喀麦隆南部）地表渗漏以及附近的里约热内卢和Kribi-Campo子盆地产地的原油样品的体积和分子地球化学参数。 ），气相色谱–质谱（GC-MS）和同位素比质谱（IRMS）。该研究的目的是评估油的成分，评估渗出油与产油区之间的关系，并强调数据对于该地区石油勘探的重要性。石油饱和馏分的色谱图显示出来自里约热内卢次流域Lokele海上石油的轻度（Peters and Moldowan规模的PM1，1993年）的生物降解，杜阿拉盆地的渗油达到严重（PM 6+）。Pr / n‐C图₁₇（1.3- 5.0）相对于pH /正-C ₁₈（0.8-2.6），用于将样品进一步支持温和降解一些样品（Lokele，科尔，Ebome）中，并表明从Lokele和科尔字段油（里约热内卢德尔Rey子盆地）和Ebome油田（Kribi-Campo子盆地）起源于具有重要海洋贡献的混合有机物。Lokele，Kole和Ebome油样品的Pr / Ph比（1.8–2.3），以及渗漏油（Douala盆地）和Lokele，Kole油的V /（V + Ni）比（<0.5） Ebome场和Ebome场表明源自有氧-低氧环境中沉积的烃源岩。CPI（1.0–1.1）表明Lokele和Ebome油起源于成熟的烃源岩，C ₃₁ 22S /（S + R）（0.57至0.63）和C ₃₀的比率Lokele ，Kole和Moudi样品的-βαH/ C _30- αβH（0.18-0.23）表明早期的油窗成熟。两个V /（V + Ni）的比（0.06-0.22）和δ ¹³ C（-26.96至-24.89‰）用于油的相关性，与来自杜阿拉盆地示出从给油关系最密切的渗漏的油洛克场。喀麦隆南部不同盆地中成熟的II / III型烃源岩的存在表明该地区的石油勘探潜力巨大。