Geochemical characteristics and oil source correlation of reservoirs in Lufeng 15 drape structural belt, Pearl River Mouth Basin
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摘要:
珠江口盆地陆丰15披覆构造带南、北部分别与陆丰22洼、陆丰15洼毗邻,常规的油源对比指标无法确定构造带上S2-1和S5-1油藏的油源,2个洼陷都有可能向其供烃。为揭示原油的成因来源,对该地区原油及烃源岩开展了生物标志物、碳同位素及含氮化合物等特征的精细对比。在研究区原油及源岩中新检测出4个C24四环萜烷:脱-A-奥利烷、脱-A-羽扇烷、新C24四环萜烷及C24 17,21-开环藿烷。研究对比发现,S2-1和S5-1油藏原油中C24四环萜烷分布特征与陆丰22洼文昌组烃源岩更加吻合,具有更强的亲缘关系。此外,全油碳同位素和正构烷烃单体烃碳同位素指示S2-1和S5-1油藏明显区别于陆丰15洼生成的原油,预示着其原油具有陆丰22洼烃源岩的贡献。含氮化合物示踪参数指示S2-1油藏具有近源充注特征,进一步验证了陆丰22洼烃源岩对S2-1和S5-1油藏的重要贡献。
Abstract:The north and south parts of Lufeng 15 drape structural belt in the Pearl River Mouth Basin are adjacent to Lufeng 22 Sag and Lufeng 15 Sag, respectively. Conventional oil source correlation indicators cannot determine the oil source of the S2-1 and S5-1 reservoirs in the structural belt, and the two adjacent sags may supply hydrocarbons to them. To reveal the origin and source of crude oils, the biomarkers, carbon isotopes and nitrogen-containing compounds of crude oils and source rocks in this area were compared. Four C24 tetracyclic terpanes were detected from crude oils and source rocks in the study area: des-A-oleanane, des-A-lupane, new C24 tetracyclic terpane and C2417,21-secohopane. The distribution of C24 tetracyclic terpanes in crude oil from S2-1 and S5-1 reservoirs are more consistent with the source rocks of Wenchang Formation in Lufeng 22 Sag in a close relationship. In addition, the carbon isotopes of whole oil and n-alkane monomers indicate that the S2-1 and S5-1 reservoirs are significantly different from those in the Lufeng 15 Sag, indicating that they are contributed by the source rocks of Lufeng 22 Sag. The tracer parameters of nitrogen-containing compounds indicate that the S2-1 reservoir has the characteristics of near-source charging, which further verifies the conclusion that the S2-1 and S5-1 reservoirs have important contributions from the Lufeng 22 Sag source rocks.
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表 1 样品信息表
Table 1. Information of the samples
样品类型 构造位置 井号 深度/m 岩性 层位 数量/个 烃源岩 陆丰15洼缓坡带 W15-1 3 489~3 501 灰色泥岩 文三段 1 3 609~3 744 灰色泥岩 文四段 4 W15-2 3 312~3 318 灰色泥岩 文三段 1 3 414~3 579 灰褐色泥岩 文四段 10 W15-3 3 227~3 239 灰色泥岩 文三段 1 3 257~3 401 灰褐色泥岩 文四段 1 陆丰22洼洼中隆 W22-1 3 306~3 370 灰褐色泥岩 文三段 3 3 408~3 420 灰褐色泥岩 文四段 2 原油 陆丰15披覆构造带 S5-1 / / 下珠江组 1 S2-1 / / 下珠江组 4 陆丰15洼缓坡带 W15-2 / / 文昌组 2 W15-4 / / 下珠江组 2 油砂 陆丰22洼洼中隆 W22-1 3 288~3 534 黄色细砂岩 文昌组 5 注:“/”代表无数据。 表 2 研究区文昌组烃源岩的有机质丰度指标
Table 2. Index of organic matter abundance in source rocks of Wenchang Formation in the study area
洼陷 层位 沉积相 TOC/% S1/(mg/g) S2/(mg/g) Pg(S1+S2)/(mg/g) 氯仿沥青“A”/% 总烃/10−6 陆丰15洼 文昌组 半深湖—深湖 陆丰22洼 文昌组 半深湖—深湖 注:表中数据为 。
表 3 研究区文昌组烃源岩干酪根显微组分
Table 3. Kerogen microscopic components in source rocks of Wenchang Formation in the study area
井名 深度/m 层位 干酪根显微组分/% 惰性组 镜质组 壳质组 腐泥组 W15-1 3609~3621 文昌组 0 3 22 75 3654~3666 文昌组 0 3 29 68 3688~3700 文昌组 0 2 26 72 3732~3744 文昌组 0 5 29 66 W15-2 3414~3420 文昌组 0 22 0 78 3423~3429 文昌组 0 6 0 94 3453~3459 文昌组 0 4 0 96 3471~3477 文昌组 0 13 0 88 3489~3495 文昌组 0 36 0 64 3513~3516 文昌组 0 11 3 86 3528~3534 文昌组 0 6 0 94 3543~3549 文昌组 0 8 0 92 3558~3564 文昌组 0 3 0 97 3573~3579 文昌组 0 7 0 93 W15-3 3257~3269 文昌组 0 3 34 63 3290~3302 文昌组 0 2 29 69 3320~3332 文昌组 0 3 25 72 3350~3362 文昌组 0 2 23 75 3389~3401 文昌组 0 3 26 71 W22-1 3306~3318 文昌组 0 8 25 68 3333~3345 文昌组 0 3 23 74 3358~3370 文昌组 0 2 18 80 3408~3420 文昌组 0 2 17 81 表 4 S2-1和S5-1油藏原油的族组成
Table 4. The group compositions of crude oils in S2-1 and S5-1 reservoirs
油藏 原油编号 层位 族组成/% 饱和烃 芳烃 非烃 沥青质 S5-1 S5-1-1 下珠江组 78.16 10.00 4.74 3.42 S5-1-2 下珠江组 62.46 10.73 6.31 6.31 S2-1 S2-1-1 下珠江组 69.10 11.46 6.60 9.03 S2-1-2 下珠江组 66.15 16.49 1.60 1.22 S2-1-3 下珠江组 62.08 10.96 3.79 13.34 S2-1-4 下珠江组 60.80 12.96 3.86 9.26 表 5 原油及族组成碳同位素数据
Table 5. Carbon isotope data of crude oil and group composition
构造位置 井名/油藏名 样品类型 层位 编号 δ13C/‰ 原油 饱和烃 芳烃 非烃 沥青质 陆丰15洼缓坡带 W15-2 原油 文昌组 W15-2-1 −29.6 −30.7 −29.7 −28.7 −28.8 W15-4 原油 下珠江组 W15-4-1 −29.8 −30.4 −28.1 −27.6 −28.1 原油 下珠江组 W15-4-2 −29.7 −30.5 −28.0 −27.7 −28.1 陆丰15披覆构造带 S5-1 原油 下珠江组 S5-1-1 −28.5 / / / / 原油 下珠江组 S5-1-2 −28.4 / / / / S2-1 原油 下珠江组 S2-1-1 −28.6 / / / / 原油 下珠江组 S2-1-2 −28.2 −29.3 −27.7 −27.9 −27.8 原油 下珠江组 S2-1-3 −28.3 −29.0 −28.2 −28.3 −28.5 原油 下珠江组 S2-1-4 −28.5 −29.1 −27.9 −28.2 −28.5 陆丰22洼洼中隆 W22-1 油砂 文昌组 W22-1-2 −29.0 −29.2 −28.6 −28.3 −28.3 油砂 文昌组 W22-1-3 −28.6 −28.9 −28.1 −28.2 −28.3 油砂 文昌组 W22-1-4 −27.9 −28.5 −27.2 −27.1 −27.0 油砂 文昌组 W22-1-5 −27.9 −28.8 −27.1 −27.1 −26.9 -
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