珠江口盆地HZ26-6构造“双古”领域油气成藏特点与富集规律

Oil and gas accumulation characteristics and enrichment regularity in the Prepaleogene-Paleogene field of HZ26-6 structure in Pearl River Mouth Basin,China

研究珠江口盆地HZ26-6构造“双古”领域油气成藏期次和油气成藏条件,探讨油气成藏特点与富集规律。在借鉴前人研究成果的基础上,通过铸体薄片鉴定、包裹体均一温度测定等手段,厘清了HZ26-6构造“双古”领域三大油气主力成藏期及对应的流体充注类型,即13.8~10 Ma B.P.的低熟原油充注期,10~5.3 Ma B.P.的成熟原油充注期,5.3 Ma B.P.以来的天然气充注期;依据实际的地质、钻井、测井、地震等资料梳理了HZ26-6构造“双古”领域三大油气成藏关键条件,即以“早期低熟缓慢生油,晚期高熟快速生气”为特点的烃源条件,以“裂缝带风化叠加改造成储,转换带砂砾岩体规模成储”为特征的储层条件,以“通源断裂多期跨层输导,深缝浅砂侧向差异运移”为特征的输导条件。HZ26-6构造“双古”领域具有“早油晚气,宽窗强供;扇加潜山,规模储集;断缝断砂,高效输导;递进充注,整装成藏”的油气成藏特点,以及“油型盆地早油晚气条件下,宽窗强势供烃、‘双古’整装成藏”的油气富集规律。

Based on the previous research results,by means of casting thin section identification and inclusion homogenization temperature measurement,this paper reveals the three major hydrocarbon accumulation periods and corresponding fluid charging types in the“Prepaleogene-Paleogene”field of HZ26-6 structure in the Pearl River Mouth Basin,studies the hydrocarbon accumulation periods and conditions and discusses the hydrocarbon accumulation characteristics and enrichment rules.The result shows that 13.8~10 Ma B.P.is the charging period of low mature crude oil,10~5.3 Ma B.P.is the charging period of mature crude oil.From 5.3 Ma B.P.has been the natural gas charging period.Based on the actual geological,drilling,logging and seismic data,three key conditions for hydrocarbon accumulation in HZ26-6 structure are sorted out,that is,the source conditions characterized by slow oil generation in early stage with low maturity,rapid gas generation in late stage with high maturity,and the reservoir conditions characterized by weathering and superposition of fracture zone to transform into reservoir,and large-scale sandstone rock mass to transform into reservoir.The transport conditions are characterized by multi-stage cross-bed transport of source-connected fault and lateral differential transport of shallow sand in deep fractures.In general,the HZ26-6 structure is characterized by formation of early oil and late gas,wide window strong hydrocarbon supply,fan delta+buried hill,large-scale reservoir,fractured sand,high-efficiency transport,progressive filling,integrated reservoir forming of HZ26-6 structure.It reveals the oil and gas accumulation law of formation of early oil and late gas in oil-type basin and the law of oil and gas accumulation by strong hydrocarbon supply with wide window and integrated reservoir formation in Prepaleogene-Paleogene field.