复杂油气藏油气运移的地球化学特征——以胜坨油田为例

东营凹陷胜坨油田原油划分为4个组群。组群1是由下第三系沙河街组三段下亚段烃源岩提供的成熟油,主要分布于宁海、坨一区西部;组群2是由沙河街组四段上亚段烃源岩提供的成熟油,主要分布于坨二、三区及一区东部,是胜坨地区的主要原油组群;组群3为混源油,油源是沙河街组三段下亚段和四段上亚段两套成熟烃源岩所提供,分布局限;组群4为低熟油,是由民丰洼陷沙河街组四段上亚段高伽马蜡烷烃源岩在低成熟阶段提供的烃类,仅分布于胜北断层北侧。利津洼陷沙河街组三段下亚段烃源岩形成的油气沿坨94断层向上运移,分别从东、西两个充注点在坨一区西部和宁海地区聚集成藏;利津洼陷沙河街组四段上亚段烃源岩形成的油气沿坨94断层向上运移,在坨一区东部聚集成藏。坨二、三区8砂组都源自沙河街组四段上亚段烃源岩,具有两次油气充注过程。早期成藏发生在东营组沉积末期,民丰洼陷沙河街组四段上亚段烃源岩早期生成的油气主要在沙河街组三段上亚段8砂组以下(包含8砂组)储层成藏;晚期成藏发生在明化镇时期,民丰洼陷沙河街组四段上亚段烃源岩晚期形成的油气主要在8砂组以上(包含8砂组)沙河街组二段—东营组储层成藏。早期油气运移的充注点位于胜北断层,晚期油气运移的充注点位于南北向断层北部。

Geochemical study on hydrocarbon migration in complex reservoirs: taking Shengtuo oilfield as an example

Crude oils of Shengtuo oilfield in Dongying depression can be divided into 4 groups.Group 1 is mature oil sourced from the lower 3~(rd) member of Eogene Shahezhen Fm,which is distributed mainly in Ninghai and western Tuo-1 block.Group 2 is mature oil sourced from the upper 4~(th) member of Shahezhen Fm,which is distributed mainly in Tuo-2 block,Tuo-3 block and the eastern part of Tuo-1 block.It is the major crude oil group in Shengtuo area.Group 3 is mixed oils sourced from the lower 3~(rd) member and the upper 4~(th) member of Shahezhen Fm,with a restricted distribution.Group 4 is low-mature oil generated from source rocks with high gammacerane in the lower 3~(rd) member of Shahezhen Fm in Minfeng sag during low maturity period,which are distributed only on the northern side of Shengbei fault.Hydrocarbons that have been generated from the source rocks in the lower 3rd member of Shahezhen Fm in Lijin sag may migrate upward along Tuo 94 fault and are accumulated in the western part of Tuo-1 block and Ninghai area from both the eastern and western charging points.Hydrocarbons that have been generated from the source rocks in the upper 4~(th) member of Shahezhen Fm in Lijin sag may migrate upward along Tuo 94 fault and are accumulated in the eastern part of Tuo-1 block.The 8~(th) sandstone units in Tuo 2 and 3 blocks have experienced two oil and gas charging stages from the source rocks in the upper 4~(th) member of Shahezhen Fm.The early reservoiring occurs at the end of deposition of Dongying Fm,and the oil and gas have accumulated mainly in the sandstone reservoirs below the 8~(th) sandstone unit(including the 8~(th) sandstone unit itself) in the upper 3~(rd) member of Shahezhen Fm.The late reservoiring occurs during the deposition of Minghuazhen Fm,and the oil and gas have accumulated mainly in the sandstone reservoirs above the 8~(th) sandstone unit(including the 8~(th) sandstone unit itself) in the 2~(nd) member of Shahezhen Fm and Dongying Fm.The early migration has been charged from Shenbei fault,while the late migration has been charged from the northern part of the S-N trending fault.