ETR在严重生物降解油油源对比中的应用——以辽东湾地区JX1-1油田为例

Application of ETR in Oil-source Correlation for Severely Biodegradaed Crude Oil——By Taking JX1-1 Oilfield for Example

以辽东湾地区JX1-1油田为例,从成因意义、热稳定性和受生物降解的影响大小等3个方面探讨长链三环萜烷指数ETR[ETR=(C28三环萜烷+C29三环萜烷)/(C28三环萜烷+C29三环萜烷+Ts)]在严重生物降解油油源对比中的适用性。研究表明,ETR在湖相沉积环境中具有与伽马蜡烷/C30藿烷相似的指相意义,可以反映湖盆的水介质条件;在生油窗内同一套烃源岩样品的ETR随深度(成熟度)增加无明显变化,具有很好的热稳定性;在ETR与C19/C23三环萜烷相关图中不同降解程度(最高可达8级)的原油样品随参数的变化表现出与烃源岩一致的相关变化趋势,反映ETR未受生物降解作用的影响或影响较小。ETR与C19/C23三环萜烷相关图版可以有效地区分沙一段和沙三段烃源岩,可用于JX1-1油田严重生物降解油的油源对比。对比结果表明,JX1-1油田不同来源类型原油的空间分布具有明显的规律性,JX1-1E部分的原油主要来源于沙三段烃源岩,JX1-1部分的主体原油来源于沙三段和沙一段烃源岩,且沙一段烃源岩的相对贡献有由北往南增大的趋势。不同来源类型原油的空间分布状态与地质背景高度符合。

JX1-1 Oilfield in Liaodong Bay was taken for example,applicability of ETR[=(C28+C29)/(C28+C29+Ts)] in the oil-source correlation for severely biodegradaed crude oil was studied in its original signification,thermic stability and tolerance of biodegradation.The correlation of ETR with Pr/Ph,gammacerane/C30 hopane ratios suggested that ETR had similar origin signification with gammacerane/C30 hopane ratio,and was closely related to water chemical conditions in lacustrine environments.There was no change in ETR of each source rock interval with the increase of depth in the oil window,which indicated ETR had excellent thermic stability.ETR of oil samples at different biodegraded levels decreased as C19/C23 tricyclic terpane ratio increased,and displayed a similar locus with the source rock samples,it was suggested that ETR was less affected by biodegradation.Correlatograph built by ETR and C19/C23 tricyclic terpane ratio could distinguish the samples from Es3 and Es1 source rocks,and be used to the oil-source correlation for oils from JX1-1 Oilfield.The results indicate that distribution of oils from different source rocks in JX1-1 Oilfield presents apparent regularity,oils in the area of JX1-1E mainly come from Es3 source rocks,oils in the area of JX1-1 mainly come from Es3 and Es1 source rocks.Relative contribution of Es1 source rocks presents increasing trend from the north to south in JX1-1 Area.Distributive condition of oils from different source rocks is highly consistent with that of geology setting.