辽东湾坳陷LX油田浅层特稠油藏成藏过程及模式

Shallow Super Heavy Oil Reservoir Accumulation Process and Model in LX Oilfield,Liaodong Bay Depression

针对LX油田浅层（明化镇组和馆陶组）特稠油藏复杂的油藏模式,充分利用地球化学、储层和包裹体等地质资料,在研究原油来源的基础上,恢复了该区东营组的成藏时期,并对成藏期内原油油品性质的变化及稠化特征进行了研究。结合浅层辫状河道沉积储层与含油性的分析,建立了浅层特稠油藏的成藏过程及模式,结果表明：（1）浅层明化镇组和馆陶组成藏与深层东营组油藏破坏相关,东营组储层在早期（28~25 Ma,东营组沉积末期）成藏并发生初步生物降解作用以及原油演化过程中,密度先增大、粘度后增大的性质使得油品性质在一定程度上变差,降低了对盖层条件的要求,为晚期（5~0 Ma）原油在盖层条件极差的明化镇组和馆陶组储层中成藏创造了必要条件;（2）浅层明化镇组和馆陶组辫状河道砂体纵向叠置关系与原油遭受的边充注边降解的过程共同形成了含油饱和度及油品性质在垂向上的旋回性,这与储层岩性的旋回性相对应,基于此建立了浅层油气充注模式,解释了现今特稠油垂向分布特征。

In order to investigate the complex accumulation model of super heavy oils in LX oilfield （Minghuazhen and Guantao formations）, integrated data including geochemical, petrophysical and fluid inclusion analysis were applied in this study to reconstruct the charge history in Dongying Formation, and to characterize the evolution process of oil properties and therefore densification during the charge period. Based on the combined analysis on both the shallow braided channel reservoir and oil saturation, the accumulation processes and model of super heavy oil in shallow reservoirs were established, the result as follows： （1）The hydrocarbon accumulation in shallow Minghuazhen and Guantao formations is strongly associated with the destroy of deep Dongying oil reservoirs. The hydrocarbon in Dongying Formation was accumulated during 28 to 25 Ma and thereafter suffered biological degradation. During the oil evolution history, the density was increased firstly and then the viscosity was increased, which reduces the oil properties and decreases the requirement to cap rock sealing capacity. The dynamic evolution processes made it possible that crude oil could accumulate in the Minghuazhen and Guangtao formations which have poor sealing capacity during 5~0 Ma. （2）The vertical cyclicity of the oil saturation and oil properties is ascribed to the vertical stacking pattern of braided channel sandy bodies in Minghuazhen and Guantao formations as well as the fact that crude oil were suffered from biological degradation during the charging time. This is corresponding to the cycles of reservoir lithology. In term of these analysis, we established the hydrocarbon charge models and characterized the vertical distribution of crude oils.