琼东南盆地崖城13-A构造潜山天然气成藏条件与成藏模式

Hydrocarbon Accumulation Conditions and Models in Buried Hill of Yacheng 13-A Structure in Qiongdongnan Basin

琼东南盆地潜山油气藏勘探形势复杂,近年在陵南低凸起、松南低凸起均有勘探失利。为进一步剖析琼东南盆地成藏条件与成藏模式,以YC13-A-A井为主要研究对象,通过包裹体分析、薄片观察、盆地模拟、地震资料和测录井资料,对YC13-A构造成藏条件与成藏模式进行分析。结果表明:YC13-A构造天然气为高成熟-过成熟天然气,天然气来源于崖南凹陷以及莺歌海盆地古近系崖城组烃源岩。中生界潜山顶部风化剥蚀以及内幕形成的孔隙和裂缝作为储层,构造脊、砂体和断层为气体的运移提供了良好的输导条件。受到古潜山上覆巨厚泥岩以及泥岩快速沉降的影响,导致欠压实形成弱超压,从而提供了良好的封盖条件。各成藏控制因素的耦合,为天然气成藏提供了有利成藏条件。YC13-A构造主要由西侧莺歌海盆地、东侧崖南凹陷古近系崖城组烃源岩供烃,供烃动力充足,通过断层、构造脊、砂体向潜山风化壳直接充注,具有双凹供烃、双类输导、双重封堵、晚期成藏的成藏特征。

The buried hill oil and gas reservoirs in the Qiongdongnan Basin are complex for exploration.In recent years,exploration has failed in the Lingnan Low Uplift and Songnan Low Uplift.To further analyze the hydrocarbon accumulation conditions and models of the reservoirs in the Qiongdongnan Basin,this study focuses on YC13-A-A well as the primary subject.The hydrocarbon accumulation conditions and models of the YC13-A-A structure were analyzed through inclusion analysis,thin section observation,basin simulation,seismic data,and logging data.The results indicate that the natural gas in the YC13-A structure is highly mature to mature over came from source rocks in the Paleogene Yacheng Formation of the Yanan Sag and Yinggehai Basin.The pores and fractures formed by weathering and denudation at the top and inner of the Mesozoic buried hill serve as reservoirs.The structural ridges,sand bodies,and faults provide good transport conditions for gas migration.Affected by the thick mudstones overlying the ancient buried hill and the rapid sedimentation of the mudstones,under-compaction leads to weak overpressure,which provides good sealing conditions.The combination of various reservoir control factors provides favorable conditions for natural gas accumulation.The source rocks of the YC13-A structure mainly came from the Paleogene Yacheng Formation in the Yinggehai Basin on the west and the Yanan Sag on the east.The hydrocarbon supply is sufficient and directly fills the weathering crust of the buried hill through faults,structural ridges,and sand bodies.It has the characteristics of double-sag hydrocarbon supply,double-type transport,double blocking,and late accumulation.