变质岩潜山油气藏储层特征及评价

Reservoir feature and evaluation of metamorphic buried-hill reservoir

采用岩石薄片、X射线衍射、扫描电镜、成像测井等多种分析手段,对渤海海域太古界变质岩储层的岩性特征和储集空间类型进行了综合研究,探讨了暗色矿物体积分数对孔隙度和裂缝密度的影响。通过大量数据分析,建立了孔隙度、裂缝密度与不同岩性暗色矿物体积分数的定量关系。研究结果表明:暗色矿物在碎裂岩中体积分数较低,而在片麻岩中体积分数较高,角闪石体积分数与孔隙度呈负相关关系,黑云母体积分数与孔隙度呈正相关关系;不同岩性中暗色矿物体积分数对孔隙度的影响界限值为5%和15%,对裂缝密度的影响界限值为10%;当暗色矿物体积分数小于10%时,构造条件对裂缝发育的影响更为关键。文中结合岩心分析、风化指数、录井、测井等资料,建立了太古界变质岩潜山油气藏储层分带评价方案,自上而下划分为强风化破碎带、次裂缝带、主裂缝带、致密带和内幕裂缝带。

Based on the mineralogical analysis from rock slice,XRD,SEM,and FMI well log,the lithology types and reservoir space types of the archaeozoic basement gas reservoir in Bohai Sea area is systematically analyzed,and the impact of dark mineral on reservoir quality is also discussed.According to statistics of dark mineral type and volume,the quantitive relation of dark mineral type,volume fraction and fracture density is established.Result shows that dark mineral volume fraction is low in cataclastic and high in gneiss.Amphibole and porosity are negatively correlated,while biotite and porosity are positively correlated.The influence limit of dark minerals volume fraction of different lithology on porosity is 5%and 15%respectively.The influence limit on fracture is 10%.When dark mineral volume fraction is less than 10%,it presents no obvious correlation,but tectonic condition presents greater influence on fractures.Finally,based on core analysis,weathering index,element log data,and well log data,the evaluation of the archaeozoic metamorphic buried-hill reservoir is built,and five zones,including weathering zone,secondary fracture zone,primary fracture zone,tight zone and inside hill fracture zone,are classified.