准噶尔盆地玛北地区三叠系百口泉组岩石物理相

Petrophysical facies of Triassic Baikouquan Formation in northern Mahu Sag,Junggar Basin

准噶尔盆地玛北地区三叠系百口泉组储层非均质性较强,多因素综合分析成为近年来精细储层研究的重要手段。通过岩心、铸体薄片、测井曲线、粒度等资料,开展综合储层沉积微相、成岩相和裂缝相特征的岩石物理相研究,并对所划分的岩石物理相进行聚类分析,开展对研究区有利储层的预测。结果表明:①扇三角洲沉积微相主要发育分流河道、辫状分支水道、水下分流河道及水下分流间湾等4种微相;②成岩相包括3种致密化成岩相(压实致密成岩相、伊/蒙充填成岩相和硅质胶结成岩相)和2种扩容性成岩相(绿泥石衬边弱溶蚀成岩相和不稳定组分溶蚀成岩相);③在平缓斜坡背景下,由于局部发育水平缝,裂缝密度小于1条/m,对储层物性影响较小;④遵循“沉积微相+成岩相+裂缝相”叠合原则,厘定了岩石物理相的分类,划分出了水下分流河道-绿泥石衬边弱溶蚀成岩相等10种岩石物理相;⑤PF1对应Ⅰ类储层,物性最好,主要发育在百二段,百三段发育规模较小;PF2对应Ⅱ类储层,物性中等,在百口泉组储层中相对较发育;PF3对应Ⅲ类储层,物性相对较差,在百三段较为发育。玛北地区岩石物理相的研究方法,可以为百口泉组油气扩边勘探提供指导。

The reservoir heterogeneity of Triassic Baikouquan Formation in northern Mahu Sag of Junggar Basin is strong,and multi factor comprehensive analysis has become an important means of fine reservoir research in recent years.Through core description,casting thin section,logging curve and grain size analysis,the studies on petrophysical facies including reservoir sedimentary microfacies,diagenetic facies and fracture facies were carried out,and cluster analysis on the divided petrophysical facies was carry out to predict favorable reservoirs in the study area.The results show that:(1)Fan delta sedimentary microfacies are mainly composed of distributary channel,braided branch channel,underwater distributary channel and underwater distributary bay.(2)Diagenetic facies include three kinds of tight diagenetic facies(compacted tight diagenetic facies,illite/smectite filling diagenetic facies and siliceous cementation diagenetic facies)and two kinds of dilatancy diagenetic facies(chlorite lining weak dissolution diagenetic facies and unstable component dissolution diagenetic facies).(3)Under the background of gentle slope,the fracture density is less than 1/m due to the local development of horizontal fractures,which has little impact on reservoir physical properties.(4)According to the superposition principle of“sedimentary microfacies+diagenetic facies+fracture facies”,the classification of petrophysical facies was determined,and 10 kinds of petrophysical facies were divided,such as underwater distributary channel-chlorite lining weak dissolution diagenesis facies and so on.(5)PF1 corresponds to typeⅠreservoir,with the best reservoir physical properties,mainly developed in Bai 2 member,and the development scale of the Bai 3 member is relatively small.PF2 corresponds to typeⅡreservoir with medium physical properties and relatively developed in Baikouquan Formation.PF3 corresponds to typeⅢreservoir,with relatively poor physical properties and relatively developed in Bai 3 member.The research method of petrophysical facies in northern Mahu Sag can provide guidance for oil and gas exploration of Baikouquan Formation.