通南巴气田须家河组致密砂岩储层特征及分类评价

Characteristics and classification evaluation of tight sandstone reservoir in Xujiahe Formation of Tongnanba Gas Field

通南巴气田须家河组储层具有特低孔、基质致密、裂缝局部发育、非均质性强的特征,储层精细分类评价对储层甜点的准确认知至关重要。文中从研究区的各项岩心分析化验资料入手,明确了各层系储层储集空间类型多样,孔喉以微孔微细喉为主,沉积微相差异导致不同层系具有不同的有利岩性,在各层系的砂体中都规模发育多期次、多类型的张开缝和半充填缝,裂缝主要起沟通有效渗流通道的作用。在此基础上,优选孔隙度、基质渗透率、启动压力、最大进汞饱和度等关键参数,确定出储层的物性下限和细分界线,分别在须四段、须二上亚段、须二下亚段中各参数界限区间内分析沉积微相和主控岩性的分布,采用数理统计的方法利用6个关键参数分层系建立了储层的储能品质分类标准,并综合裂缝识别评价成果和气测全烃等将储层综合划分为4类,Ⅰ,Ⅱ类层是研究区优质储层和开发动用的重点储层类型。综合分类储层的空间展布和裂缝发育程度预测等成果,实现了分层系分类储量区的精细刻画。研究成果为通南巴气田须家河组致密砂岩气藏的合理高效开发奠定了基础。

The reservoir in Xujiahe Formation of Tongnanba Gas Field has the characteristics of ultra-low porosity,tight matrix,locally developed fractures and strong heterogeneity.The precise classification and evaluation of the reservoir is crucial for accurate understanding of the"sweet spot"of the reservoir.From the analysis and testing data of various cores in the study area,it is believed that there are various types of reservoir spaces in each layer,with micropores and micro throat being the main type of throat.Due to the differences in sedimentary microfacies,there are different favorable lithologies in different layers,and multiple stages and types of open and semi-filled fractures are developed in each layer of the sand bodies.The fractures mainly serve to communicate effective seepage channels.On this basis,key parameters such as porosity,matrix permeability,starting pressure and maximum mercury saturation were selected to determine the lower limit and subdivision boundary of the reservoir′s physical properties.The distribution of sedimentary microfacies and main controlling lithology was analyzed respectively within each boundary interval of the Xu-4 member,upper Xu-2 submember,and lower Xu-2 submember.A classification criteria for reservoir quality were established through six key parameters by using mathematical statistical methods.Based on the results of fracture identification and evaluation,as well as the total hydrocarbon content in gas logging,the reservoirs are comprehensively divided into four categories.Among them,Class I and II reservoirs are high-quality reservoirs and key reservoir types for development and utilization in the research area.Finally,the comprehensive classification of the spatial distribution of reservoirs and the prediction of the degree of fracture development have achieved a fine characterization of the classified reserve areas in the layered system.The research results have laid the foundation for the efficient development of tight sandstone reservoir in Xujiahe Formation of Tongnanba Gas Field.