摘要
目前储层分类方案较多,大多受控于地区差异特征,普遍缺乏经济性约束,推广应用具有一定的局限性。并且海上勘探开发具有高成本、高风险的特点,为了提高海上勘探效率,降低成本,明确海上低渗储层特征并对其进行分类评价研究具有重要意义。因此,在对低渗储层特征及成因分析的基础上,结合产能特征,综合应用物性分析、高压压汞、恒速压汞、扫描电镜及核磁共振等多种实验分析来表征储层孔喉结构特征,进而对储层进行分类。北部湾盆地流沙港组以长石岩屑砂岩和长石岩屑石英砂岩为主,主要孔喉半径小于5μm,喉道多为微细喉,低渗成因主要是埋深引起的强压实作用;其次是局部沉积环境影响的高泥质、分选差也会使储层物性变差。通过优选比采油指数、渗透率、孔隙度、主要孔喉半径、最大连通孔喉半径、主要流动孔喉半径均值、有效孔隙度以及可动流体饱和度等参数进行储层综合评价,建立海上低渗储层分类评价标准。将低渗储层分为5类,其中Ⅰ类储层主要流动孔喉半径均值大于3μm,有效孔隙度大于10%,可动流体饱和度大于50%,比采油指数大于1 m^(3)/(d·MPa·m),多元分类系数小于3,为海上低渗优质储层;Ⅱa类储层多元分类系数3~5,为低渗有效储层;Ⅱb类储层多元分类系数5~8,为低渗可动用储层;Ⅲ类、Ⅳ类储层较差,海上难以开发。通过储层分类,在后期开发过程中,明确开发井型、调整开采方式、优化注采系统等,对提高海上低井网开发效率,降低成本具有重要意义。
Currently,numerous reservoir classification schemes exist,but regional differences constrain most and lack economic constraints,which limits their widespread adoption and application.Considering the high cost and high risk of offshore exploration and development,it is essential to define the characteristics and classification evaluation of offshore low-permeability reservoirs for improving exploration and development efficiency.Therefore,based on the analysis of low-permeability resevoir characteristics and genesis,and combined with production capcaity features,a combination of experimental analyses,including physical property analysis,high-pressure mercury displacement,constant-rate mercury displacement,scanning electron microscopy,and nuclear magnetic resonance,is employed to characterize reservoir pore throat structures,thereby classifying reservoirs.The rock type of the Liushagang Formation in Beibuwan Basin is dominated by feldspar lithic sandstone and feldspar lithic quartz sandstone.The radius of the main pore throat is less than 5μm,and the throat is primarily a micro-fine throat.Its low permeability is mainly caused by strong compaction due to burial depth;in some areas,it is also caused by high mud content and poor sorting under the influence of the sedimentary environment.Based on the analysis of the characteristics and genesis of low-permeability reservoirs,the characteristics of pore throat structure were studied by physical property analysis,high-pressure mercury injection,constant-velocity mercury injection,cast thin sections,scanning electron microscope,nuclear magnetic resonance,and other kinds of experimental studies,and combined with the productivity characteristics,specific production index,permeability,porosity,main pore throat radius,maximum connected pore throat radius,mean radius of main flowing pore throats,effective porosity,and movable fluid saturation were selected to evaluate the reservoir comprehensively.The classification evaluation criteria were established,and the low-permeability reservoirs were divided into ClassⅠ,Ⅱa,Ⅱb,Ⅲ,and Ⅳ.The ClassⅠreservoir is a high-quality reservoir among the offshore low-permeability reservoirs,with the mean radius of main flowing pore throats greater than 3μm,effective porosity greater than 10%,movable fluid saturation greater than 50%,and the productivity index greater than 1 m^(3)(/d·MPa·m).The multivariate classification coefficient is less than 3.Class Ⅱa reservoirs have a multivariate classification coefficient between 3 and 5,indicating they are effective low-permeability reservoirs.Class Ⅱb reservoirs have a coefficient between 5 and 8,suggesting they are developable low-permeability reservoirs.Class Ⅲ and Ⅳ reservoirs are poor and difficult to develop offshore.Through reservoir classification,it is of great significance to improve the development efficiency of offshore low well patterns and reduce costs by clarifying the development well type,adjusting the production method,and optimizing the injection-production system in the later development process.
作者
邓孝亮
汪紫菱
钟佳
詹冶萍
DENG Xiaoliang;WANG Ziling;ZHONG Jia;ZHAN Yeping(Hainan Branch of CNOOC(China)Limited,Haikou 570311,China;Zhanjiang Branch of CNOOC(China)Limited,Zhanjiang 527057,China)
出处
《复杂油气藏》
2025年第4期460-470,共11页
Complex Hydrocarbon Reservoirs
关键词
储层特征
产能特征
低渗储层分类
流沙港组
北部湾盆地
南海北部
reservoir characteristics
productivity characteristics
classification of low permeability reservoirs
Liushagang Formation
Beibuwan Basin
Northern South China Sea
