摘要
碳酸盐岩储层经历了复杂的沉积、成岩和构造作用,内部发育着不同尺度的孔、洞、缝结构,往往表现出强烈的非均质性,常规力学实验难以全面评估其内部结构对岩石力学参数的影响。为此,以四川盆地震旦系灯影组灯四段藻白云岩为例,利用微米CT扫描和纳米压痕实验,系统表征了孔洞、藻凝块及白云石的微观结构特征和力学属性,然后结合均匀化理论提出了一种藻白云岩的岩石力学性质跨尺度评价方法,并揭示了白云石与藻凝块在力学性能上的差异及其对宏观力学参数的影响规律。研究结果表明:①白云石矿物展现出更高的微观强度、更低的塑性变形以及更强的抗裂缝扩展能力,而藻凝块的微观力学参数具有更强的分散性;②白云石与藻凝块在微观层面的弹性模量、硬度及断裂韧性之间呈现良好的线性相关性,通过均匀化方法预测得到的藻白云岩宏观弹性模量和泊松比分别是单轴实验测得值的1.90和1.39倍;③藻白云岩弹性模量随孔洞发育程度增加逐渐降低,其预测范围逐渐收窄,而泊松比与之相反,孔洞纵横比和微裂纹进一步控制宏观力学性质,当孔洞纵横比为0.087~0.202或裂缝线密度为0.30~0.63条/m时,均匀化预测结果与实验值一致。结论认为,该方法不仅避免了传统岩心采集中成本高昂和实验重复性差的问题,还有效降低了传统均匀化方法导致的高估现象,为复杂碳酸盐岩储层的精细力学参数表征提供了新思路,为复杂储层的力学建模与参数预测奠定了理论基础。
Under the action of complex sedimentation,diagenesis and tectonism,different scales of pores,vugs and fractures are developed inside carbonate reservoirs,and strong heterogeneity is often exhibited,which makes it difficult to apply conventional mechanical experiments to comprehensively evaluate the influence of the internal structures on the rock mechanical parameters.Taking the algal dolomite of the 4th Member of Sinian Dengying Formation(Deng 4 Member)in the Sichuan Basin as an example,this paper systematically investigates the microstructural characteristics and mechanical properties of pores,algae clots and dolostone by virtue of micro-CT scanning and nanoindentation experiment.Then,a cross-scale evaluation method for rock mechanical properties of algal dolomite is proposed according to the homogenization theory,and the differences in the mechanical performance between dolostone and algae clot and their influences on macroscopic mechanical parameters are revealed.The following results are obtained.First,dolostone exhibits higher microscale strength,smaller plastic deformation,and greater resistance to fracture propagation,while algae clot is more disperse in microscopic mechanical parameters.Second,dolostone and algae clot present a good linear correlation in microscopic elastic modulus,hardness and fracture toughness.The macroscopic elastic modulus and Poisson's ratio of algal dolomite predicted by means of homogenization method are 1.90 and 1.39 times the uniaxial experimental values,respectively.Third,with the increasing pore development degree,the elastic modulus of algal dolomite decreases gradually,and its prediction range gets narrow gradually,whereas Poisson's ratio exhibits the opposite trend.Additionally,pore aspect ratio and microfissures further control macroscopic mechanical properties.The homogenization predictions align well with experimental results when the aspect ratio ranges from 0.087 to 0.202,or the fracture linear density falls between 0.30 and 0.63 fractures per meter.In conclusion,this method not only addresses the high core acquisition cost and poor experimental reproducibility,but also effectively reduces the overestimate caused by traditional homogenization method.It provides a new idea for the fine characterization of mechanical parameters of complex carbonate reservoirs,as well as a theoretical foundation for mechanical modeling and parameter prediction of complex reservoirs.
作者
李皋
上官自然
杨旭
李红涛
冯佳歆
李明昊
李泽
LI Gao;SHANGGUAN Ziran;YANG Xu;LI Hongtao;FENG Jiaxin;LI Minghao;LI Ze(State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation//Southwest Petroleum University,Chengdu,Sichuan 610500,China;Engineering and Technology Research Institute,PetroChina Southwest Oil&Gasfield Company,Deyang,Sichuan 618300,China)
出处
《天然气工业》
北大核心
2025年第5期124-135,共12页
Natural Gas Industry
基金
国家自然科学基金项目“井下碳酸盐岩裂缝多物理场耦合变形与渗流机理研究”(编号:51674217)
四川省自然科学基金项目“超深层裂缝性气层钻井复杂工况井筒瞬态流动特性及井口回压控制压力反馈规律研究”(编号:2023NSFSC0929)。
关键词
纳米压痕
微米CT扫描
藻白云岩
多尺度力学性质
岩石力学
灯四段
均匀化方法
Nanoindentation
Micro-CT scanning
Algal dolomite
Multi-scale mechanical properties
Rock mechanics
Deng 4 Member
Homogenization method
