基于NMR与CMP实验的致密砂岩孔喉结构表征方法  

Characterization method of pore throat structure in dense sandstone based on NMR and CMP experiments

作　　者：李浩[1] 樊志强[1] 谢雨芯 巩肖可 郝博斐 孙龙[1] 雷小兰[1] 闫健[2] LI Hao;FAN Zhiqiang;XIE Yuxin;GONG Xiaoke;HAO Bofei;SUN Long;LEI Xiaolan;YAN Jian(Changqing Oilfield Branch Second Gas Production Plant,Yulin Shaanxi 719000,China;Xi’an Shiyou University,Xi'an 710065,China)

机构地区：[1]长庆油田分公司第二采气厂,陕西榆林719000 [2]西安石油大学,西安710065

出　　处：《地质科技通报》2025年第1期25-35,共11页Bulletin of Geological Science and Technology

基　　金：国家自然科学基金项目(52174031)。

摘　　要：致密砂岩储层孔隙结构复杂、纳米孔隙发育,需集成多种技术对孔隙结构进行综合表征,以更好地认识储层。在优选6块延长组长71储层代表性岩心基础上,采用场发射扫描电子显微镜(FESEM)、恒速压汞(CMP)和核磁共振(NMR)等方法,研究了岩心样品的孔隙类型及结构特征。采用CMP数据对NMR孔隙分布进行了修正,识别了喉道半径与孔隙半径的分布范围,建立了适用于致密砂岩的孔隙半径分类方法。研究结果表明,目标储层可动水与不可动水孔隙度之比仅为0.14~0.47,渗流能力差。将NMR与CMP数据相结合可精确识别出目标储层喉道半径中值为0.151~0.525μm,孔隙半径中值为4.38~9.76μm。孔隙内赋存水类型分为可动水、束缚水和黏土结合水,对应的饱和度平均值分别为23.4%、14.8%和9.4%。微小孔(T_(2)<T_(2c1))、中孔(T_(2c1)<T_(2)<T_(2c2))和大孔(T_(2c2)<T_(2))的平均孔隙度分别为3.12%、3.42%和1.35%。孔喉半径r_(2c1)可作为储层渗流能力划分的评价指标,r_(2c1)的降低会导致微小孔(即吸附孔)孔隙度的降低,以及中孔和大孔(即渗流孔)孔隙度的增加。研究成果为优选致密砂岩优质储层,提高致密油采收率提供了参考和借鉴。[Objective]The pore structure of tight sandstone reservoirs is complex,featuring the presence of nanopores,which is essential to integrate multiple technologies for a systematic characterization of the pore structure to enhance the understanding of these reservoirs.[Methods]Six representative cores from the Chang 71 Chang Yanchang reservoir were selected for analysis.The pore types and structural characteristics of the core samples were examined using field emission scanning electron microscopy(FESEM),constant rate mercury injection(CMP),and nuclear magnetic resonance(NMR).The NMR pore distribution was adjusted based on CMP data,allowing for the identification of distribution ranges for the throat and pore radii,and a pore size classification method tailored for tight sandstone was developed.[Results]Findings indicate that the ratio of the movable water porosity to the immovable water porosity of the target reservoir is only 0.14-0.47,indicating poor seepage capacity.The integration of NMR and CMP data enabled accurate characterization of the reservoir,identifying a median throat radius of 0.151-0.525μm and a median pore radius of 4.38-9.76μm.The pore types include mobile water,bound water,and clay-bound water,with average saturation values of 23.4%,14.8%,and 9.4%,respectively.The average porosities of the small pores(T_(2)<T_(2c1)),medium pores(T_(2c1)<T_(2)<T_(2c2)),and large pores(T_(2c2)<T_(2))were found to be 3.12%,3.42%,and 1.35%,respectively.The parameter r2c1 serves as an evaluation index for the classification of reservoir seepage capacity.A decrease in r_(2c1) leads to a decrease in the porosity of small pores(i.e.,adsorption pores)and an increase in the porosity of medium and large pores(i.e.,seepage pores).[Conclusion]The research findings offer valuable insights for the selection of high-quality tight sandstone reservoirs and the enhancement of tight oil recovery.

关 键 词：致密砂岩 孔隙结构 孔径分布 喉道 恒速压汞(CMP) 核磁共振(NMP) 

分 类 号：P618.130.21[天文地球—矿床学]