致密砂岩三元孔喉结构特征:以鄂尔多斯盆地三叠系延长组7段致密砂岩为例OA北大核心CSTPCD
Ternary pore structure characteristics of the tight sandstone:a case study from the Chang 7 Member of the Triassic Yanchang Formation in the Ordos Basin,China
致密砂岩的孔隙结构特征对于致密油藏的勘探开发至关重要,然而,目前有关不同尺度孔隙形态特征差异的研究较少,给致密油藏的勘探评价带来了较大挑战.为此,本文利用铸体薄片、扫描电镜、压汞测试分析鄂尔多斯盆地三叠系延长组7段致密砂岩孔隙结构特征.研究结果表明:致密砂岩具有由复合孔隙、颗粒孔隙和晶间孔隙组成的三元孔隙结构特征.复合孔隙结构为刺球模型,其半径大,连通性强;颗粒孔隙结构为羽毛球模型,其孔隙半径和连通性处于中等水平;晶间孔隙结构为颗粒填充的包络面,这类孔隙半径小、连通性差.在致密砂岩内部,剩余粒间孔隙和溶蚀孔隙主要影响致密砂岩储集空间,复合孔隙主要影响致密砂岩连通性.由于复合孔隙在形成过程中具有多条连接通道,因此该类孔隙相比其他孔隙具有更高的连通性.当致密砂岩中复合孔隙占比较高时,流体在其中的流动过程会更为均匀,进而形成较大面积且含油饱和度高的砂体.临近烃源岩、溶蚀作用强烈、复合孔隙占比高的致密储层是致密油藏开发利用的有利区.总之,致密砂岩孔隙形态的多元性揭示了不同类型孔隙对储层储集性和连通性的影响差异,本文研究成果可为致密砂岩勘探评价提供地质依据.
The analysis of pore structure characteristics in the tight sandstone is crucial for the exploration and development of tight oil reservoirs.However,there are few studies on the differences of pore morphological characteristics at different scales,which poses great challenges to the exploration and evaluation of tight reservoirs.Thus,casting thin sections,scanning electron microscopy and mercury intrusion tests were employed to examine the pore structure characteristics of the tight sandstone from the Chang 7 Member of the Triassic Yanchang Formation in the Ordos Basin,China.The results show that the tight sandstone exhibits a ternary pore structure comprised of combined pores,particle pores and intergranular pores.Combined pores form a spiny ball model with large radius and strong connectivity.Particle pores represent a shuttlecock model with medium radius and connectivity.The intergranular pores create an envelope surface filled with particles.These intergranular pores have small radius and poor connectivity.Within the tight sandstone,residual intergranular pores and dissolution pores are the primary contributors to the reservoir space,while permeability is primarily controlled by combined pores.Due to the formation of multiple connecting channels during diagenesis,combined pores exhibit higher connectivity compared to other types of pores.A high proportion of combined pores results in a more uniform fluid flow process,leading to the formation of larger,highly oil-saturated sand bodies.The sandstones that are dominated by combine pores,undergo strong dissolution,and are located near the source rocks represent the most favorable area for the exploitation and development of tight sandstone reservoirs.Overall,the study demonstrates that morphological diversity of tight sandstone pores reveals the varied impact of different pore types on reservoir storage and connectivity.These research findings provide a geological foundation for the exploration and evaluation of tight sandstone reservoirs.
王伟;朱玉双;梁正中
榆林学院化学与化工学院,陕西榆林,719000西北大学地质学系,陕西西安,710069
地质学
致密砂岩孔隙结构分形鄂尔多斯盆地
tight sandstonepore structurefractal dimensionOrdos Basin
《中南大学学报(自然科学版)》 2024 (004)
1361-1373 / 13
国家自然科学基金资助项目(42062011,42362023);陕西省教育厅青年项目(22JK0630);陕西省科技厅一般项目(2023-JC-QN-0347);中国科学院洁净能源创新研究院-榆林学院联合基金资助项目(YLU-DNL Fund 2022012)(Projects(42062011,42362023)supported by the National Natural Science Foundation of China;Project(22JK0630)supported by the Department of Education of Shaanxi Province;Project(2023-JC-QN-0347)supported by the Department of Science and Technology of Shaanxi Province;Project(YLU-DNL Fund 2022012)supported by the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy,CAS)
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