Abstract: In order to provide basis for reservoir prediction, the characteristics of nanometer-micron pore throat in dense conglomerate reservoir and its relationship with physical properties and productivity are discussed. Through thin slice observation, scanning electron microscope, high pressure mercury pressure, constant speed mercury pressure and physical properties test, a systematic analysis of reservoir space types, pore throat distribution, connectivity and physical properties is carried out. The results show that the pore types including dissolved pores, intercrystalline pores, primary intergranular pores, microcracks,with the feldspar solution pores and debris solution pores have the greatest contribution to porosity, followed by intercrystalline pores of clay minerals. The distribution shape of pore throat is bimodal, and the radius of most pore throat is less than 1 μm. The pore is connected by few large throat and micro-fracture, resulting in poor correspondence between porosity and permeability. Comprehensive analysis of pore size classification, reservoir physical properties and reservoir productivity shows that pore types have a controlling effect on reservoir physical properties and productivity. The porosity and permeability, gas content and productivity of reservoirs are lower when more capillary and microcapillary are developed in the pores. This explains the difference between the exploration efficiency of relatively high porosity reservoirs and relatively low porosity reservoirs. Geological conditions for the development of nanocapillary and microcapillary are discussed. It is suggested that the prediction of sedimentary facies and the study of diagenetic facies should be strengthened in reservoir prediction.

Key words: Tight, Sandy conglomerage, Reservoir, Pore structure, Reservoir physical property, Xujiaweizi area

摘要： 探讨致密砂砾岩储层中纳米-微米孔喉的特征及其与物性、产能的关系,为储层预测提供依据。通过薄片观察、扫描电镜、高压压汞、恒速压汞、物性测试手段对储集空间的类型、孔喉分布、连通性和物性特征开展系统分析。研究表明,致密砂砾岩发育溶蚀孔、黏土矿物晶间孔、原生粒间孔、微裂缝等微孔,长石溶孔和岩屑溶孔对孔隙度的贡献最大,黏土矿物晶间孔次之;孔喉的分布形态呈双峰状,绝大多数孔喉的半径小于1μm,孔隙仅与少数大喉道和微裂缝连通,导致孔喉连通性整体较差,造成孔隙度与渗透率的对应关系不佳。综合孔径分类、储层物性、储层产能分析表明,孔径类型对储层物性和产能具有控制作用,孔隙中纳毛细管、微毛细管越发育,储层的孔隙度(渗透率)、含气性、产能越低,反之越高,这从微观上解释了相对高孔隙储层和相对低孔隙储层勘探成效相差较大的原因。探讨了纳毛细管、微毛细管发育的地质条件,建议储层预测应加强沉积相平面预测和成岩相研究。

关键词: 致密, 砂砾岩, 储层, 孔隙结构, 物性, 徐家围子