鄂尔多斯盆地中部上古生界砂岩储集层特征

Characteristics of Upper Palaeozoics Sandstone Reservoirs in the Middle of Ordos Basin

鄂尔多斯盆地上古生界砂岩储集层主要为三角洲分流河道砂体;岩石类型主要为石英砂岩、岩屑石英砂岩和岩屑砂岩,成分成熟度和结构成熟度中等差;孔隙度较小,渗透率较低,总体上为低孔、低渗储集层;储集空间以晶间孔和溶蚀孔为主,孔隙喉道以中喉型为主;孔喉组合类型以复合粒间孔+晶间孔+溶蚀粒内孔+细喉型+中喉型组合为主,其次是晶间孔+溶蚀粒间孔+细喉型组合;孔隙结构演化受控于成岩作用。根据储集层岩性、孔喉组合,结合孔隙度、渗透率、孔喉直径、排驱压力、30MPa下的进汞量等特征参数作为评价指标,可将研究区储集层划分为4类。

The upper Palaeozoic sandstone reservoirs in Ordos Basin are mainly consisted of delta distributary channel sandstones, the rock types are mainly of quartz sandstones, debris-quartz sandstones and debris sandstones, composition maturity and structural maturity are mid-poor, porosity is less, permeability is lower, of which low porosity and low permeability reservoirs are made up, inter-crystal pores and dissolved pores are dominated in reservoir space, the pore throat is mainly of mid-throat, the pore assemblage is mainly of the assemblage of inter-granular pore+intercrystal pore+dissolved intergranular pore+mid throat, the next is the assemblage of intercrystal pore+ intercrystal pore + dissolved intergranular pore + mid throat, the next is the assemblage of intercrystal pore + dissolved intergranular pore + fine throat, the evolution of pore structure is controlled by diagenesis. Based on reservoir lithology, pore throat assemblage, in combination with the parameters of porosity, permeability, pore throat diameter, expulsion pressure, mercury rate at 30 MPa are used for evaluation indexes, by which the reservoirs in the studied are divided into 4 types.