准噶尔盆地玛湖凹陷百口泉组低渗透率砾岩储层分类

以准噶尔盆地玛湖凹陷百口泉组低渗透砾岩储层为研究对象,采用物性分析、铸体薄片、恒速压汞、核磁共振等岩心平行实验,开展储层特征及主控因素分析,提出储层分类评价指标与测井表征方法。储层优势岩性主要为细砾、粗砂、小中砾岩;孔隙类型主要包括剩余粒间孔、粒内溶孔、晶间溶孔、微裂缝等;岩石粒度、泥质杂基含量、孔隙类型、孔隙结构是影响储层的主控因素。岩石粒度相对较低的细砾岩、粗砂岩,泥质杂基含量越低,剩余粒间孔越发育,储层的物性越好;原生剩余粒间孔隙越发育,有利于次生溶蚀孔隙的发育。次生溶蚀孔隙中粒内溶孔呈零星或孤立分布,微晶间溶孔喉道较小,对储层孔隙性的改善明显,但对渗透性的改善有限;砾岩储层渗透率的大小主要受控于喉道半径大小,即喉道半径越大,渗透率越高。建立了包括岩石粒度、泥质杂基、孔隙度、渗透率、孔喉因子等在内的砾岩储层的评价指标,最终形成了储层分类评价标准。

Classification and Log Evaluation to Low Permeability Conglomerate Reservoir of Baikouquan Formation in Mahu Depression Junggar Basin

Taking the low permeability conglomerate reservoir of Baikouquan formation in Mahu depression Junggar Basin as a research target,analyzed are the characteristics of reservoir and main controlling factors with the help of parallel experiments including physical analysis results,cast thin section,constant pressure mercury,and NMR.Then,indexes of classification evaluation and logging characterization methods are proposed.Results show that the dominant lithologies of reservoir are coarse sand,fine conglomerate,small-medium conglomerate.The pore types include residual intergranular pores,intergranular dissolved pores,intragranular solution pores,and micro-fracture.The reservoirs are mainly controlled by factors of rock size,argillaceous matrix,pore types and pore structures.The coarse sand and fine conglomerate with relative small particle size have relatively well physical properties.When the content of argillaceous matrix is small and the residual intergranular pores are well developed,the reservoir show good physical properties.The well development of primary residual intergranular pore is beneficial to the development of secondary dissolution pore.With sporadic and isolated distribution of grain dissolution pore and small throat of crystallites dissolved pore,the secondary dissolution pore improve the porosity of reservoir obviously,but permeability limitedly.Overall,the permeability of conglomerate reservoir is controlled by throat radius,the larger the throat radius,the higher the permeability.The rock size,argillaceous matrix,porosity,permeability,and pore throat factor are selected as evaluation index of conglomerate reservoir,and corresponding evaluation methods of well logging are established.Ultimately,the classification and evaluation standards of reservoir are formed.