三角洲前缘致密储层特征及其主控因素——以定边地区长6油层组为例

Characteristics and main controlling factors of tight reservoirs in delta front:a case study of Chang 6 in Dingbian area,Ordos Basin

阐明微相控制下的致密储层展布及其微观特征,对揭示致密油差异富集规律,实现有利储层的评价具有重要意义。综合运用铸体薄片、粒度分析、扫描电镜和高压压汞等技术手段,对长6段致密储层样品进行测试,获得孔隙类型和孔喉结构特征,结合沉积微相研究成果认为,定边地区长6发育三角洲前缘亚相,长石砂岩为储层主要岩石类型,储集空间主要为粒间孔-溶孔组合。孔隙度主要集中在8.01%~11.41%,平均为10.25%;渗透率一般在(0.10~1.04)×10^(-3)μm^(2),平均0.47×10^(-3)μm^(2),主要属于低孔特低孔-特低渗超低渗小孔微细喉型储层。微相对储层物性及平面展布具有明显的控制作用。压实作用是储层致密的主因,其次是胶结作用;溶蚀作用以及绿泥石膜对压实及胶结作用的抑制,利于原生孔隙的保存。

It is great significant to clarify the reservoir display and microscopic characteristics under the microphilic control,and to achieve the evaluation of oil differences enrichment.By casting thin section,particle size analysis,scanning electron microscope and high pressure mercury injection,the tight reservoir samples of Chang 6 member are tested,and the pore types and pore throat structure characteristics are obtained.Combined with the research results of sedimentary microfacies,it is considered that Chang 6 member in Dingbian area develops delta front subfacies.Feldspar sandstone is the main type of the reservoir,and the reservoir space is mainly intergranular pore-dissolved pore combination.Porosity is concentrated in 8.01%-11.41%,with an average porosity of 10.25%.The permeability is generally 0.10×10^(-3)-1.04×10^(-3)μm^(2),with an average value of 0.47×10^(-3)μm^(2),belonging to the micro-throat reservoir with low porosity,extra-low porosity,extra-low permeability and ultra-low permeability.Micro-facies can obviously control reservoir physical properties and distribution.Compaction is the main cause of reservoir compactness,followed by cementation,dissolution and chlorite film inhibit compaction and cementation,very beneficial to the preservation of primary pores.