鄂尔多斯盆地富县地区延长组沉积特征及物性分析

从沉积相、成岩作用角度研究了三叠系延长组储层的物性特征和主控因素, 认为延长组主要发育有水下分流河道、河口坝、席状砂及分流间湾等沉积微相, 三角洲前缘水下分流河道是最佳储层, 平均孔隙度10.85% , 平均渗透率0.613 ×10-3μm2。储层所经历的成岩作用中, 压实作用对砂岩物性的影响较大, 水下分流河道砂体压实后, 其原始孔隙度损失13.6%; 胶结作用对储层物性有一定的破坏性, 但早期胶结物可使剩余原生粒间孔隙得以保存, 其中的易溶组分又为次生粒间孔隙的形成奠定了物质基础; 溶蚀作用可大大改善储层的物性; 构造微裂缝仅在局部起沟通喉道的作用。整体属于低孔、低渗型储层, 并以粒间溶孔和粒内溶孔为主要孔隙类型。沉积相在宏观上控制了砂体的类型、规模、原始物性条件及空间分布, 成岩作用在微观上影响了储层孔隙演化与储层物性的变化, 而构造裂缝可以在局部改善储层的物性。

Depositional features and properties analysis of Yanchang Formation in Fuxian area, Ordos Basin

Physical p roperties characteristics and controlling factors of Triassic Yanchang Formation reservoir are studied by depositional facies and diagenesis. The authors have considered that the main depositional microfacies of the Yanchang Formation include subaqueous distributary channel, mouth bar, sheet sand and interdistributary bay. Subaqueous distributary channel of delta front is the best reservoirwith average porosity 10.85% and per-meability 0.613 ×10-3 μm2. Among all the diagenesis reservoir experienced, compaction has greater effect to sandstone physical properties. After the sands of subaqueous distributary channel compacted, the original porosity reduced 13.6%. Cementation has certain destructive action to reservoir physical p roperties, but the remaining primary intergranular pores can be preserved by early cement and the soluble components also provided material base to secondary intergranular pores. Dissolution can imp rove the reservoir physical properties greatly; structural micro-cracks only play path function locally. The reservoir is low in porosity and low in permeability on the whole, and the main pore types are dissolved pores between grains and dissolved pores in grains. Sedimentary facies control the sandbody type, size, original physical p roperties and spatial distribution in macro-level, diagenesis impact the evolution of reservoir pore and the change of reservoir physical properties in micro-level. The structural cracks can improve reservoir physical p roperties in partial.