神木气田上古生界砂岩储层特征及其主控因素

Reservoirs characteristics and the main control factors of upper paleozoic erathom in Shenmu gasfield

鄂尔多斯盆地神木气田上古生界二叠系多层系含气,但主力含气层段为太原组和山西组。为指导气田储层有效预测与井位部署,根据常规薄片、铸体薄片、粒度分析、常规物性及压汞等测试手段,研究了主力层段储层特征及其控制因素,认识到太原组以岩屑石英砂岩和石英砂岩为主,山西组岩性以岩屑石英砂岩和岩屑砂岩为主,太原组石英含量总体高于山西组,砂体分布均受三角洲分流河道的控制;主力层段物性均较低,属于低-特低孔、低-特低渗储层,但低孔、低渗背景上存在相对较高孔渗的储层;太原组储层孔隙类型以溶孔为主,砂岩中值半径大,排驱压力低,最大进汞饱合度高,孔隙结构总体上优于山西组;沉积、成岩系统研究认为,分流河道有利相带控制下的粗粒颗粒分布对储层物性具有较强的控制作用;溶蚀作用是改善砂岩储渗条件的最关键因素。

The permian of upper palaeozoic in Shenmu gas-field of ortos basin is multi-layers gas, but the main gas-bearing formation is taiyuan and shanxi group. To offer guidance for reservoir prediction and well deployment of this gas field, the reservoir characteristics of the main formation and their control factors are investigated based on the analyses of routine thin-section, cast thin-section, grain size, routine physical property and mercury-injection measurement. It is held that taiyuan group is mainly lithic-quartz sandstone and quartz sandstone, Shanxi formation is mainly lithic-quartz sandstone and lithic sandstone, quartz content of taiyuan is generally higher than shanxi group, sandbodies distribution of them are under the control of the delta distributary channel. Main layer property is low, belongs to the low-low porosity, low-low permeability reservoir, but it still has relatively high permeability reservoir in the low porosity and low permeability background. The pore type of taiyuan reservoir is mainly dissolved-pore, its sandstone median radius is big, expulsion pressure is low, the largest saturation into mercury is high, on the whole the pore structure is better than shanxi group. The research of deposition and diagenesis synthetically shows, the coarse particles distribution under the controlling of distributary channel of favorable facies have stronger control function for reservoir physical properties, dissolution is the most critical factor for improving the physical property of sandstone reservoir.