神木气田太原组储层特征及其控制因素

Reservoir characteristics of Upper Carboniferous Taiyuan Formation in Shenmu Gasfield and their controlling factors

鄂尔多斯盆地神木气田上石炭统太原组具有不同于二叠系山西组、石盒子组和石千峰组的储层特征.为指导该气田储层预测与井位部署,根据常规薄片、铸体薄片、常规物性和粒度分析,研究了太原组储层特征及其控制因素.认识到太原组储层主要发育在太2段,砂体分布受潮控三角洲平原分流河道控制,具有砂岩粒度较粗、成分成熟度好—中等、结构成熟度中等的特征;储层孔隙类型以岩屑溶孔为主,成岩相以黏土+硅质胶结岩屑溶孔与晶间孔相及黏土+硅质+碳酸盐胶结岩屑溶孔与晶间孔相为主,物性较低,属于特低孔、低渗储层.神木气田太原组储层发育程度与粒度、岩屑含量和溶蚀作用息息相关,粒度越粗,岩屑含量相对越高,溶蚀作用越强,储层越发育.相反,石英含量升高不利于储层发育,压实、交代和胶结作用也不利于储层发育.

The Upper Carboniferous Taiyuan Formation has the reservoir characteristics different from the Permian Shanxi Formation,Shihezi Formation and Shiqianfeng Formation in Shenmu Gasfield,the northeastern Ordos Basin,Central China.To offer guidance for reservoir prediction and well deployment of this gas field,the reservoir characteristics of Taiyuan Formation and their control factors are investigated based on the analyses of routine thin-section,cast thin-section,routine physical property and grain size.It is held that the reservoirs mostly develop in the second member of Taiyuan Formation,the sandstone distribution is controlled by the distributary channels of tide-dominated delta plain and the sandstone has relatively coarse grain-size,good--moderate composition maturity and moderate texture maturity.The pore types of the reservoirs are mainly rock fragment-dissolution pores and the diagenesis facies mainly include clay+quartz cementation and rock fragment-dissolution and intracrystalline pore faices and clay+quartz+carbonate cementation and rock fragment-dissolution and intercrystal pore faices.The porosity and permeability of the reservoirs are relatively low and they belong to super-low permeability and porosity reservoirs.The reservoir development of Taiyuan Formation in Shenmu gas field is related with grain-size,rock fragment content and dissolution process.The higher the rock fragment content in the reservoirs,the stronger the dissolution process and the coarser the gain-size of the sandstones,the more developed the reservoirs.On the contrary,the increase of quartz content restrains the development of the reservoirs,and compaction,replacement and cementation also go against the reservoir development,whatever the cements are clay,quartz or carbonate.