Genetic type and characteristics of micro-pore of Chang 6 reservoir in Yongjin area,Zhidan Oilfield of Ordos Basin

Based on the rock thin section observation,cast image analysis,scanning electron microscope and capillary pressure curves,pore genetic type and pore structure of Chang 6 reservoir in Yongjin area,Zhidan Oilfield are analyzed and studied.The result shows that Chang 6 reservoir is characterized by low porosity and ultra-low permeability.The pore types mainly include primary intergranular pore,secondary intergranular dissolved pore and intragranular dissolved pore.Feldspar corrosion is the main cause of the forming of secondary pore.Middle-small pore and fine-micro throat are the main pore throat characteristics,which provides the major reservoir space and seepage channel of Chang 6 reservoir.The pore structure is divided into three types.Middle-small pore and fine throat(type Ⅰ) and small pore and micro throat(type Ⅱ) are considered as the dominated reservoirs of Chang 6,and micro pore and micro throat(type Ⅲ) is non-effective reservoir.