玛湖凹陷二叠系风城组页岩油储层孔隙结构及分类评价

准噶尔盆地玛湖凹陷下二叠统风城组为盆地西北缘的主力烃源岩,具有较大的页岩油勘探前景.利用场发射电子扫描显微镜以及高压压汞等测试手段,对研究区玛页1井风城组页岩油储层的孔隙结构进行了精细研究和分类评价.研究结果表明:①玛湖凹陷风城组页岩油储层以薄层状或块状云质、粉砂质、钙质或硅质泥岩为主,且泥岩中常发育大量白云石、方解石...

Pore structure and classification evaluation of shale oil reservoirs of Permian Fengcheng Formation in Mahu Sag

The Lower Permian Fengcheng Formation in Mahu Sag is the major source rock in the NW Junggar Basin，with great prospects for shale oil exploration. The pore structure of shale oil reservoirs of Fengcheng Formation in well Maye 1 in the study area was studied and classified by means of field emission electron scanning microscope and high-pressure mercury injection. The results show that： （1）The shale oil reservoir of Fengcheng Formation in Mahu Sag is dominated by thin-layer or massive dolomitic，silty，calcareous or siliceous mudstone， and a large amount of dolomite，calcite and siliceous bands，lumps or patches are often developed in the mudstone. （2）The pore types of shale oil reservoirs of Fengcheng Formation in the study area are mainly intergranular pores， matrix dissolved pores，intragranular dissolved pores，intercrystalline pores，intracrystalline dissolved pores and microfractures，among which matrix dissolved pores and intercrystalline pores are the most developed. The physical properties of the shale oil reservoirs are poor，the porosity values range from 0.4% to 17.7% and are mostly less than 3.0%，and the permeability value are mostly less than 0.03 mD，with the maximum of 2.90 mD，belonging to low porosity and extra-low permeability reservoirs.（3）The pore volume of samples in the study area is generally small，with an average of 0.25 cm³. The average values of average coefficient，sorting coefficient，skewness， peakedness and coefficient of variation is 13.95，2.44，0.97，1.25 and 0.17，respectively. The maximum mercury saturation is low，with an average of³7.23%，and the efficiency of mercury-ejection is low，with an average of only 25.73%.（4）The shale oil reservoirs in the study area can be divided into three types： Ⅰ， Ⅱ and Ⅲ. Among them，type Ⅰ shale oil reservoirs with good physical properties and good internal pore connectivity have good prospects for oil and gas exploration and development.