Tight Oil Reservoir Characteristics And Saturation Evaluation Method Research

Tight oil has a good resource prospect in China,it is the most realistic field of unconventional oil resources,and is the most important replacement field in future oil exploration.There are difficulties in evaluation of oil saturation in tight oil reservoirs in Jurassic Lianggaoshan-Shaximiao Formation,Gongshanmiao Oilfield,Central Sichuan Basin,because of small porosity,poor pore structure and high calcareous content.The purpose of this study is to carry out matching petrophysical experiments,clarify reservoir characteristics,establish saturation models based on reservoir characteristics,and interpret oil saturation by logging data.Research showing:?Lithology is dominated by feldspar lithic sandstone,mineral components are mainly quartz and plagioclase,some samples have a high calcite content;main distribution range of porosity is 2-10%,main distribution range of permeability is 0.01-0.5mD,the porosity is small,and the permeability is low;residual intergranular pore,feldspar dissolving pore and debris dissolving pore are the main storage space.?Physical property is controlled by lithology,the lower the content of calcium and the higher the content of feldspar,the better the physical property is;dissolution modification control pore structure,the more obvious the alteration is,the better the pore structure is;physical and pore structure control oil-bearing property,the better the physical property and pore structure,the better the oiliness.?The calculation model of calcium and porosity with normalized logRT and AC parameters is established on the basis of the double influence of the calcium content and the oil-bearing property of the resistivity,and the deep lateral resistivity is corrected by calcium content.?A variable parameter Archie model with calcareous content and porosity is established,and the absolute error of saturation calculation is less than 5%.The method has good applicability in the tight oil reservoir,solves the problem of accurate calculation of saturation,and provides a reliable saturation parameters for the subsequent reservoir evaluation.