Research On Saturation Evaluation For Tight Oil Reservoir In Jinghe Oilfield

The average porosity of Chang 7 Formation of the Jinghe Oilfield in the Ordos Basin is 6.95%,the average permeability is 0.148×10^-3?m²,and the pore and throat distribution is very complex,where it is a typical low-porosity ultra-low permeability tight oil reservoir.Due to the complexity of its microscopic pore structure,the error in calculation of reservoir saturation is very large,which directly affects the accuracy and fineness of logging evaluation.In order to improve the accuracy of saturation calculation and improve the evaluation ability of tight reservoirs,10 reservoir rock samples of the Chang 7Formation were selected to conduct in-depth research on tight reservoirs in the thesis.Based on geological,well logging and experiment,the data were obtained through core experiments,physical property analysis,nuclear magnetic resonance experiments,high pressure mercury intrusion experiments,etc.,and reservoirs were explored to analyze reservoir physical properties and microscopic pores.Structure,influence factors and control factors affecting the calculation of saturation were analyzed.And in tight oil reservoirs,reservoir seepage and storage capacity greatly affected by the complexity of microscopic pore structure were found.Because the Archie formula cannot meet the saturation calculation requirements of tight reservoirs,the m and n obtained from the rock power experiment were fitted and compared with various parameters to establish a saturation evaluation model consistent with the characteristics of Chang 7 reservoirs.The relative value of the measured values,and the analysis of its application effect,found that the correlation between the two is very low,and the results of different rock layers of the same rock are also very different.After fitting the resistivity increase coefficient to the water saturation,the correlation between conductivity and water saturation was high.The combination of experiments and analysis shows that in addition to microscopic pore structure,factors such as shale content and conductivity also affect the calculation of tight oil reservoir saturation and other parameters.The establishment of the saturation evaluation model provides some support for the logging evaluation for tight oil.