Comprehensive Evaluation Of Fracturability Of Shale Oil Reservoir

The reason why recovery efficiency of shale oil resources in China is low is that the fracturing effect of the target block is unsatisfactory,although China is rich in shale oil resources.In this paper,a universal fracturability evaluation model is to established to provide a theoretical basis for the fracturing of shale reservoir.The typical shale samples of the Qingshankou Formation is taken as the research object,and the geological and mechanical characteristics of the reservoir are studied by the XRF element analysis experiment,QEMSCAN mineral analysis experiment,uniaxial compression experiment and triaxial compression experiment.Based on the analysis of the influence of various parameters on the shale fracturability,a fracturability model and evaluation criteria suitable of shale oil reservoir were established.The results as follows:(1)By comparing the shale distribution characteristics of Qingshankou Formation and Nenjiang Formation in the target block,shale oil of Qingshankou Formation is more suitable for exploitation.(2)XRF element analysis and QEMSCAN mineral analysis of samples from Qingshankou Formation experimental wells show that,Shale has strong heterogeneity,and the inorganic elements are mainly Si,Al,K,Ca,with large longitudinal differences.The three wells have large differences in the content of brittle minerals of quartz and feldspar.The fracturability coefficients calculated by the mineral method are 0.39,0.63,0.51,and the relationship is H258>DA86> TY1,which is consistent with the field test results.(3)Mechanical experiments on shale samples from well TA1 show that,a small strain occurrs when the core was damaged,indicating that the shale has good brittleness;Within a certain range,as the confining pressure increases,the compressive strength and elastic modulus increase,and the Poisson's ratio decreases.The fracturability coefficients calculated by the mechanical experiment were 0.49,0.87,0.59,and the relationship was H258> DA86> TY1.(4)The comprehensive fracturability coefficient is 0.46,0.77,0.57,and the order of magnitude is H258> DA86> TY1,which is highly consistent with the on-site effect.It is also predicted that the daily oil production of well TY1 is about 3.49 t/d.