Evaluation of the Utilization Rate of Shale Oil in Different Occurrence States During CO2 Huff-n-puff Process by Two-dimensional Nuclear Magnetic Resonance Technology
The complexity of the development of shale oil with the state of free oil and adsorbed-absorbed oil is different,and the exact measurement of the utilization rate of shale oil with different state is of great significance for the efficient development of shale oil.An evaluation method for the utilization rate of shale oil at different occurrence states during CO2 huff-n-puff process has been founded by two-dimensional nuclear magnetic resonance technology and CO2 huff-n-puff experiments.The total utilization rate obtained from this method is almost the same as the values calculated by the mass variation of shale core saturated with oil,which verifies the accuracy of the method.Furthermore,the variation of the adsorbed/absorbed oil and free oil with CO2 huff-n-puff cycles can be clearly observed in the t2-t1 two-dimensional nuclear magnetic resonance spectrum.The free oil in shale core is easier to be extracted by CO2 than the adsorbed/absorbed oil.The increase of pressure and huff-n-puff cycles can enhance the utilization rate of adsorbed/absorbed oil.At 10 MPa after 5 cycles of CO2 huff-n-puff,the utilization rates of adsorbed/absorbed oil and total can reach 73.6%and 91.1%.The exact evaluation on the utilization rate of shale oil with the state of adsorbed-absorbed oil is conducive to the optimizing of the production technology and enhancing the shale oil recovery.
shale oiladsoradsorbed and absorbed oilfree oilCO2 huff-n-puffnuclear magnetic resonance technology