| Abstrakt: |
In order to evaluate the oil displacement effect of CO2 huff-n-puff of shale oil reservoirs and the mobilitv of crude oil under different scales of pore throats, a natural core of Ghang7 reservoir in Zhidan OП Region of Yanchang Oilfield was selected, based on high temperature and high pressure CO2 huff-n-puff in long cores and residual oil in short cores online NMR test experiments, and on the basis of evaluating the oil displacement effect, the mixed -phase state of CO2 and the displacement law at different pressure measurement points were analvzed, the effect of mixed-phase huff-n-puff was compared with that of non-mixed-phase huff-n-puff at nano- and micron-scale pore throats, and the mobilitv of crude oil in different scale spaces of shale oil reservoirs was evaluated. The studv shows that the effect of CO2non-mixed-phase huff-n-puff was poor, the pressure inside the core increase was not obvious, and the pressure affecting range is small; under the condition of injecting the same pore volume multipli-er, the recoverv efficiencv was increased bv 8. 24 percentage points compared with CO2 non-mixed-phase huff-n-puff; the production pressure difference in the first 2 cvcles of CO2 mixed-phase huff-n-puff was large, the dis-tance between CO2 mixed-phase huff-n-puff intervals was long, and the characteristics of CO2 mixed-phase displacement were obvious; in the whole pore throat of the rock sample, the proportion of micron-level pores was low, and nano-and submicron-level pores were the the main contributor of the crude oil. The studv results can provide an important reference for shale reservoirs to replenish formation energv and improve recoverv efficiencv. [ABSTRACT FROM AUTHOR] |
