稠油油藏水平井CO2吞吐产气特征及注气量计算改进柱体模型OA

The application of CO2 huff-and-puff in horizontal wells can significantly improve development effect of heavy oil reservoirs.In order to clarify oil production increase mechanism and potential of CO2 huff-and-puff in hori-zontal wells,and to achieve rapid and accurate calculation of injection volume of huff-and-puff in horizontal wells,long core experiments are conducted with horizontal and vertical placement.By comparing gas production character-istics and oil production differences between horizontal wells and vertical wells,orthogonal experiments are carried out to determine the main controlling factors of huff-and-puff in horizontal wells and optimal injection volume.Final-ly,an improved cylinder model is established based on theoretical derivation.The results show that huff-and-puff in vertical wells includes 2 stages of low-gas-content front breakthrough and"gas wall"breakthrough.The spatial and temporal differences in attic-oil production and gas-oil mass transfer between vertical wells and horizontal wells cause the difference in incremental oil of CO₂ huff-and-puff.Horizontal wells can increase oil recovery by 6.14 per-centage points compared with vertical wells.CO₂ injection volume is the most sensitive factor affecting huff-and-puff effect.The improved cylinder model considers"outward expansion"of gas-drive front at heel and toe ends,intro-ducing correction coefficients related to oil saturation and viscosity of heavy crude oil.The verification result of field application indicates that the relative error between actual calculation results and numerical-simulation optimization results is less than 10%.The research provides a rapid and effective calculation method for the formulation of huff-and-puff plans for such horizontal wells.