Lithologic Reservoirs ›› 2026, Vol. 38 ›› Issue (1): 172-179.doi: 10.12108/yxyqc.20260115

• PETROLEUM ENGINEERING AND OIL & GAS FIELD DEVELOPMENT • Previous Articles    

Numerical simulation on the coupling of flow and geomechanics during CO2 huff and puff in shale oil reservoirs

ZHANG Qingfu(), ZHANG Shiming, CAO Xiaopeng, LYU Qi, LI Zongyang, YU Jinbiao, WANG Yong   

  1. Exploration and Development Research Institute, Sinopec Shengli Oilfield Company, Dongying 257015, Shandong, China
  • Received:2025-03-25 Revised:2025-06-23 Online:2026-01-01 Published:2026-01-23

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Abstract:

A component model was used to describe fluid flow and phase changes, and an embedded discrete fracture model was constructed to characterize hydraulic fractures. The constitutive relationship of matrix and fracturing fracture proppant was established, and the influence of stress field under different mechanical and development parameters on the diversion capacity and field development effect of hydraulic fractures was studied. The results show that: (1) The development of shale oil reservoir through CO2 huff and puff is a complex process of multi-component and multi-field coupling, accompanied by repeated changes in the formation pressure field and stress field during shale oil development. Under the influence of fluid-solid coupling effect, proppants will deform and embed into the fracture boundary layer, resulting in variation of the hydraulic fracture aperture, conductivity coefficient, porosity and permeability of shale oil reservoirs, which has a significant impact on the development effect of shale oil reservoir. (2) A higher elastic modulus of proppant reduces deformation during the development, leading to smaller fracture closure. Larger proppant diameter is more conducive to maintaining the fracture aperture. (3) A higher elastic modulus of the matrix reduces proppant embedment, leading to smaller fracture closure and better maintaince of fracture conductivity.

Key words: numerical simulation, embedded discrete fracture, fluid-solid coupling, CO2 huff and puff, proppant, elastic modulus, diversion coefficient, shale oil reservoir

CLC Number: 

  • TE349

Fig. 1

Flow chart of phase state calculation"

Fig. 2

Schematic diagram of hydraulic fracture proppant model"

Fig. 3

Schematic diagram of embedded discrete fractures"

Fig. 4

Schematic diagram of variable positions in fluid-solid coupling grid elements"

Fig. 5

Geometry and computational grid of reservoir models validated by component model"

Table 1

Component state parameters"

组分 摩尔分数/% 相对分子
质量		 临界
压力/MPa		 临界
温度/K		 偏心
因子
CO2 2.11 44.01 73.80 304.20 0.225
N2 8.24 28.01 33.94 126.20 0.039
C2 5.27 30.07 46.09 288.74 0.008
C13 10.55 169.52 24.05 715.36 0.365
C37+ 73.83 465.83 9.36 962.28 0.818

Table 2

Binary interaction coefficient of components"

组分 CO2 N2 C2 C13 C37+
CO2 0 0.000 03 0.004 11 0.043 09 0.100 60
N2 0.000 03 0 0.003 50 0.045 61 0.106 02
C2 0.004 11 0.003 50 0 0.024 62 0.074 49
C13 0.043 09 0.045 61 0.024 62 0 0.015 00
C37+ 0.100 60 0.106 02 0.074 49 0.015 00 0

Fig. 6

Comparison of cumulative production between established model and commercial software"

Fig. 7

Numerical simulation model of CO2 huff and puff in shale oil reservoir"

Table 3

Basic parameters of shale oil reservoir model"

储层
厚度/
m		 基质
孔隙度/
%		 基质
渗透率/mD		 压裂
段数/段		 压裂缝半长/m 压裂缝渗透率/D 吞吐
开始
时间/d		 吞吐
周期/a		 注气
时间/a
33 5 0.01 18 100 1 920 1 0.5

Fig. 8

Variation of hydraulic fracture permeability during different stages of CO2 huff and puff in shale oil reservoir"

Fig. 9

Variation of matrix permeability during different development stages of CO2 huff and puff in shale oil reservoir"

Fig. 10

Influence of stress-field on CO2 huff and puff oil production of shale oil reservoir"

Fig. 11

Variation of fracture aperture with different proppants elastic modulus"

Fig. 12

Distribution of pressure and CO2 saturation of CO2 huff and puff in shale oil reservoir with different proppants elastic modulus"

Fig. 13

Variation of hydraulic fracture aperture of CO2 huff and puff in shale oil reservoir with different proppant diameters"

Fig. 14

Variation of fracture aperture of CO2 huff and puff in shale oil reservoir with different matrix elastic modulus"

Fig. 15

Variation of hydraulic fracture aperture of CO2 huff and puff in shale oil reservoir under different initial fracture conditions"

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