Fig.1

CT scanning results and visualized physical models for different types of core samples from the Daniudi gas field"

Fig.2

Silicon-based microfluidic chip manufacturing and gas/water flow visualization experiment workflow"

Fig.3

High-temperature， high-pressure microfluidic experiment results of tight sandstone on silicon-based chip samples from the Daniudi gas field （Class Ⅰ pore throats）"

Fig.4

High-temperature， high-pressure microfluidic experiment results of tight sandstone on silicon-based chip samples from the Daniudi gas field （Class Ⅱ pore throats）"

Fig. 5

Schematic diagram showing the reservoir formation process under gas-water displacement simulation in the Daniudi gas field"

Table 1

Formation water occurrence patterns and their characteristics in the Daniudi gas field"

地层水赋存模式	主要影响因素	形成机理	赋存类型	示意图（微流控实验）
孔道壁面上残余水膜	毛细管力	流动通道窄，毛管阻力大，残余水膜较厚	毛管水（次生可动水）
狭长孔道处残余水柱	毛细管力	孔道狭长细小，毛管阻力大，驱替压力不足，滞留形成水柱	毛管水（次生可动水）
狭窄喉道处残余水柱	贾敏效应	喉道尺寸小，毛管阻力极大，贾敏现象严重，卡断形成水柱	束缚水
盲端-角隅处残余水滴	通道连通性	通道连通性差，被气体压力封闭	束缚水

Fig. 6

Schematic diagram showing the simulation experiment of the Daniudi gas field depletion"

Table 2

Trapped gas occurrence patterns and displacement mechanisms for CO2 flooding for different types of trapped gas in the Daniudi gas field"

滞留气类型	主要影响因素	形成机理	驱替机理	示意图（微流控实验）
盲端-角隅处滞留气	通道连通性	无有效通道沟通，气体被压缩封闭	剥离水膜， 传质扩散置换甲烷
绕流形成滞留气	毛细管力和 驱替压力	驱替压差较低，毛细管力为动力，驱替小孔道，封闭大孔道；驱替压差较高，驱替压力为动力，驱替大孔道，封闭小孔道	剥离水膜， 驱替作用滞留气
卡断形成滞留气	贾敏效应	喉道狭窄，贾敏效应产生附加毛管阻力；喉道处水膜增厚，产生水锁现象，缩小喉道直径，加剧贾敏效应，增大气流阻力	驱替作用释放滞留气
“H型”孔道处滞留气	毛细管力	毛管指进优先通过孔隙2条“边路”向前突破；水依靠模型亲水性进入“H型”孔道的“桥”，压缩“桥”上的气体形成封闭气	束缚水的运移与重新分布， 驱替作用滞留气

Fig. 7

Distributions of CO2， gas， and water in the three classes of pore throats after CO2 flooding in the Daniudi gas field"

Fig. 8

Analysis of the residual water production of class Ⅰ pore throats in the Daniudi gas field （NMR， T2 spectra）"

Fig.9

Micro- and nano-scale simulation model of CO2 flooding for natural gas recovery of the Daniudi gas field （Class Ⅰ pore throats）"

Fig.10

CO2 injection PV vs. recovery degree of the Daniudi gas field（Class Ⅰ pore throats）"

Fig. 11

Comparison of recovery degree after CO2 injection for the three classes of pore throats in the Daniudi gas field"

Fig.12

CO2 injection vs. natural gas recovery degree at varying temperatures and different time for rock samples from the Daniudi gas field （only with diffusion considered）"

Fig.13

CO2 injection vs. natural gas recovery degree at varying temperatures and different time for rock samples from the Daniudi gas field （CO2 injection rate： 5 μm2/s）"

Fig. 14

CO2 injection vs. natural gas recovery degree at varying displacement pressures and different time for rock samples from the Daniudi gas field"

Fig. 15

CO2 injection at different time vs. natural gas recovery degree for rock samples from the Daniudi gas field"