基于复杂渗流机理的页岩气藏压后数值模拟研究

doi:10.13809/j.cnki.cn32-1825/te.2020.01.004

Abstract

Abstract:

In shale gas reservoirs with natural fractures, the artificial fractures and natural fractures communicate with each other after fracturing. The traditional dual media model can not accurately reflect the impact of natural fractures on well production. In order to investigate the influence on shale gas well productivity caused by gas transport in nanometer-size pores, the mathematical model of multi-stage fractured horizontal well in shale gas reservoir is built, which considers the influence of the complex flow mechanism such as the viscous flow, Knudsen diffusion, surface diffusion, adsorption layerand gas desorption. Discrete fracture model（DFM） is used to simplify the fracture and finite element method is applied to solve the model. The numerical simulation results of Pingqiao shale gas reservoir indicate that the free gas in fracture system mainly contributes to shale gas production in the early stage, and the average recovery of adsorbed gas is only 10.1 %. The existence of unmodified reservoir makes the influence of bedrock permeability on cumulative production greater. The density and connectivity of fracture networks have dominant effects on gas production and its decline trend.

Key words: Pingqiao shale gas reservoir, discrete fracture model, flow mechanism, production decline, post-fracturing simulation

CLC Number:

TE332

WANG Wei,LI Yang,CHEN Zuhua,YAO Jun,MEI Junwei,REN Jianhua,MA Bo. Post-fracturing numerical simulation of shale gas reservoir based on complex flow mechanisms[J].Reservoir Evaluation and Development, 2020, 10(1): 22-29.

Figures/Tables 10

Fig. 1

Fig. 2

Table 1

Simulation parameters of fractured horizontal well in shale gas reservoir"

参数	值
初始气藏压力 $p i$ /Pa	4.3×10⁷
井底压力 $p w$ /Pa	5×10⁶
基岩固有渗透率 $k ∞$ /m²	5×10^-20
基岩孔隙度 $? m$	0.05
基岩平均孔喉半径 $r i$ /m	5×10^-9
天然裂缝开度 $b$ /m	5×10^-6
天然裂缝间距 $a$ /m	0.1
人工裂缝半长 $x f$ /m	100
人工裂缝间距 $y f$ /m	75
人工裂缝开度 $d f$ /m	0.005
人工裂缝改造长度 $X e$ /m	300
气藏温度T/K	366.15
基岩颗粒密度 $ρ R$ /（kg·m^-3)	2 600
Langmuir体积 $V L$ /（m³·kg^-1）	0.004 1
Langmuir压力 $p L$ /Pa	4.7×10⁶
吸附气分子直径 $d m$ /m	3.8×10^-10
临界温度 $T c$ /K	191.05
临界压力P_c/Pa	4.64×10⁶
人工裂缝渗透率应力敏感系数d_F/（1·Pa^-1）	1×10^-6
天然裂缝渗透率应力敏感系数d_f/（1·Pa^-1）	1×10^-7
压裂段数	20

Table 1

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Post-fracturing numerical simulation of shale gas reservoir based on complex flow mechanisms

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