地学数值模拟技术(1)

F g ( R o , m a x ) 1 . 6 9 1 ( R o , m a x ) 4 - 2 3 . 2 1 6 ( R o , m a x ) 3 9 0 . 9 5 0 ( R o , m a x ) 2 - 2 3 . 9 2 8 ( R o , m a x ) - 2 . 8 3 1
cV dH
S and V — the diffusion area, m2, and volume of coal seam, m3;
c — average bulk density of coal, t/m3;
dC — free gas concentration difference, m3/ m3 -coal;
verticle direction
along cleats and faults
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资源与地球科学学院
煤层气成藏动力学过程模拟 地学数值模拟技术 概述
数学模型
• General description of the process ——by mass conservation
Q=QQ g s
Qg — quantity of gas generated by coal organic material, m3/t;
地质模型
In geological history, coalbed methane……
Factors control the process
The process
palaeo-tectonic development history
Gas generating
coal bearing series forming history
——Maturation history of coal organic material is a key to
access gas generation history
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资源与地球科学学院
煤层气成藏动力学过程模拟 地学数值模拟技术 概述
数学模型
• Dissipation of CBM Qd ——through different ways
地学数值模拟技术
韦重韬 教授 博士生导师 资源与地球科学学院 2009年
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提纲
• 概述 • 数值模拟核心技术 • 煤层气成藏动力学过程模拟 • 油气盆地模拟技术 • 煤层气井排采过程模拟
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资源与地球科学学院 地学数值模拟技术 课程提纲
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资源与地球科学学院
煤层气成藏动力学过程模拟 地学数值模拟技术 概述
P o p P o v/(1 ) P tt Pop and Pcl — reservoir pressures before and after cap outburst takes place, Pa;
• Diffusion dissipation quantity Qdi ——concentration diffusion
C — free gas concentration in coal reservoir or cap, m3/ m3-coal or m3/ m3-cap;
DZ2C2
C t
0
d Qs — gas storing in coal reservoir, m3/t;
Qd —gas dissipated from the coal reservoir, m3/t;
• Gas GΒιβλιοθήκη Baiduneration Qg ——by thermal simulation test of coal organic matter
QF(R )M g
g o,m ax
n Ro, max —vitrinite reflectance of coal, %;
In Qinshui Basin:
Mn —pure organic material in coal (dry, ash-free) , t/t-coal; and Fg(Ro, max)
burial history
storing in the coal reservoir
dissipating
from the coal seam
palaeo-geothermal history coal reservoir physical features other factors
A better understanding of this process would significantly improve evaluation of CBM reservoirs fora coalbed methane exploitatio3n.
dH —athickness of cap rock, m a
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Δt — the time diffusion occurs, sec.
资源与地球科学学院
煤层气成藏动力学过程模拟 地学数值模拟技术 概述
数学模型
• Capoutburst dissipation quantity Qob ——simplified arithmetic
Q=QQ+Q d di
ob pe Qdi — diffusing from coal reservoir to cap, m3/t;
Qob —flow through cap via cap outburst, m3/t;
Qpe —permeating through coal reservoir to open passages or open atmosphere, m3/t.
资源与地球科学学院
煤层气成藏动力学过程模拟 地学数值模拟技术 概述
地质模型
Ground surface Opening fault
Coal organic matter generates gas
diffusion dissipation in Cap outburst dissipation permeation dissipation
D — diffusion coefficient, m2/s; t — evolution time, sec.; Z — points at the normal direction which is vertical to coal bed plane, m.
then:
Qdi D S dCt