电加热强化页岩气解吸的数值模拟

Numerical simulation of enhancing desorption of shale gas by electrical heating

根据电流连续性原理、能量守恒方程和Langmuir吸附模型,建立了多电极加热强化页岩气解吸的数学模型,利用有限差分法进行了求解。讨论了不同电极分布方式下页岩气藏的电场、温度场分布及其对页岩气解吸的影响。结果表明:五点电极加热时电能大部分集中在电极附近,电极附近温度上升较快,地层加热不均匀;排式电极加热方式能够较均匀地加热地层,页岩气解吸效果较好,相对于五点电极加热,解吸率增加约1倍。加热功率为30 k W时,排式电极加热1 a页岩气解吸率达到24.64%,说明了电加热是一种有效的强化页岩气解吸技术。地层温度随加热电功率的增加线性增加,但功率越高,解吸率增加越慢。

An electrical heating method for enhancing desorption of shale gas is proposed.The mathematical model of the multi-electrode heating is established based on the electric current continuity principle,energy conservation law and Langmuir adsorption model,and it is numerically calculated by finite difference method.The effects of electrical energy and temperature distribution in the shale gas reservoir on the desorption of shale gas under different electrode arrangement patterns are discussed.It is shown that the most electrical energy under 5-port electrode arrangement pattern is distributed near the electrodes,and therefore the temperature in the reservoir is uneven;the reservoir can be evenly heated under row-type electrode arrangement pattern,good electrical heating effect can be obtained,and comparing with 5-port electrode arrangement pattern,the desorption ratio of shale gas can be increased one times under this electrode arrangement pattern.When the reservoir is heated one year using electrical power of 30 kW,the desorption ratio of shale gas can reach to 24.64%,which shows that electrical heating is an effective method to enhance the desorption of shale gas.The reservoir temperature linearly increases with electrical power increasing,but the increasing rate of the desorption ratio decreases with electrical power increasing when electrical power is high enough.