注热CO_2驱替增产煤层气试验研究

当前煤变质程度高、割理不发育及煤储层压力低等因素严重制约着我国煤层气的开采与利用。为完善注CO_2驱替增产煤层气的基础理论研究,利用自主研发的煤层瓦斯驱替装置探讨了不同注气温度与注气压力条件下CO_2对煤层瓦斯驱替置换的效果,并分析了注气温度与压力对煤体的变形与渗透率的影响。研究发现:驱替气体注气压力与温度是影响CH_4产出率与CO_2储存量的关键因素,提高注气温度与注气压力能够在单位时间内驱替出更多的CH_4并存储更多的CO_2;注气压力由2 MPa增至4 MPa,CH_4产出率可提高6.7%~17.4%,CO_2储存量可提高78.60/%~99.7%;注气气体温度从28℃上升至60℃,CH4_产出率与CO_2储存量分别增加40.0%~43.8%和23.8%~38.4%,而驱替置换比降低8.4%~20.2%;驱替压力与温度的增加会使得煤体轴向应变增加98.1%和104.7%;常温注气试验后煤体渗透性下降37.1%~71.3%,提高驱替温度可使渗透率下降幅度降低19.8%~64.3%。

Experimental investigation on enhancing coalbed methane recovery by injecting high temperature CO2

The high metamorphic grade and low bedding development of coal，along with the low reservoir pressure of gas have seriously restricted the development and usage of coalbed methane.In order to promote the fundamental research on enhanced coal bed methane recovery，a series of laboratory experiments were conducted on raw coal specimens by using special equipment，which is designed and developed independently，to investigate the effect of different injecting pressure and temperature of CO2 The results show that，the pressure and temperature of injected CO2 are the main factors which have impact on output rate of CH4 and CO2 storage，higher injection pressure and temperature can lead to more CH4 output and CO2 storage and more rapider rate of CH4 output and CO2 storage，the increase of CO2 pressure，from 2 MPa to 4 MPa，can result in the increase of CH4 output rate，from 6.7% to 17.4%，and CO2 storage (78.6%-99.7%)；the increase of injecting temperature (28 ℃ to 60 ℃) can lead to the increase of CH4 output rate (40.0%-43.8%) and CO2 storage (23.8%-38.4%)，but reduce the replacement ratio，which is from 8.4% to 20.2%.The increase of injection pressure and temperature can cause greater deformation of coal samples，the axial strain can increase by 98.1% and 104.7%.The permeability of coal decreases about 37.1%-71.3% after room temperature displacement experiment but the reduction become less when the injection temperature increases，which become 19.8%-64.3%.