无越流补给含水层对煤层气排采影响的数值模拟

Numerical simulation of the influence of no-flow recharge aquifer on CBM drainage

沁水盆地南部煤层气井具有“高产水、低产气”的特征,然而也有部分井存在“高产水、高产气”的现象。一般来说,煤层气井高产水,多与沟通含水层相关。针对这种情况,基于沁水盆地柿庄南区块煤储层地质条件,结合煤层气直井排采的实际情况,利用数值模拟方法,采用气水两相多组分的三维煤储层模拟软件(SIMEDWin)模拟煤层气井排采中,沟通无越流补给含水层对储层压力变化及煤层气水产出规律的影响。结果表明:与无含水层影响的煤层气井对比,沟通无越流补给含水层的煤层气井远井地带压降幅度显著,高产气时间久,累积产气量多,排水量大,但见气时间较晚;含水层渗透率越大,气井日产气峰值越高;气井日排水量越大,产气速度也会越快,但产气速度在排水量达到一定值时不再增大。综合考虑,沟通无越流补给高渗透率含水层,增大日排水量到一定值更有利于柿庄南区块煤层气的增产。

Coalbed methane wells in southern Qinshui Basin have the characteristics of high water yield and low gas yield,while some wells present high water yield and high gas yield characteristics.Generally speaking,the high water yield of coalbed methane wells is mostly related to the aquifer with recharge.In this case,based on the coal reservoir geological condition of Shizhuangnan Block and the actual situation of coalbed methane vertical well production,the influence of non-flow recharge aquifer on reservoir pressure variation and CBM outflow rule was simulated by using a three-dimensional coal reservoir simulation software(SIMEDWin)with gas and water two phases and multiple components.The simulation results show that compared with the CBM Wells without connected aquifer,the CBM Wells that communicate with the confined aquifer without leakage water complement have significant pressure drop range in the far well zone,the time of high gas production is long,with large cumulative gas production and water discharge,but late gas discovery time.The higher the permeability of aquifer,the higher the peak value of gas production of the CBM Wells.The higher the daily water discharge of a gas well,the faster the gas will be produced,but the production rate will not increase when water discharge reaches a certain value.Considering comprehensively,similar to the high-permeability aquifer(lens aquifer)in Shizhuangnan Block,increasing the daily displacement to a certain value is more conducive to the increase of CBM production.