CAJ | 학술논문

基于朗格缪尔模型、菲克第二扩散定律和达西定律,综合考虑重力和气体压缩效应的影响,推导出描述煤层气和水渗流规律的基本偏微分方程组(并给出定解条件),且利用有限差分法对该数学模型进行了数值求解.计算结果表明,该模型能够有效模拟煤层气水平井的生产动态.通过对比是否考虑非稳态扩散和气体压缩效应时不同裂隙渗透率下的产气动态可知,忽略非稳态扩散和压缩效应,将人为缩短达到气体峰值产量的时间,增大产气峰值;将降低气体膨胀能,低估气井后期产能.煤岩裂隙渗透率越高,气井产能受渗透率回归效应影响越大,峰值产量的持续时间越短且产量下降速度快.因此在煤层气藏开采过程中,应根据气井的产气动态调整井底流压,建立合理的储层压力系统,以降低渗透率回归效应带来的不利影响.
기우랑격무이모형、비극제이확산정률화체서정률,종합고필중력화기체압축효응적영향,추도출묘술매층기화수삼류규률적기본편미분방정조(병급출정해조건),차이용유한차분법대해수학모형진행료수치구해.계산결과표명,해모형능구유효모의매층기수평정적생산동태.통과대비시부고필비은태확산화기체압축효응시불동렬극삼투솔하적산기동태가지,홀략비은태확산화압축효응,장인위축단체도기체봉치산량적시간,증대산기봉치;장강저기체팽창능,저고기정후기산능.매암렬극삼투솔월고,기정산능수삼투솔회귀효응영향월대,봉치산량적지속시간월단차산량하강속도쾌.인차재매층기장개채과정중,응근거기정적산기동태조정정저류압,건립합리적저층압력계통,이강저삼투솔회귀효응대래적불리영향.
Based on the Langmuir equation,Fick unsteady diffusion law and Darcy equation,the partial differential equations and the definite conditions which describe the mechanism of coal gas and water flow were established in consideration of gravity and compression.The method of finite difference was presented to solve the equations.It can be concluded that the model and algorithm are available on predicting the productivity of coaibed methane horizontal well.According to the productivity results under different fissure permeability,we can conclude that the peak time will be artificially shortened and the peak gas rate will be exaggerated,the energy of gas expansion is decreased and the productivity is underestimated if the unsteady diffusion and the compression are ignored.The higher fissure permeability is,the greater the effect of permeability reversion on productivity.The shorer the duration of peak gas rate is,the faster the decline rate will be.In order to reduce the disadvantage of the effect of permeability reversion,a thoughtful bottom hole flowing pressure should be set during production to establish a reasonable pressure system.