煤层气藏水平井渗流规律与压力动态分析

通过气体拟压力代替Langmuir吸附公式中的压力,得到了煤层气藏水平井拟稳态渗流的数学模型。采用积分变换和分离变量等方法求解了数学模型,给出了Laplace变换空间解。绘制并分析了吸附因子、储容比、窜流系数和渗透率模数对典型曲线的影响。通过分析指出,拟稳态流的双对数压力导数曲线会出现明显的“V”形曲线,并且储容比和煤层气吸附系数主要影响“V”形曲线的深浅,而窜流系数主要影响“V”形曲线出现时间的早晚。渗透率变异系数主要影响典型曲线的晚期形态,而对早期形态没有影响。 

Transient pressure analysis of horizontal well for coalbed methane

The mathematical models of the pseudo-steady state percolation of horizontal coalbed methane(CBM)well may be obtained by use of the gas pseudo-pressure to replace the pressure in Langmuir adsorption formula.Owing to the fact that the flow equation of permeability's depending on the change in pore pressure is of strong nonlinearity,the models may be solved by use of regular perturbation method and Laplace transform and the zero-order perturbation solution can be obtained through numerical inversion.The change rule of pseudo-pressure along with the changes in the deformation,adsorption,fracture storage and interporosity flow is discussed.All of these results indicated that the pseudo-steady state double-log pressure derivative curve may show "V" shape which can be influenced by storage ratio and adsorption coefficient,the present time of "V" shaped curve can be influenced by channelling coefficient,as wll as the permeability deformation coefficient can only influence the later stage shape of curves.