物质平衡法在煤层气藏生产动态预测中的应用

针对煤层气井的生产特点,综合考虑煤层甲烷吸附/解吸特性、煤岩基质膨胀/收缩特性和储层有效应力的影响,通过引入等效半径模型,结合真实气体拟压力函数,建立了基于物质平衡法的压裂直井与水平井生产动态预测数学模型。实例计算结果表明:基于物质平衡法的压裂直井与水平井生产动态预测方法,能够利用少量现有数据完成生产动态预测,并对相对渗透率的变化趋势进行分析,可减少计算所需参数,降低计算量。通过对比煤层气压裂直井和水平井生产动态预测结果发现,在相同地质条件下,水平井的单井产能高于压裂直井(前者约为后者的2.3倍),且水平井的开采周期比压裂直井短。因此,在针对具体储层条件选择井型时,应在经济评价的基础上,综合分析两种井型的适用性,优选完井参数。

Application of material balance method to productivity forecast in coalbed methane reservoir

Aimed at the production characteristics of coalbed methane wells, a performance prediction mathematical model based on material balance method is established for fractured vertical well and horizontal well, in which the adsorption of coalbed methane, coal swelling/shrinkage and effective stress are concerned, equivalent well diameter model is introduced, pseudo pressure function is combined. The performance prediction can be achieved based on few available data by mathematical model. The change of relative permeability is analyzed. The parameters needed and calculated amounts are decreased. The individual well deliverability can be effectively enhanced through adopting horizontal wells rather than fractured vertical wells under the same geologic conditions and the productivity is about 2.3 times of vertical wells. The lead time is shortened. The applicability of horizontal wells and fractured vertical wells should be analyzed based on economic evaluation.