Experimental evaluation of interlayer interference during commingled production in a tight sandstone gas reservoir with multi-pressure systems

With consideration of its effectiveness and efficiency, commingled production of coalbed methane has been widely adopted for a multi-layer reservoir, though strong interlayer interference and backflow may occur. In this paper, techniques have been developed to experimentally evaluate the performance of commingled production in a tight sandstone gas reservoir with interlayer interference. Core samples with different physical properties are then employed to evaluate the performance of multi-pressure commingled production with long cores, while its interlayer interference is characterized. Gas is mainly produced from a relatively high pressure layer at the early stage, when backflow occurs in a relatively low pressure layer. During the commingled production stage, the relatively low pressure layer with good physical properties will contribute the most to gas production. Furthermore, the larger the net gas production rate is, the shorter the backflow time will be. In addition to honoring the power-law relationship between flow rate and backflow time, shut-in operation has imposed a negative impact on the multi-layer commingled production.