Experiments on gas supply capability of commingled production in a fracture-cavity carbonate gas reservoir

Abstract: The CT scan, mercury intrusion test and commingled production physical simulation experiment of pore-, cavity-, and fracture–cavity-type cores were conducted to study the effects of interlayer heterogeneity, drawdown pressure, water saturation and water invasion on gas supply capacity. The experimental results were verified by the radial numerical model of multilayer commingled production based on the Eclipse software. The experimental results show that: the fracture–cavity-type reservoir with strong seepage capability makes great contribution to gas production in the early stage, while the pore- and cavity-type reservoirs with weak seepage capability make more contribution to gas production in the middle and late stages; the absolute permeability of reservoir affects its contribution to productivity, while the relative permeability of reservoir affects the total recovery; the “dynamic supply balance” state among various reservoirs can be achieved under a reasonable drawdown pressure; although the gas production capacity of the fracture–cavity-type reservoir is less affected by edge and bottom water, water breakthrough will first occur in this type reservoir and block other reservoirs, significantly reducing the commingled gas supply capacity and recovery. Key words: fracture–cavity carbonates, micropore structure, high temperature and high pressure physical modeling, commingled production, gas supply capacity