Single-Point Formula and Application of Gas Well Considering Threshold Pressure Gradient

Gas reservoir with low permeability exists threshold pressure gradient during fluid flow. Different from traditional binomial deliverability equation. Traditional binomial deliverability equation is hard used to analyze gas well productivity, and is also impossible to establish Single-Point Formula. Based on the thought of deducing single-point productivity formula by binomial deliverability equation, single-point formula of gas well in low permeability gas reservoirs considering threshold pressure gradient has been deduced. It is shown that compared with conventional single-point productivity Formula, the number of the empirical parameter in the single-point formula of gas well in low permeability gas reservoirs has become two from one, but can't be solved by conventional method. In this paper, the least square method is proposed to determine two empirical parameters quickly and accurately. The example shows that the absolute open flow rate calculated by single-point productivity Formula and calculation method in this paper, compared with the results of productivity test, the error is only 3.4%.The method is feasible and the result is reliable, it provides theoretical basis for determining the reasonable production of gas wells in low permeability gas reservoirs.