Trinomial Deliverability Equation of Gas Well with Semi-spherical Flow Considering Non-Darcy Effect

Abstract

AbstractFor thick gas reservoirs with a small degree of opening (less than 1/3), the flow near the bottom of the reservoir showed characteristics of spherical flow. Due to the complexity of reservoir properties, low permeability gas reservoirs generally had slippage effect, stress sensitivity effect and start-up pressure gradient. Therefore, in order to truly reflect the flow characteristics of low permeability gas reservoirs based on Darcy’s law, this paper established a hemispherical gas well productivity equation by introducing a pseudo-pressure function, which considered the gas slippage effect, stress sensitivity, start-up pressure gradient and skin effect. The example analysis showed that stress sensitivity had the greatest impact on the productivity of hemispherical gas wells, but the effects of slippage effect and start-up pressure gradient cannot be ignored. When the gas well production pressure difference was large, the effects of stress sensitivity and slippage effect were more obvious. Furthermore, the greater the pressure difference, the more pronounced the effect, but the effect of the start-up pressure gradient was the opposite. The newly established calculation method was closer to the actual situation. It is more suitable for the production prediction of low permeability thick gas reservoirs with less opening (less than 1/3). The research results had certain guiding significance for the evaluation of gas well productivity in low permeability thick gas reservoirs.KeywordsSemi-spherical flowNon-darcy flowThick gas reservoirGas well productivity