Overriding sand bodies of Jurassic Shaximiao Formation in Tianfu gas field are developed vertically, and the formation pressure of gas-producing layer varies greatly from shallow to deep. There are distributions of pressure coefficients from ultra-low pressure, low pressure to normal pressure. Due to the multiple influences of storage, gas-bearing property and formation pressure, the error of gas reservoir productivity prediction is always great. For this problem, taking the tight gas of Tianfu gas field as an example, gas reservoir production levels were divided according to the main factors of productivity firstly, and the equivalent cylinder model of gas reservoir under different production levels was established. According to the characteristics of gas reservoir, Redlich-Kwong equation of state was selected to deduce and calculate the total mass of methane in equivalent cylinder under formation conditions. Then, according to the total mass, a gas production prediction model was established to realize the productivity prediction of gas reservoir of multi-pressure system. And the following research results were obtained.The equivalent cylinder model of gas reservoir integrates the main factors of productivity in the study area, and a semi-theoretical and semi-empirical productivity prediction model is constructed through theoretical derivation and statistical analysis, which is more meaningful than mathematical statistics. Based on Redlich-Kwong equation of state, the model fully refers to the formation conditions and fluid characteristics in the study area, which is helpful to improve the prediction accuracy. Using actual data, compared with multiple regression method to predict gas production, the productivity prediction method based on equivalent cylinder model has smaller error.

Sichuan Basin  /  tight sandstone gas  /  productivity prediction  /  equivalent cylinder model  /  gas reservoir of multi-pressure system  /  Redlich-Kwong equation