Rate Decline Analysis of Fractured Gas Well by Genetic Hybrid Optimization

According to the characteristics of gas reservoir development and requirement of production management, a new method for analyzing rate decline in fractured well is presented in this paper, which overcomes the disadvantage that conventional rate decline analysis can be used only to determine deliverability and predict gas well performance but not to determine formation parameters. The presented rate decline analysis method of fractured gas well is based on the change of unstable flow rate, and such parameters as permeability, skin factor, average formation pressure and well bore storage factor are determined by matching productivity data. This new method requires no well shuts down and gas well productivity is not impacted, so, the method can completely take the role of gas well shutting down test to obtain gas reservoir performance parameters, In this paper, a mathematical model of transient rate at variable flowing pressure is presented. By means of the model, the interpretation for fractured well rate decline data can be worked out. The daily production log and time are used to interpret formation parameters. Aiming at the difficulty of data interpretation parameter estimation, the genetic algorithm is used to optimize the way, the fractured well production performance data are interpreted to determine formation parameters and the degree of formation damage. The method provides a more economical mean for gas reservoir development monitoring.