Study On The Law Of Single Well Production Decline In JY Shale Gas Reservoirs

Shale gas is different from conventional gas beacause of its long exploitation time and production cycle. After the large-scale hydraulic fracturing, the initial production of shale gas well is very high. High production rate will decline rapidly after a period of time, and will be in a very long period of time with low production. Therefore, study on the production decline law is significant for the development and production of gas field. Now, there are some mature methods to research production decline law which are Arps decline curve, Fetkovich decline curve, Blasingame decline curve and Agarwal-Gradner decline curve. There are some methods to research production decline law of shale gas well which are "power law loss ratio" rate decline model and stretched exponential equations.Established the correlation between pseudo production rate and the time in material balance to analyse the decline laws for the 8 constant production wells of JY shale gas reservoir, and calculated its the recoverable reserves based on modern production decline curves. Through the application of "power law loss ratio" rate decline model, stretched exponential equations and Duong decline curves, studied the decline laws of constant pressure production wells, and predicted its production as well. The affecting factors of the declining production of gas well is analysed by linear relationship, cluster analysis and numeral simulation.The pseudo production rate of the eight constant production wells decreased by power function with the time in material balance, so the duration and yield of stable production can be estimated. The results of recoverable reserves obtained from the 4 modern production decline curves were close, so it was reliable to certain degree. The research on production decline for the constant pressure well YY6-2HF of JY gas reservoir indicated that the traditional way of Arps decline analysis is no more suitable for shale gas. "Power law loss ratio" rate decline model, stretched exponential equations and Duong decline curves accorded with the production history of YY6-2HF, however, satisfactory results of prediction was obtained only from Valko's stretched exponential equations. Three methods were applied to analyse the affecting factors of the production decline and the results can be concluded as follows:formation pressure and fracture operation had noticeable effects on the production and reducing yield of shale gas well, but the influence of geological factors and the diffusion of adsorbed gas were negligible.