Abstract
Study shows that decline exponents of gas wells in Sulige Tight Gas Field vary during their life cycle. However, decline analysis methods with variable decline exponent have not been developed so far. To address this problem, a simple-yet-effective method is proposed. In this method, the fracture linear flow regime and the channel linear flow regime, which appear two straight lines on the coordinate axis ( 1 / q vs. t ), respectively, are used to carry out the decline analysis. Each regime has a different slope and intercept (in the form of 1 / q vs. t ), which leads to a useful graphical technique for predicting gas rate. The graphical technique is verified by matching actual gas rate and predicting future gas rate trend. Theoretically, the influence of the two slopes and intercepts in the graphical technique on the rate decline is also studied. Aiming at decline analysis for tight gas wells with variable decline exponents, this paper proposes a novel method using linear flow characteristics, which ingeniously avoids the establishment of an empirical method to deal with variable decline exponent. The method in this study can help for better understanding of decline analysis of tight gas wells in a theoretical manner.
Highlights
IntroductionArps decline-curve method [1] is not applicable for tight gas reservoir
As we all know, Arps decline-curve method [1] is not applicable for tight gas reservoir
Yu [8] presented a new improved methodology to determine a more accurate b to be used in the Arps decline curve analysis for tight gas reservoirs by developing relationship between Qcum, Qcum, t-∞, qt, and t
Summary
Arps decline-curve method [1] is not applicable for tight gas reservoir. Duong [3] introduced an empirically decline model based on long-term linear flow for tight gas reservoirs. Yu [8] presented a new improved methodology to determine a more accurate b to be used in the Arps decline curve analysis for tight gas reservoirs by developing relationship between Qcum, Qcum, t-∞, qt, and t. Dought and Moridis [10] developed a simple, Excel-based tool for the analysis of the complex problem of gas production from a hydraulically fractured tight/shale gas reservoir, based on curve fitting a semianalytical solution to production decline data. The rate-decline type curves have been developed based on a semianalytical model The method they proposed whether is applicable to tight gas is not mentioned.
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