Decline curve analysis using rate normalized pseudo-cumulative function in a boundary dominated gas reservoir

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• 作者：Md. Shahin Alom ; ^{shahin.alom@mobilbd.com} ; ^{sxalom@gmail.com} ; Mohammad Tamim ; Mohammed Mahbubur Rahman
• 关键词：Decline curve ; Decline type curve ; Pseudo-cumulative production ; Pseudotime ; Pseudopressure ; New material balance pseudotime (Ta)
• 刊名：Journal of Petroleum Science and Engineering
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：150
• 期：Complete
• 页码：30-42
• 全文大小：846 K
• 卷排序：150

文摘

The use of a new material balance pseudotime function given as pseudo-cumulative production divided by flow rate, allows to obtain a flow equation that has the form of a harmonic decline (b=1). This equation permits the decline analysis of variable pressure/variable rate production data for single-phase gas flow. The incorporation of pseudo-cumulative function in gas decline curve analysis provides a convenient approach to handle variations in viscosity compressibility values more rigorously with pressure since viscosity compressibility ratio is a function of cumulative production. The pseudopressure drop normalized flow rate versus rate normalized pseudocumulative production decline type analysis is superior to use then rate time decline analysis because of independence in step size of time intervals in the determination of viscosity-compressibility normalization factor or pseudo-cumulative function. The application of the new time transform (rate normalized pseudocumulative function) compressed the data which shows a significant improvement in smoothness that results in better curve fitting. The rate normalized pseudo-cumulative function does not have any significant effect on transient behavior in decline curve analysis. It is observed that the behavior is identical between new material balance time and traditional material balance time during early time. The proposed method provide a useful and direct approach to compute initial-gas-in-place (G) and reservoir properties (A, k) in one step, without any iterations. Thus this method is relatively easy and can provide the same information as conventional pressure transient analysis. This method is strictly valid for boundary dominated gas reservoir.