Modified Power Law Exponential Decline for Tight Gas
Modified Power Law Exponential Decline for Tight Gas
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DOI：
10.2118/2009-198
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发表时间：
2009
影响因子：
0.8
通讯作者：
L. Mattar;S. Moghadam
中科院分区：
文献类型：
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作者：
L. Mattar;S. Moghadam
传统的递减方法不适用于致密气威尔斯井。双曲线递减常用于预测产量和估计气井的预期最终采收率（EUR）。该方法仅在井处于边界主导流（BDF）状态并且双曲线b值在0到1的范围内时有效。然而，致密气藏的大部分生产数据处于瞬变流状态，而不是BDF状态。这导致B的值大于1，并且预测可以显著高估储量。最近开发的“幂律指数递减”方法似乎是有前途的预测产量在瞬态和BDF制度。在本文中，我们研究了不同情况下的幂律指数下降的适用性。我们评估其行为在瞬态和边界主导的流态，特别是线性和径向瞬态流。在BDF制度下，我们还研究了油藏规模对递减参数的影响。我们将幂律指数递减与油藏分析模型的递减进行了比较，并对幂律指数递减进行了相应的修正。此外，幂律方程的任何参数的敏感性进行了研究。利用合成数据检验了幂律指数递减法预测致密气威尔斯井产量的有效性。
Traditional decline methods do not work for tight gas wells. A hyperbolic decline is often used for forecasting the production rate and estimating the expected ultimate recovery (EUR) of a gas well. This method is only valid when the well is in the Boundary-Dominated Flow (BDF) regime, and hyperbolic b-values are in the range of 0 to 1. However, most of the production data from tight gas reservoirs is in the transient flow regime and not in the BDF regime. This results in values of b bigger than 1, and a forecast which can significantly overpredict the reserves. The recently developed “power law exponential decline” method seems to be promising in predicting the production rate over both transient and BDF regimes. In this paper, we examine the applicability of the power law exponential decline for different cases. We evaluate its behavior during both the transient and boundary-dominated flow regimes, and specifically for linear and radial transient flow. In the BDF regime, we also study the effect of reservoir size on the decline parameters. We compare the power law exponential decline with the decline from analytical reservoir models, and we modify it accordingly. Furthermore, the sensitivity of the power law equation to any of its parameters is studied. The validity of the power law exponential decline in forecasting production in tight gas wells is tested using synthetic data.