Abstract Forecasting production in shale gas reservoirs accurately has been of growing interest in the industry. Horizontal wells with multiple fractures are commonly utilized to develop shale reservoirs, which indicates that the dominant flow regime observed will be linear flow for several years. Until now, it has been widely recognized that the rate-transient data analysis is the most efficient approach to estimate rate, where it appears as a straight line on the plot of normalized pressure vs. square root of time in linear flow. However, the traditional square-root-of-time plot may result in overestimation of reservoir properties and will not allow us to forecast production with confidence in shale gas reservoirs. In this paper, a new analytical methodology is put forward to analyze the rate-transient data from fractured wells in shale gas reservoirs producing at a constant flowing-pressure, which incorporates both slip flow/Knudsen diffusion of bulk gas and surface diffusion of adsorbed gas directly into the model. These flow mechanisms cannot be well described by traditional models. Depending on flow discrepancies from conventional reservoirs, the modified pseudo-pressure and pseudo-time equations to account for these critical transport mechanisms are constructed. In addition, a new procedure for rate-transient data analysis applying the proposed model is presented in details, which is reliable and easy to utilize. The novel approach is validated against numerically simulated cases and field observations. Comparisons between the new approach and traditional method are conducted by a number of test cases. The results demonstrate that the newly developed model dramatically eliminates the inaccuracy of production forecast and provides a more reliable estimated ultimate recovery (EUR). This work should provide an efficient guidance to assist analysts in evaluating hydrocarbon production accurately in shale gas reservoirs.

中文翻译：

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一种结合滑流和表面扩散效应的页岩气藏速率瞬态分析新模型

摘要 准确预测页岩气藏产量越来越受到业界的关注。多裂缝水平井通常用于开发页岩储层，这表明观察到的主导流态将是几年的线性流。直到现在，人们普遍认为速率瞬态数据分析是估计速率的最有效方法，它在线性流中的归一化压力与时间的平方根的关系图中显示为一条直线。 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 然而，传统的时间平方根图可能会导致对储层特性的高估，并且无法让我们对页岩气储层的产量进行可靠的预测。在本文中，提出了一种新的分析方法来分析恒流压下生产的页岩气藏压裂井的速率瞬变数据，该方法将本体气体的滑流/Knudsen扩散和吸附气体的表面扩散直接结合到模型中. 传统模型无法很好地描述这些流动机制。根据与常规储层的流量差异，构建了修正的伪压力和伪时间方程来解释这些关键传输机制。此外，详细介绍了应用所提出模型的速率瞬态数据分析的新程序，该程序可靠且易于使用。这种新颖的方法在数值模拟案例和现场观察中得到了验证。新方法与传统方法之间的比较是通过多个测试用例进行的。结果表明，新开发的模型极大地消除了生产预测的不准确性，并提供了更可靠的估计最终采收率 (EUR)。这项工作应为帮助分析人员准确评估页岩气藏油气产量提供有效指导。