PNAS:新方法估计页岩地层的天然气产量

关键词:新方法,页岩地层,天然气产量

科研人员提出了一种估计水力压裂井产出的天然气产量的方法。此前对页岩气生产的估计主要依赖于为传统油气井建立的模型,它们与富含天然气的页岩的水平井相比具有不同的几何形状。

Tad Patzek及其同事分析了水平井的天然气生产的最简单模型,它符合天然气开采过程的基本物理和几何形状。

这组作者报告说,来自新完成的井的天然气产量应该以与这口井的生产时间的平方根成反比的速率开始下降;最终,气体扩散导致井压下降,而气体产量以指数方式减少。这组作者把他们的模型与德克萨斯州Barnett页岩的超过8000口井的天然气生产数据进行了比较,结果发现它准确预测了大约2000口井的情况,这些井的产量在过去10年里已经开始以指数方式减少。剩下的6000口井太年轻,这个模型无法预测指数衰减何时出现,但是这让这组作者能够建立井寿命的上界和下界,以及井能够生产的天然气的数量。

这组作者说,这种产量估计可能随着获取更多的数据而变得越来越准确。(生物谷Bioon.com)

生物谷推荐的英文摘要

Proceedings of the National Academy of the Sciences of the United States of America                 doi: 10.1073/pnas.1313380110

Gas production in the Barnett Shale obeys a simple scaling theory

Tad W. Patzeka,1, Frank Maleb, and Michael Marderb

Natural gas from tight shale formations will provide the United States with a major source of energy over the next several decades. Estimates of gas production from these formations have mainly relied on formulas designed for wells with a different geometry. We consider the simplest model of gas production consistent with the basic physics and geometry of the extraction process. In principle, solutions of the model depend upon many parameters, but in practice and within a given gas field, all but two can be fixed at typical values, leading to a nonlinear diffusion problem we solve exactly with a scaling curve. The scaling curve production rate declines as 1 over the square root of time early on, and it later declines exponentially. This simple model provides a surprisingly accurate description of gas extraction from 8,294 wells in the United States’ oldest shale play, the Barnett Shale. There is good agreement with the scaling theory for 2,057 horizontal wells in which production started to decline exponentially in less than 10 y. The remaining 6,237 horizontal wells in our analysis are too young for us to predict when exponential decline will set in, but the model can nevertheless be used to establish lower and upper bounds on well lifetime. Finally, we obtain upper and lower bounds on the gas that will be produced by the wells in our sample, individually and in total. The estimated ultimate recovery from our sample of 8,294 wells is between 10 and 20 trillion standard cubic feet.

(责任编辑:xiyang.zhang)

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