Predicting production and estimated ultimate recoveries for shale gas wells: A new methodology approach
Predicting production and estimated ultimate recoveries for shale gas wells: A new methodology approach
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DOI：
10.1016/j.apenergy.2017.09.119
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发表时间：
2017-11
期刊：
影响因子：
11.2
通讯作者：
Ke Wang;Haitao Li;Jun-chao Wang;Beibei Jiang;Chengzhong Bu;Qing Zhang;Luo Wei
中科院分区：
文献类型：
--
作者：
Ke Wang;Haitao Li;Jun-chao Wang;Beibei Jiang;Chengzhong Bu;Qing Zhang;Luo Wei
超致密或页岩气威尔斯井的产量剖面主要受改造裂缝的影响，具有典型的特征--产量递减初期递减较快，之后递减速度减慢，直至产量趋于平稳。储层工程师关注的是如何通过简单方便的方法，在页岩气井生产历史较短的情况下准确预测未来产量和估计最终采收率（EUR）。由于准确的裂缝和储层参数复杂且难以有效获得，因此数值和解析方法并不总是足够准确。因此，经验方法由于其简单和有效而被广泛引入行业。虽然传统的Arps递减分析不适用于超致密或页岩气威尔斯井，因为这些模型是基于主要由边界控制流控制的常规储层，然后已经提出了几种针对致密或页岩气威尔斯井的经验方法。最广泛使用的经验方法是瓦尔科的拉伸指数产量递减（SEPD）和Duong的裂缝性油藏产量递减（Duong方法），但有一定的局限性。本研究详细分析了Arps方法、SEPD方法和Duong方法的基本理论，以确定其局限性背后的原因。随后，提出了一种新的经验方法，以估计可靠的未来产量和欧元为主导的油藏。新方法是基于产量和时间之间的经验关系，在一个裂缝占主导地位的流动制度，并考虑了时间的影响，压裂时间指数。通过理论分析和四川盆地（中国）页岩气威尔斯井的不同经验应用，将所提出的方法与SEPD和Duong的方法进行了比较。结果进一步证明了SEPD方法低估了产量，特别是对于产能较低的页岩气威尔斯井，而Duong方法高估了产量，并且在缓慢递减阶段受到不可逆递减的显著影响。同时，比较表明，所提出的方法优于其他两种方法在产量预测和欧元估计，在短期和长期的生产历史。
Production profile of super-tight or shale gas wells is mainly influenced by the reformed fractures and leads to a typical characteristic—decline in production is rapid at the beginning of the decline period, after which it slows down until the production levels off. Reservoir engineers focus on how to predict accurate future production and estimated ultimate recovery (EUR) in the presence of a short production history of shale gas well through simple and convenient means. Numerical and analytical methods are not always accurate enough owing to accurate fracture and reservoir parameters, which are complex and challenging to be obtained efficiently. Therefore, empirical methods have been widely introduced in the industry owing to their simplicity and efficiency. While traditional Arps’s decline analyses are not suitable for super-tight or shale gas wells as these models are based on convention reservoirs that are mainly dominated by boundary dominated flow, then several empirical methods targeting tight or shale gas wells have been proposed. The most widely used empirical methods are Valko’s stretch exponential production decline (SEPD) and Duong’s rate decline for fractured dominated reservoir (Duong’s method) but with some limitations. This study analyzes the basic theories of Arps’s methods, SEPD, and Duong’s method in detail to ascertain the reason behind their limitations. Subsequently, a new empirical method is proposed to estimate reliable future production and EURs for fracture-dominated reservoirs. The new methodology is based on the empirical relationship between production and time in a fracture-dominated flow regime, and considers the influence of time on the fracture time exponent. The proposed method is compared to SEPD and Duong’s method through theoretical analyses and different empirical applications of shale gas wells in the Sichuan Basin (China). The results have further proved that SEPD underestimates the outcomes, particularly for shale gas wells with low productivity, and Duong’s method overestimates the outcomes and is significantly influenced by an irreversible decline in the slow decline stage. Meanwhile, the comparisons have shown that the proposed approach performs better than the other two methods in both production forecast and EUR estimation, in both short and long production histories.