Optimising well orientation in hydraulic fracturing of naturally fractured shale gas formations
Optimising well orientation in hydraulic fracturing of naturally fractured shale gas formations
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优化天然裂缝性页岩气地层水力压裂井定向
DOI：
10.1016/j.jngse.2021.104141
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
R. Rafati
中科院分区：
文献类型：
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作者：
J. Sherratt;Amin Sharifi Haddad;Filip Wejzerowski;R. Rafati
水力压裂和天然裂缝之间的复杂相互作用通常导致高度复杂的裂缝网络，这可能导致绕过资源，损害开发的经济可行性。在这项研究中，天然裂缝的影响，从水力压裂威尔斯井生产的影响进行了研究，使用最近开发的裂缝放大方法（FUM）。通过利用FUM捕捉复杂裂缝网络的分布，提出了一种新的想法，改变井的方向，以优化采收率。结果表明，在天然裂缝间距为15ma的情况下，对于与σ hmax成至少60°角的天然裂缝，井向与标准方位最大变化30°，采收率可提高15%。提高的采收率是天然裂缝和应力取向相互补充的结果，以帮助水力裂缝更深地传播到地层中。它还表明，随着天然裂缝密度的增加（裂缝间距减小），改变井的方向的效果变得更加显着。当天然裂缝有两个垂直面时，改变井的方位也进行了研究。然而，在这些情况下，没有找到最佳方向，这表明储层中的天然裂缝需要具有较强的平均方向性，以支持有利的井方向变化。一个简单的经济分析表明，一个小的井的方向变化可以允许更大的井距，这可能导致直接降低开发页岩油气藏的成本。结果还表明，这对不同天然气价格的项目的净现值的积极影响，并迅速积极的净现值状态，降低投资风险。
Complex interactions between hydraulic fractures and natural fractures often result in highly complex fracture networks that might lead to bypassed resources damaging the economic viability of developments. In this study the impact of natural fractures of the formation on production from hydraulically fractured wells is studied using a recently developed fracture upscaling method (FUM). By capturing the distribution of complex fracture networks using FUM, a novel idea of changing the well orientation to optimise recovery is proposed. It is shown that with a natural fracture spacing of 15 ma small change in well orientation up to 30° from the standard orientation can increase the recovery by up to 15% for natural fractures at an angle of at least 60° with σ h m a x. The increased recovery is a result of the natural fractures and stress orientation complementing each other to assist the propagation of hydraulic fractures deeper into the formation. It is also shown that as natural fracture density increases (fracture spacing decreases) the effect of changing the well orientation becomes more significant. Changing the well orientation when there are two perpendicular planes of natural fractures is also investigated. However, no optimal orientation can be found in these cases, suggesting there needs to be a strong average directionality of the natural fractures in the reservoir to support a beneficial well orientation change. A simple economic analysis shows a small well orientation change can allow a larger well spacing which could lead to a direct reduction in the cost of developing a shale reservoir. The results also show the positive effect this has on the NPV of the project with different gas prices, and a rapid positive NPV status reducing the risk of investment.