Subsidence of hydrocarbon fields is induced by the depletion of reservoirs and connected aquifers, which causes the compaction of geologic layers. A fundamental requirement of subsidence models is then capturing the mechanical behaviour of such layers with proper constitutive laws.

This paper refers to the case of two gas reservoirs from the Adriatic basin, where a time delay of subsidence with respect to production was observed. This phenomenon has been reported for other fields worldwide, also occurring when subsidence rates do not immediately vanish after the end of production. In those cases, numerical simulations based on elasto-plastic constitutive models did not provide a satisfactory match of subsidence history, even though very accurate reconstructions of pore pressure evolution were used. This motivated a further insight into the time-dependent behaviour of the sandy reservoir materials. Thus, the results of an exhaustive laboratory investigation were interpreted with an elasto-viscoplastic model from the literature, implemented by the authors in a commercial Finite Element code. The satisfactory reproduction of the experimental results proved the adequacy of the model for the materials of concern and allowed determining the parameters that were then used in the new one-way coupled field simulations. A very good agreement was finally obtained between simulation results and field monitoring data in terms of reservoir compaction, maximum settlements, settlement history and extent of the subsidence bowl.

油气田的沉降是由储层和相连含水层的枯竭引起的，这会导致地质层的压实。下沉模型的一个基本要求是用适当的本构法则捕捉这些层的机械行为。

本文以亚得里亚海盆地的两个气藏为例，在这些气藏中观察到与生产相关的沉降时间延迟。这种现象已在世界范围内的其他油田中出现，当生产结束后下沉率没有立即消失时，也会发生这种现象。在这些情况下，基于弹塑性本构模型的数值模拟无法提供令人满意的沉降历史匹配，即使使用了非​​常准确的孔隙压力演变重建。这激发了对砂质储层材料随时间变化的行为的进一步了解。因此，详尽的实验室研究的结果是用文献中的弹粘塑性模型解释的，由作者在商业有限元代码中实施。实验结果的令人满意的再现证明了模型对于相关材料的充分性，并允许确定随后用于新的单向耦合场模拟的参数。在储层压实、最大沉降、沉降历史和沉降碗范围方面，模拟结果与现场监测数据最终获得了非常好的一致性。