Abstract Oil saturated carbonate reservoirs typically display anomalously high porosities compared to their water filled counterparts, and this has been largely documented in the literature. Nevertheless, no porosity model has been proposed yet to quantify the evolution of porosity preservation by oil under burial. This paper presents a Porosity Depth Saturation model (PDS model) for carbonate reservoirs, that quantifies for the first time the evolution of porosity with depth and oil saturation for a given charging time. The PDS model formulation decouples compaction from porosity preservation. The mechanical and chemical compaction is defined phenomenologically from the Schmoker and Halley (1982) compaction trend, but applied to the water domain only. The computation of the porosity preservation is based on 2 new concepts: the porosity preservation potential that is solely a function of time of charge, and the porosity preservation α factor that is a function of fluid saturation. The work focuses on a large and laterally homogeneous carbonate reservoir. The relations between porosity, oil saturation and depth are extracted from the associated reservoir geomodel and analyzed to define the porosity preservation α factor. The PDS model is tested on a specific reservoir facies and provides the porosity evolution with depth and saturation at any time of charge. It indicates that even at a low water saturation, such as irreducible water condition of an oil reservoir, a reduced amount of water still suffice to reduce somewhat the porosity with burial. From the current reservoir condition, it is shown that the PDS model, solely based on porosity, depth and residual water saturation, can back-calculate the time of charge of a reservoir. Not only the PDS model proposes an initial time of charge in line with the findings of an independent study, but it can also provide relative and quantified charging time for the various zones within the reservoir, offering a level of granularity never achieved before.

中文翻译：

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Porosity Depth Saturation (PDS) 模型：在碳酸盐岩油藏中埋藏孔隙度保存的量化，以及在推断石油充注时间中的应用

摘要 与充满水的对应物相比，油饱和碳酸盐岩储层通常表现出异常高的孔隙度，这在文献中有大量记载。然而，尚未提出孔隙度模型来量化埋藏石油对孔隙度保存的演变。本文提出了碳酸盐岩储层的孔隙度深度饱和度模型（PDS 模型），该模型首次量化了给定充注时间下孔隙度随深度和含油饱和度的演变。PDS 模型公式将压实与孔隙度保持分离。机械和化学压实是从 Schmoker 和 Halley (1982) 压实趋势的现象学定义的，但仅适用于水域。孔隙度保持率的计算基于两个新概念：孔隙度保持潜力仅是充注时间的函数，孔隙度保持 α 因子是流体饱和度的函数。工作重点是大型横向均质碳酸盐岩储层。从相关的储层地质模型中提取孔隙度、含油饱和度和深度之间的关系并进行分析以定义孔隙度保存α因子。PDS 模型在特定的储层相上进行了测试，并提供了在任何充电时间随深度和饱和度变化的孔隙度演变。这表明即使在低含水饱和度，例如油藏束缚水条件下，减少的水量仍然足以降低埋藏孔隙度。从目前的储层条件可以看出，仅基于孔隙度的 PDS 模型，深度和剩余水饱和度，可以反算水库的充电时间。PDS 模型不仅提出了与独立研究结果一致的初始充电时间，而且还可以为储层内的各个区域提供相对和量化的充电时间，提供前所未有的粒度水平。