ABSTRACT One of the major aspects of rock‐physics forward modelling is to predict seismic behaviour at an undrilled location using drilled well data. It is important to model the rock and fluid properties away from drilled wells to characterize the reservoir and investigate the root causes of different seismic responses. Using the forward modelling technique, it is possible to explain the amplitude responses of present seismic data in terms of probable rock and reservoir properties. In this context, rock‐physics modelling adds significant values in the prospect maturation process by reducing the risk of reservoir presence in exploration and appraisal phases. The synthetic amplitude variation with offset gathers from the forward model is compared with real seismic gathers to ensure the fidelity of the existing geological model. ‘Prospect A’ in the study area has been identified from seismic interpretation, which was deposited as slope fan sediments in Mahanadi basin, East Coast of India. The mapped prospect has shown class‐I amplitude variation with offset response in seismic without any direct hydrocarbon indicator support. The existing geological model suggests the presence of an excellent gas reservoir with proven charge access from the fetch area, moderate porosity and type of lithology within this fan prospect. But, whether the seismic response from this geological model will exhibit a class‐I amplitude variation with offset behaviour or ‘dim spot’ will be visible; the objective of the present study is to investigate these queries. A rock‐physics depth trend analysis has been done to envisage the possibilities of class‐I reservoir in ‘Prospect A’. Forward modelling, using a combination of mechanical and chemical compaction, shows the synthetic gas gathers at ‘Prospect A’, which are class I in nature. The study has also depicted 2D forward modelling using lithology and fluid properties of discovery well within similar stratigraphy to predict whether ‘dim spot’ will be seen in seismic. The estimated change in synthetic amplitude response has been observed as ∼5% at contact, which suggests that the changes will not be visible in seismic. The study connects the existing geological model with a top‐down seismic interpretation using rock‐physics forward modelling technique to mature a deep‐water exploratory prospect.

中文翻译：

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预测地震行为的岩石物理正演模型：以印度东海岸马哈纳迪盆地勘探目标为例

摘要 岩石物理学正演建模的主要方面之一是使用钻井数据预测未钻井位置的地震行为。对远离钻井的岩石和流体特性进行建模以表征储层并研究不同地震响应的根本原因非常重要。使用正演建模技术，可以根据可能的岩石和储层特性来解释当前地震数据的振幅响应。在这种情况下，岩石物理建模通过降低勘探和评估阶段存在储层的风险，为前景成熟过程增加了重要价值。将正演模型随偏移道集的合成振幅变化与真实地震道集进行比较，以确保现有地质模型的保真度。研究区的“A 矿区”已从地震解释中确定，其沉积为印度东海岸马哈纳迪盆地的斜坡扇沉积物。在没有任何直接碳氢化合物指示剂支持的情况下，绘制的远景已显示出 I 级振幅随偏移响应的地震。现有的地质模型表明，在这个扇远景区内存在一个优良的气藏，已证实可以从取水区进入、中等孔隙度和岩性类型。但是，该地质模型的地震响应是否会表现出具有偏移行为的 I 级振幅变化或“暗点”将是可见的；本研究的目的是调查这些疑问。已经进行了岩石物理深度趋势分析，以设想“前景 A”中 I 类储层的可能性。正向建模，使用机械和化学压实的组合，显示合成气聚集在“前景 A”，属于 I 类。该研究还描述了使用相似地层内发现井的岩性和流体特性的二维正演建模，以预测地震中是否会看到“暗点”。在接触处观察到合成振幅响应的估计变化约为 5%，这表明这些变化在地震中是不可见的。该研究使用岩石物理正演建模技术将现有地质模型与自上而下的地震解释联系起来，使深水勘探前景成熟。该研究还描述了使用相似地层内发现井的岩性和流体特性的二维正演建模，以预测地震中是否会看到“暗点”。在接触处观察到合成振幅响应的估计变化约为 5%，这表明这些变化在地震中是不可见的。该研究使用岩石物理正演建模技术将现有地质模型与自上而下的地震解释联系起来，使深水勘探前景成熟。该研究还描述了使用相似地层内发现井的岩性和流体特性的二维正演建模，以预测地震中是否会看到“暗点”。在接触处观察到合成振幅响应的估计变化约为 5%，这表明这些变化在地震中是不可见的。该研究使用岩石物理正演建模技术将现有地质模型与自上而下的地震解释联系起来，使深水勘探前景成熟。