Rock physics analyses of data from a wildcat well 7117/9-1 drilled in the Senja Ridge area, located in the Norwegian Barents Sea, reveal changes in stiffness within the fine-grained Paleogene Sotbakken Group sediments, caused by the transformation of opal-A to opal-CT, and opal-CT to quartz. These changes manifest as flat spots on 2D seismic profiles. These flat spots were mistaken as hydrocarbon–water contacts, which led to the drilling of well 7117/9-1. Rock physics analyses on this well combined with a second well (7117/9-2) drilled further NW and updip on the Senja Ridge indicate overpressure within the opal-CT-rich zones overlying the opal-CT to quartz transformation zones in the two wells. The absence of opal-A–opal-CT and opal-CT–quartz flat spots on seismic in the second well is attributed to differences in the temperature and timing of uplift. Amplitude v. angle (AVA) modelling indicates both the opal-A–opal-CT and opal-CT–quartz interface points plot on the wet trend, whereas modelled gas–brine, oil–brine and gas–oil contacts fall within quadrant-I. These findings will be useful in understanding the nature of compaction of biogenic silica-rich sediments where flat spots could be misinterpreted as hydrocarbon-related contacts in oil and gas exploration.

中文翻译：

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巴伦支海 Senja Ridge 附近古近系 Sotbakken Group 内的成岩相关平坦点

对位于挪威巴伦支海 Senja Ridge 地区钻探的 7117/9-1 野猫井数据的岩石物理学分析揭示了细粒古近系 Sotbakken Group 沉积物中的硬度变化，这是由蛋白石-A 的转化引起的蛋白石-CT，蛋白石-CT 石英。这些变化表现为二维地震剖面上的平点。这些平坦点被误认为是碳氢化合物-水接触面，从而导致了 7117/9-1 井的钻探。对该井的岩石物理分析与第二口井 (7117/9-2) 在 Senja Ridge 上进一步钻探和上倾表明两口井中蛋白石 CT 至石英转化带上覆的富含蛋白石 CT 的区域内超压. 在第二口井中没有蛋白石-A-蛋白石-CT 和蛋白石-CT-石英平坦点，这归因于温度和隆升时间的差异。振幅与角度 (AVA) 建模表明蛋白石-A-蛋白石-CT 和蛋白石-CT-石英界面点都绘制在湿润趋势上，而模拟的气-卤、油-卤和气-油接触落在象限内一世。这些发现将有助于了解生物成因富含二氧化硅的沉积物的压实性质，其中平坦点可能被误解为石油和天然气勘探中与碳氢化合物相关的接触。