Thermal modelling of magmatic intrusions in the Gjallar Ridge, Norwegian Sea: implications for vitrinite reflectance and hydrocarbon maturation
Thermal modelling of magmatic intrusions in the Gjallar Ridge, Norwegian Sea: implications for vitrinite reflectance and hydrocarbon maturation
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DOI：
10.1111/j.1365-2117.2007.00347.x
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发表时间：
2008-03
期刊：
影响因子：
3.2
通讯作者：
W. Fjeldskaar;H. M. Helset;H. Johansen;I. Grunnaleite;I. Horstad
中科院分区：
文献类型：
--
作者：
W. Fjeldskaar;H. M. Helset;H. Johansen;I. Grunnaleite;I. Horstad
广泛的岩浆活动发生在挪威近海的Vøring盆地，与早新生代裂谷作用有关。北大西洋在古新世-始新世过渡期的断裂引发了强烈的火山活动。在该地区有许多低于3 km深度的岩浆岩床。它们主要是层平行的，与它们的横向范围相比很薄。火成岩侵入体、岩床和岩脉影响了温度历史，因此在油气前景分析中需要考虑。我们已经计算了温度和成熟度的影响，在Gjallar地区的沉积层与单岩床和岩床复合体的侵位。120 m厚的岩床产生的理论镜质组反射率（%R0）比距岩床100 m处的正常值高0.8%。本文计算了由7个厚度从8到80 m不等的岩床群引起的镜质体反射率变化。结果表明，计算的热剖面可以解释观察到的井中镜质组反射率的变化。还模拟了一个横跨Gjallar海岭的二维剖面，其中包括许多岩浆侵入体。剖面上模拟的地质发展和温度历史表明，在所调查的井段中存在显著的成熟效应。根据这项工作，在该地区观察到的岩床群可能会增加一倍以上的部分干酪根已转化为石油在（目前）深度为4公里。
Extensive magmatic activity took place in the Vøring Basin, offshore Norway, related to the Early Cenozoic rifting. The break‐up of the North‐Atlantic at the Palaeocene–Eocene transition induced strong volcanism. There are numerous magmatic sills below 3 km depth in the area. They are predominantly layer parallel and thin compared with their lateral extent. Igneous intrusions, sills and dykes affected the temperature history, and thus need to be taken into account in petroleum prospect analysis. We have calculated the temperature and maturity effects in the sedimentary layers in the Gjallar area associated with the emplacement of single sill and sill complexes. A 120‐m‐thick sill produces a theoretical vitrinite reflectance (%R0) 0.8% higher than normal at a distance of 100 m from the sill. Vitrinite reflectance changes caused by a swarm of seven sills varying from 8 to 80 m in thickness were calculated. It is shown that the calculated thermal profile can account for the observed shift in vitrinite reflectance in the well. A two‐dimensional section crossing the Gjallar Ridge, consisting of numerous magmatic intrusions, is also modelled. The modelled geological development and temperature history over the profile show that there are significant maturation effects in the interval under investigation. Based on this work, the sill swarm observed in the area could more than double the fraction of the kerogen that has been transformed to petroleum at the (present) depth of 4 km.