Variation in thermal history styles around the Irish Sea and adjacent areas: implications for hydrocarbon occurrence and tectonic evolution
Variation in thermal history styles around the Irish Sea and adjacent areas: implications for hydrocarbon occurrence and tectonic evolution
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爱尔兰海及邻近地区热历史样式的变化：对油气赋存和构造演化的影响
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
R. Bray
中科院分区：
文献类型：
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作者：
P. Green;I. Duddy;R. Bray
摘要热历史是决定爱尔兰海地区油气远景的主要因素。磷灰石裂变径迹分析（AFTA®）在勘探威尔斯井中的早期应用显示，第三纪早期的古温度约为110°C或更高。最近在爱尔兰海和邻近地区的研究，使用AFTA和镜质组反射率（VR）的组合，揭示了至少三个额外的古热事件：前二叠纪（>290 Ma），晚二叠世至中三叠世（260至220 Ma）和早白垩世（140至110 Ma）。早期古热效应的其他证据，其时间仅限于间隔300至150 Ma，可能反映了这些或其他事件。在某些地区，早期影响涉及极高的古地理梯度。早白垩世梯度是不受约束的，因为缺乏威尔斯井，其中古温度反映这一幕。东爱尔兰海盆地南部威尔斯井的AFTA和VR得出的早第三纪古温度定义了一个一致的线性深度剖面，梯度仅为10°C km−1。该区域北部的威尔斯井也确定了大致一致的剖面，但梯度要高得多。低梯度被认为反映了热流体的流动，而北部的高梯度可能与该地区的岩浆活动有关。我们对早第三纪古热效应的首选解释涉及约1.5至2公里的后三叠纪沉积物的埋藏和热流体流动的热效应，可能从北到南，并与火成岩活动相结合。这种解释与地质证据是一致的，并得到了构造数据、声速数据和地球化学观测的支持。这些事件的不同组合导致整个地区的热历史风格多种多样。东爱尔兰海盆地的南部，含有主要的石油和天然气的积累，其特点是最适合的热历史条件的生成和保存的碳氢化合物到今天。在邻近地区，热历史更为复杂，迄今已查明的热历史一般不太适合保存至今的碳氢化合物。这些地区的未来勘探将需要彻底了解石炭纪烃源岩的热历史，以确定最有前景的地区。
Abstract Thermal history is a major factor in determining hydrocarbon prospectivity in the Irish Sea region. Early application of Apatite Fission Track Analysis (AFTA®) to exploration wells revealed early Tertiary palaeotemperatures around 110°C or more. More recent studies in the Irish Sea and adjacent areas, using a combination of AFTA and vitrinite reflectance (VR), have revealed at least three additional palaeo-thermal episodes: pre-Permian (>290 Ma), late Permian to mid-Triassic (260 to 220 Ma) and Early Cretaceous (140 to 110 Ma). Other evidence of early paleo-thermal effects, for which timing is only constrained to the interval 300 to 150 Ma, may reflect these or additional episodes. In some areas, early effects involved extremely high palaeogeothermal gradients. Early Cretaceous gradients are unconstrained due to a lack of wells in which palaeotemperatures reflect this episode. Early Tertiary palaeotemperatures derived from AFTA and VR in wells from the southern part of the East Irish Sea Basin define a consistent linear depth profile with a gradient of only 10°C km−1. Wells from the north of the region also define a broadly consistent profile but with a much higher gradient. The low gradients are thought to reflect flow of hot fluids while the high gradients to the north may be associated with igneous activity in that region. Our preferred interpretation of the early Tertiary palaeo-thermal effects involves a combination of burial by around 1.5 to 2 km of post-Triassic sediment and the thermal effects of hot fluid flow, probably from north to south and associated with igneous activity. This interpretation is consistent with geological evidence and is supported by structural data, sonic velocity data and geochemical observations. Different combinations of these episodes lead to a wide variety of thermal history styles across the region. The southern part of the East Irish Sea Basin, containing major accumulations of oil and gas, is characterized by the most suitable thermal history conditions for generation and preservation of hydrocarbons to the present day. In adjacent regions, thermal histories are more complex, and those identified to date are generally less suitable particularly for preservation of hydrocarbons to the present day. Future exploration in these areas will require a thorough understanding of the thermal history of Carboniferous source rocks in order to define the most prospective regions.