Regional uplift in the English Channel: quantification using sonic velocity
Regional uplift in the English Channel: quantification using sonic velocity
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DOI：
10.1144/gsl.sp.1998.133.01.08
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
A. Law
中科院分区：
文献类型：
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作者：
A. Law
英国天然气勘探和生产有限公司持有的大量油井数据库的分析，使区域估计隆起的英吉利海峡地区来自井下声速的异常测量。剖面隆起或表观侵蚀的估计值可根据盆地中威尔斯井之间声速/走时的变化得出，该变化与定义盆地速度/走时和深度关系的函数有关;正常压实关系。然而，这些估计对正常压实关系中的误差以及威尔斯井之间的沉积相和/或成岩作用的变化极其敏感。在这项研究中，这些问题已被最大限度地减少使用区域持久性，均质厚相，如页岩，并通过仔细约束正常的压实关系的“回剥”表观侵蚀值，以确定“剩余表观侵蚀”。从中、上侏罗纪开始，已确定了三个时间段的明显侵蚀，大致对应于富勒土、牛津粘土和基迈里奇粘土地层。对这些值求平均值并如上所述对其进行限制，可得到对英吉利海峡盆地总隆起的可靠估计，不确定性约为20%。这项研究的结果表明，该地区内的大规模隆起，最大的Purbeck-Isle的怀特断层带和中通道高反转轴。在Purbeck-Isle of Wight断层带以北，表观侵蚀计算估计隆起500 m或更少，表明该地区在盆地反转期间可能保持相对稳定。与AFTA/VR（磷灰石裂变径迹/镜质组反射率）古温度数据的等效估计值相比，声波引起的隆起在反演区域的误差范围内是相似的。然而，在更稳定的地区，如Purbeck-Isle of Wight断层带以北，计算的明显侵蚀表明几乎没有发生隆起，而来自AFTA/VR模型的隆起估计仍然很重要。
Abstract Analysis of the substantial well database held by British Gas Exploration and Production Ltd enables regional estimates of uplift for the English Channel area to be derived from anomalous measurements of downhole sonic velocity. Estimates of section uplift, or apparent erosion, can be derived from variations in sonic velocity/travel-time between wells in a basin relative to a function defining the velocity/travel-time and depth relationship for the basin; the normal compaction relationship. These estimates are, however, extremely sensitive to errors in the normal compaction relationship, and to variations in sedimentary facies and/or diagenesis between wells. In this study, these problems have been minimized using regionally persistent, homogeneous thick facies such as shales and by carefully constraining the normal compaction relationship by ‘backstripping’ apparent erosion values to determine ‘residual apparent erosion’. Apparent erosion has been determined for three intervals from the Mid- and Upper Jurassic, broadly corresponding to the Fuller’s Earth, Oxford Clay and Kimmeridge Clay Formations. Averaging these values and constraining them as above results in robust estimates of total uplift across the English Channel Basin, with uncertainties of around 20%. The results of this study suggest kilometre-scale uplift within the area, with maxima over the Purbeck-Isle of Wight Fault Zone and the Mid Channel High inversion axes. To the north of the Purbeck-Isle of Wight Fault Zone the apparent erosion calculations estimate uplift of 500 m or less, suggesting that this area may have remained relatively stable during basin inversion. When compared to equivalent estimates from AFTA/VR (apatite fission track/vitrinite reflectance) palaeotemperature data, the sonic-derived uplift is similar within errors in inverted areas. However, in more stable areas such as to the north of the Purbeck-Isle of Wight Fault Zone, calculated apparent erosion indicates that little uplift has occurred, whereas uplift estimates derived from AFTA/VR models are still significant.