Physical properties of the shallow sediments in late Pleistocene formations, Ursa Basin, Gulf of Mexico, and their implications for generation and preservation of shallow overpressures
Physical properties of the shallow sediments in late Pleistocene formations, Ursa Basin, Gulf of Mexico, and their implications for generation and preservation of shallow overpressures
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DOI：
10.1016/j.marpetgeo.2009.01.018
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发表时间：
2009-04
影响因子：
4.2
通讯作者：
N. Binh;T. Tokunaga;T. Nakamura;K. Kozumi;M. Nakajima;M. Kubota;H. Kameya;M. Taniue
中科院分区：
文献类型：
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作者：
N. Binh;T. Tokunaga;T. Nakamura;K. Kozumi;M. Nakajima;M. Kubota;H. Kameya;M. Taniue
了解沉积地层中异常高流体压力的演变对于分析水文地质过程和评估钻井风险至关重要。我们构建了一个二维盆地模型，并进行了数值模拟，以增加对墨西哥湾深水区Ursa盆地更新世和全新世地层中流体流动和浅层超压历史的了解。我们测量了沉积物的物理性质，如孔隙度和渗透率，在实验室和估计原位孔隙压力从预固结压力。通过室内试验，获得了孔隙度与有效应力的关系。孔隙度-有效应力关系也可从井下密度测井和实测孔隙压力中获得。将得到的孔隙度-有效应力和孔隙度-渗透率关系应用于二维盆地模拟。结果表明，高孔隙压力发展后不久，沉积物沉积。孔隙压力比的峰值与质量输送沉积物的高沉积速率和Ursa通道的切口有关。从覆盖层厚的地区向覆盖层薄的地区的侧向流动至少发生在30 ka以来。目前的孔隙压力和温度分布表明，侧向流动在盆地中重新分配热量的作用。
Understanding the evolution of abnormally high fluid pressures within sedimentary formations is critical for analysing hydrogeological processes and assessing drilling risks. We have constructed a two-dimensional basin model and have performed numerical simulations to increase the understanding of the history of fluid flow and shallow overpressures in the Pleistocene and Holocene formations in the Ursa basin, deepwater Gulf of Mexico. We measured physical properties of sediments, such as porosity and permeability, in the laboratory and estimated in situ pore pressures from preconsolidation pressures. We obtained porosity–effective stress relationships from measurements of bulk density, grain density and preconsolidation pressures in the laboratory. Porosity–effective stress relationships were also obtained from downhole density logs and measured pore pressures. The porosity–effective stress and porosity–permeability relationships obtained were applied in two-dimensional basin simulations. Results showed that high pore pressures developed shortly after sediment deposition. Peaks in pore pressure ratios were related to high sedimentation rates of mass transport deposits and the incision of the Ursa channel. Lateral flows from the area where the overburden is thick towards the area where it is thin have occurred at least since 30ka. Present pore pressure and temperature distributions suggest that lateral flows play a role in re-distributing heat in the basin.