Coupled fluid flow, heat and mass transport, and erosion in the Alberta basin: implications for the origin of the Athabasca oil sands
Coupled fluid flow, heat and mass transport, and erosion in the Alberta basin: implications for the origin of the Athabasca oil sands
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DOI：
10.1139/e04-052
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发表时间：
2004-09-01
影响因子：
1.4
通讯作者：
Mendoza, CA
中科院分区：
文献类型：
--
作者：
Adams, JJ;Rostron, BJ;Mendoza, CA
利用二维耦合流体流动、热输运和溶质输运数值模型模拟了与Laramide构造反弹相关的区域地形驱动流动系统，以复制当前地层水的盐度和温度分布，并研究了Athabasca油砂的富集。之前对该系统的建模是重复的，该模型预测了在油砂沉积过程中，由于高渗透率，所有盆地地层水都被淡水反复替代。为了与阿尔伯塔盆地现在的温度和盐度分布相匹配，对模式水文地层、渗透率和热通量进行了调整。这个修正的模型沿着Mannville含水层而不是上泥盆统含水层引导流体，并复制了目前的盐度分布，假设在60 Ma左右瞬时上升。使用新的渗透率，主要含水层的流体通量减少了两个数量级，导致主要的传导性热传输。因此，由于模拟通量低，阿萨巴斯卡油砂的成因不能用溶解相石油输运来解释。模型模拟表明，较高地形梯度的持续侵蚀产生了类似的流动模式，但流体通量、温度和水头在5800万年中均匀减少。在模拟的最后阶段，侵蚀速率的增加在隆起附近产生了亚静水压力，这引发了盆地内的流动逆转。盖层白垩纪含水层变薄和Mannville渗透率分布导致Peace河附近排放，与Peace河油砂和solonetzic土壤带一致。区域地形驱动的流动通过流体通量的减小、扰动带附近的欠压以及小尺度起伏驱动的局部流动子系统的发展而逐渐衰减。
Regional topography-driven flow systems related to Laramide tectonic rebound were simulated using two-dimensional, coupled fluid-flow, heat transport, and solute transport numerical models to replicate present formation water salinity and temperature distributions and investigate the accumulation of the Athabasca oil sands. Previous modelling of this system was replicated, and it predicted repeated replacement of all basin formation water with freshwater during deposition of the oil sands due to high permeabilities. To match present Alberta basin temperature and salinity distributions, model hydrostratigraphy, permeabilities, and heat fluxes were adjusted. This revised model conducts fluids along the Mannville aquifer, rather than the Upper Devonian aquifer, and replicates present salinity distributions, assuming instantaneous uplift around 60 Ma. Fluid fluxes in principal aquifers decrease by two-orders of magnitude using new permeabilities, resulting in primarily conductive heat transport. Thus, genesis of the Athabasca oil sands cannot be explained by dissolved-phase petroleum transport due to low simulated fluxes. Model simulations representing constant erosion of a higher topographic gradient produce similar flow patterns, but fluid fluxes, temperatures and hydraulic heads uniformly decrease over 58 million years. Increased erosion rates in the last stage of simulations produce sub-hydrostatic pressures near the uplift, which trigger a flow reversal in the basin. Thinning of the capping Cretaceous aquitard and Mannville permeability distribution causes discharge in the vicinity of the Peace River, coincident with Peace River oil sands and solonetzic soil zones. Regional topography-driven flow gradually decays via diminishing fluid fluxes, underpressuring near the disturbed belt, and development of local flow sub-systems driven by small-scale relief.