Mudstone Compaction Trends and their Use in Pore-Pressure Prediction
Mudstone Compaction Trends and their Use in Pore-Pressure Prediction
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泥岩压实趋势及其在孔隙压力预测中的应用
DOI：
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发表时间：
2008
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影响因子：
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通讯作者：
J. Jahren
中科院分区：
文献类型：
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作者：
N. Mondol;K. Bjørlykke;J. Jahren
预测沉积盆地孔隙压力的一般方法是利用泥岩中声波走时和/或地震层速度与深度/有效应力的关系。孔隙压力，然后估计从广义压实趋势的分歧。成功地将泥岩压实趋势转换为孔隙压力预测的关键是将泥岩表征为岩性和结构变化的函数，并建立孔隙度/密度/速度/渗透率与有效应力之间的关系。沉积盆地在沉积相、构造发展和成岩历史等方面具有很强的非均质性。因此，沉积盆地中的流体输运在很大程度上受盆地充填的非均匀性控制。超压的产生是由压实（孔隙度损失）产生的流体通量和沿通往地表的最具渗透性通道的渗透率沿着的函数。干酪根流体的生成和矿物的脱水作用可能会增加这种流体通量，但渗透率是决定超压发展的最关键参数。通过一系列室内实验，研究了纯蒙皂石、高岭石、粉土及其混合物的速度、孔隙度、密度、渗透率与有效应力的关系。压实试验表明，对于相同的孔隙度，粘土矿物的渗透率变化为10 4至10 5倍。富蒙皂石泥岩的渗透率较低，即使在浅埋或中等埋深下也有形成超压的潜力。假设垂直流动的计算表明，如果形成密封的页岩的有效渗透率小于0.1-0.01 nD（毫微度），则将达到破裂压力。实验结果的速度/孔隙度/密度/渗透率与有效应力的良好表征泥岩之间的关系进行了比较，表现出密切的匹配的现场数据，证实实验数据可以是有用的，以区分泥岩孔隙压力预测。
A general way of predicting pore pressure in sedimentary basins is to use relationships of sonic travel time and/or seismic interval velocity versus depth / effective stress in mudstones. Pore pressure is then estimated from the divergence from generalized compaction trends. The key to a successful conversion of mudstone compaction trends to pore-pressure prediction is to characterize the mudstones as functions of lithology and textural variations and to establish relationships between porosity/density/velocity/ permeability versus effective stress. Sedimentary basins are awfully heterogeneous as functions of sedimentary facies, tectonic development, and diagenetic history. Fluid transport in sedimentary basins is therefore controlled largely by the heterogeneity of the basin fill. Overpressure generation is the function of fluid flux generated by compaction (porosity loss) and the permeability along the most permeable pathways to the surface. Generation of fluids from kerogen and dehydration of minerals may add to this fluid fluxes, but permeability is the most critical parameter determining the development of overpressure. A series of laboratory measurements were conducted to investigate the relationships between velocity/porosity/density/permeability versus effective stress for pure smectite, kaolinite, and silt, and their mixtures. Experimental compaction has shown that the permeability of clay minerals vary by a factor of 10 4 to 10 5 for the same porosity. The smectite-rich mudstones have very low permeability compared to others and have potentiality to develop overpressure even at shallow or moderate burial depth. Calculations assuming vertical flow show that fracture pressure will be reached if the effective permeability of the shale forming the seal is less than 0.1-0.01 nD (nanodarcies). The experimental results of relationships between velocity/porosity/ density/permeability versus effective stress of well-characterized mudstones were compared to the field data which demonstrated a close match, confirming that experimental data can be useful to distinguish mudstones for pore-pressure prediction.