摘要
以南华北盆地和渤海湾盆地新近系明化镇组和馆陶组热储层的砂岩样品为例,进行孔隙特征测试,主要包括X射线衍射、比表面积、微CT扫描及土工实验等,并在此基础上对砂岩的实际渗透性能进行测试。结果表明,随着砂岩泥质含量增加,比表面积和表观孔隙率整体上分别呈增加和降低趋势。砂岩沉积过程中的复杂旋回会造成内部孔隙分布的不均匀性,形成局部狭窄的喉道,削弱渗透能力。高泥质含量的干燥砂岩在渗透实验中容易发生黏土矿物浸水膨胀崩解,从而改变内部孔隙结构,使得测试结果出现较大变化。对于上述孔隙型砂岩,经典渗透率模型难以给出较高的预测精度。在实际地热井开采与回灌过程中,应慎重选取预测模型,并评估其计算结果。
Taking typical sandstones from Minghuazhen formation and Guantao formation of Neogene in southern North China Basin and Bohai Bay Basin as the example,their pore characteristics were tested through XRD,specific surface area,micro CT scanning and geotechnical analysis. Then the actual permeability of sandstones was also tested. Results show that as the clay content increased,the specific surface area and apparent porosity tend tended to increase and decrease,respectively. Complex sedimentary cycles may cause non-uniform pore distribution of sandstones,thereby forming narrow local throats and reducing the permeability. For air-dried sandstones with high clay contents,soaking swelling,dissolution and disintegration of clay minerals were inclined to occur during the test,thereby expand the inner pore paths and enlarge the actual permeability. For the above pore-type sandstones,conventional empirical model did not give satisfied prediction accuracy. During the practical exploitation and reinjection of geothermal wells,it should be careful to choose the permeability prediction model and evaluate the corresponding calculation results.
引文
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