川东南志留系泥岩盖层水岩相互作用的实验模拟及其研究意义

通过水岩反应模拟实验,可研究分析在不同的成岩环境下,盖层岩石的水岩反应对储层形成以及油气保存方面的影响。选取川东南地区志留系龙马溪组盖层泥岩,在30℃,1MPa;80℃,20MPa和160℃,40MPa的温压条件下,与淡水和含乙酸流体进行水岩反应实验模拟。结果显示:在常温常压下,泥岩与淡水仅发生非常微弱的水岩反应,说明在地表淡水弱的水动力条件下,对泥岩盖层破坏是非常有限的;而高温高压下,含乙酸的流体对盖层泥岩的破坏力要高于常温常压下的淡水,但是溶蚀率也很微弱,并且相对于同种条件下的灰岩和云岩的溶蚀率还要低得多。研究区内,当有具有溶蚀性的热流体活动时,在志留系泥岩渗透率低和难溶蚀2个因素的叠加阻挡作用下,大量的流体在碳酸盐岩层中滞留,与围岩发生充分的水岩作用。 

Simulation experiment of water-rock interaction in Silurian mudstone cap formation and its significance in Southeast Sichuan Basin

The influence of water-rock interaction of cap rock on reservoir formation and hydrocarbon preservation under different environments was analyzed with simulation experiment of water-rock interaction.The mudstone cap rock samples from the Silurian Longmaxi Formation in the Southeast Sichuan Basin were selected to react with freshwater and acetic fluid under different temperature and pressure conditions of 30 ℃,1 MPa;80 ℃,20 MPa and 160 ℃,40 MPa,respectively.Under normal temperature and pressure,the interaction between mudstone and fresh water was very weak,suggesting that the interaction was not destructive to cap rock under weak hydrodynamic force;however,acetic fluid under high temperature and pressure was more destructive than fresh water under normal conditions.Yet the solubility of mudstone was much lower than that of carbonate under the same conditions.In the study area,when hydrothermal fluid moved,more fluid was occluded in carbonate and reacted with rock because of low permeability and solubility of the Silurian mudstone.