基于岩心流动试验的德州市馆陶组松散砂岩渗透性分析OA

In order to reveal the permeability evolution mechanism of loose sandstone during geothermal re-injection,taking the unconsolidated sandstone of Guantao dormation in Dezhou city in Shandong province as the research object(φ25mm×50mm),by using core flow meter,multi-factor control test has been carried out.The influence of temperature(20～100℃),confining pressure(5～20 MPa)and injection rate(1.0～2.5mL/min)on permeability has been analyzed systematically.It is showed that the increase of tem-perature will lead to the overall decrease of rock permeability,which is closely related to the thermal ex-pansion effect of rock particles.The higher the temperature,the greater the gravel discharge.The critical pressure of pore closure in unconsolidated sandstone(buried depth is 1311～1312m)of Guantao formation in Dezhou city is about 15 MPa.At this point,the pore structure undergoes critical closure,and the perme-ability will drop by 48.9%.The change in permeability of loose sandstone under low injection rate is weak and negligible,but the increase of injection rate will significantly increase the amount of fluid carrying gravel and affect the overall permeability of rock mass.It is speculated that high injection rate is the domi-nant factor inducing blockage in the near wellbore area of the reinjection well.It is suggested that the injec-tion strategy of"first low and then stable,step lifting"should be carried out in the recharge design.