富CO2流体对深部碎屑储层影响机制模拟研究

深部流体中富含CO2,进入沉积盆地之后可与碎屑岩储集层相互作用,改变储层物性.利用压实成岩模拟装置,采用粒径为0.3～0.5 mm的长石颗粒为研究对象,开展了注入CO2的模拟试验,并通过分析流体中的化学成分变化监测发生的化学反应.注入CO2后取样表明,Si、Ca、Na的离子浓度在注入CO2后28h轻微下降;但在注入67h后Si和Na离子浓度上升,Ca离子浓度下降;注入150h后的取样表明,Ca离子浓度升高.加入CO2后试验砂体的孔隙度和渗透率下降,但渗透率降低的速率更快.表明CO2进入沉积盆地的初期,由于形成CaCO3沉淀和钙蒙脱石等新矿物,砂体渗透率降低,储层物性变差.

Simulation Study on the Mechanism of Effect of CO2 Enriched Fluid on Deep Clastic Reservoirs

CO2 is enriched in deep fluids,it reacts with clastic reservoirs after it enters into a depositional basin,thus changes of reservoir physical properties are induced.A compacted diagenetic device is used to conduct a CO2 injection simulation experiment by using feldspars with diameter of 0.3~0.5mm.Chemical reaction is detected on the changes of chemical compositions of the fluid.The sample of injected CO2 indicates that the concentrations of Si,Ca and Na are reduced slightly 28 hours after CO2 injection,while the concentrations of Si and Na are raised and Ca concentration is reduced 67 hours after injection.The sample taken after 150 hours shows that Ca concentration is raised.The permeability and porosity of the test sandbody are reduced after CO2 injection,but permeability decrease is faster.It shows that permeability reduces and reservoir physical property becomes poor because of the creation of new minerals of CaCO3 deposition and smectites at the initial stage of CO2 injection.