Experimental Study On The Rock Permeability Under The Jet Of Supercritical Carbon Dioxide

Supercritical carbon dioxide is a new type of drilling fluid.It has the characteristics of low viscosity,high density and good diffusivity.Meanwhile,due to these advantages,it can also be used to prevent the hydration and protect the reservoir.It has a good prospect of exploring for the unconventional reservoir because of its features.However,the influence of supercritical carbon dioxide flowing during the well bottom and wellbore has not been reported yet.It is crucial to study the mechanical properties and permeability influenced by the supercritical carbon dioxide jetting flow for promoting the development of drilling and completion theory.Firstly,based on the numerical simulations,the physical model of supercritical carbon dioxide jet injection has been established.The distributions of jet flowing field and rock's internal flow field have been simulated.The mechanism of permeability influenced by supercritical carbon dioxide has been analyzed.Compared to the simulations of the water and nitrogen,it shows that temperature stress and stress fluctuations are formed inside the rock caused by the jet flow.As a result,it leads to the jetting anatonosis caused by the formation and extension of rock fracture.Secondly,the jetting anatonosis experiments of supercritical carbon dioxide have been studied and we get the following results.(1)As the injection pressure is increasing,the curve of permeability is rising rapidly and then leveling off.(2)As the injection temperature is increasing,the permeability keeps rising.To some degree,the effect of low pressure is better than the high pressure's.(3)With the rising temperature of the formation,the permeability of the rock shows the linear increases.(4)As the jetting time is increasing,the permeability is rising rapidly and then leveling off.Finally,the physical properties of the rock before and after the jetting flow have been studied and we get the following results.(1)With the increasing injection pressure and temperature,the strength of rock is decreasing gradually.(2)As the jet time is rising,the rock strength is decreasing rapidly and then tends to a certain value.(3)The elasticity modulus is declining after the jetting.As the increasing temperature,the Poisson's ratio is increasing.The rock changes from elasticity to plasticity when the jet flow acts on it.In this paper,based on the experimental study and theoretical analysis of supercritical carbon dioxide,it shows that the mechanism of jet flow increasing the permeability.The physical parameters of formation influenced by the supercritical carbon dioxide are analyzed.As a result,it provides the theoretical basis for the reservoir exploration and protection by the supercritical carbon dioxide.