Study On Flow Corrosion Characteristics Of Tube In Multivariate Thermal Fluid Environment

Completion fluid is used at all stages from drilling the formation to putting the well into production.This results in frequent contact of the completion fluid with the oil well tube material.With the use of integrated tube string in the development of deep well and ultra-deep wells in oil fields,the completion fluid often contains O₂,CO₂,Ca²⁺,K⁺,HCO^3-,Cl^-and other corrosive media,leading to the corrosion reaction of oil well tube made of ordinary materials more easily,resulting in wall thinning and fracture.This brings great security risks and economic losses to the development of oil and gas fields.In this paper,the corrosion problem of the commonly used oil well tube in the multivariate thermal fluid environment is simulated in the laboratory.Using weight loss method to measure the corrosion rate of P110 steel and TP140V steel under different density completion fluid(Ca Cl2,KCOOH),ambient temperature and flow rate.The surface corrosion morphology and product composition of the two materials were measured by SEM,EDS and XRD,and the causes and influencing factors of tube corrosion caused by completion fluid were analyzed.The main conclusions include:(1)In the multivariate thermal fluid environment,the density of Ca Cl2 directly affects the content of dissolved oxygen in the solution,and then changes the corrosion rate of oil well tube.As the density of KCOOH increases,on the one hand,the content of dissolved oxygen in the solution decreases linearly,slowing down the corrosion of the material,and on the other hand,the electrical conductivity of the solution increases,promoting the corrosion of the material.The promoting effect is greater than the inhibiting effect,which makes the corrosion rate of both P110 steel and TP140V steel increase with the increase of KCOOH density.(2)In Ca Cl2 solution,the corrosion rate of P110 steel reaches the maximum at the critical temperature of 150?.With the increase of temperature,the effectiveness of the corrosion product film is improved,which plays a protective role on the metal matrix.In the KCOOH solution,the corrosion rate of P110 steel and TP140V steel is opposite with the increase of temperature.(3)The increase of flow rate,on the one hand,makes the content of dissolved oxygen in the solution increase,accelerates the corrosion reaction,and the corrosion products generated increase accordingly.On the other hand,the larger flow rate makes the corrosion products fall off on the surface of the material,and the corrosive medium directly contacts with the metal matrix,and the corrosion degree intensifies.Under the synergistic action of these two factors,the corrosion process of P110 steel and TP140V steel in the completion fluid is accelerated.