Various aspects of the mechanism of C02 corrosion are reviewed, together with a discussion about the validity of a number of simplifications which can be used with models for predicting the corrosion rate. A "worst case" rate can often be predicted. To this end a number of parameters has been identified, the

influence of which has to be accounted for. The effects of protective corrosion product layers and of dissolved corrosion product on pH needs to be included in the prediction. More quantitative information about the effect of flowpattern and flowrate is needed. For wet gas pipelines, the prediction of the effect of injection of glycol as a measure against corrosion is of special interest. Predictive models consisting of a system of rules and equations can be conveniently developed in computer spreadsheets.

The control of multiphase flow corrosion in oil and gas industry is one of the biggest challenging tasks. Since the 1990s, several organizations have established and operated large-scale flow loops to simulate and reproduce the field service environment of oil and gas pipelines. Based on comparison and investigation of the above loops, a new and advanced system, including several four inches internal diameter loops for studying corrosion under multiphase flows, was successfully built by us. By using this system, multiphase flows with various combinations of gas, water, oil and sand can be realized at the highest temperature of 140 oC and the highest pressure of 10 Mpa. Moreover, some loops in this system can adjust pipeline at different angels from 0 to 90°, which allow horizontal/vertical/sloping conditions to be simulated in laboratory. Many advanced measuring and monitoring technologies, such as Particle Imaging Velocimetry (PIV), high speed video camera and LPR/ER probe, are employed for simultaneously recording flow events and corrosion rates. An inhouse plane three-electrode probe is employed for conducting in situ electrochemical measurements. Such technologies would allow deep researching of corrosion behaviors and mechanisms in multiphase flow environments. Moreover, a new software based on Fluent and the existing multiphase corrosion models was developed to realize the numerical simulation of multiphase flow in loop. 

Ferrous iron is typically present in the brines of oil and gas production. Soluble iron is considered to adversely affect the performance of scale inhibitors against calcium carbonate scale. However, it is particularly difficult to prevent the oxidation of ferrous iron to form ferric iron with even trace amounts of oxygen in laboratory testing conditions. The oxide species of ferric iron have less solubility than the ferrous iron, and ferric hydroxide may adsorb scale inhibitors on its surface. Therefore, the presence of ferrous iron in laboratory testing poses a challenge for evaluating its effect on scale inhibitor performance.  Recently, Kinetic Turbidity Test (KTT) has become a more recognized testing method for scale inhibitor evaluation. It is a novel laboratory test method using an Ultraviolet-Visible (UV-Vis) spectrophotometer to monitor the formation of scales at various dosages of tested products as a function of reaction time. In the presence of ferrous iron, in order to keep oxygen away from the ambient environment during the test, the instrument was placed into an anaerobic chamber for maintaining low level of oxygen environment (< 1 ppm O2 in the chamber) during the testing process. This paper presents the approach to conduct KTT in the present of ferrous iron, and compares the testing data with and without ferrous irons on scale inhibitor performance by KTT and anaerobic bottle testing for both calcite and calcium sulfate inhibition. The selected inhibitor chemistries include four different types of phosphonates (Phosphonate A, B, C, and D) and five polymer inhibitors (Polymer A, B, C, D, E). Results show that KTT provides an efficient and data-driven approach for evaluating scale inhibitor performance in the presence of ferrous iron. The mechanisms of scale formation and scale inhibitor performance under the effects of iron were discussed. This paper provides insight for scale treatment chemistry and dosage in the presence of iron.