Mercury in gas and oil deposits: corrosion problem

Mercury naturally occurs in gas and oil deposits in a wide range of concentrations covering six orders of magnitude: up to 5 mg/m3 in natural gas and up to 600 ppm (mg/kg) in crude oil. Mercury in hydrocarbons poses a number of technological and environmental problems: contamination of equipment and products with this extremely toxic element, poisoning of catalysts, and initiates intensive corrosion of technological equipment, thereby enhancing accident risk. Metal mercury causes rapid electrochemical corrosion of aluminum alloys (e.g., heat exchangers) and liquid metal embrittlement (LME) of steel leading to heavy accidents. The novel technology based on Zeeman atomic absorption spectroscopy enables rapid selective mercury determination in crude oil, gas condensate, naphtha and natural gas. Examples of the technology application for gas, oil and oil products are presented.

EFFECT OF CONDUCTIVITY IN CORROSION PROBLEM USING BOUNDARY ELEMENT METHOD AND GENETIC ALGORITHM

Boundary element method applications with inverse solution are used to apply the indirect analysis for modeling of corrosion problem. Laplace equation has been used to model the electrical potential in the electrolyte surface. In this paper a computer modeling has been developed to visualize the effect of conductivity value in corrosion problem. Genetic algorithm is used to create the conductivity value based on the mechanics of natural selection and genetics. The boundary element method is then calculating the potential value of the whole domain. FORTRAN and MATLAB program have been developed to calculate and visualize the potential distribution in the domain. Two-dimensional example problems are analyzed to demonstrate the application of the proposed boundary element modeling procedure.

Laboratory Study on Corrosion Mechanism of Production System in In Situ Combustion

The corrosion problem of a production system has been affecting the normal operation of an in situ combustion project. Because the environment of production system is significantly different in tubing, gas, liquid, and temperature in in situ combustion, the problem of the corrosion should be treated differently according to its origin. Based on the main environment of gas-liquid of the production system of in situ combustion, the corrosion of steel in N80 and J95, which are commonly used in oilfield, is studied in different temperature and pressure conditions. The results show that under the condition of 50°C and 3 MPa, the corrosion of the well is the most serious. Based on the analysis of corrosion causes in the production system, the corrosion under the protection of modified sacrificial anode in the liquid phase environment was studied. The results of comparative analysis show that the modified material had the dual protection effect of sacrificial anode and film-forming protection and could slow down the corrosion in different temperature ranges.

Collaboration solves long standing corrosion problem

External pitting corrosion has been a long standing issue for stainless steel pressure equipment systems on Woodside offshore facilities. Experience has shown that this pitting cannot be effectively managed by inspection and, as a result, the current policy is that piping replacement should be planned once the presence of significant pitting corrosion has been identified. All Woodside offshore facilities have 316-grade stainless steel pressure equipment which is experiencing active external corrosion pitting to varying degrees. This represents the potential for hundreds of millions of dollars in piping replacement across the company. STOPAQ is an established product for the mitigation of external corrosion in carbon steel equipment however, it has not previously been used at Woodside on stainless steel equipment to address pitting corrosion. Through collaboration with the Woodside Future Laboratory at Monash University, Materials and Corrosion Engineering, Woodside Energy Limited has challenged the old established theory regarding the mechanism of pitting in stainless steel and a test program has been devised to validate the new way of thinking, which postulates that elimination of moisture and oxygen from the pits, by the application of an impervious layer like STOPAQ, will stifle the corrosion reaction and arrest the pitting. A recently completed test program at Monash which utilised computed tomography (CT) scanning, to very accurately determine the volume of corrosion pits, has confirmed that the application of STOPAQ to pitted stainless steel is very effective at mitigating this type of corrosion.

The case method: study of a corrosion problem

The aim of the present work is the application of the case method as teaching-learning methodology for the study of a corrosion problem, in order to obtain more active learning of the student. The educational innovation has been applied in 2018/2019 academic year in the subject of “Manufacturing Processes of Building Materials” imparted in the fourth course of the Chemical Engineering Degree in the Higher Technical School of Industrial Engineering in the Polytechnic University of Valencia. Such educational innovation consists in the description by the lecturer of a real situation about a corrosion problem, so that the students can analyse it and propose solutions individually and in group. At the end of the case it is added questions to help to the students in the analysis. This activity is realized in class, which is evaluated using a rubric. The evaluation of the educational innovation proposed is realized by the scores of the students, the polls of the students, and the autoevaluation of the lecturer. The results show the high scores obtained by the students in the case method and the high grade of satisfaction of the students after applying the educational innovation. The case method permits that the students know real situations that they could find in a professional future, which increase the motivation towards the subject of study.

The Corrosion of Cast Duplex Stainless Steels in Seawater and Sour Brines

Modern duplex stainless steels have been in use since the early 1970s and cast versions of the wrought alloys were soon in demand for pumps and valves. Since that time a range of cast duplex stainless steels have been developed with a wide range of compositions, but all with approximately 50/50 austenite/ferrite phase balance and deliberate additions of nitrogen. This paper presents some comparative corrosion data on a range of cast duplex stainless steels, mainly in seawater. The differences in performance related to composition and microstructure are discussed. Corrosion data in lower chloride brines are also presented to show the limits of use of some lower alloyed duplex materials. In addition to oxidizing chloride solutions, some data are presented on cast duplex stainless steels in reducing brines containing H2S, where the main corrosion problem is sulfide stress corrosion cracking. Finally, the importance of using a suitable technical specification, over and above ASTM, combined with selecting a suitably skilled foundry in order to obtain satisfactory castings is discussed.

Combination Application Strategy of Non-Metal Compound Pipe and its Verification

The service environment of Yanchang oilfield was researched. The corrosion environment of the oil and gas area of Yanchang group is different, the summer rainstorm is frequent and the landslide debris flow is easy to occur. The theoretical analysis and pilot test of pipeline performance have been carried out. We suggest that the steel pipeline, t FRP pipeline and the flexible composite pipe for high pressure transmission can be used in Yanchang group. The combined application strategy of steel pipeline, FRP pipeline and flexible composite pipe for high pressure transmission was proposed and verified. The results show that the combined application strategy effectively slows down the pipeline corrosion problem, reduces pipeline leakage accidents caused by accidental landslides, and reduces environmental pollution accidents caused by accidents such as pipeline corrosion and leakage. The tracking and analysis of pipeline combined application strategy for up to 5 years, the results show that the pipeline combined application strategy is more economical. It is concluded that the combined application strategy of steel pipelines, FRP pipelines and Flexible Composite Pipe for High Pressure Transmissions can ensure smooth operation of pipelines and save costs in the development of oil and gas fields, and it is recommended to popularize.