Oilfield Pipelines Research Articles

Investigation of Factors Influencing the Autoclave Tests Results of Internal Anticorrosive Polymer Coatings

Polymer coatings are one of the most common methods for protecting metal structures from corrosion damage. For example, in the oil and gas industry, polymer coatings are used to protect the inner surfaces of oilfield pipelines. Forecasting the service life of the coating is an unsolved problem. Existing test methods allow to assess the quality of coating application and compliance with the declared properties, for example, resistance at a certain temperature, but do not allow to understand the expected service life or degradation dynamics. One solution to this problem may be the development of existing methods of autoclave testing of coatings with the addition of more criteria for assessing degradation. This paper considers the methodological features of autoclave testing with rapid pressure relief. The decompression autoclave test was considered from the point of view of the principles of its conduct and evaluation of test results. The tests were carried out in environments containing hydrogen sulfide and carbon dioxide. The main object of the tests was anticorrosive polymer powder coatings applied in industrial conditions. The work assessed the influence of the following factors on the test result: pressure relief time, test cycle, and coating quality. Attention was also paid to the evaluation methods; aside from the adhesion assessment, optical microscopy and the evaluation of the microhardness of coatings were used. As a result of the work carried out, it was shown that the pressure relief rate within 5 s affects the test results. An increase in micropores and a drop in the microhardness of coatings after cyclic autoclave tests were also shown. The method of assessing the degradation of coatings using microhardness also showed the convergence of the results with the traditional method of assessing adhesion. The results of the work can be used to modify the autoclave testing method and transition to resource forecasting.

Influences of the Water Cut of Pumping Oil and the Mineralization of the Associated Water on the Rate of Sludging

The problem of the formation of organic deposits on the inside surfaces of borehole equipment and oilfield pipelines, which is urgent for all active oil fields, was considered in the study. The formation of these deposits leads to decreased lifespans for oilfield equipment and accidents involving oil pipelines and wells. The aim of our work was to estimate the dependencies of the organic deposition’s formation-rate factor on the water cut of the investigated water–oil emulsion and the mineralization of the water phase. Examination via generation of asphaltene–resin–paraffin deposits on the surfaces of cold rods was carried out with a “Cold Finger” CF-4 unit. Coefficients of specific oil sludging, fluid sludging and rate sludging have been determined. It has been defined that in the definite oilfields, the rate of sludging does not increase as the water content in the emulsion increases. As water-phase mineralization increases, this value remains practically constant.

Identification and Phylogenetic Analyses of Anaerobic Sulfidogenic Bacteria in Two Algerian Oilfield Water Injection Samples

Corrosion of metallic oilfield pipelines by microorganisms is a costly but poorly understood phenomenon. For the first time, sulfidogenic communities in injection waters of two Algerian oilfields, Tin Fuin Tabankort (IT3) and Stah (IS2) were examined using the 16S rRNA gene cloning and sequencing approach. Water samples were inoculated into selective medium for sulfate-reducing bacteria and incubated under anaerobic conditions at 45 °C. The total number of culturable sulfidogenic microorganisms in the samples obtained from the two sampled waters (IT3 and IS2) was 2.4 × 105 cells/mL and 3.9 × 104 cells/mL, respectively. Scanning electron microscopy analyses showed different morphological forms reflecting the diversity of sulfidogenic communities. 16S rRNA gene sequencing and phylogenetic diversity analyses revealed that both water reservoirs harbor large amounts of anaerobic bacteria. However, a majority of all the sequences analyzed (e.g., 34% in the IS2 and 84% in the IT3 samples) were not assigned to any known bacterial group, suggesting that subsurface waters harbor very large sulfidogenic anaerobic microbial communities of as yet undescribed bacterial phyla. Proteobacteria were found to be the most dominant phylum in the IS2 sample (49%); however, no Proteobacteria were detected at the IT3 production well. The Firmicutes phylum (10%) was detected in the two water samples, whereas Bacteroidetes phylum (7%) was retrieved only in IT3. The most abundant related genera were: Desulfotomaculum, Porphyrobacter, Hyphomicrobium, Acidocella, Comamonas, Ramlibacter, Pseudomonas, Enterobacter and Flavitalea. No shared operational taxonomic units were observed among the two samples analyzed, demonstrating the uniqueness of each subsurface water well. This study demonstrates the diversity of the sulfidogenic bacteria that might play a critical role in the souring mediated corrosion of metallic oilfield pipelines. This information could help oilfield companies develop better anticorrosion treatments and strategies.

Development and study of corrosion inhibitors based on tall oil

One of the serious troubles faced by the oil and gas industry is corrosion wear of equipment and pipelines. The major part of failures of the oilfield equipment and pipelines is the result of corrosion damage, so protection of equipment from corrosion is one of the most urgent scientific and technical issues. One of the most common ways to control corrosion is inhibitor protection. The paper presents the results of studies of corrosion inhibitors synthesized on the basis of polyethylene polyamines and three varieties of light tall oil in the presence of alcohol solvents using the stillage residue of butyl alcohols rectification. The optimal parameters of synthesis and the ratio of basic raw reactants and solvents have been determined. The inhibitory properties of the synthesized samples were evaluated by changes in the rate of corrosion and the value of their protective efficiency. It has been shown that the best of the synthesized samples is not inferior to the industrial reactant Sonkor 9601 in terms of the protective effectiveness, and in the area of low concentrations (up to 40 g/t) exceeds the basic inhibitor.

Effect of Carbonitride Precipitates on the Corrosion Resistance of Low-Alloy Steels under Operating Conditions of Oil-Field Pipelines

An investigation into the corrosion resistance of steels with various contents of carbon and microalloying elements was carried out. It was shown that the presence of a large amount of nanosized (2–3 nm and less) precipitates of the interphase type, particularly niobium carbonitride and vanadium carbonitride, leads to a decrease in the corrosion resistance of hot-rolled sheet products. It was found that, after heat treatment of rolled products at 710 °C, the corrosion resistance of the metal is improved. One of the reasons for this is a decrease in the amount of interphase precipitates, which negatively affect the corrosion resistance of steel, while particles formed in austenite and ferrite do not have such an effect. To ensure high corrosion resistance of steels for oil-field pipelines, microalloying with niobium instead of vanadium is advisable, as well as heat treatment at temperatures above 710 °C.

Modeling of Heavy-Oil Flow with Regard to Their Rheological Properties

With the depletion of traditional energy resources, the share of heavy-oil production has been increasing recently. According to some estimates, their reserves account for 80% of the world’s oil resources. Costs for extraction of heavy oil and natural bitumen are 3–4 times higher than the costs of extracting light oil, which is due not only to higher density and viscosity indicators but also to insufficient development of equipment and technologies for the extraction, transportation, and processing of such oils. Currently, a single pipeline system is used to pump both light and heavy oil. Therefore, it is necessary to take into account the features of the heavy-oil pumping mode. This paper presents mathematical models of heavy-oil flow in oil-field pipelines. The rheological properties of several heavy-oil samples were determined by experiments. The dependencies obtained were used as input data for a simulation model using computational fluid dynamics (CFD) methods. The modeling condition investigates the range of shear rates up to 300 s−1. At the same time, results up to 30 s−1 are considered in the developed computational models. The methodology of the research is, thus, based on a CFD approach with experimental confirmation of the results obtained. The proposed rheological flow model for heavy oil reflects the dynamics of the internal structural transformation during petroleum transportation. The validity of the model is confirmed by a comparison between the theoretical and the obtained experimental results. The results of the conducted research can be considered during the selection of heavy-oil treatment techniques for its efficient transportation.

Effect of Chemical Composition and Parameters of Microstructure on Corrosion Resistance of High-Strength Rolled Products from Low-Alloy Steels in Aqueous Environments

The effect of the chemical composition and microstructural parameters on the corrosion resistance of low-alloy steels serving in oilfield pipelines is studied. The causes of lowering of the corrosion resistance of the steels are determined. Recommendations are given for raising this characteristic without lowering the strength of the steels.

The use of the method of controlling the electrochemical parameters of aqueous solutions to combat complications in the operation of oil field pipelines

Corrosion of equipment in the oil and gas complex is a global problem, as it contributes to huge material costs and global disasters that violate the environment. Corrosion control methods used to protect equipment do not always ensure the absolute safety of the operation of oil and gas facilities. Moreover, they are quite expensive. The developed method for controlling the electrochemical parameters of aqueous solutions to combat complications during the operation of oil-field pipelines provides the necessary protection against corrosion. The method is economical and environmentally friendly, since it does not require the use of chemical reagents. The test results have shown a very high efficiency in dealing with complications in oil fields.

Study on aerobic corrosion characteristics of gas injection pipe wall in oil field under dry / wet interaction condition

By studying the corrosion behavior of oilfield pipelines in different oxygen content and corrosive medium under simulated ambient air/air foam flooding environment, the dry/wet interaction between the surface and the interface of the service casing is caused by the air displacement/air foam flooding, which greatly aggravates the aerobic corrosion process. The corrosion process changed from localized corrosion to uniform corrosion with the increase in dry and wet cycles. Pitting corrosion occurs in the early stages of dry and wet cycles, and the increase in chloride concentration and oxygen content will accelerate the initiation and development of pitting.

The methodology of redundant design schemes and the method of contour minimization for tracing systems of field gas and oil pipelines

The goal of the work is to develop a methodology and a method for optimizing the tracing of oil and gas field pipelines. The analysis showed that the solution to this problem does not receive due attention from both designers and specialists in the automation of design solutions. The paper proposes to solve this problem on the basis of redundant design schemes that represent a graph of possible routes for the passage of field pipelines. As a method, the procedure of the contour (coordinatewise relative to the contour variables) minimization of the cost function of the life cycle of the pipeline system is proposed. A procedure for rejecting inefficient connections in the column of an excessive scheme of field pipelines is proposed. The proposed methodology and method are implemented in the TRACE-NG software package, which is successfully used in practice to substantiate the structure and parameters of pipelines for various technological purposes. Findings. The proposed methodology, method and software package are an effective computing tool useful for designers.

The influence of aggressive environmental factors on the corrosion-mechanical wear and the risk of depressurization of oil field pipelines

The work is devoted to assessing the risk of depressurization of field pipelines operating under the conditions of the combined action of a corrosive environment and mechanical impurities. For a comparative assessment of the contribution of the corrosion factor to the fracture process, studies have been carried out on the development of corrosion processes on 20A and 09G2S steels in field media of different aggressiveness. The rate of destruction of the pipe metal under the influence of mechanical impurities was studied using the adapted ASTM G65 methodology, which makes it possible to evaluate the complex effect of corrosion and mechanical factors. Based on the data obtained during the study, equations were derived that characterize changes in the corrosion rate depending on the value of the hydrogen index (pH), degree of mineralization, CO2 content and temperature of the production medium and the content of solids. Using the obtained dependences, a methodology was developed for predicting the risk of depressurization of field pipelines depending on the composition of the transported medium and the dynamics of its change during field development. Application of the developed methodology will allow assessing the risks of depressurization under the influence of corrosion-mechanical factors in the design of oil field pipelines.

Investigating the mechanisms of shape distortion of the heat-affected region during electric-arc welding of oilfield pipelines

The article studies the issue of the influence of the most encountered in practice defects of welded joints of a one-piece joint, formed in the process of applying a weld when connecting oilfield pipelines to a joint by electric arc manual welding, on the strength characteristics of a welded joint by scrutinizing the condition of the pipe material close to the heat-affected zone. As a test sample, a butt welded joint with obvious defects was used. The geometric parameters of the welded joint were measured using standard means and the hardness of the heat-affected zone was determined by the Rockwell method in certain areas with justification of the welding process. The reason for softening is established. The change in the geometry of the heat-affected area is due to the accumulation of filler material during its melting on one side of the weld with a decrease in welding speed. Recommendations are given for the prevention of the destruction of welded structures and the occurrence of emergency situations in oilfield pipelines.

Calculation of the rate of bulk fluid flow by exponential and logarithmic expressions

A formula is presented to calculate the rate of bulk fluid flow in accord with hydrodynamic flow parameters and physical-chemical characteristics of pumping fluids. The formula was derived based on a model knowledge of fluid flow as a continuous sequence of strains — rotations of fluid fragments by the action of shear stress. Laboratory testing of volumetric flow rate depending on the hydrodynamic flow parameters and physical-chemical properties of liquids performed on a turbulent rheometer and as working fluids used ethanol and gasoline. The power and logarithmic dependences of the volume velocity were also checked using real data from the operation of oilfield pipelines. The results obtained satisfactory agree with the calculated data.

TEST OF WELDED CONNECTIONS FROM THERMALLY STRENGTHENED STEELS OF SPIRAL-TIERED PIPES

Background Oil field pipelines are a system of sequentially connected elements (pipes, fittings, pipe parts), so the failure of any of them leads to a stop in the transportation of the product and economic losses. When analyzing the places of destruction of welded samples of thermally hardened steels and the value of the relative transverse constriction, it was found that in the range of relative thicknesses of the «soft» layer, when the strength of the welded samples is at the level of thermally hardened base metal , destruction occurs both on the base metal at a distance from the weld, and along the weakened area in the heat-affected zone. At large values, the destruction of welded samples occurs, as a rule, along a weakened area near the weld. A characteristic feature of fracture of welded specimens in a weakened area is a decrease in the relative transverse narrowing as compared to when the fracture occurs in the thermally hardened base metal at a distance from the weld, although, as is known, the value of the relative transverse narrowing for thermally hardened metal is lower than for normalized. Aims and Objectives To develop recommendations on the choice of parameters for the hydraulic testing of the pipeline in the area of 266-505 km in the Tyumen region. Results Based on the results of theoretical and experimental studies, as well as taking into account the basic principles of the fracture mechanics, recommendations have been developed for choosing the parameters of the hydraulic testing regime for an oil pipeline at a section of 266-505 km in the Tyumen region. Crack depths obtained 3.9-4.3 mm correspond to acts of technical failures of the oil pipeline on the site 335-337 km. Conducting scientific research in Russia and abroad to increase the strength, ductility, crack resistance of large-diameter pipes and their welded joints, refinement of methods, design estimates will allow the development of new Building Codes and Regulations, State Standards, update regulatory and technical documentation, significantly reduce financial expenses for accident recovery, reconstruction, overhaul and to ensure the economic and environmental safety of the main and field pipelines of the Russian Federation.

Application of vegetable oil amide derivatives in oil field pipeline anticorrosion

Based on rapeseed oil and soybean oil, and diethylenetriamine and formaldehyde, a plant oil derived amide inhibitor was synthesized. The inhibition performance of plant oil derived amide inhibitor on A13 steel in 1 mol / L hydrochloric acid was studied by weight-loss experiment, electrochemical analysis and quantum chemical calculation. The adsorption behavior and mechanism of the inhibitor on A13 steel surface were revealed. The results of electrochemical experiments were consistent with the results of weight loss tests. The contact angle test results showed that the plant oil derived amide inhibitor can significantly enhance the hydrophobicity of A13 steel surface. The thermodynamic parameters show that the adsorption of plant oil derived amide inhibitor on A13 steel surface was self. The results of quantum chemical calculation showed that there are a lot of active sites in the structure of amide inhibitor derived from vegetable oil.

The use of sprayed powders to create coatings in the welds of oilfield pipelines

The most damaged elements of oil field pipelines are welded joints, the life of which often does not exceed one or two years. The problem of anticorrosive protection of internal surfaces of welded pipe joints has not been solved to date. In this paper, the possibility of applying powder protective stainless coatings to the inner edges of the pipe adjacent to the annular weld is considered. The research of corrosion resistance and mechanical properties of pipe welded joints is presented.

Selection of effective corrosion inhibitors for bischofite solutions and simulated medium of formation waters

Questions of the corrosion inhibitors selection for protection of oil-field pipelines have been studied in the article. Results of research of technological and anticorrosive properties of the corrosion inhibitors in mediums simulating industrial environments are presented. The methodological approaches to selection of the corrosion inhibitors on a stage of laboratory experiments on an example of Kaverdinsky gas-condensate deposites have been described. It was found that all the surfactants tested in the simulated medium of the formation waters show a protective effect of more than 90% with a dosage of 1 g/dm3. It is recommended to use bischofite solution with a mass fraction of 24% MgCl2 and corrosion inhibiting 0.1% КI-1M admixture to protect industrial gas pipelines from carbon dioxide corrosion. This composition provides a degree of corrosion protection to 99.6%. The results of industrial tests confirmed the effectiveness of complex system – bischofite solution with a mass fraction of 24 % MgCl2 and addition of 0.1% KI-1M corrosion inhibitor. The cationic surfactants KI-1M, St, SRK and amphoteric surfactants EM and KAPB effectively protect in simulating medium and provide a degree of protection from carbon dioxide corrosion to 91.2-98.9%.

Failure Analysis of Inlet Pipeline of a Spray Cooler

Abstract Corrosion perforation occurs frequently in oil field pipelines under strong oxidation environment. The causes for the failure of spray cooler after approximately 87,600 h in service have been investigated. To determine the failure mechanisms of pipes, material characterization and numerical analysis are conducted on the inlet pipeline. Ultrasonic thickness measurement is performed to check the corrosion rate and corrosion type of the pipe. Scanning electron microscopy is employed to observe the microscopic corrosion morphology of the pipeline. The microstructure of the corrosion products and the cause of corrosion are investigated using energy dispersive spectroscopy (EDS). Chemical composition and metallographic structure investigations are conducted to study the characteristics of the materials. Finite element analysis of the pipeline is employed to evaluate the deformation and stress distribution of the corrosion product film with a fluid–solid coupling model. Results of this investigation indicate that the reason of failure was the existence of strong oxidizing substances and the uneven distribution of corrosion rate that resulted from fluid accelerating corrosion.

Effect of Non-Metallic Inclusion Chemical and Phase Composition on Corrosion Resistance of Carbon and Low Alloy Steels in Water Media Typical for Oilfield Pipeline Operating Conditions

Results of studying the effect of the chemical and phase composition of non-metallic inclusions on the corrosion resistance of carbon and low-alloy steels in neutral aqueous media characteristic of the operating conditions of oilfield pipelines are presented. It is shown that the corrosivity of complex nonmetallic inclusions present in modern steels depends on their chemical and phase composition, the optimization of which can prevent an unfavorable effect of these inclusions on steel corrosion resistance under oilfield pipeline operating conditions. A method for reducing the corrosivity of non-metallic inclusions based on aluminum-magnesium spinel is its oxide component modification with calcium and/or titanium, which contribute to its conversion into a globular form. An increase in corrosivity of complex non-metallic inclusions, the oxide component of which consists of various components, and correspondingly a large amount of corundum among oxide components, results in a reduction of steel corrosion resistance. An increase in the content of calcium and magnesium oxides leads to a reduction in the corrosivity of complex inclusions. In producing steels with increased corrosion resistance for oil field pipelines it is advisable to provide production methods aimed at preventing formation of adverse types of non-metallic inclusions.

TOP OF LINE HYDRATE DEPOSITION IN GAS-WATER STRATIFIED FLOW

Background When operating pipelines, it is important to adequately predict the intensity of hydrated deposits, which allows you to plan various preventive and treatment measures. Aims and Objectives Development of a mathematical model of the hydrate deposition rate under gas-water stratified flow in pipelines. Methods The method is based on solving the equations of conservation of mass, momentum and energy of multiphase flows of multicomponent flows with physicochemical transformations under stratified flow regime. Results A mathematical model of the hydrate deposition rate in multi-phase oilfield pipelines under stratified flow regime is developed. Conclusion A mathematical model of top of line hydrate deposition in gas-water stratified flow is developed.