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Corrosion is a major cause of structural deterioration in marine and offshore structures. It affects the life of process equipment and pipelines, and can result in structural failure, leakage, product loss, environmental pollution and the loss of life. Pitting corrosion is regarded as one of the most hazardous forms of corrosion for marine and offshore structures. The total loss of the structure might be very small, but local rate of attack can be very large and can lead to early catastrophic failure. Pitting corrosion is a localized accelerated dissolution of metal that occurs as a result of a breakdown in the protective passive film on the metal surface. It has been studied for many years; however, the structural failure due to pit characteristics is still not fully understood. Accurate pit depth measurements, precise strength assessment techniques, risk analysis due to pitting, and the mathematical relationship of the environmental factors that causes pitting failure are also factors, which need further understanding. Hence this paper focuses on these issues. It reviews and analyses the current understanding of the pitting corrosion mechanism and investigates all possible factors that can cause pitting corrosion. Furthermore, different techniques employed by scientists and researchers to identify and model the pitting corrosion are also reviewed and analysed. Future work should involve an in-depth scientific study of the corrosion mechanism and an engineering predictive model is recommended in order to assess failure, and thereby attempt to increase the remaining life of offshore assets.

Modelling of pitting corrosion in marine and offshore steel structures – A technical review

Molecular dynamics and Monte Carlo simulations as powerful tools for study of interfacial adsorption behavior of corrosion inhibitors in aqueous phase: A review

This work provides an overview of the most common polymeric corrosion inhibitors for the oil and gas industry Exploration, production and transportation of petroleum and natural gas products constantly deal with highly corrosive environments due to oxygen, acid stimulation, CO2 and H2S contamination Therefore, versatile materials are required in order to keep corrosion rates in control Unlike small molecule corrosion inhibitors, polymers possess multi-functionality and better film-forming capabilities, which could significantly improve protective barrier properties In this article, polymeric architectures tested in relevant oil and gas media are compiled in order to highlight certain moieties capable of complex formation with the metal surface or chelation on corrosive agents resulting to improved corrosion inhibition

Polymeric corrosion inhibitors for the oil and gas industry: Design principles and mechanism

Abstract Over the decades, corrosion has resulted in loss of lives accorded with damage costs in almost all engineering fields. Thus, it is seen as an environmental threat with catastrophic attributes, which calls for day-to-day research on its final resolution. Recent studies have proven organic green corrosion inhibitors (OGCIs) from plant extracts with biodegradable, environmentally accommodative, relatively cheap, and nonharmful features as the most perfect approach of tackling the problem. This review gives succinct discussion on the mechanisms, classifications, and active functional groups of OGCIs. Measuring ways and factors influencing their efficiency are presented. Also, various plant extracts used as OGCIs in preventing material corrosion in corrosive media coupled with their respective findings, applied characterization techniques, and future challenges are presented. The significance of values obtained from simulating presented mathematical models governing OGCI kinetics, adsorption isotherm, and adsorption thermodynamics is also included. In conclusion, recommendations that will broaden the usage of OGCIs from plant extracts for inhibiting corrosion of materials are presented for prospective researchers in the field of corrosion.

Organic green corrosion inhibitors (OGCIs): a critical review

In order to ensure smooth and uninterrupted flow of oil and gas to the end users, it is imperative for the field operators, pipeline engineers, and designers to be corrosion conscious as the lines and their component fittings would undergo material degradations due to corrosion. This paper gives a comprehensive review of corrosion problems during oil and gas production and its mitigation. The chemistry of corrosion mechanism had been examined with the various types of corrosion and associated corroding agents in the oil and gas industry. Factors affecting each of the various forms of corrosion were also presented. Ways of mitigating this menace with current technology of low costs had been discussed. It was noticed that the principles of corrosion must be understood in order to effectively select materials and to design, fabricate, and utilize metal structures for the optimum economic life of facilities and safety in oil and gas operations. Also, oil and gas materials last longer when both inhibitors and protective coatings are used together than when only batch inhibition was used. However, it is recommended that consultations with process, operations, materials, and corrosion engineers are necessary in the fitness of things to save billions of dollars wasted on corrosion in the oil and gas industries.

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Corrosion problems during oil and gas production and its mitigation

Waterflooding is a process where water is injected into an oil reservoir to supplement its natural pressure for increment in productivity. The reservoir properties are highly heterogeneous, its states change as production progresses which require varying injection and production settings for economic recovery. As water is injected into the reservoir, more oil is expected to be produced. There is also likelihood that water is produced in association with the oil. The worst case is when the injected water meanders through the reservoir, it bypasses pools of oil and gets produced. Therefore, any effort geared toward finding the optimal settings to maximize the value of this venture can never be over emphasized. Waterflooding can be formulated as an optimal control problem. However, traditional optimal control is an open-loop solution, hence cannot cope with various uncertainties inevitably existing in any practical systems. Reservoir models are highly uncertain. Its properties are known with some degrees of certainty near the well-bore region only. In this work, a novel data-driven approach for control variable (CV) selection was proposed and applied to reservoir waterflooding process for a feedback strategy resulting in optimal or near optimal operation. The results indicated that the feedback control method was close to optimal in the absence of uncertainty. The loss recorded in the value of performance index, net present value (NPV) was only 0.26%. Furthermore, the new strategy performs better than the open-loop optimal control solution when system/model mismatch was considered. The performance depends on the scale of the uncertainty introduced. A gain in NPV as high as 30.04% was obtained.

Optimal feedback control of oil reservoir waterflooding processes

Selection of controlled variables (CVs) plays a crucial role in overall operational performance. Existing approaches for CV selection based on the self-optimizing control (SOC) strategy are model-driven. Selection of CVs using rigorous nonlinear process models requires linearization around nominal operating point. Inevitably, these approaches not only result in large losses as a result of linearization errors, but also are difficult to be adopted for practical applications due to the requirement of a rigorous model. In this paper, a novel data-driven approach, where the necessary conditions of optimality (NCO) are directly approximated by CVs using operational data in a single regression step is proposed for selecting CVs based on SOC. The new approach does not require evaluation of derivatives so that process models associated with commercial simulators can be directly used for CV selection. The effectiveness of the proposed approach is demonstrated using a 3-stream heat exchanger network (HEN) case study.

Data-driven Self-optimizing Control

In this paper, static and dynamic optimization of a reservoir waterflooding process for enhanced oil recovery was studied. The dynamic optimization was achieved using receding horizon (RH) algorithms. Two forms of RH which are moving-end and fixed-end RH were formulated and compared. MATLAB Reservoir Simulator (MRST) from SINTEF was used for reservoir simulation. The objective function to be maximized is net present value (NPV) of the venture while the control variable is water injection rate. Sequential quadratic programming (SQP) was applied for the optimization. It was found out that fixed-end RH gave the highest NPV with improvements of 0.81% and 1.49% over static and moving-end RH strategies respectively.

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Optimization of petroleum reservoir waterflooding using receding horizon approach

Environmental regulations all over the world are becoming more restrictive concerning the release of atmospheric pollutants associated with the flue gases of combustion systems, particularly the emission of sulphur dioxide SO2. Hence, the need for producers to improve their existing technology and to start considering alternative means of isolating sulphur from fuels has become incumbent. Adsorptive desulphurization of crude oil was investigated using activated manganese dioxide, AM in batch reactor. Results showed that desulphurization efficiency was increased on increasing contact time and sorbent dose. There was 49% reduction of crude oil sulphur content after the process. The respective R2 value of pseudo-first order and pseudo-second order reaction model were 0.8162 and 0.9951 when the experimental data were fitted into them. Thus, pseudo-second-order reaction model better described the desulphurization process with chemisorptions being the rate limiting step. However, there is need to improve on methods and adsorbents that will result in complete removal of sulphur from crude oil. Also, the effects of desulphurization on other physico-chemical properties of crude oil should be examined for future research work.

Alhaji Shehu Grema

Papers

Corrosion problems during oil and gas production and its mitigation

Optimal feedback control of oil reservoir waterflooding processes

Data-driven Self-optimizing Control

Optimization of petroleum reservoir waterflooding using receding horizon approach

Kinetics Analysis and Dosage Effects of Manganese Dioxide Adsorbent on Desulphurization of Crude Oil