Platform Jacket Research Articles

Structural Design and Horizontal Wave Force Estimation of a Wall-Climbing Robot for the Underwater Cleaning of Jackets

Currently, divers face significant safety risks when cleaning marine organisms from the steel structures of offshore underwater platform jackets. Consequently, utilizing robots instead of divers to carry out underwater biofouling removal operations will be an important development direction for the underwater maintenance of offshore platforms in the future. In this study, a wall-climbing robot was designed to clean marine organisms from the underwater surface of a platform jacket leg. The overall structure of the underwater cleaning wall-climbing robot is introduced, including the cleaning actuator and the variable curvature-adapted connecting rod mechanism. The corresponding relationship between the variable curvature-adapted connecting rod mechanism and the jacket leg is analyzed in detail. The variable curvature-adapted connecting rod mechanism was optimized using a genetic algorithm to ensure that the underwater cleaning wall-climbing robot can adapt to a minimum diameter of 1 m for the jacket leg. By drawing on Airy wave theory and random wave theory, the Airy wave parameters for waves were analyzed under different sea conditions, considering practical application scenarios. By using Fluent software 2022, a 2D numerical wave tank was constructed to simulate waves under various sea conditions, and the wave surface shapes for different sea states were determined. By building on the Morison equation, a method for calculating the horizontal wave forces on the underwater cleaning wall-climbing robot using the equivalent area and equivalent volume is proposed. By using the two aforementioned methods, the horizontal wave forces on the underwater cleaning wall-climbing robot under specific sea states were determined. The horizontal wave forces of the underwater cleaning wall-climbing robot under different sea conditions were analyzed and simulated in a 3D numerical wave tank. By comparing the theoretical analysis results with the numerical simulation results, where the maximum difference at the extreme points is approximately 11%, the feasibility of the proposed horizontal wave force estimation method was verified.

Study on Implementation and Optimization of Cathodic Protection for Offshore Oil Platform Jacket

Study on Implementation and Optimization of Cathodic Protection for Offshore Oil Platform Jacket

A CFD Analysis of Decommissioned Oil Platforms Jackets on the Brazilian Coast

Every facility reaches the last phase in its life cycle, which is decommissioning. Since the last decade, this subject has been gaining importance in Brazil’s offshore oil and gas companies. For jacket type rigs, one of the methods widely applied after idling the production is the conversion of these structures into artificial reefs (ARs). There are several critical aspects for choosing the best strategy for cutting and sinking a platform jacket, ensuring the success of an AR from a biological point of view. One of them is the influence of marine currents and their fluid-structure interaction which, by maximizing local upwelling and back vortex effects, favours the growth of aggregated flora and fauna. This study consists in the application of computational fluid dynamics (CFD) techniques for studying the marine flow around a disassembled and sunk jacket in the seabed for the purpose of converting it into an artificial reef. An FVM (Finite Volume Method) from a commercial software (most recent version of ANSYS FLUENT®) is applied with the upwind scheme. A k-ε turbulence model on steady state is chosen. Field data about Brazilian coastal currents are collected and analysed from the amount of information available on a Brazilian Navy's meteoceanographic program. Next, different combinations of cutting and sinking a jacket are studied, always keeping a minimum 55m free water column. The objective is to verify where the formation of local upwelling regions - that is, where the vertical velocity component reaches values equal or greater than 10% of the magnitude of the free flow velocity - is more significant, without decreasing back eddy formation. It is observed that the dismemberment of the jacket with the positioning of its parts in an increasing height sequence in the direction of the prevailing current is favourable to generate local upwelling while tipping the structure at 90° to the prevailing current results in the most voluminous back eddy region.

Estudo de viabilidade para a reutilização de plataformas offshore fixa como substrutura de torres eólica

Com o objetivo de dar um outro uso às plataformas offshore fixa com o tempo de vida útil vencidas, principalmente aquelas situadas em campos com condições ambientais favoráveis para instalação de turbinas eólicas offshore, o presente trabalho de pesquisa ressalta a importância de avaliar a possibilidade de reutilização de uma plataforma (jaqueta) submetida ao carregamento de uma torres de 10 MW, considerando sobre tudo as novas condições de operação. Para isso se tem em conta as análises dos elementos que conformam a estrutura (jaqueta) de modos a atinar as suas respetivas razões de tensões. Considerou-se o carregamento da torre eólica de maneira pontualmente distribuído sobre os 4 nós no topo das pernas principais da jaqueta. A estrutura investigada apresenta uma jaqueta de 16,85 m de altura, com a área da mesa inferior de 9,95 m x 9,95 m e 6,75 m x 6,75 m na mesa superior. O sistema estrutural foi desenvolvido com base à utilização do software OrcaFlex V10.3, que permite analisar as razões de tensões (“Unity Check”) incluído os efeitos de segunda ordem por meio da utilização do Método dos Elementos Finitos (MEF). Desta forma, os resultados obtidos ao longo das análises para avaliar o comportamento estrutural apontam para o fato de que a jaqueta investigada não atende aos critérios de projeto para dar suporte a torres eólicas de 10 MW.

Hydrodynamic Load Analysis and Experimental Study of Grouting Clamp under Wave and Ocean Current

The repair of offshore platform jackets is an important research direction in marine engineering, among which the grouting clamp reinforcement is the most widely used. In order to solve the hydrodynamic force of the grouting hoop under the joint action of wave and current in the complex sea condition, the Morison formula is used to analyze the linear wave load on the grouting hoop; then, based on the Morison formula, load force under the combined action of the wave and the ocean current on the clamps in different installation states was determined; finally, the screw jack and car jack were used to carry out the experiment of preventing the clamp from falling off. The mechanical grouting clamp experiment and the wedge tooth experiment were carried out at the same time. The innovative design of the mechanical grouting clamp, analyzed analogously through relevant experimental results and numerical analysis results confirmed that the reinforcement and repair method of the designed grouting clamp is of great help to the safety and reliability of the offshore platform jacket.

An assessment of fish and marine growth associated with an oil and gas platform jacket using an augmented remotely operated vehicle

Scientists, industry and regulators are seeking to understand the influence of oil and gas infrastructure in our oceans to mitigate its impacts and maximise environmental benefits. This project equipped a standard work-class ROV with a light-weight stereo-video camera system to collect high definition imagery of fish and habitats formed by marine growth associated with Woodside Energy's Goodwyn Alpha Platform jacket (GWA) 138 km offshore of Dampier, north-west Australia. ROV video surveys were rapidly performed by industry on four faces of the GWA jacket, from the surface to the seabed at 130 m, yielding 1 h and 14 min of imagery. The stereo-video cameras continued to film during standard ROV operations collecting a further 150 h of HD imagery, used to build a comprehensive fish species list. A total of 8676 individual fish from at least 57 species and 20 families, with an estimated combined mass of 8719 kg, were recorded from the vertical transects of four faces of the jacket. An additional 43 fish species from 21 families were recorded via rapid assessment of a subset of the additional, standard ROV operations imagery. The jacket was characterised by abundant Caranx sexfasciatus (bigeye trevally), Pseudanthias spp. (basslets), Heniochus diphreutes (schooling bannerfish), Labridae sp. (wrasse) and Acanthurus spp. (surgeonfish). Several fish important to the demersal scalefish fishery in the region were observed, including: Lutjanus argentimaculatus (mangrove jack), Lutjanus erythropterus (crimson snapper), Lutjanus malabaricus (saddletail snapper), Lutjanus russellii (Moses' snapper). Eleven broad marine growth types were observed with encrusting/enveloping species (brown algae, filamentous mat, coralline algae, calcite) and hard corals (Tubastrea sp.) present in the greatest coverage. Both marine growth and fish assemblages changed markedly with depth. The addition of a lightweight stereo-video system to an industrial ROV and the allocation of short amounts of time for rapid vertical surveys provided important information on the ecology of an oil and gas platform jacket. Future industrial ROV campaigns should consider utilising this approach to gather scientific information that may have value in the context of decommissioning comparative assessments and, more generally, improves our understanding of the impact of oil and gas infrastructure in our oceans.

Topology optimization design for offshore platform jacket structure

Offshore jacket platform is widely used as production or oil recovering platform in the shallow sea, and is also applied to the offshore wind turbine supporting structure in the recent years. The jacket structures are normally designed to be conservative and bulky according to various design codes. In this work, a structural optimization design method for jacket platform structure has been developed based on topology optimization theory. The topology optimization method is applicable at an early design stage, which can determine the initial structure and force transmission path. The whole design space is chosen as design variables, and the goal is to maximize the structural stiffness. A set of constraints based on multi-criteria design assessment is applied according to standard requirements, which includes stress, deformation, vibration and design variable constraints. The optimization results are compared with the original platform for static performance, dynamic performance and Ultimate Carrying Capacity (UCC). Results show that the optimized structure show a 13.7% reduction in the global mass, 46.31% reduction in the maximum equivalent stress, and large ultimate carrying capacity ability under the same environmental loads. It is demonstrated that the proposed topology optimization method is capable of effectively determining the optimal design of jacket platform structures.

Energy dissipation in high-energy ship-offshore jacket platform collisions

Ship collisions with offshore structures may be characterized by large amounts of kinetic energy that can be dissipated as strain energy in either the ship, or the installation, or shared by both. In this paper a series of FE numerical simulations are performed with the aim of providing a clearer understanding on the strain energy dissipation phenomenon, particularly upon the ship-structure interaction. Ships of different dimensions and layouts are modelled for impact simulations. Likewise, three platform jacket models of different sizes and configurations are considered. The collision cases involve joints, legs, and braces and are simulated for several kinetic energy amounts of the vessels and different impact orientations. An overview of the plastic deformation mechanisms that can occur in both ship and jacket structure is also given. The results from the various models with different collision scenarios are compared in terms of the strain energy dissipation with respect to the different ship/installation strength ratios. From the FEA simplified approaches are also derived in terms of the relative stiffness of the two structures for assessing the responses and energy absorptions of the two structures. The conclusions drawn from this study can be applied to a broader range of collision assessment of offshore steel jacket platforms subjected to high-energy ship impacts.

Sensitivity analysis of pile-founded fixed steel jacket platforms subjected to seismic loads

The sensitivity of the seismic response parameters to the uncertain modeling variables of pile-founded fixed steel jacket platforms are investigated using the Tornado diagram and the first-order second-moment techniques. The effects of both aleatory and epistemic uncertainty on seismic response parameters have been investigated for an existing offshore platform. The sources of uncertainty considered in the present study are categorized into three different categories: the uncertainties associated with the soil–pile modeling parameters in clay soil, the platform jacket structure modeling parameters, and the uncertainties related to ground motion excitations. It has been found that the variability in parameters such as yield strength or pile bearing capacity has little effect on the seismic response parameters considered, whereas the global structural response is highly affected by the ground motion uncertainty. Also, some uncertainty in soil–pile property such as soil–pile friction capacity has a significant impact on the response parameters and should be carefully modeled. Based on the results, it is highlighted that which uncertain parameters should be considered carefully and which can be assumed with reasonable engineering judgment during the early structural design stage of fixed steel jacket platforms.

Modeling Options for Drill-Cuttings Management

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 164983, ’Modeling the Options for Managing Drill-Cuttings Piles on Decommissioning,’ Sean Hayes, SPE, Genesis, and Liz Galley, CNR International, prepared for the 2013 SPE European HSE Conference and Exhibition, London, 16-18 April. The paper has not been peer reviewed. Advances in modeling techniques allow quantitative prediction of long-term trends in cuttings-pile characteristics and environmental risks, providing firm direction in mitigating risks. Modeling involving fluid dynamics, soil mechanics, scientifically verified 3D dispersion modeling, contaminant degradation, and seabed recovery was used in several scenarios: the extant pile, moving the pile across the seabed using suction pumps, backflush discharges related to retrieving the pile, and disturbance from remaining jacket footings ultimately falling into the pile after several hundred years. Introduction The Murchison platform is located in 156 m of water in the northern North Sea and is operated by CNR International. Drilling operations had been conducted at the field since the 1970s, ending in 2008. Discharges of drill cuttings and drilling mud have resulted in the formation of a drill-cuttings pile beneath the platform jacket structure. Between 1980 and 2000, oil-based muds were used and oil-contaminated discharges took place in line with normal permitted operations, and the cuttings pile now in place is consequently oil-contaminated. Fig. 1 shows the location of the Murchison platform and the local bathymetry, and Fig. 2 illustrates the jacket base. The Convention for the Protection of the Marine Environment of the North- East Atlantic (OSPAR) Commission Recommendation 2006/5 sets out a management regimen for such oily-cuttings piles, depending largely on thresholds against which the level of pollution attributable to a historical cuttings pile may be measured in order to determine whether the level of pollution could be significant. An assessment of the Murchison pile was submitted to the commission in 2008 as part of the regulator’s implementation report, concluding that the Murchison pile did not exceed the relevant criteria and that it could be left to degrade by natural processes. For those piles that can be demonstrated to have characteristics below OSPAR thresholds, the recommendation states that no further action is required and that the cuttings piles may be left in situ to degrade naturally. The Murchison field is in the process of being put forward for decommissioning, and the assessment made in 2008 regarding the rate of oil loss and the persistence footprint has been re-evaluated. By use of records of the discharges made from the platform, survey data from the Murchison cuttings pile, and industry data sources on the composition of drill-cuttings piles, a model of the existing pile has been constructed and used to understand the present condition and long-term fate of the pile.

Magnus: Use of Conductor-Sharing Wellhead Technology To Access Additional Hydrocarbons

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 124233, ’Magnus: Utilisation of Conductor Sharing Wellhead Technology To Access Additional Hydrocarbons via a Slot Constrained Platform,’ by S.E. Hicks, A. Moore, SPE, and M. Honey, SPE, BP plc; I.R. Farmer, Schlumberger; B. Smart, SPE, and R. Ekseth, SPE, Gyrodata; and D. Brown, SPE, Cameron, originally prepared for the 2009 SPE Offshore Europe Oil and Gas Conference and Exhibition, Aberdeen, 8-11 September. The Magnus platform in the UK northern North Sea has been producing since 1983, with all 20 original slots now occupied. Additional infill- and extended-reach-drilling production targets were identified, and a means of access was required while maintaining base field production. Platform modifications were selected because of significant commercial advantage over alternative developments. The Magnus jacket was modified to permit running of four additional large conductors into which two smaller casings could be installed. Introduction Magnus is the most northerly currently operated field on the UK continental shelf. Discovered in 1974, first production was established in 1983. Continual field development has resulted in more than 90 wells including exploration, appraisal, and development wells. In 1995, production from a now-full well template plateaued, and a program of well-intervention work was begun. Extensive subsurface work focused on EOR mechanisms across discrete reservoir panels and identified multiple new injection and offtake points that would be required to optimize field production from each respective area. By the late 1990s, it became apparent that sidetrack options from existing wells alone would not permit full optimization of the Magnus EOR program. The complexity and tapered profile of the Magnus-platform jacket prevented introduction of more than seven new drilling slots. To use newly constructed slots fully, conductors would have to be “split,” permitting two wells from surface to be installed per conductor. The full-length paper outlines the major challenges posed by conductor-sharing well design and outlines some solutions found to aid successful well delivery. Magnus Extension Project (MEP) Platform Modification. The MEP was sanctioned in 2004, and the most suitable aspect for new well slots was found to be the east side of the platform, the same side as the drilling package. Only the east face of the platform allowed new conductors to be installed without clashes with existing infrastructure. With the east face selected for new-slot location, options of seven 30-in. slots or four 46-in. slots were identified. MEP financial criteria necessitated provision of eight new wells, hence construction work for four new 46-in. “splitter” slots began in 2005. Conductor Guide Frames. Installation of six conductor guide frames per new well slot was performed external to the platform jacket. The guide frames incorporated an asymmetric funnel design to guide rigid conductor pipe, incrementally building vertical deviation to 4° at seabed. Five of these preinstalled guide frames are installed subsea, and one was installed above sea level.

HSE Management in a Drilling Environment

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 117813, "HSE Management in a Drilling Environment," by Andrew May, Alain Moonen, and Stewart Logan, Qatar Shell GTL, and Jackie Allinson, CW International, originally pre pared for the 2008 Abu Dhabi In ternational Petroleum Exhibition and Conference, Abu Dhabi, UAE, 3–6 November. The paper has not been peer reviewed. Since the beginning of the Pearl gas-to-liquid (GTL) drilling activities in Qatar's North field in 2004, five drilling rigs have been used and, to date, it has been a 4-year, 3-million-man-hours lost-time-incident (LTI)-free operation. Recognizing the industry challenges of introducing large numbers of inexperienced staff on the drilling rigs, introduction of a pro-gram of proactive health, safety, and environment (HSE) management by engaging all levels of the organizations of the operator and contractors has resulted in a top-quartile HSE and operational performance. Introduction After drilling and testing an appraisal well in 2004 and a data-acquisition well in 2006, the Pearl GTL development campaign began in earnest with two rigs (one a new build) drilling over two offshore jackets. During 2008, a land rig was taken on contract to drill two water-injection wells to dispose of condensed water from offshore. Also in 2008, an ambitious project matured to perform simultaneous operations in a hydrogen sulfide environment, consisting of drilling and completing wells while simultaneously perforating, acid stimulating, and cleaning up precompleted wells from temporary decks on the platform jacket. Creating an HSE-Enabling Environment Creating an HSE-enabling environment that is conducive to open, honest, and no-blame relationships generating hazard-reducing ideas is a result of a mix of many elements that require continuous focus and buy-in. The creation begins at the contract-tender stage where the minimum HSE requirements are set out as an initial qualifying hurdle and where the HSE performance of each contractor is reviewed during the evaluation process. Then, in the period between the award of the contracts and the start of operations, project-kickoff meetings with participation of the operator, drilling contractors, third-party contractors, subcontractors, and office and on-site staff are used as a vehicle to develop the "One Team" approach to HSE. Openness, honesty, mutual trust, and full commitment are the key requirements for all parties involved to accept HSE as a core value and have fully aligned HSE aspirations. At the commencement of the operational phase, all the enabling elements of the preparation phases, including detailed hazard analysis and the generation of HSE cases, are approached with great enthusiasm. This enthusiastic approach is key and produces clear and effective outcomes.

Assessment of Offshore Platforms Under Subsidence—Part II: Analysis and Results

An assessment of three offshore platforms in the Valhall field of the North Sea is described in this paper. Ultimate strength and reliability analyses were performed for the jacket-type platforms for four levels of sea floor subsidence. The nonlinear structural models of the platform elements, joints, and associated soil-structure interaction are summarized in a companion paper by Gebara et al., 2000, “Assessment of Offshore Platforms Under Subsidence—Part I: Approach,” ASME J. Offshore Mech. Arct. Eng., 122, pp. 260–266. Similarly, environmental loads and reliability acceptance criteria are presented by Pawsey et al., 1998, “Characterization of Environmental Loads on Subsiding Offshore Platforms,” OMAE98, Lisbon, Portugal, and Stahl et al., 1998, “Acceptance Criteria for Offshore Platforms,” OMAE98, Lisbon, Portugal, respectively. This paper describes the procedures employed and results obtained for ultimate strength and reliability analysis. Ultimate platform strength was calculated using a pushover analysis in which environmental loads for increasingly rare events were applied incrementally until the platform failed. Failure was defined as formation of a limiting mechanism in the platform structure or foundation. Structural reliability analysis was performed to estimate the annual probability of platform failure as a function of subsidence level. The platform structural system was modeled in terms of two major subsystems that were assessed as likely to fail: (i) the platform deck, and (ii) the platform jacket and piles. Uncertainties were included in the loads, structural components, and soil strengths based on industry experience and data. First and second-order reliability methods (FORM/SORM) were used to estimate the annual failure probabilities. Consideration was given to the correlated nature of the failure modes due to the common environmental loads. The reliability results were compared with predefined acceptance criteria to judge the suitability of continued operations. [S0892-7219(00)00304-6]

In-time fatigue monitoring using neural networks

Abstract This paper presents a new methodology for fatigue monitoring of fixed offshore structures. The accumulated fatigue damage on selected joints, caused by actual loading conditions, will be assessed through a data acquisition and processing system installed on board. Based on measurements of upward jacket displacements and feedforward backpropagation neural networks, the calculation of fatigue damage is performed in-time. This information, along with inspection reports, could be used to improve further inspection and repair of the platform jacket. A simplified structural numerical model takes into account, as much as possible, the dynamical structural conditions of a platform installed on Campos Basin, RJ, Brazil, in order to match the paper's conclusions to the actual behaviour of fixed offshore structures.

Monobore Completions and Novel Wireline Perforating of High-Angle Wells in the Nelson Field

The Nelson field gas-lift completions were designed to optimize production, enhance safety and reliability, and minimize well-maintenance costs. The completions are of a near-monobore design and include an annular safety system, which is regarded as a major safety benefit during gas lift. The single-trip completions were batch installed in eight high-angle (up to 70{degree}) predrilled wells. This paper presents details of the completion design and the approach taken to planning and installing the completions. The paper also describes the use of a novel technique for perforating the platform wells with wireline guns.

Salvaging and Reusing Jacket and Deck Structures of Offshore Platforms

Reusing salvaged offshore oil and gas production jacket and/or deck structures is a means of reducing the construction cost and schedule. The decision to salvage, refurbish, and reinstall an unused jacket and/or deck structure(s) can benefit oil companies in two ways. First, the platform must be removed to meet environmental regulations; second, the platform's jacket and deck can be reused on future projects, resulting in construction-cost and schedule savings. The primary objective of this paper is to present a framework within which decision makers can identify a salvage process and reuse a platform when it is no longer in production. The second objective is to document the cost and schedule savings obtained when the platform's jacket and deck are reused. The data presented in this paper can be used by oil and gas companies to determine whether the reuse of a salvaged structure is a cost-effective alternative to building a new structure.

Optimum Design of Three‐Dimensional Framework Structures

A method for optimal design of large‐scale framework structures is presented. The approach is based on a reanalysis technique in combination with suboptimization for each member group in the structure. The suboptimization is performed using a nonlinear programming algorithm based on sequential quadratic programming. Given the topology and material quality, the cross‐sectional dimensions of wide‐flange and hollow‐section members are treated as design variables and the minimum weight or cost solution is sought. The structural problem is formulated using the matrix displacement method. Large three‐dimensional rigidly jointed frames subjected to multiple loading cases are analyzed. Constraints can be imposed on maximum Von Mises stresses, beam stability, and the fatigue damage at nodal points. The approach is general, robust, and efficient in that it avoids numerous global structural analyses. The practical engineering utility of the method is emphasized. Case studies of an offshore deck module and a platform jacket structure are included. Future work should focus on a refined formulation of the fatigue constraint.

Experimental Evaluation of Damping in a Steel Tubular Member of an Offshore Platform Jacket in Air

Abstract Pluck tests were performed on a major diagonal member of an offshore platform jacket in the fabrication yard to develop data for assessment of structural damping. The initial displacements were varied in order to investigate dependence of damping on amplitude. The response histories were typically composed of six or seven vibrational modes having closely spaced frequencies in the 3.4–4.2-Hz range. System identification was accomplished using an output error approach. Response histories reconstructed from the system parameters identified by this method exhibit excellent fidelity to the corresponding recorded data traces. The analysis results support the assumption of linear system behavior and lead to a suggested value of 0.002 for the critical damping ratio.

Effects of discarded drill muds on microbial populations

Drilling operations from platforms in the North Sea result in the production of large quantities of drill cuttings. These are a variable mixture of rock chippings, clays and original drilling fluids. Drilling mud is cleaned on the platform to remove rock chips before re-use of the mud. The rejected fraction from the clean-up plant (the cuttings) contains some of the base drilling fluid, and this can lead to an organically rich input to the sea-bed. Cuttings are discarded immediately underneath the platform jacket and thus build-up over the natural seabed sediment. In many cases this cuttings pile may cover considerable areas of seabed, leading to seabed biological effects and potential corrosion problems. Different types of cuttings have different environmental impacts, this being partly dependent upon their hydrocarbon component. Diesel-oil based cuttings contain significant amounts of toxic aromatic hydrocarbons, whereas low-toxicity, kerosenebased cuttings contain less. Both types of cuttings support an active microbiological flora, initiated by hydrocarbon oxidation. This paper presents a study of microbiological degradation of hydrocarbons in cuttings piles around two North Sea platforms. Results indicate that there is a close correlation between microbiological activity and hydrocarbon breakdown in the surface of cuttings piles and that both of these parameters reach their maximum values closer to the platform when low-toxicity muds are in use.

Biodeterioration problems of North Sea oil and gas production—A review

The North Sea is both a highly corrosive and highly biologically productive environment. Oil and gas production structures in this environment not only suffer from the physical effects, corrosion, wave and storm action, of being immersed in this environment, but also the effects of biological activity. Such biodeterioration problems occur both on the external and internal surfaces of the structure and the internal surfaces of any plant or pipework which contains, or has contained, water. The platform jacket may experience biological problems due to external macro- and microfouling or to internal microfouling. Pipelines, risers and topside systems have usually all been hydrostatically tested leaving residual water and possible sites for bacterial activity. Waterflooding with seawater and the separation of produced water from oil also provide sites suitable for biological activity and associated corrosion, slime and blockade problems. This paper reviews these areas in the light of recent advances in investigation and uderstanding of the problems.