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For many years, the oil and gas industry has strived to develop environmentally friendly organophosphorus-based scale inhibitors. The natural polymer chitosan has recently gained significant importance for various upstream oil and gas applications. We earlier reported the synthesis of phosphonated chitosan (PCH) under conventional conditions in a two-step pathway via the Kabachnik–Fields reaction. This earlier work showed that PCH displayed good performance against calcite scaling and weak efficiency for barite scaling using a high-pressure dynamic tube-blocking rig at 80 bar and 100 °C using a produced water composition from the Heidrun oilfield, Norway. The mechanochemical synthesis approach has recently emerged as a powerful, green, and sustainable protocol in several industrial and academic applications. Herein, we report for the first time the synthesis of PCHvia the Moedritzer–Irani reaction using the ball-milling technique under liquid-assisted grinding conditions. The static inhibition performance of PCH is investigated, for the first time, against the gypsum scale and the calcite scale based on the NACE Standard TM0374-2007 protocol. The results are compared to the commercial polysaccharide, carboxymethyl inulin, (CMI), and aminotrismethylenephosphonic acid (ATMP) scale inhibitors. Furthermore, PCH was screened against the Heidrun calcite scale using static jar tests. The thermal stability and calcium compatibility properties of the mechanochemically synthesized PCH were investigated. The polymer exhibited an outstanding inhibition efficiency against both oilfield scales. It was also found that PCH showed excellent thermal stability after 7 days at 130 °C and excellent calcium compatibility properties at high calcium ion concentrations. Density functional theory (DFT) simulations were carried out to gain atomic insight into the interaction of PCH, CMI, and ATMP with the mineral surface. [ABSTRACT FROM AUTHOR]

Stringent and periodic iteration of regulations related to the monitoring of chemical releases from the offshore oil and gas industry requires the use of ever changing, rapidly developing and technologically advancing techniques. Passive samplers play an important role in water column monitoring of produced water (PW) discharge to seawater under Norwegian regulation, where they are used to; i) measure aqueous concentrations of pollutants, ii) quantify the exposure of caged organisms and investigate PW dispersal, and iii) validate dispersal models. This article summarises current Norwegian water column monitoring practice and identifies research and methodological gaps for the use of passive samplers in monitoring. The main gaps are; i) the range of passive samplers used should be extended, ii) differences observed in absolute concentrations accumulated by passive samplers and organisms should be understood, and iii) the link between PW discharge concentrations and observed acute and sub-lethal ecotoxicological end points in organisms should be investigated. [ABSTRACT FROM AUTHOR]

During offshore petroleum production, large volumes of produced water are continuously discharged. The environmental impact from such discharges is typically assessed with numerical models, which simulate the transport and dilution of the produced water plume in order to predict environmental concentrations of its chemical constituents. In this study we investigate the effects of model resolution (800 m and 4 km) on produced water dispersion. We also compare two different types of models, a Lagrangian particle model, and an Eulerian grid-based ocean model to assess the Eulerian consistency of the Lagrangian model. We consider a point source off the coast of mid-Norway, during two different seasons (winter and spring). In general, the two models are in reasonable agreement. We find a substantial difference in tracer distribution and concentrations between the two resolutions, and to a lesser extent between seasons; in particular, the 800 m model shows lower concentrations along the coast. • We model an idealised produced water release with an Eulerian and a Lagrangian model. • We achieve equivalent results with the two modelling approaches. • We discuss the implications of ocean model resolution for produced water modelling. [ABSTRACT FROM AUTHOR]

Produced water is a mixture of dispersed oil in water, dissolved organic, and inorganic particles. Membrane technology is a potential process to meet future discharge standards and regulations on the Norwegian Continental Shelf (NCS). Fouling minimization with back-pulsing technique was assessed in this study. The influence of produced water properties i.e., oil concentration, oil types, particles and membrane flux during the back-pulsing was investigated. α-Al2O3 MF membranes (nominal pore sizes; 0.1, 0.2 and 0.5 µm) were tested. Results show that control of fouling rates is better at low oil concentrations, low flux, larger oil droplet size and no fine oil/particles. Selection of membrane pore sizes depends on the feed properties. At low oil concentration (i.e., 50 ppm) and low flux (i.e., 250 l.m-2.hr-1 (LMH), a pore size of 0.5 µm resulted in the lowest fouling rates, whereas for higher oil concentrations and low flux and presences of fine particles the 0.2 µm pore size performed better. At high flux (i.e., 500 LMH), high oil concentrations and presences of particles the 0.1 µm membrane had the lowest fouling rates. A permeate quality of <5 ppm could be achieved even though the oil in the feed was increased from 50 to 350 ppm of oil in water. [ABSTRACT FROM AUTHOR]

Abstract: This case study demonstrates how natural heterogeneities of formation and injection waters can be applied to a number of production related applications, extending into the mature life of a reservoir. Break-through of injection water, identification and characterisation of production intervals and evaluation of responses to operational events are some of the possible applications during production. The Oseberg Øst oil field in the North Sea represents a complex situation with commingled production from all Brent Group formations. The Sr isotope composition is an excellent parameter for defining the natural baseline of formation water, with a good spatial resolution and vertical stratification. Aquifer water from the Utsira Formation is injected for pressure support, and reinjection of produced water has also been applied since the onset of water production. Utsira Formation water has high Mg, low Ba and low Sr content compared to the reservoir formation waters. Isotopic compositions (δD and 87Sr/86Sr) are also distinct. A non-reactive behaviour of Ba and Sr is verified from binary cross-plots and geochemical modelling. Break-through of injection water could be identified in five production wells based on Ba/Mg ratios. In one of the reservoir compartments (Beta Saddle), water injection points were changed after approximately three years. The Ba/Mg ratio could also identify the second injection water break-through in one of the wells due to an intermediate period of higher formation water content. Since the Sr content in the Utsira water is low, the 87Sr/86Sr ratio is a good natural tracer for formation water movements even at high ratios of injected water. In particular, the vertical stratification of 87Sr/86Sr is useful for quantifying production from different intervals in commingled wells. A methodology for using operational events, such as production allocations or shut-ins, for characterisation of production zones is discussed. [Copyright &y& Elsevier]

Oseberg Sør field, operated by Hydro Oil & Energy, is situated 130 km west of the Norwegian coast on the eastern flank of the Viking Graben structure. It comprises a sequence of fault-bounded structural units of varying geological complexity. Within these units, the reservoir intervals are of moderate to poor quality and can exhibit strong contrasts in permeability and formation water composition. Reservoir support is provided by combined injection of gas and Utsira aquifer water. The wells are a combination of platform and subsea and comprise extended reach horizontals with complex geometry and lesser numbers of vertical wells. Detailed scale predictions have been performed to identify the scaling risk for each producer. From these, it was identified that the major risk to well performance and integrity was CaCO3 precipitation in the upper tubing with potential failure of the downhole safety valve. The risk varied from negligible to severe and reflected the variable composition of the produced water and well operating conditions. The scale predictions provided the basis for a technical and economic evaluation to identify an appropriate scale-management strategy for Oseberg Sør. For those wells completed with downhole chemical injection lines, the option to use these for scale inhibition was considered cost effective. In other wells where this option was not available, scale inhibitor injection into the gas lift system or squeezing using a viscosified treatment was considered viable. The paper will provide the technical and economic reasoning for the scale-management strategy selected along with field case histories fur each treatment type (i.e., experience with treatment using chemical injection lines, injection of scale inhibitor into the gas lift system, and squeezing). [ABSTRACT FROM AUTHOR]

The in vitro estrogen receptor (ER) agonist and androgen receptor (AR) antagonist potencies of offshore produced water effluents collected from the Norwegian Sector were determined using recombinant yeast estrogen and androgen screens. Solid phase extraction (SPE) concentrates of the effluents showed E2 agonist activities similar to those previously reported for the United Kingdom (UK) Continental Shelf (<0. 1–4ngE2L−1). No activity was detected in the filtered oil droplets suggesting that produced water ER activity is primarily associated with the dissolved phase. Targeted analysis for methyl-to nonyl-substituted alkylphenol isomers show the occurrence of known ER agonists in the analysed samples. For the first time, AR antagonists were detected in both the dissolved and oil associated phase at concentrations of between 20 and 8000μg of flutamide equivalents L−1. The identity of the AR antagonists is unknown, however this represents a significant input into the marine environment of unknown compounds that exert a known biological effect. It is recommended that further analysis using techniques such as bioassay-directed analysis is performed to identify the compounds/groups of compounds that are responsible in order to improve the assessment of the risk posed by produced water discharges to the marine environment. [Copyright &y& Elsevier]

A pressure simulator modelling the dynamic overpressure history in sedimentary basins is developed using a pressure compartment methodology. Simple models for porosity reduction are used for controlling pressure generation, and different empirical models are used to estimate the lateral and vertical sealing/dissipation mechanisms. The equations describing the flow of formation water between the pressure compartments are used to calculate the resulting pressure dissipation on a geological time scale. The methodology is tested and applied to the Jurassic Fangst Group in the Halten Terrace area, offshore Norway. Dynamic allocation and an explicit numerical solution technique ensure a fast and accurate solution of the flow equations. The results suggest: (a) the probable mechanisms and processes that have generated the overpressure, (b) the timing and location of hydraulic fracturing and (c) the nature and behaviour of the overpressure in addition to the overpressure history. [Copyright &y& Elsevier]