The SPE has split the former "Management & Information" technical discipline into two new technical discplines:
- Data Science & Engineering Analytics
The SPE has split the former "Management & Information" technical discipline into two new technical discplines:
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Using renewable energy can help the oil and gas industry to reduce emissions while getting a stable, high-quality power supply. The renewable energy system can even be used to help the oil and gas facilities with enhanced oil recovery (EOR). These are the results from a project Floating Power Plant (FPP) has just finished with Lundin Energy Norway, NOV-APL, Semco Maritime, Cefront Technologies, and Aalborg University using floating wind and wave power to support an offshore oil and gas facility. The project developed three different designs to see if the concepts set up by the partners were usable solutions from an engineering point of view and as a commercial business case. 'We have shown that using renewable energy in the oil and gas industry is a good idea," said Anders Køhler, the chief executive officer of FPP.
Kallesten, Emanuela (University of Stavanger, Norway) | Andersen, Pål Østebø (University of Stavanger, Norway) | Berawala, Dhruvit Satishchandra (University of Stavanger, Norway) | Korsnes, Reidar Inge (University of Stavanger, Norway) | Madland, Merete Vadla (University of Stavanger, Norway) | Omdal, Edvard (ConocoPhillips, Norway) | Zimmermann, Udo (University of Stavanger, Norway)
Summary Understanding the effect of typical water‐related improved oil recovery techniques is fundamental to the development of chalk reservoirs on the Norwegian Continental Shelf (NCS). We investigate the contribution and interplay of key parameters influencing the reservoir's flow and storativity properties, such as effective stresses, injecting fluid chemistry, and geomechanical deformation. This is done by developing a mathematical model that is applied to systematically interpret experimental data. The gained understanding is useful for improved prediction of permeability development during field life. The model we present is for a fractured chalk core whereby fluids can flow through the matrix and fracture domains in parallel. The core is subject to a constant effective stress above the yield, resulting in time‐dependent compaction (creep) of the matrix, while the fracture does not compact. Reactive brine injection causes enhanced compaction but also permeability alteration. This again causes a redistribution of injected flow between the two domains. A previous version of the model parameterizing the relation between chemistry and compaction is here extended to quantify the effect on permeability and see the effect of flow in a fracture‐matrix geometry. A vast set of experimental data were used to quantify the relations in the model and demonstrate its usefulness to interpret experimental data. Two outcrop chalk types (Aalborg and Liège) being tested at 130°C and various concentrations of Ca‐Mg‐Na‐Cl brines are considered. However, assumptions were required, especially regarding the fracture behavior because directly representative data were not available. The tests with inert injecting brine were used to quantify the effect of matrix and fracture mechanical compaction on permeability trends. To be able to explain the tests with reactive brine, an important finding is that permeability not only decreased because of enhanced porosity reduction but also because of a quantifiable chemistry‐related process (dissolution/precipitation). Sensitivity analyses were performed regarding varying fracture width, injection rate, and chemistry concentration to evaluate the effect on chemical creep compaction and permeability evolution in fractured cores. The model can be used to highlight parameters with great influence on the experimental results. An accurate quantification of such parameters will contribute to refining laboratory experiments and will provide valuable data for upscaling and field application.
Summary Numerical and analytical 1D solutions are presented to interpret the link between geochemical alterations and creep compaction (compaction under constant effective stress) in chalk cores. Chemically reactive flow enhancing chalk compaction is of significant importance for enhanced oil recovery (EOR), compaction, and subsidence in North Sea chalk reservoirs. The focus of this study is on Ca-, Mg-, and NaCl brines that interact with the chalk by the dissolution of calcite and the precipitation of magnesite. An explicit analytical solution is derived for the steady–state ion and dissolution–rate distributions at a given injected composition and injection rate. A mathematical description of creep compaction is proposed on the basis of applied affective stresses and rock ability to carry these stresses as a function of porosity. The reaction and compaction models are then coupled as follows: The compaction rate is assumed, which is enhanced by the dissolution rate, which can vary spatially. Furthermore, the solid volume changes by mineral dissolution and precipitation. Brine–dependent and nonuniform compaction is hence built into the model by means of the dissolution–rate distribution. The model is validated and parameterized against data from a total of 22 core samples from two chalk types (Åalborg and Liege) where reactive and inert brines were injected from ambient to Ekofisk–reservoir conditions (130°C). Experimentally measured effluent concentrations, distributions in mineralogy after flooding, and creep–compaction behavior were matched. Our model is the first to link a vast set of data on this subject and predict performance under new experimental conditions. This also represents a first step in upscaling such results from the laboratory toward the field. Our interpretations indicate that the two chalk types would respond differently chemically and by compaction to changes in the concentration and injection rate. Brines injected through Liege chalk appeared to approach stable oversaturation, while in Åalborg, the equilibrium condition was in agreement with geochemical calculations.
Kallesten, Emanuela (University of Stavanger) | Østebø Andersen, Pål (The National IOR Centre of Norway) | Berawala, Dhruvit Satishchandra (University of Stavanger) | Korsnes, Reidar Inge (The National IOR Centre of Norway) | Vadla Madland, Merete (University of Stavanger) | Omdal, Edvard (The National IOR Centre of Norway) | Zimmermann, Udo (University of Stavanger)
Abstract Understanding the impact of typical water-related IOR techniques is fundamental to the development of chalk reservoirs on the Norwegian Continental Shelf (NCS). We investigate the contribution and interplay of key parameters influencing the reservoir's flow and storativity properties such as effective stresses, injecting fluid chemistry and geomechanical deformation. This is done by developing a mathematical model which is applied to systematically interpret experimental data. The gained understanding is useful for improved prediction of permeability development during field life. The model we present is for a fracture chalk core where fluids can flow through the matrix and fracture domains in parallell. The core is subject to a constant effective stress above yield resulting in time-dependent compaction (creep) of the matrix, while the fracture does not compact. Reactive brine injection causes enhanced compaction, but also permeability alteration. This again causes a redistribution of injected flow between the two domains. A previous version of the model parameterizing the relation between chemistry and compaction is here extended to quantify the impact on permeability and see the impact of flow in a fracture-matrix geometry. A vast set of experimental data was used to quantify the relations in the model and demonstrate its usefulness to interpret experimental data. Two outcrop chalk types (Aalborg and Liege) being tested at 130 °C and various concentrations of Ca-Mg-Na-Cl brines are considered. However, assumptions were required especially regarding the fractures behavior since directly representative data were not available. The tests with inert injecting brine were used to quantify the impact of matrix and fracture mechanical compaction on permeability trends. To be able to explain the tests with reactive brine, an important finding is that permeability not only decreased due to enhanced porosity reduction, but also because of a quantifiable chemistry related process (dissolution-precipitation). Sensitivity analyses were performed regarding varying fracture width, injection rate and chemistry concentration to evaluate the impact on chemical creep compaction and permeability evolution in fractured cores. The model can be used to highlight parameters with great influence on the experimental results. An accurate quantification of such parameters will contribute to refining lab experiments and will provide valuable data for upscaling and field application.
Klewiah, Isaac (University of Stavanger, Norway) | Piñerez Torrijos, Iván Darío (University of Stavanger, The National IOR Centre of Norway, Norway) | Strand, Skule (University of Stavanger, Norway) | Puntervold, Tina (University of Stavanger, Norway) | Konstantinopoulos, Miltiadis (Technical University of Crete, Greece.)
Abstract Adsorption of polar crude oil components exert a major impact on chalk wetting, and adsorption effects have been reported on water-wet pure Stevns Klint outcrop chalk (>99% CaCO3). Aalborg chalk is a silica-rich material also used as analogue rock material for chalk reservoir studies. This work aims to characterize the impact silica minerals will have on polar crude oil component adsorption, and core wettability. Silica-rich (6-8 At %) Aalborg chalk cores with initial water saturation (Swi) of 10% were flooded with a crude oil with acid and base numbers (AN and BN) equal to 0.35 mg KOH/g of oil. Effluent crude oil samples were analyzed, detecting changes in the AN and BN concentrations at the core outlet. Wettability was determined by spontaneous imbibition (SI), and further confirmed by chromatographic wettability tests. Adsorption of polar crude oil components was observed to be an instantaneous process. The adsorption of polar acidic components onto the Aalborg chalk surfaces was less profound as previously observed in Stevns Klint chalk. However, adsorption of polar basic components was significantly higher in Aalborg chalk, which could be explained by the presence of negatively charged silicate surfaces. The water wetness of the Aalborg Chalk core was significantly reduced after the crude oil exposure. This comparative study on both Aalborg and Stevns Klint chalk highlights the impact of silica content on adsorption of polar components and initial wetting. The findings contribute with essential information for the development of theoretical and chemical models to describe initial reservoir wetting and explain oil production profiles in chalk reservoirs during normal water injections, or during wettability alteration with Smart Water.
Small-scale tests have been conducted to investigate the quasi-static behaviour of laterally loaded, non-slender piles installed in cohesionless soil. For that purpose, a new and innovative test setup has been developed. The tests have been conducted in a pressure tank such that it was possible to apply an overburden pressure to the soil. As a result of that, the traditional uncertainties related to low effective stresses for small-scale tests have been avoided. A normalisation criterion for laterally loaded piles has been proposed based on dimensional analysis. The test results using the novel testing method have been compared with the use of the normalisation criterion. Introduction For offshore wind turbines, the monopile foundation concept is often employed. Typically, the monopile foundation concept consists of an open-ended steel tube, which is either drilled or driven into the seabed. The pile diameter, D, and the embedded pile length, Lp, are usually in the range of 4–6 m and 15–30 m, respectively. Hence, the slenderness ratio, Lp/D, is in the order of 4 to 7, and therefore the piles exhibit a rather rigid body motion. The Winkler model approach is traditionally employed in the design of offshore monopiles. In this approach, the interaction between the soil and the pile is modelled by means of uncoupled nonlinear springs. The stiffness of the nonlinear springs is described by means of p-y curves. These curves describe the soil resistance acting on the pile wall as a function of the pile deflection. Design regulations of the American Petroleum Institute (API, 2000) and Det Norske Veritas (DNV, 2010) recommend the use of the p-y curve formulation proposed by O'Neill and Murchison (1983) for piles situated in cohesionless soils. The formulation has been validated by Murchison and O'Neill (1984) through tests on piles with diameters up to approximately 2 m and length-to-diameter ratios larger than 10. However, the formulation has not been validated for piles with Lp/D ≈5 and D =4–6 m. The static and the cyclic behaviour of non-slender piles has in recent years been investigated by means of small-scale tests at 1 g and by means of centrifuge tests. LeBlanc et al. (2010a), LeBlanc et al. (2010b), Lombardi et al. (2013), and Peralta and Achmus (2010) investigated the accumulation of pile rotation for non-slender piles exposed to long-term cyclic loading by means of small-scale tests at 1 g. Klinkvort and Hededal (2010) and Haigh (2014) have carried out model tests of non-slender piles by means of centrifuge testing. Jardine et al. (2012) have carried out a literature review of cyclically loaded offshore piles. Nowadays, the design of monopile foundations for offshore wind turbines is primarily driven by the dynamic behaviour. The natural frequency of the wind turbines is typically designed to be between the rotor frequency and the blade passing frequency (cf. Haigh, 2014). However, in order to understand the cyclic behaviour of non-slender piles, a better understanding of the static behaviour of non-slender piles is needed. An extensive test program has been carried out at Aalborg University in order to investigate the behaviour of non-slender piles in sand exposed to static lateral loading. Piles with diameters of 60 to 100 mm, embedded pile lengths of 240 to 500 mm, and slenderness ratios of 3 to 6 have been tested. Hence, the scale in comparison with real monopiles is between 1:40 and 1:100.
ABSTRACT A modified contour diagram is created for the Frederikshavn Sand in the undrained case for a relative density of ID = 80 %. It can be used to estimate the number of cycles to failure for a given combination of pore pressure, average and cyclic load ratio. The diagram is based on a series of undrained cyclic triaxial tests, which have been performed at the Geotechnical Laboratory at Aalborg University. In order to ensure offshore conditions, the tests were fully saturated and performed with a relative density of 80 %. During cyclic loading, special attention was given to the development of pore pressure and deformation.
ABSTRACT An extensive model test program has been carried out in order to assess the behavior of a tension leg moored substructure as support of a floating offshore wind turbine (FOWT). The floater was inspired by an industrial design. The tests focused on the ultimate limit state (ULS) behavior, therefore no aerodynamic or gyroscopic effects were included, i.e. the turbine hub was represented by a lumped mass, and focus was given to wave forces and dynamic behavior. The model tests have been conducted in the 3D deep water basin of the Hydraulics and Coastal Engineering Laboratory at the University of Aalborg at a scale of 1:80. The model tests were made with a range of monochromatic, bichromatic and irregular waves. All waves are modeled long crested and were run with and without sub and super harmonics. Three different structure layouts were tested, i.e. the tests were run with substructure only, with a rigid tower representation and with a flexible tower representation. Three submerged load cells measured the response of the tendons, and two accelerometers measured the response of the total structure, being located at the substructure - tower interface and in the nacelle. The paper intends to describe the setup of the test and presents some selected interim results.
ABSTRACT Extreme sea states, which the IEC 61400-3 (2008) standard requires for the ultimate limit state (ULS) analysis of offshore wind turbines are derived to establish the design basis for the conceptual layout of deep water floating offshore wind turbine foundations in hurricane affected areas. Especially in the initial phase of floating foundation concept development, site specific metocean data are usually not available. As the areas of interest are furthermore not covered by any design standard, in terms of design sea states, generic and in engineering terms applicable environmental background data is required for a type specific conceptual design. ULS conditions for different return periods are developed, which can subsequently be applied in siteindependent analysis and conceptual design. Recordings provided by National Oceanic and Atmospheric Administration (NOAA), of hurricanes along the US east coast and the Gulf of Mexico (1851–2009) and Japanese east coast (1951–2009) form the basis for Weibull extreme value analyses to determine return period respective maximum wind speeds. Unidirectional generic sea state spectra are obtained by application of the empirical models for hurricane generates seas by Young (1998, 2003, and 2006), requiring maximum wind speeds, forward velocity and radius to maximum wind speed. An averaged radius to maximum sustained wind speeds, according to Hsu et al. (1998) and averaged forward speed of cyclonic storms are applied in the initial state. In a second step the influence of the forward velocity is investigated and related to the assumption of an extended fetch. & Geostructures; Peter Bak Frigaard, Hydraulics and Coastal Engineering Laboratory, Department of Civil Engineering, Aalborg University. INTRODUCTION Not all industrialized countries, in fact only a minority, are blessed with shallow coast areas, i.e. shelf seas, like the traditional offshore wind nations, e.g. UK, Denmark and recently Germany.
Foglia, Aligi (Department of Civil Engineering, Aalborg University) | Ibsen, Lars Bo (Department of Civil Engineering, Aalborg University) | Andersen, Lars Vabbersgaard (Department of Civil Engineering, Aalborg University) | Roesen, Hanne Ravn (Department of Civil Engineering, Aalborg University)
ABSTRACT: Offshore wind farms are a promising renewable energy source. The monopod bucket foundation has the potential to become a reliable and cost-effective concept for offshore wind turbines. The bucket foundation must be designed by accounting for the cyclic loading which might endanger the turbine functioning. In this article a 1g physical model of bucket foundation under horizontal and moment cyclic loading is described. A testing program including four tests was carried out. Every test was conducted for at least 30000 cycles, each with different loading features. The capability of the model to represent the cyclic loading is discussed based on example results. INTRODUCTION Wind converters are nowadays a promising alternative to fossil fuels. Over the last two decades a growing investment made wind energy feasible. The research has achieved encouraging results being capable of lowering significantly the price of wind energy. Onshore wind power plants are by now realistically in competition with fossil fuels. Over the last years the offshore wind energy cost dropped drastically, although it is still 2 to 3 times higher than that of coal or gas (Beedie, 2011). A key factor of the offshore wind farm overall cost is the foundation and its installation technology. In the last ten years a cost-effective foundation concept for offshore wind turbine has been developed at Aalborg University, the monopod bucket foundation. The bucket foundation, or suction caisson, was widely adopted by the oil and gas sector as an anchor for floating platforms or as a spread-out shallow foundation for jacket structures. Such foundation consists of an upturned steel bucket installed in 10–50 m water depth by means of a suction-assisted penetration. For these reasons the overall CAPEX of an offshore wind farm can be markedly lowered by adopting the bucket foundations.