Microbial hydrogen consumption leads to a significant pH increase under high-saline-conditions: implications for hydrogen storage in salt caverns

Salt caverns have been successfully used for natural gas storage globally since the 1940s and are now under consideration for hydrogen (H2) storage, which is needed in large quantities to decarbonize the economy to finally reach a net zero by 2050. Salt caverns are not sterile and H2 is a ubiquitous electron donor for microorganisms. This could entail that the injected H2 will be microbially consumed, leading to a volumetric loss and potential production of toxic H2S. However, the extent and rates of this microbial H2 consumption under high-saline cavern conditions are not yet understood. To investigate microbial consumption rates, we cultured the halophilic sulphate-reducing bacteria Desulfohalobium retbaense and the halophilic methanogen Methanocalculus halotolerans under different H2 partial pressures. Both strains consumed H2, but consumption rates slowed down significantly over time. The activity loss correlated with a significant pH increase (up to pH 9) in the media due to intense proton- and bicarbonate consumption. In the case of sulphate reduction, this pH increase led to dissolution of all produced H2S in the liquid phase. We compared these observations to a brine retrieved from a salt cavern located in Northern Germany, which was then incubated with 100% H2 over several months. We again observed a H2 loss (up to 12%) with a concurrent increase in pH of up to 8.5 especially when additional nutrients were added to the brine. Our results clearly show that sulphate-reducing microbes present in salt caverns consume H2, which will be accompanied by a significant pH increase, resulting in reduced activity over time. This potentially self-limiting process of pH increase during sulphate-reduction will be advantageous for H2 storage in low-buffering environments like salt caverns.publishedVersio

Ultralydsmålinger under høyt trykk - En undersøkelse av solubilisering av 1-heksanol i natrium dodecylsulfat som funksjon av trykk

Ny apparatur for lydhastighetsmålinger under trykk har blitt testet, og tilpasset rubidium-klokke teknikk. Det ble deretter gjort studier på solubiliseringsprosessen som funksjon av trykk, der en variert mengde av 1-heksanol ble løst opp i en konstant konsentrasjon av natrium dodecylsulfat-løsning (SDS). Alle målinger er foretatt over kritisk micellekonsentrasjon, CMC. Data fra tetthetsmålinger ved atmosfæretrykk og lydhastighetsmålinger i trykkintervall 1-1400bar ved 298,15K, dannet grunnlaget for beregning av termodynamiske størrelser, partielt molart volum, V2, og partiell molar kompressibilitet, K2. Partielle molare størrelser ved uendelig fortynning og , for det aktuelle system er blitt funnet til å øke med surfaktant konsentrasjon, men avtar med økende trykk. Den partielle molare kompressibiliteten ved uendelig fortynning av alkohol, , er brukt videre til beregning av partisjonskoeffisient, K02V02K02Kx. Tolkning av resultatene ble utført ved å se på endringen i henholdsvis volum, , og kompressibilitet, , for alkohol/surfaktant ved en overgang fra vann- til micellefase. Det ble funnet at K02V∆02K∆x avtar initielt og når minimum ved 400 bar, for så deretter å øke igjen ved videre kompresjon

When Culture Takes Over

Purpose: The purpose of this thesis is to examine how trainees in a big Swedish telecommunications company are being socialized into becoming the future leaders of the company Theoretical framework: In our theoretical framework we have focused upon existing research that theorizes the relation between leadership, culture and socialization, with particular focus on the way this relation has been established within transformational leadership research. Methodology: The study is based on qualitative research and the inductive method has been used. We have conducted semi structured interviews with participants and interpreted their answers. Findings: Our study is based on a company’s socialization of trainees into leadership. We have conducted interviews with current trainees and managers about this process and their view of leadership. Discussion: The theoretical distinction between transformational and transactional leadership has been an essential theory in our discussion that has assisted us to discuss the interplay between leadership, culture and socialization. Through socialization individuals are adapting to the culture and become transactional leaders. This, however, could be perceived as management rather than as leadership. Transformational leadership is substituted by the culture. Conclusion: In this case study we have found that the trainee program which is aiming to create the leaders of the future is creating the managers of the future. The reason for this is that the strong culture is influencing the socialization process which in turn is facilitating the creation of transactional leaders. We also found that organizational culture is substituting leadership in this organization which might be preferable for the organization. Culture has taken over the role of leadership within the organization

Combined Low Salinity Brine Injection and Surfactant Flooding in Mixed−Wet Sandstone Cores

The concept of surfactant flooding has long been recognized as a promising supplement to water-based enhanced oil recovery methods. In recent years, core displacement experiments performed on clastic rock samples using low salinity brine as injection fluid have proven to give a moderate increase in crude oil recovery. This paper presents a new hybrid EOR process where the effect of low salinity brine injection is combined with surfactant flooding. An anionic surfactant formulation was selected to give low interfacial tension (IFT) in a low salinity environment containing 0.50 wt % NaCl. The surfactant forms Winsor type I microemulsion at this salinity. Improved surfactant solubility and reduced adsorption or retention is among the advantages of using surfactant at low salinity conditions. This paper reports core flood experiments performed on outcrop sandstone cores using crude oil as the oil phase. Results show high oil recovery of more than 90% of original oil in place (OOIP) when surfactant is used in tertiary mode, i.e., after secondary waterflood. Destabilization of oil layers caused by change in brine salinity and simultaneous mobilization of the residual oil at low IFT is discussed as the possible underlying mechanism for the combined process of low salinity water injection with surfactant flooding. Low surfactant retention under these conditions may makes this hybrid EOR process more economically attractive compared to applying low salinity waterflood or surfactant flooding separately

Motivera medarbetare

Bakgrund: Betydelsen av medarbetare i kunskapsintensiva företag har på senare tid blivit allt viktigare eftersom företagets värde ligger i medarbetares kunskap. Detta har lett till ett intresse att motivera medarbetare i kunskapsintensiva företag. Syfte: Syftet med vår uppsats är att undersöka vad som motiverar anställda i arbetet i kunskapsintensiva företag. Metod: I arbetet har vi använt oss av den deduktiva processen. Vi har genomfört kvalitativa intervjuer på två fallföretag, E.on och Grant Thornton. Teoretiska perspektiv: Vår teoretiska referensram bygger på de fyra motivationsteorierna: behovsteorier, kognitiva teorier, sociala teorier och arbetskaraktäristiska teorier. Vi har även använt teorier som behandlar inre och yttre motivation. Empiri: Det empiriska materialet består av semistrukturerade intervjuer med respondenter på E.on och Grant Thornton. Resultat: Motivation tycks vara individbaserat men vi har dock kunnat dra några generella slutsatser. De slutsatser vi kan dra är att personal i kunskapsintensiva företag känner bristande motivation vid monotona arbetsuppgifter och känner sig speciellt motiverade i situationer där de styrs av inre motivationsfaktorer. Självbestämmande och tydlig definierad arbetsroll behövs i samverkan med varandra för att individer ska känna sig motiverade