A statistical analysis of well production rates from UK oil and gas fields – Implications for carbon capture and storage

The number of wells required to dispose of global CO2 emissions by injection into geological formations is of interest as a key indicator of feasible deployment rate, scale and cost. Estimates have largely been driven by forecasts of sustainable injection rate from mathematical modelling of the CO2 injection process. Recorded fluid production rates from oil and gas fields can be considered an observable analogue in this respect. The article presents statistics concerning Cumulative average Bulk fluid Production (CBP) rates per well for 104 oil and gas fields from the UK offshore region. The term bulk fluid production is used here to describe the composite volume of oil, gas and water produced at reservoir conditions. Overall, the following key findings are asserted: (1) CBP statistics for UK offshore oil and gas fields are similar to those observed for CO2 injection projects worldwide. (2) 50% probability of non-exceedance (PNE) for CBP for oil and gas fields without water flood is around 0.35 Mt/yr/well of CO2 equivalent. (3) There is negligible correlation between reservoir transmissivity and CBP. (4) Study of net and gross CBP for water flood fields suggest a 50% PNE that brine co-production during CO2 injection could lead to a 20% reduction in the number of wells required

The Spectral Action for Dirac Operators with skew-symmetric Torsion

We derive a formula for the gravitational part of the spectral action for Dirac operators on 4-dimensional manifolds with totally anti-symmetric torsion. We find that the torsion becomes dynamical and couples to the traceless part of the Riemann curvature tensor. Finally we deduce the Lagrangian for the Standard Model of particle physics in presence of torsion from the Chamseddine-Connes Dirac operator.Comment: Longer introduction and conclusion adde

Chiral Asymmetry and the Spectral Action

We consider orthogonal connections with arbitrary torsion on compact Riemannian manifolds. For the induced Dirac operators, twisted Dirac operators and Dirac operators of Chamseddine-Connes type we compute the spectral action. In addition to the Einstein-Hilbert action and the bosonic part of the Standard Model Lagrangian we find the Holst term from Loop Quantum Gravity, a coupling of the Holst term to the scalar curvature and a prediction for the value of the Barbero-Immirzi parameter

Spectral action for torsion with and without boundaries

We derive a commutative spectral triple and study the spectral action for a rather general geometric setting which includes the (skew-symmetric) torsion and the chiral bag conditions on the boundary. The spectral action splits into bulk and boundary parts. In the bulk, we clarify certain issues of the previous calculations, show that many terms in fact cancel out, and demonstrate that this cancellation is a result of the chiral symmetry of spectral action. On the boundary, we calculate several leading terms in the expansion of spectral action in four dimensions for vanishing chiral parameter $\theta$ of the boundary conditions, and show that $\theta=0$ is a critical point of the action in any dimension and at all orders of the expansion.Comment: 16 pages, references adde

Impact of maximum allowable cost on CO2 storage capacity in saline formations

Injecting CO2 into deep saline formations represents an important component of many greenhouse gas reduction strategies for the future. A number of authors have posed concern over the thousands of injection wells likely to be needed. However, a more important criterion than the number of wells is whether the total cost of storing the CO2 is market bearable. Previous studies have sought to determine the number of injection wells required to achieve a specified storage target. Here an alternative methodology is presented whereby we specify a maximum allowable cost (MAC) per tonne of CO2 stored, a priori, and determine the corresponding potential operational storage capacity. The methodology takes advantage of an analytical solution for pressure build-up during CO2 injection into a cylindrical saline formation, accounting for two-phase flow, brine evaporation and salt precipitation around the injection well. The methodology is applied to 375 saline formations from the UK Continental Shelf. Parameter uncertainty is propagated using Monte Carlo simulation with 10,000 realisations for each formation. The results show that MAC affects both the magnitude and spatial distribution of potential operational storage capacity on a national scale. Different storage prospects can appear more or less attractive depending on the MAC scenario considered. It is shown that, under high well injection rate scenarios with relatively low cost, there is adequate operational storage capacity for the equivalent of 40 years of UK CO2 emissions

Class and income in Australia

This article presents the findings from an analysis of the relationship between class location and income. The class schemas employed in these analyses derive from the work of Wright, Poulantzas, Carchedi, Barbara and John Ehrenreich and Goldthorpe. In the context of the Australian workforce, individual class location is found to be significantly related to income level. A properly specified causal model incorporating class and other relevant factors can explain between approximately 33 and 37 per cent of the variation of income among Australians in the workforce

Structural and motivational mechanisms of academic achievement: a mediation model of social‐background effects on academic achievement

This paper takes up ongoing discussions on the inequality of educational opportunities and formulates a conceptual model to link separate lines of research. Our particular focus is on combining motivational and structural approaches into a mediation model that explains differences in academic achievement. In the literature, four main mechanisms of social reproduction are discussed. Two main pathways refer to (1) parents’ expectations regarding their children’s academic success and (2) replicating cultural capital through intra‐familial cultural practices. (3) Parents’ perception of children’s abilities depends on social position and is influential for expectations of success. (4) For all three pathways, we expect effects on students’ motivational characteristics, which in turn influence academic achievement. We test our conceptual model by structural equation modelling using longitudinal data from primary school students in Germany. Empirical evidence is in line with the assumptions in the model. Cultural reproduction and expectations of success can be seen as the key components of the model. However, both chains of reproduction are related to each other by parents’ perception of child’s ability, and their effects are mediated by child’s motivational characteristics