Adaptive hierarchical upscaling of flow in heterogeneous reservoirs based on an a posteriori error estimate

This paper treats the upscaling of the absolute permeability in a heterogeneous reservoir. By replacing the fine scale permeability tensor with an upscaled, or effective permeability tensor, a modelling error is introduced. An a posteriori error estimate on this modelling error is formulated and tested. An implementation of the theory, based on domain decomposition coupled with a hierarchical representation of the absolute permeability field, is given. As hierarchical basis functions we have chosen the Haar system, which leads to a wavelet representation of the permeability. The wavelet representation offers a natural upscaling technique which resembles the highcut filters commonly used in signal analysis. This procedure represents an adaptive upscaling method. The numerical results show that this method conserves both the dissipation and the mean velocity in the problem fairly well. The a posteriori error estimate on the modelling error coupled with domain decomposition methods constitutes a powerful modelling tool.     

High matrix interference affecting detection of PAH metabolites in bile of Atlantic hagfish (Myxine glutinosa) used for biomonitoring of deep-water oil production

The characteristic biology and wide distribution of hagfish species makes them relevant for use in pollution biomonitoring at great water depths, particularly in regions where deep-water oil production may take place. The exposure of fish to petrogenic contaminants can normally be detected from the level of polycyclic aromatic hydrocarbon (PAH) metabolites in bile fluid. Some of these metabolites are strong fluorophores, allowing analytical detection by means of simple fluorometric techniques such as fixed wavelength fluorescence (FF) and synchronous fluorescence scanning (SFS). In the present study bile from Atlantic hagfish (Myxine glutinosa) collected in pristine areas (Barents Sea and southwestern Norway) displayed strong bile fluorescence levels, suggesting the presence of PAH contaminants. However, gas-chromatography-mass spectrometry (GC-MS) analyses ruled out PAHs as the origin for this fluorescence signal. Rather, the bile of Myxine contains components resulting in unusually strong background fluorescence interfering at the wavelength pairs used for detection of PAH metabolites. Possible background for the observed matrix interference and implications for detection of PAH metabolites in hagfish is discussed.     

Acidic compounds in biodegraded petroleum

Twelve oil samples have been characterised by titration, FT-IR and chromatographic analysis to determine the differences between the organic acid composition of biodegraded and non-biodegraded oils. The biodegraded oils have higher total acid and total base contents, both by titration and extraction. The molecular weight ranges of the extracted acids are lowest in the biodegraded oils, and the equivalent weight calculations indicate a dominance of multi-functional molecules. Gel permeation chromatography gives a molecular weight range with most of the molecules between 300 and 500 g/mol. FT-IR shows that the extracted acids from biodegraded oils are more carboxylic and aliphatic while the non-degraded oils are more phenolic. Molecular analysis of the derivatised extracts give UCM envelopes for biodegraded oils, and no molecular identification. The results indicate that the acidic constituents in biodegraded oils are a product of the biodegradation, as the composition is very different from the non-biodegraded oils.     

Implicit Treatment of Compositional Flow

In basin modeling the thermodynamics of a multicomponent multiphase fluid flux are computationally too expensive when derived from a cubic equation of state and the Gibbs equality constraints. In this article we present an alternative implicit molar mass formulation technique using binary mixture thermodynamics. The two proposed solution methods are based on a hybrid smoother, Gauss–Seidel–Galerkin at each time-step with analytical computation of the derivatives. The new algorithm overcomes the difficulty of choosing an optimal relaxation parameter and reduce significantly the numerical effort for the computation of the molar masses. Numerical results are presented which show significant improvements with respect to previous methods.     

Symmetry and M-Matrix Issues for the O-Method on an Unstructured Grid

More sophisticated discretization methods than the traditional control-volume finite-difference methods, have been proposed by Aavatsmark et al. in recent papers for solving the mass balance equations for porous media flow. These methods are based on a local representation of fluxes across cell-edges of control volumes (CVs). This paper will focus on mathematical properties of the discrete operator that arises when an elliptic term of the form ???(K?p) is discretized based on these discretization principles.     

基于多期DEM和滑坡强度的滑坡风险评估

滑坡危险性定量评估是滑坡风险评估中的关键和难点,也是当前国际风险管理研究中的热点问题.以滑坡密集分布的黑方台南塬为研究区,以32处典型滑坡为研究对象,依据多期三维数字高程模型(DEM),提出了一种基于强度的滑坡危险性定量评估技术方法.根据多期三维地形信息的解译及野外调查,编制多期滑坡分布图,计算滑坡活动的频率.利用GIS技术,利用滑坡体积与速度的乘积计算滑坡强度.将滑坡危险性定义为滑坡频率和滑坡强度的乘积,同时调查和分析了黑方台地区各类承灾体的类型、价值及其在相应滑坡强度下的易损性,在此基础上开展了单体滑坡风险评估和黑方台南塬滑坡风险区划.     

Numerical methods for flow in a porous medium with internal boundaries

Flow of fluids and transport of solutes in porous media are subjects of wide interest in several fields of applications: reservoir engineering, subsurface hydrology, chemical engineering, etc. In this paper we will study two-phase flow in a model consisting of two different types of sediments. Here, the absolute permeability, the relative permeabilities and the capillary pressure are discontinuous functions in space. This leads to interior boundary value problems at the interface between the sediments. The saturation S_w will be discontinuous or experience large gradients at the interface. A new solution procedure for such problems will be presented. The method combines the modified method of characteristics with a weak formulation where the basis functions are discontinuous at the interior boundary. The modified method of characteristics will provide a good first approximation for the jump in the discontinuous basis functions, which leads to a fast converging iterative solution scheme for the complete problem. The method has been implemented in a two-dimensional simulator, and results from numerical experiments will be presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Offshore and shipping activities in the Norwegian Arctic areas: The environmental dimension: Case: Norsk Hydro''s drilling of well 7316/5-1, autumn 1992

This paper describes how Norsk Hydro planned and executed the safety, environment and emergency preparedness matters related to the exploration drilling of well 7316/5-1, the most northern well drilled on the Norwegian continental shelf. This well (1992) was Norsk Hydro's first experience with the new above-mentioned regulations. For later wells, Norsk Hydro developed both how to use and implement these new regulations.     

Modified adaptive local–global upscaling method for discontinuous permeability distribution

The paper is devoted to the upscaling method appropriate for single-phase flow in media with discontinuous permeability distribution. The suggested algorithm is a modification of the iterative adaptive local–global upscaling developed by Chen and coauthors. The key feature of this method is a consistency between local and coarse global calculated characteristics. In this work, we apply a modified procedure to determine the boundary conditions used in the local fine-scale computation. To increase the accuracy of these boundary conditions on each iteration, we involve an additional preliminary step based on the results of coarse scale calculations from the previous iteration. Numerical tests show an essential improvement of the accuracy of upscaled flow rates for most of the realizations of statistical permeability distribution. Although the developed method is universal, its efficiency increases with increasing of permeability contrast.