bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decommissioning Concrete Structures - Environmental and Safety Challenges
Authors: Knudsen Søren 
Published: February 2011

Abstract
The OSPAR convention requires that almost all offshore oil and gas installations have to be removed when they are no longer in active use. There are currently approximately 832 oil & gas production facilities in the North Sea many of which will be abandoned in the coming decades.
In the decommissioning of offshore oil and gas installations, there is a continuous focus on keeping environmental and safety risks as low as reasonably practicable (ALARP). This paper will describe the assessment of decommissioning solutions from an environmental point of view, as a basis for submitting a decommissioning programme. The paper is primarily based on experiences gained from ongoing and completed decommissioning projects in the North Sea (Ekofisk tank, Brent Bravo/Delta and Frigg & MCP01). The focus of this paper is restricted to the decommissioning of concrete substructures.
Decommissioning concrete structures typically involves larger environmental and safety considerations than steel structures, as they tend to be more polluted from trapped oil, sludge, etc. Furthermore, several of these structures have not been designed with the intention for later removal and may involve large safety risks during a refloating operation.
Some of the major conclusions with regard to decommissioning of concrete substructures are: Ensuring a reliable decision-basis must not be under-estimated, as this is vital to support the difficult decommissioning options selection. This could be made by means of e.g. offshore sampling / surveysOnshore preparation, such as pilot-scale testing of tools and laboratory testing, can in some cases be beneficial and save time offshoreThe environmental and safety risk considerations play an important part in the fine balance between the company's wish to ensure a good reputation by removing all traces of their activities, and substantial practical safety and technical safety challenges associated with a ‘removal all’ operation.In some cases, partial removal or ‘leave in place’ could be the best decommissioning solution in relation to HSE.
HSE Compliance in Romania
Authors: Ebrahimian A.. , Stefanescu E.. 
Published: February 2011

Abstract
Drilling activities in Romania have been ongoing for over 154 years. After world war two, Romania became a communist state under USSR thumb until 1989. Shortly after they became members of the EU.
People working in the Oil & Gas industry in Romania were exposed to safety hazard risks leading to a number of accidents with some fatalities. Since OMV took up the majority shares and ownership of Petrom, both HSE and QA/QC respected industry standards have been properly addressed and are now fully implemented on all rig operations on contract to OMV Petrom Romania.
In 2008 OMV Petrom -HSE/Drilling Department set up a Safety Observation Program and implemented use of this program on all OMV Petrom rig operations.
The objective was to encourage people working on OMV Petrom rigs to highlight hazards and associated risks so corrective actions could be implemented in order to mitigate all those hazards and associated risks. Our aim is to make a safer working environment at the rig-site to enable people to work in safe conditions. We will highlight the statistics from our Safety Observation Program in tables and charts in this SPE Paper.
Transforming HSE Performance, It's Not Harder Than You Think
Authors: Kraus Brian , Rowley Peter 
Published: February 2011

Abstract
Many of us who have interacted with senior executives from leading oil and gas companies over the last few years on the subject of HSE performance have observed a marked shift in their engagement on this aspect of their business performance. There seems to be a shared impression that HSE performance will have markedly increased impact on their businesses going forward. On the back of this very real concern, many are taking material actions to secure a step change in their safety and environmental performance: hiring respected mainstream operational personnel to lead their HSE function; investing in capacity/skills development for HSE professionals to increase their effectiveness in addressing the needs of the business; taking a hard look at the efficacy of established management and audit programs (too much paper, not enough results?); investing in information management systems so they can have access to real time reliable performance indicators; and, critically, initiatives to reduce accident statistics (especially focused on fatalities and contractors' activities) and deliver meaningful reductions in their environmental footprints.
Underpinning all of these actions is a clear sense that substantial, very well-intentioned activity and investment in HSE aspects of the business has not been hitting the mark and yielding too little return in terms of performance improvement. The very serious recent events on the US Gulf Coast and at a refinery in the US Pacific Northwest have added fuel to this fire. The need for approaches which will secure a step-change in performance on the front line in the global oil and gas industry has never been greater.
It is broadly accepted that accidents have their origin in behavioral dynamics. In addition, the linkage between behaviors of front line personnel (including design engineers) and the behaviors of their leaders up and down the line is well-understood.
Adaptive Regularization in the Ensemble Kalman Filter for Reservoir History Matching
Authors: Tong Yao , Zhang Yanfen , Oliver Dean S. 
Published: February 2011

Abstract
Using a small ensemble size with the ensemble Kalman filter (EnKF) to update numerical reservoir models has proved to be an efficient method of reservoir history matching but, unless some type of localization is used, the standard EnKF update with a small size ensemble can lead to poor parameter estimates due to spurious correlations between observations and model variables. To reduce the impact of spurious correlations on model variable updates, distance-dependent localization has been widely used and is frequently effective at eliminating spurious correlations beyond a predefined distance. However, distance-dependent localization is not always appropriate for assimilating non-local observations, or when the prior covariance is complex due to previous data assimilation. Since the updates of parameters and state variables in the EnKF algorithm are largely determined by the Kalman gain, an improvement in Kalman gain estimation will in turn result in improved estimates of state and model variables. Several adaptive Kalman gain estimation methods, including the bootstrap sampling method, have been proposed recently with promising results but with residual small-amplitude high-frequency noise in the estimate of the Kalman gain.
In this paper, we propose a thresholding method for improving the Kalman gain estimation to completely eliminate correlations that are unreliable. We show that by screening the Kalman gain using an adaptive, element-wise threshold level, much of the noise in the estimate of the Kalman gain is removed at a low computational cost. We apply the new thresholding method and the previously developed bootstrap screening EnKF to a deepwater field with approximately 200,000 unknown model parameters. Results from both adaptive EnKF methods are better than results from manual history matching and are comparable to results from a standard EnKF method with distance-based localization.
Using a Committee Machine With Artificial Neural Networks To Predict PVT Properties of Iran Crude Oil
Authors: Alimadadi F.. , Fakhri A.. , Farooghi D.. , Sadati S.H.. H. 
Published: February 2011

Summary
Reservoir-fluid properties are very important in material-balance calculations, well testing, and reserves estimates. Ideally, those data should be obtained experimentally. Sometimes, the results obtained from experimental tests are not reliable or accessible.
In this study, we predict the pressure/volume/temperature (PVT) properties by a new artificial-neural-network (ANN) model using component mole percent, solution gas/oil ratio (GOR) (Rs), bubblepoint pressure (Pb), reservoir pressure, API oil gravity, and temperature as input data.
The employed ANN model is from the committee machine type. The designed model processes its inputs using two parallel multilayer perceptron (MLP) networks, and then recombines their results. The results obtained show that the committee-machine model is a dependable network for prediction of PVT properties in reservoirs among the other ANNs and empirical correlations.
Investigating the Evolution of Underwater Gas Releases
Authors: Borello L.. , Baldanzi E.. 
Published: February 2011

Abstract
Underwater gas releases were investigated by experimental tests to analyze the potential hazards deriving from accidental ruptures of offshore pipelines in the oil & gas industry. The evolution of the gas released by the ruptures located in relatively shallow waters has been accurately analyzed in order to evaluate the hazards associated with the toxic and flammable gases reaching the sea surface. The experimental activity has been carried out to better characterize the gas dispersion source term.
An underwater gas release from a pressurized pipeline generates a subsea gas plume that breaks down in bubbles and could reach the neutral buoyancy level below the sea surface. The size and rising velocity of the bubbles affect the momentum of the gas reaching the sea surface, while the lateral spreading of the bubbles and the gas dissolution in water influence the bubbling area and the actual flow rate dispersed in the atmosphere. Another important phenomenon is the neutralization of the gas due to the diffusion in the air just above the sea surface. These parameters represent the basic information required to determine the behavior of the gas above the sea surface and the source term for atmospheric dispersion.
The experimental activity consisted in discharging a gas in an open tank filled with water. A set of lab tests was performed to evaluate the plume evolution for underwater releases of a neutral gas in shallow waters. The liquid velocity and gas hold-up were monitored along the plume length for different gas flow rates.
A benchmarking activity on underwater gas release models was performed comparing model equations with the experimental measurements. As a result of this work, a more accurate approach for determining the source term of atmospheric dispersion of a subsea gas plume is proposed.
Advanced Methods for Flash Fire Risk Assessment
Authors: Borello L.. , Podenzani F.. , Lorenzini F.. , Baldanzi E.. 
Published: February 2011

Abstract
Flash fire is one of the main potential hazards of oil & gas operations. The development of the flammable cloud is directly correlated to the explosion risk. Gas cloud evolution strongly depends on the source term definition. Commercial models, specifically developed and tuned for industrial plants risk assessment often simplify the phenomena affecting the source term, introducing errors and non-conservative assumptions. Excessive simplifications become particularly critical in case of accidents in non obstructed areas, where an accurate evaluation of the extension of flammable (and explosive) clouds is fundamental to assess the risks for assets, personnel or population.
In this paper various phenomena characterizing the source term are analyzed in some typical discharge configurations, in order to introduce a robust methodology based on realistic assumptions. Diversity of scenarios has been investigated to examine the factors that can affect the gas dispersion.
The loss of integrity of a high pressure pipeline was studied in order to understand how the high momentum jet influences the atmospheric dispersion of the gas: computational fluid dynamics (CFD) simulations were compared with commercial models and ad hoc approaches.
The evolution of a thermodynamically dense gas cloud from zero momentum sources was analyzed in a benchmarking activity with literature data, CFD approach and commercial models.
The flammable gas dispersion from subsea ruptures was also investigated. Even for this kind of event the dispersion of the flammable gas is highly influenced by the source term, which is strongly uncertain. A dense/light gas released by a subsea rupture usually generates a bubbling area at sea surface. The surface gas source is characterized by an immediate dilution with air.
The main purpose of this study is the reduction of the errors associated with inaccuracies of the source term definition and gas dispersion in the consequence analysis studies.
Soil Contamination From High Velocity, Atomized Incidental Oil Releases, A Complete Predictive Approach
Authors: Borello L.. , Bonuccelli M.. , Raucci L.. , Antico L.. 
Published: February 2011

Abstract
Oil wells blow-out events are characterized by the uncontrolled releases in atmosphere of multiphase hydrocarbon mixtures. The upper well section under blowout conditions is always characterized by the presence of annular flow with the most part of the oil transported in form of droplets. A further atomization occurs at the discharge, typically in critical flux conditions. The droplets ejected at sound velocity in the atmosphere exchange momentum with the gas jet rising at different elevations depending on the size, the jet momentum and the meteorological conditions. The granulometric distribution of the droplets also strongly affects the following aerosol dispersion and fallout. The aerosol dispersion follows two different mechanisms: Gaussian dispersion for the small droplets (with a spreading phenomenon strongly dependent on diffusion effects), ballistic dispersion (with a spreading dependent on stochastic variations in wind direction and speed). During the fallout phase a not negligible amount of oil mass evaporates changing both the droplets dimension and the oil compositions. The typically long duration of the blowout event makes a short term approach (with constant meteorological condition during the event) not realistic. A long term approach, taking into account the typical meteorological classes distribution and persistency in the involved area has to be considered for the correct prediction of the oil fallout to the ground. This process generates to the ground surface an areal source term for the following infiltration phenomenon. These areal sources are characterized by wide extensions and significant distances from the well (more than 10 km in some cases).
Most of the complex processes and phenomena, which are described above, result not completely treated in literature and specific models had been developed and implemented in a in-house software (3) as described in this paper. The overall model has been validated with real blowout contamination data.
Multiscale Parameterization and History Matching in Structured and Unstructured Grid Geometries
Authors: Bhark E. , Rey A. , Datta-Gupta A. , Jafarpour B. 
Published: February 2011

Abstract
We present the development and field application of a workflow for multiscale reservoir model calibration that seamlessly integrates production data into reservoir description from the facies to the grid-cell scale. To start with, the permeability field is parameterized using a novel grid-connectivity-based transformation basis that can be applied with any model geometry including unstructured and corner-point grids. The parameterization basis functions emerge from spectral decomposition of the grid-connectivity Laplacian and are related to the structural harmonics of the grid. To reconcile data with model resolution during history matching, we first use the coarsest scale basis functions to identify the large scale variability. Additional smaller-scale basis elements are then adaptively incorporated to successively refine the model to a level supported by data resolution. During refinement, the inclusion of more detailed basis functions into the parameterization is determined by generic modal frequency when the prior model is unavailable, or using prior information when available. In the final step of the workflow a streamline-based inversion is performed to locally adjust the reservoir model at grid-cell resolution along coarse scale preferential flow paths defined during the previous step using the parameterization.
We demonstrate the suitability and effectiveness of the developed workflow through application to an offshore turbidite reservoir with frequent well intervention including shut-ins and recompletions. The static model has over three-hundred thousand cells, a complex channelized interpretation with faults, four injector-producer pairs with deviated wells and over eight years of production history including water-cut and pressure data. The grid connectivity-based parameterization effectively updates the prior regional permeability at scales and in locations warranted by the data, while preserving the geologic continuity and avoiding ad hoc redefinition of regions given the sparse well pattern. The multiscale calibrated permeability field indicates flow communication previously unrecognized in static geologic interpretation or manual history matching.
An Evaluation of Criteria for Dynamic Gridding during Reservoir Simulation of Water Flooding and Solvent Injection
Authors: Lavie G. , Torres J. A , Kamp A. M. 
Published: February 2011

Abstract
Some hydrocarbon recovery processes are characterized by the existence of sharp saturation and/or concentration fronts. Examples of such processes are VAPEX, in situ combustion, or water flooding of heavy oil reservoirs in presence of viscous fingering. In order to simulate correctly what happens around the fronts, small grid sizes need to be used. If however the whole reservoir is gridded very finely, computational time becomes prohibitive. In order to circumvent this problem, dynamic gridding, also callled, automatic mesh refinement may be used. During the computation, the computational grid is adapted to the dynamics of the flow. This requires the use of an estimator in order to decide where to refine or to coarsen the grid. In this work we studied dynamic gridding for a water flooding problem. We implemented this problem using the mixed hybrid finite element method in 2-D on a triangular grid. The resulting code was validated by comparison to a commercial reservoir simulator. From literature, we adapted an a posteriori estimator that had been derived for incompressible flow, and we used this to refine our grid on each time step. We show that the grid refinement criterion captures relatively well the sharp saturation front. Heterogeneities are also well captured. The code is able to reproduce some tendencies of viscous fingering, although more time is required to avoid definitely the numerical disperion and dynamic gridding influence. This work is a preamble for a second work considering simulation of the VAPEX process using dynamic gridding. For this we decided to switch to the finite volume method, for which a second code was developed which is shortly mentionned in the perspectives. We think that dynamic gridding may be a solution that will allow the simulation of processes such as VAPEX and in situ combustion at reservoir scale, using effective grid refinement in the region of the front.
Compositional Simulation Using the Advanced Peng-Robinson Equation of State
Authors: Wei Yizheng , Chen Zhangxin , Satyro Marco , Dong Chao , Deng Hui 
Published: February 2011

Abstract
During compositional reservoir simulations where underground fluid composition strongly affects the modeling of recovery processes, flash calculations are commonly employed to help determine the correct number of equilibrium phases, the corresponding compositions, and the phase amount of each phase.
Cubic equations of state (EOS) are widely used in the representation of volumetric and phase equilibria due to their simplicity and solvability. Commonly used cubic EOS such as Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) have well known limitations in predicting liquid phase properties for polar compounds.
In this paper, we present a compositional reservoir simulator equipped with the advanced Peng-Robinson EOS and an efficient and robust multiphase flash algorithm that can accurately predict the phase equilibrium. This method utilizes Michelsen's stability test (Michelsen, 1982) and a combination of accelerated successive substitution and a minimum-variable Newton-Raphson (MVNR) method for fast convergence.
The advanced Peng-Robinson (APR) EOS adds volume translation and a flexible attractive temperature-dependent term to the original PR EOS for accurate PVT and saturation property correlation for polar compounds. Examples of pure compounds and mixtures are tested. Computational results show that the developed simulator provides a more detailed description and better understanding of complex dynamic underground fluid phase behavior that may occur during oil recovery processes.
Probabilistic Collocation Based Kalman Filter for Assisted History Matching
Authors: Li Weixuan , Oyerinde Dayo , Stern Dave , Wu Xiao-Hui , Zhang Dongxiao 
Published: February 2011

Abstract
In this paper, we study the application of the probabilistic collocation based Kalman filter (PCKF) approach to history matching. Kalman filter is a classical approach for data assimilation and model calibration that has been widely used with success. It updates state variables (i.e., model input and output parameters) based on their correlations, which is challenging to compute efficiently for non-linear models. A popular alternative to estimating the correlations is to use an ensemble of models, which is the basis of the Ensemble Kalman filter (EnKF). The PCKF is an alternative to the EnKF in the sense that it estimates the correlations between the state variables from the Polynomial Chaos Expansion (PCE). The coefficients in the PCE are determined by the Probabilistic Collocation Method (PCM). In this paper, the PCKF method is applied to a synthetic reservoir model that mimics a deep water deposit of amalgamated channel complexes. This model exhibits complex flow patterns under different production scenarios making it useful for testing the PCKF algorithm. Acceptable history matches were obtained with a relatively small number of simulations. Our study suggests that PCKF may be a useful way to reduce the size of the ensemble required in Kalman filter methods, thus improving the efficiency of the history matching process.